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Summary Bacteria within the Ralstonia solanacearum species complex cause devastating diseases in numerous crops, causing important losses in food production and industrial supply. Despite extensive efforts to enhance plant tolerance to disease caused by Ralstonia, efficient and sustainable approaches are still missing. Before, we found that Ralstonia promotes the production of gamma‐aminobutyric acid (GABA) in plant cells; GABA can be used as a nutrient by Ralstonia to sustain the massive bacterial replication during plant colonization. In this work, we used CRISPR‐Cas9‐mediated genome editing to mutate SlGAD2, which encodes the major glutamate decarboxylase responsible for GABA production in tomato, a major crop affected by Ralstonia. The resulting Slgad2 mutant plants show reduced GABA content, and enhanced tolerance to bacterial wilt disease upon Ralstonia inoculation. Slgad2 mutant plants did not show altered susceptibility to other tested biotic and abiotic stresses, including drought and heat. Interestingly, Slgad2 mutant plants showed altered microbiome composition in roots and soil. We reveal a strategy to enhance plant resistance to Ralstonia by the manipulation of plant metabolism leading to an impairment of bacterial fitness. This approach could be particularly efficient in combination with other strategies based on the manipulation of the plant immune system, paving the way to a sustainable solution to Ralstonia in agricultural systems. [ABSTRACT FROM AUTHOR]

Microbial pathogens and other parasites can modify the development of their hosts, either as a target or a side effect of their virulence activities. The plant‐pathogenic bacterium Ralstonia solanacearum, causal agent of the devastating bacterial wilt disease, is a soilborne microbe that invades host plants through their roots and later proliferates in xylem vessels. In this work, we studied the early stages of R. solanacearum infection in the model plant Arabidopsis thaliana, using an in vitro infection system. In addition to the previously reported inhibition of primary root length and increase in root hair formation at the root tip, we observed an earlier xylem differentiation during R. solanacearum infection that occurs in a HrpG‐dependent manner, suggesting that the pathogen actively promotes the development of the vascular system upon invasion of the root. Moreover, we found that the phytohormone auxin, of which the accumulation is promoted by the bacterial infection, is required for the R. solanacearum‐triggered induction of root hair formation but not earlier xylem differentiation. Altogether, our results shed light on the capacity of R. solanacearum to induce alterations of root developmental pathways and on the role of auxin in this process. [ABSTRACT FROM AUTHOR]

Summary: Bacterial pathogens inject effector proteins inside plant cells to manipulate cellular functions and achieve a successful infection. The soil‐borne pathogen Ralstonia solanacearum (Smith), the causal agent of bacterial wilt disease, secretes > 70 different effectors inside plant cells, although only a handful of them have been thoroughly characterized. One of these effectors, named RipI, is required for full R. solanacearum pathogenicity. RipI associates with plant glutamate decarboxylases (GADs) to promote the accumulation of gamma‐aminobutyric acid (GABA), which serves as bacterial nutrient.In this work, we found that RipI can also suppress plant immune responses to bacterial elicitors, which seems to be unrelated to the ability of RipI to induce GABA accumulation and plant cell death.A detailed characterization of the RipI features that contribute to its virulence activities identified two residues at the C‐terminal domain that mediate RipI interaction with plant GADs and the subsequent promotion of GABA accumulation. These residues are also required for the appropriate homeostasis of RipI in plant cells and the induction of cell death, although they are partially dispensable for the suppression of plant immune responses.Altogether, we decipher and uncouple the virulence activities of an important bacterial effector at the biochemical level. [ABSTRACT FROM AUTHOR]

The intestinal microbiota help regulate hibernation in vertebrates. However, it needs to be established how hibernation modulates the gut microbiome and intestinal metabolism. In the present study, we used an artificial hibernation model to examine the responses of the gut microbiota of the Strauchbufo raddei to the environmental changes associated with this behavior. Hibernation significantly lowered the diversity of the microbiota and altered the microbial community of the gut. Proteobacteria, Firmicutes, and Bacteroidota were the major bacterial phyla in the intestines of S. raddei. However, Firmicutes and Proteobacteria predominated in the gut of active and hibernating S. raddei, respectively. Certain bacterial genera such as Pseudomonas, Vibrio, Ralstonia, and Rhodococcus could serve as biomarkers distinguishing hibernating and non‐hibernating S. raddei. The gut microbiota was more resistant to environmental stress in hibernating than active S. raddei. Moreover, metabolomics revealed that metabolites implicated in fatty acid biosynthesis were highly upregulated in the intestines of hibernating S. raddei. The metabolites that were enriched during hibernation enabled S. raddei to adapt to the low temperatures and the lack of exogenous food that are characteristic of hibernation. A correlation analysis of the intestinal microbiota and their metabolites revealed that the gut microbiota might participate in the metabolic regulation of hibernating S. raddei. The present study clarified the modifications that occur in the intestinal bacteria and their symbiotic relationship with their host during hibernation. These findings are indicative of the adaptive changes in the metabolism of amphibians under different environmental conditions. [ABSTRACT FROM AUTHOR]

Bacterial wilt, caused by Ralstonia pseudosolanacearum (Rpsol) and R. solanacearum (Rsol), poses a significant challenge to solanaceous plant cultivation worldwide, particularly in tropical and subtropical regions. Even though Brazil is recognized as one of the centres of origin and diversity of Rsol, in certain regions of this large country there is an emerging prevalence of Rpsol in production fields. Therefore, this study aimed to comprehensively investigate the adaptive traits of Rpsol and Rsol using a polyphasic approach. A diverse collection of isolates from both species was assessed for their physiological, biochemical, ecological and pathogenic traits. Rsol isolates demonstrated greater adaptability to a broader range of temperature, salinity and pH. They also exhibited enhanced abilities in biofilm formation and bacteriocin production. Conversely, Rpsol isolates exhibited a broader utilization of carbon sources and displayed a wider spectrum of resistance to inhibitory substances. Moreover, they demonstrated higher infectivity towards different solanaceous hosts, showing a faster invasion and colonization process in the roots and stems of tomato plants compared to Rsol isolates. Based on our findings, we concluded that Rsol exhibited greater physiological and ecological adaptability, while Rpsol showed greater pathogenic and biochemical adaptability. These results suggest that the coexistence of both species is maintained through a balance of distinct traits within each species. [ABSTRACT FROM AUTHOR]

This document provides the conclusions of the pest survey card that was prepared in the context of the EFSA mandate on plant pest surveillance (M‐2020‐0114) at the request of the European Commission. The full pest survey card for Ralstonia syzygii subsp. indonesiensis is published and available online in the EFSA Pest Survey Card gallery at the following link and will be updated whenever new information becomes available: https://efsa.europa.eu/plants/planthealth/monitoring/surveillance/ralstonia-syzygii-indonesiensis [ABSTRACT FROM AUTHOR]

Plant‐pathogenic Ralstonia strains cause bacterial wilt disease by colonizing xylem vessels of many crops, including tomato. Host resistance is the best control for bacterial wilt, but resistance mechanisms of the widely used Hawaii 7996 tomato breeding line (H7996) are unknown. Using growth in ex vivo xylem sap as a proxy for host xylem, we found that Ralstonia strain GMI1000 grows in sap from both healthy plants and Ralstonia‐infected susceptible plants. However, sap from Ralstonia‐infected H7996 plants inhibited Ralstonia growth, suggesting that in response to Ralstonia infection, resistant plants increase inhibitors in their xylem sap. Consistent with this, reciprocal grafting and defence gene expression experiments indicated that H7996 wilt resistance acts in both above‐ and belowground plant parts. Concerningly, H7996 resistance is broken by Ralstonia strain UW551 of the pandemic lineage that threatens highland tropical agriculture. Unlike other Ralstonia, UW551 grew well in sap from Ralstonia‐infected H7996 plants. Moreover, other Ralstonia strains could grow in sap from H7996 plants previously infected by UW551. Thus, UW551 overcomes H7996 resistance in part by detoxifying inhibitors in xylem sap. Testing a panel of xylem sap compounds identified by metabolomics revealed that no single chemical differentially inhibits Ralstonia strains that cannot infect H7996. However, sap from Ralstonia‐infected H7996 contained more phenolic compounds, which are known to be involved in plant antimicrobial defence. Culturing UW551 in this sap reduced total phenolic levels, indicating that the resistance‐breaking Ralstonia strain degrades these chemical defences. Together, these results suggest that H7996 tomato wilt resistance depends in part on inducible phenolic compounds in xylem sap. [ABSTRACT FROM AUTHOR]

The gram‐negative plant‐pathogenic β‐proteobacterium Ralstonia pseudosolanacearum strain OE1‐1 produces methyl 3‐hydroxymyristate as a quorum sensing (QS) signal through methyltransferase PhcB and senses the chemical via the sensor histidine kinase PhcS. This leads to activation of the LysR family transcription regulator PhcA, which regulates the genes (QS‐dependent genes) responsible for QS‐dependent phenotypes, including virulence. The transcription regulator ChpA, which possesses a response regulator receiver domain and also a hybrid sensor histidine kinase/response regulator phosphore‐acceptor domain but lacks a DNA‐binding domain, is reportedly involved in QS‐dependent biofilm formation and virulence of R. pseudosolanacearum strain GMI1000. To explore the function of ChpA in QS of OE1‐1, we generated a chpA‐deletion mutant (ΔchpA) and revealed that the chpA deletion leads to significantly altered QS‐dependent phenotypes. Furthermore, ΔchpA exhibited a loss in its infectivity in xylem vessels of tomato plant roots, losing virulence on tomato plants, similar to the phcA‐deletion mutant (ΔphcA). Transcriptome analysis showed that the transcript levels of phcB, phcQ, phcR, and phcA in ΔchpA were comparable to those in OE1‐1. However, the transcript levels of 89.9% and 88.9% of positively and negatively QS‐dependent genes, respectively, were significantly altered in ΔchpA compared with OE1‐1. Furthermore, the transcript levels of these genes in ΔchpA were positively correlated with those in ΔphcA. Together, our results suggest that ChpA is involved in the regulation of these QS‐dependent genes, thereby contributing to the behaviour in host plant roots and virulence of OE1‐1. [ABSTRACT FROM AUTHOR]

BACKGROUND: Tobacco bacterial wilt is a typical soil‐borne disease caused by Ralstonia nicotianae, which causes huge losses in tobacco production every year. The crude extract of Carex siderosticta Hance was shown to have antibacterial activity against R. nicotianae during our search, and the natural antibacterial components were sought after using bioassay‐guided fractionation of the compounds. RESULT: Ethanol extract of Carex siderosticta Hance with the minimum inhibitory concentration (MIC) value of 100 μg/mL against R. nicotianae in vitro. The potential of these compounds as antibactericides against R. nicotianae were assessed. Curcusionol (1), showed the highest antibacterial activity against R. nicotianae with MIC value of 12.5 μg/mL in vitro. In the protective effect tests, the control effect of curcusionol (1) was 92.31 and 72.60%, respectively, after application of 7 and 14 days, at a concentration of 1500 μg/mL, being comparable to that of streptomycin sulfate at a concentration of 500 μg/mL, confirming that curcusionol (1) showed the potential for the development of new antibacterial drugs. RNA‐sequencing, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis confirmed that curcusionol mainly destroys R. nicotianae cell membrane structure and affects quorum sensing (QS) to inhibit pathogenic bacteria. CONCLUSION: This study revealed that the antibacterial activity of Carex siderosticta Hance makes it a botanical bactericide against R. nicotianae, while curcusionol as lead structures for antibacterial development is obvious by its potent antibacterial activity. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The bacterial wilt disease caused by soilborne bacteria of the Ralstonia solanacearum species complex (RSSC) threatens important crops worldwide. Only a few immune receptors conferring resistance to this devastating disease are known so far. Individual RSSC strains deliver around 70 different type III secretion system effectors into host cells to manipulate the plant physiology. RipE1 is an effector conserved across the RSSC and triggers immune responses in the model solanaceous plant Nicotiana benthamiana. Here, we used multiplexed virus‐induced gene silencing of the nucleotide‐binding and leucine‐rich repeat receptor family to identify the genetic basis of RipE1 recognition. Specific silencing of the N. benthamiana homologue of Solanum lycopersicoides Ptr1 (confers resistance to Pseudomonas syringae pv. tomato race 1) gene (NbPtr1) completely abolished RipE1‐induced hypersensitive response and immunity to Ralstonia pseudosolanacearum. The expression of the native NbPtr1 coding sequence was sufficient to restore RipE1 recognition in Nb‐ptr1 knockout plants. Interestingly, RipE1 association with the host cell plasma membrane was necessary for NbPtr1‐dependent recognition. Furthermore, NbPtr1‐dependent recognition of RipE1 natural variants is polymorphic, providing additional evidence for the indirect mode of activation of NbPtr1. Altogether, this work supports NbPtr1 relevance for resistance to bacterial wilt disease in Solanaceae. [ABSTRACT FROM AUTHOR]

In order to determine the contribution of GmFLS2a/b to soybean resistance against I Ralstonia i , we first generated soybean I fls2a/b i mutant plants using CRISPR-Cas9-mediated genome editing. Keywords: bacterial wilt; CRISPR; disease; pathogen; Ralstonia; resistance; soybean EN bacterial wilt CRISPR disease pathogen Ralstonia resistance soybean 17 22 6 09/11/23 20231001 NES 231001 Data availability All the data and materials integral to this study are available within the article and the Supporting Information. However, upon stem injection, both mutant lines showed enhanced susceptibility, suggesting that, once I Ralstonia i is inside plant tissues, GmFLS2 contributes significantly to soybean defense against I Ralstonia i , likely by perceiving the polymorphic flg22 SP Rso sp and initiating defense signaling. [Extracted from the article]

The soilborne bacterial pathogen Ralstonia solanacearum is one of the most destructive plant pathogens worldwide, and its infection process involves the manipulation of numerous plant cellular functions. In this work, we found that the R. solanacearum effector protein RipD partially suppressed different levels of plant immunity triggered by R. solanacearum elicitors, including specific responses triggered by pathogen‐associated molecular patterns and secreted effectors. RipD localized in different subcellular compartments in plant cells, including vesicles, and its vesicular localization was enriched in cells undergoing R. solanacearum infection, suggesting that this specific localization may be particularly relevant during infection. Among RipD‐interacting proteins, we identified plant vesicle‐associated membrane proteins (VAMPs). We also found that overexpression of Arabidopsis thaliana VAMP721 and VAMP722 in Nicotiana benthamiana leaves promoted resistance to R. solanacearum, and this was abolished by the simultaneous expression of RipD, suggesting that RipD targets VAMPs to contribute to R. solanacearum virulence. Among proteins secreted in VAMP721/722‐containing vesicles, CCOAOMT1 is an enzyme required for lignin biosynthesis, and mutation of CCOAOMT1 enhanced plant susceptibility to R. solanacearum. Altogether our results reveal the contribution of VAMPs to plant resistance against R. solanacearum and their targeting by a bacterial effector as a pathogen virulence strategy. [ABSTRACT FROM AUTHOR]

Untangling how factors such as environment, host, associations among bacterial species and dispersal predict microbial composition is a fundamental challenge. In this study, we use complementary machine‐learning approaches to quantify the relative role of these factors in shaping microbiome variation of the blacklegged tick Ixodes scapularis. I. scapularis is the most important vector for Borrelia burgdorferi (the causative agent for Lyme disease) in the U.S. as well as a range of other important zoonotic pathogens. Yet the relative role of the interactions between pathogens and symbionts compared to other ecological forces is unknown. We found that positive associations between microbes where the occurrence of one microbe increases the probability of observing another, including between both pathogens and symbionts, was by far the most important factor shaping the tick microbiome. Microclimate and host factors played an important role for a subset of the tick microbiome including Borrelia (Borreliella) and Ralstonia, but for the majority of microbes, environmental and host variables were poor predictors at a regional scale. This study provides new hypotheses on how pathogens and symbionts might interact within tick species, as well as valuable predictions for how some taxa may respond to changing climate. [ABSTRACT FROM AUTHOR]

After infecting roots of tomato plants, the gram‐negative bacterium Ralstonia pseudosolanacearum strain OE1‐1 activates quorum sensing (QS) to induce production of plant cell wall‐degrading enzymes, such as β‐1,4‐endoglucanase (Egl) and β‐1,4‐cellobiohydrolase (CbhA), via the LysR family transcriptional regulator PhcA and then invades xylem vessels to exhibit virulence. The phcA‐deletion mutant (ΔphcA) exhibits neither the ability to infect xylem vessels nor virulence. Compared with strain OE1‐1, the egl‐deletion mutant (Δegl) exhibits lower cellulose degradation activity, lower infectivity in xylem vessels, and reduced virulence. In this study, we analysed functions of CbhA other than cell wall degradation activity that are involved in the virulence of strain OE1‐1. The cbhA‐deletion mutant (ΔcbhA) lacked the ability to infect xylem vessels and displayed loss of virulence, similar to ΔphcA, but exhibited less reduced cellulose degradation activity compared with Δegl. Transcriptome analysis revealed that the phcA expression levels in ΔcbhA were significantly lower than in OE1‐1, with significantly altered expression of more than 50% of PhcA‐regulated genes. Deletion of cbhA led to a significant change in QS‐dependent phenotypes, similar to the effects of phcA deletion. Complementation of ΔcbhA with native cbhA or transformation of this mutant with phcA controlled by a constitutive promoter recovered its QS‐dependent phenotypes. The expression level of phcA in ΔcbhA‐inoculated tomato plants was significantly lower than in strain OE1‐1‐inoculated plants. Our results collectively suggest that CbhA is involved in the full expression of phcA, thereby contributing to the QS feedback loop and virulence of strain OE1‐1. [ABSTRACT FROM AUTHOR]

BACKGROUND: Significant changes occurd in Daqu bricks on the 15th day of incubation, and brick color (yellow, brown, or dark) is generally used as a standard for quality evaluation by experienced workers. This study aimed to explore the basis behind the phenomenon through multi‐omics studies. The physicochemical properties of different high‐temperature Daqu were compared. Furthermore, PacBio sequencing and the ultra‐high‐performance liquid chromatographic–Q‐exactive–mass spectrometric approach were employed to analyze the differences in the microbiome and metabolome among different Daqu samples. RESULTS: Bacillus was the biomarker of yellow Daqu, Thermoactinomyces and Thermoascus were the key genera in brown Daqu, and Burkholderiales, Sphingomonas, and Ralstonia were biomarkers in dark Daqu. The physicochemical characteristics (especially the color values) of different high‐temperature Daqu showed strong correlations with the bacterial alpha diversity and the relative abundance of dominant bacterial genera. Amino acid metabolism pathways including tryptophan metabolism, β‐alanine metabolism, and arginine biosynthesis were the key factors resulting in the characteristic differences where Bacillus, Burkholderia, Ralstonia, and Sphingomonas were pivotal bacterial genera. The relative abundance of Bacillus had a positive correlation with the content of 3‐hydroxykynurenamine, l‐glutamic acid, and pantothenic acid, while it showed a negative correlation with indoleacetic acid, l‐tryptophan, N‐acetylserotonin, l‐histidine, l‐aspartic acid, phosphatidylserine, 5‐methoxyindoleacetate, and L‐serine. Burkholderia, Ralstonia, and Sphingomonas had the opposite effects. CONCLUSION: Microbes play different roles in amino acid metabolism pathways, producing different metabolites, contributing to the differences in Daqu appearance and quality. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Peritoneal dialysis (PD)‐associated peritonitis secondary to Ralstonia infection is very rare. Ralstonia pickettii is an organism that can grow in contaminated saline, water, chlorhexidine, and other medical products used in laboratories and the clinical setting. Infective endocarditis, prosthetic joint, and severe chest infections are previously reported with R. pickettii infection. We report a novel series of three cases diagnosed with PD‐associated peritonitis caused by R. pickettii, where the cases appeared consecutively to our unit during a span of 4 weeks. During the COVID‐19 pandemic, there were increased uses of non‐sterile gloves by clinical staff as a form of personal protective equipment throughout patient interaction and PD exchange, as recommended by local hospital policy for all staff attending to patient care. A multidisciplinary team root cause analysis of our cases suggested non‐sterile gloves being the likely source of environmental contamination, leading to PD‐associated peritonitis caused by R. pickettii in this scenario. [ABSTRACT FROM AUTHOR]

Bacterial wilt caused by the Ralstonia solanacearum species complex (RSSC) is a disease that negatively affects the cultivation of Solanaceae crops in Burkina Faso. Knowledge of the pathogen diversity is essential to deploy locally adapted control methods. In this study, diseased plants showing typical bacterial wilt symptoms were collected in the three main agroclimatic zones of Burkina Faso for the detection of RSSC isolates. Strain characterization was achieved through a phylogenetic and pathogenicity diversity assessment. A total of 102 isolates were sampled, and Phylotype I (Ralstonia pseudosolanacearum) was predominant (n = 101; sequevars 14, 31, 34, and 46). The remaining isolate was characterized as Phylotype IIA‐35 (Ralstonia solanacearum). Phylotypes I‐31 and I‐46 were predominant and both characterized as the most the aggressive group of strains amongst a subset of 33 representative isolates. Our findings provide valuable information as regard RSSC diversity that breeders and resistance programme should target in order to fight this pathogen in Burkina Faso and around the world. [ABSTRACT FROM AUTHOR]

Glasshouse experiments were conducted to study infection and disease development in rockwool‐grown rose plants inoculated with Ralstonia pseudosolanacearum. A R. pseudosolanacearum strain isolated from rose plants was more aggressive than strains from anthurium or curcuma. The three rose cultivars tested, Avalanche, Red Naomi, and Armando, differed in susceptibility. At 20°C, the rose strain caused hardly any symptoms over a 6‐week period, whereas at 28°C typical wilt symptoms were observed within 2 weeks after stem inoculation of Armando, the most susceptible cultivar. Inoculating roots with the rose strain resulted only in weak atypical symptoms. Nevertheless, inoculating roots of cv. Armando at a relatively low inoculum dose of 104 cfu/ml led to high densities in the base of stems in one out of two experiments. R. pseudosolanacearum occasionally spread from stem inoculated plants with symptoms in rockwool slabs. This limited spread resulted in a low infection incidence, and only of plants directly adjacent to the plants with symptoms. [ABSTRACT FROM AUTHOR]

Summary: Stellera chamaejasme has become a problematic weed in northern and south‐western grasslands of China. To evaluate a possible role of endophytes in its strong competitive capacity, the endophytic bacterial community of S. chamaejasme was investigated by culture‐dependent and independent methods, and the growth‐promoting traits of some culturable isolates as well as the benefit of endophyte ST3CS3 (Brevundimonas sp.) on host plants growth were studied. The results showed that 823 OTUs were generated with a 97% similarity level in the culture‐independent study. They were classified into 29 phyla, 61 classes, 147 orders, 237 families and 440 genera. Among them, Pseudomonas and Ralstonia were the most dominant genera in belowground parts (G) (64.25%) and aboveground parts (S) (26.54%) respectively. The diversity and species richness of endophytes in S were significantly higher than that of G (P < 0.001, t‐test). Contrary to this, the number of culturable bacteria in S was a little lower than that of G (P > 0.05, t‐test). Totally, 176 isolates belonging to 30 morphotypes were obtained in the culture‐dependent study. Among them, Acinetobacter was the most dominant genus in G (51.30%), then followed by Pseudomonas (6.09%) and Brevundimonas (6.09%), while Lysinibacillus (21.31%) was the most dominant genus in S, followed by Pseudomonas (11.48%). Growth‐promoting trait tests indicated that 93.65% of the tested isolates (63) exhibited nitrogen‐fixing, IAA‐synthesizing, phosphorus or potassium solubilizing capacity, in which 77.97% belonged to Proteobacteria, a phylum found to contain more active isolates. Pot experiments demonstrated that endophyte ST3CS3 can significantly improve host plants growth and increase its nitrogen and chlorophyll content (P < 0.01, t‐test). Therefore, we suggest that strong competitiveness of S. chamaejasme may in part be due to possession of high ratios of plant growth‐promoting proteobacterial endophytes such as Pseudomonas, Acinetobacter and Brevundimonas. [ABSTRACT FROM AUTHOR]

Cultivation of solanaceous vegetables such as eggplant and tomato is severely affected by bacterial wilt in the coastal regions of India. The causal agent Ralstonia pseudosolanacearum is soilborne bacterium, highly diverse, and able to survive in soil for many years without a host. Five bacterial wilt resistant eggplant (Solanum melongena) rootstock lines were evaluated by challenge inoculation and were found to show different levels of wilt incidence. Grafts of eggplant made on two rootstocks (S0004 and Surya) recorded reduced incidence of bacterial wilt (10 to 40%) during greenhouse evaluation while in nongrafted seedlings, the wilt incidence was 80 to 100%. Field evaluation of eggplant grafts made on Solanum torvum (Turkey berry), S0004, and Surya reduced the incidence of bacterial wilt compared to nongrafted seedlings. The lowest wilt incidence (0 and 15–40%) was observed in the field evaluations where S. torvum was used as rootstock, while the nongrafted control recorded 93–100% wilt. Tomato seedlings grafted on S. torvum, Surya, and S0004 recorded very low bacterial wilt incidence (0 to 15%) under greenhouse evaluation while the nongrafted seedlings recorded 80 to 100% wilt. Reduced bacterial wilt incidence (23 to 40%) was observed in grafts of polyhouse-grown tomato hybrid (GS-600) made on S. torvum while the nongrafted seedlings were severely affected (80 to 100%) in evaluation trials conducted for two years. From this study, it is evident that grafting of susceptible eggplant and tomato on resistant rootstocks, viz., S. torvum and Surya, could be a promising strategy in bacterial wilt management. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum species complex is a group of vascular soil‐borne plant pathogens that causes bacterial wilt on various host plants and has caused great yield losses in Thailand. In 2020 and 2021, bacterial wilt diseases were observed in Chiang Mai and Chiang Rai Province, Thailand. Approximately 19 bacterial wilt strains that were infecting 10 plant species were identified. The different bacterial wilt strains were characterized based on biovar test, phylotypes and DNA sequence of egl gene to determine their sequevar classification. The results of biovar tests by oxidation of disaccharides and hexose alcohols showed the strains belong to biovars 2T, 3 and 4. The partial egl gene sequence analysis of the strains clustered into five type groups that included phylotype IIA sequevar 1 as R. solanacearum and phylotype I, which included 4 sequevars (13, 17, 30 and 47) as R. pseudosolanacearum. The results showed that tomato, Thai eggplant and marigold were susceptible to all bacterial wilt strains. Furthermore, R. pseudosolanacearum biovar 2T phylotype I sequevar 17 was specifically pathogenic to pumpkin and cucumber, but sequevar 13 produced bacterial wilt symptoms on cucumber, and the two sequevars were non‐symptomatic on Patumma and turmeric. R. pseudosolanacearum biovar 4 phylotype I sequevar 30 was specifically pathogenic to Patumma and turmeric. This new report expands the knowledge on genetic analysis and host range diversity of the R. solanacearum species complex in Thailand. [ABSTRACT FROM AUTHOR]

The obligate mutualistic basidiomycete fungus, Leucocoprinus gongylophorus, mediates nutrition of leaf‐cutting ants with carbons from vegetal matter. In addition, diazotrophic Enterobacteriales in the fungus garden and intestinal Rhizobiales supposedly mediate assimilation of atmospheric nitrogen, and Entomoplasmatales in the genus Mesoplasma, as well as other yet unidentified strains, supposedly mediate ant assimilation of other compounds from vegetal matter, such as citrate, fructose, and amino acids. Together, these nutritional partners would support the production of high yields of leafcutter biomass. In the present investigation, we propose that three phylogenetically distinct and culturable diazotrophs in the genera Ralstonia, Methylobacterium, and Pseudomonas integrate this symbiotic nutrition network, facilitating ant nutrition on nitrogen. Strains in these genera were often isolated and directly sequenced in 16S rRNA libraries from the ant abdomen, together with the nondiazotrophs Acinetobacter and Brachybacterium. These five isolates were underrepresented in libraries, suggesting that none of them is dominant in vivo. Libraries have been dominated by four uncultured Rhizobiales strains in the genera Liberibacter, Terasakiella, and Bartonella and, only in Acromyrmex ants, by the Entomoplasmatales in the genus Mesoplasma. Acromyrmex also presented small amounts of two other uncultured Entomoplasmatales strains, Entomoplasma and Spiroplasma. The absence of Entomoplasmatales in Atta workers implicates that the association with these bacteria is not mandatory for ant biomass production. Most of the strains that we detected in South American ants were genetically similar with strains previously described in association with leafcutters from Central and North America, indicating wide geographic dispersion, and suggesting fixed ecological services. [ABSTRACT FROM AUTHOR]

The gram‐negative plant‐pathogenic β‐proteobacterium Ralstonia pseudosolanacearum strain OE1‐1 produces methyl 3‐hydroxymyristate as a quorum sensing (QS) signal via the methyltransferase PhcB and senses the chemical through the sensor histidine kinase PhcS. This leads to functionalization of the LysR family transcriptional regulator PhcA, regulating QS‐dependent genes responsible for the QS‐dependent phenotypes including virulence. The phc operon consists of phcB, phcS, phcR, and phcQ, with the latter two encoding regulator proteins with a receiver domain and a histidine kinase domain and with a receiver domain, respectively. To elucidate the function of PhcR and PhcQ in the regulation of QS‐dependent genes, we generated phcR‐deletion and phcQ‐deletion mutants. Though the QS‐dependent phenotypes of the phcR‐deletion mutant were largely unchanged, deletion of phcQ led to a significant change in the QS‐dependent phenotypes. Transcriptome analysis coupled with quantitative reverse transcription‐PCR and RNA‐sequencing revealed that phcB, phcK, and phcA in the phcR‐deletion and phcQ‐deletion mutants were expressed at similar levels as in strain OE1‐1. Compared with strain OE1‐1, expression of 22.9% and 26.4% of positively and negatively QS‐dependent genes, respectively, was significantly altered in the phcR‐deletion mutant. However, expression of 96.8% and 66.9% of positively and negatively QS‐dependent genes, respectively, was significantly altered in the phcQ‐deletion mutant. Furthermore, a strong positive correlation of expression of these QS‐dependent genes was observed between the phcQ‐deletion and phcA‐deletion mutants. Our results indicate that PhcQ mainly contributes to the regulation of QS‐dependent genes, in which PhcR is partially involved. [ABSTRACT FROM AUTHOR]

Summary: The objective of this study was to evaluate changes in the bacterial community in sugarcane silage, in distinct soil types along the storage period. We depicted the bacterial community associated with sugarcane, before and after ensiling, through a massive sequencing of the gene 16S rRNA using MiSeq platform. The ensilage process shifted the composition of the bacterial community from the heterofermentative lactic acid bacteria Leuconostoc to bacteria belonging to the genera Acinetobacter, Ralstonia and Novosphingobium. However, this shift did not convey statically significant differences in alfa diversity metrics. In addition, similarity percentage analysis showed that the bacterial Operational Taxonomic Units that were primarily responsible for the observed differences were Leuconostoc, Pseudomonas, Acinetobacter, Ralstonia, Fructobacillus, Novosphingobium, Lactobacillus, Burkholderia and Clostridium sensu stricto 1. The storage period was the most important factor responsible for changes in the bacterial community of silages. Results confirmed that the type of soil did not influence the dissimilarity found among samples. [ABSTRACT FROM AUTHOR]

Summary: Soil disease‐suppressiveness depends on complex interactions among pathogens, native microbiota, and physicochemical properties, while these interactions remain understudied. Comparing field and microcosm experiments, we investigated the significance of these interactions in disease emergence or suppression using structural equation modelling (SEM) and receiver operating characteristic curve (ROC) analyses. We observed significant differences in the relative abundance of pathogenic and beneficial microbes, alpha and beta diversity indices between disease‐conducive and ‐suppressive rhizosphere soils. The pathogenic (Ralstonia) and beneficial (Bacillus) taxa dominated disease‐conducive and ‐suppressive rhizosphere soils, respectively. Moreover, the co‐occurrences of Ralstonia with native microorganisms were positive and negative in the disease‐conducive and ‐suppressive soils, respectively. These results suggest the supportive (Rudaea) and suppressive (Enterobacter, Bacillus) role of indigenous microbes in the invasion of soil and plant systems by Ralstonia. The SEM and ROC analysis predicted that Ralstonia invaded rhizospheric microbial networks and caused peanut wilt under high than low soil phosphorus conditions. Our results suggest the importance of soil phosphorus availability in altering the microbial interactions, thus leading to soil invasion by Ralstonia. Thus, we conclude by saying that feeding soil with high amounts of available phosphorus could deplete plant‐beneficial microbes and increase the pathobiome abundance that may compromise plant health. [ABSTRACT FROM AUTHOR]

Bacterial wilt, one of the world's most destructive diseases in many crops, including eucalypt, is caused by four distinct phylogenetic lineages of the Ralstonia solanacearum species complex, recently classified in three distinct species: R. solanacearum (phylotype II), R. pseudosolanacearum (phylotype I and III) and R. syzygii (phylotype IV). In this study, we characterized 93 Ralstonia isolates obtained from eucalypt grown in different Brazilian regions using phylotype and sequevar designations and genomic fingerprinting with BOX‐PCR. In addition, we evaluated the aggressiveness of a select group of isolates in two eucalypt clones differing in resistance. We found that 89 isolates belong to R. solanacearum (phylotype II) and four to R. pseudosolanacearum (phylotype I). Unlike R. pseudosolanacearum, R. solanacearum was phylogenetically diverse and no correlation was found between sequevar and geographic origin. Most isolates grouped with reference isolates of phylotype IIA sequevar 41, whereas a few others clustered in phylotype IIB, mainly sequevar 4NPB, which is an emergent variant described affecting eucalypt for the first time. Isolates of R. solanacearum phylotype IIB were less aggressive to clone CLR371 (susceptible) whereas the R. pseudosolanacearum isolate tested was the only one pathogenic to the CLR172 (resistant) clone. Isolate aggressiveness varied between the eucalypt clones tested. The results of this study reinforce the importance of conducting molecular and aggressiveness characterization of the pathogen population to develop management strategies aimed at the deployment of host resistance in eucalypt breeding programmes. [ABSTRACT FROM AUTHOR]

In addition, the results of this study will be strengthened by comparing the current data with those for the microbiome of patients with Crohn's disease and CKD, and CKD patients without IBD. The causal link between inflammatory bowel disease (IBD) and chronic kidney disease (CKD) is not clear; therefore, we aimed to investigate the role of gut microbiota in decreasing renal function in patients with IBD. [Extracted from the article]

Background: Intestinal microbiota are recognized as an organ with important physiological functions whose alterations have been associated with common diseases including inflammatory intestinal conditions, malnutrition, type‐2 diabetes, and cardiovascular diseases. The composition and function of the microbiota in the distal part of the intestine has been mainly described, while there is limited information on the small intestine microbiota. The objective of the present study was to describe the duodenal microbiome in individuals with dyspepsia in the presence or absence of Helicobacter pylori gastric infection. Materials and Methods: Thirty‐eight biopsies from the proximal duodenum of uninfected and 37 from H pylori‐infected individuals were analyzed. Microbiota composition was assessed by PCR amplification and sequencing of 16S rRNA and ITS genes; sequences were analyzed with QIIME2. Results and Conclusions: At the phyla level, Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria, and Fusobacteria were predominant in the mucosal associated duodenal microbiota (MAM); at the genera level, we observed the predominance of Ralstonia, Streptococcus, Pseudomonas, Haemophilus, Herbaspirillum, Neisseria, and Veillonella. Microbiota α‐diversity was higher in H pylori‐infected individuals than in non‐infected ones. In terms of β‐diversity metrics, there was a statistically significant difference between groups. Also, relative abundance of Haemophilus, Neisseria, Prevotella pallens, Prevotella 7, and Streptococcus was greater in H pylori‐infected patients. In infected patients, several types of H pylori were present in duodenal MAM. Finally, the majority of duodenal samples had fungi sequences; the most common taxa observed were Recurvomyces followed by Ascomycota and Basidiomycota. [ABSTRACT FROM AUTHOR]

Pathogens deploy effector proteins that interact with host proteins to manipulate the host physiology to the pathogen's own benefit. However, effectors can also be recognized by host immune proteins, leading to the activation of defence responses. Effectors are thus essential components in determining the outcome of plant–pathogen interactions. Despite major efforts to decipher effector functions, our current knowledge on effector biology is scattered and often limited. In this study, we conducted two systematic large‐scale yeast two‐hybrid screenings to detect interactions between Arabidopsis thaliana proteins and effectors from two vascular bacterial pathogens: Ralstonia pseudosolanacearum and Xanthomonas campestris. We then constructed an interactomic network focused on Arabidopsis and effector proteins from a wide variety of bacterial, oomycete, fungal, and invertebrate pathogens. This network contains our experimental data and protein–protein interactions from 2,035 peer‐reviewed publications (48,200 Arabidopsis–Arabidopsis and 1,300 Arabidopsis–effector protein interactions). Our results show that effectors from different species interact with both common and specific Arabidopsis interactors, suggesting dual roles as modulators of generic and adaptive host processes. Network analyses revealed that effector interactors, particularly "effector hubs" and bacterial core effector interactors, occupy important positions for network organization, as shown by their larger number of protein interactions and centrality. These interactomic data were incorporated in EffectorK, a new graph‐oriented knowledge database that allows users to navigate the network, search for homology, or find possible paths between host and/or effector proteins. EffectorK is available at www.effectork.org and allows users to submit their own interactomic data. [ABSTRACT FROM AUTHOR]

The Ralstonia solanacearum species complex (RSSC) can cause bacterial wilt in a wide variety of plant species, including a number of ornamental glasshouse crops. Recently in Europe, ornamental rose plants for the production of cut flowers and propagation materials have been strongly affected by Ralstonia pseudosolanacearum, phylotype I, biovar 3. To test for the presence of the pathogen in the glasshouse, sampling of water from a drainage gutter or well may be an efficient strategy since it is known that RSSC can be released from infected root systems in the water. A protocol was developed to detect low densities of R. pseudosolanacearum in drain water collected from rose growers. Drain water was filtered through a bacterial filter, the filtrate was collected and target bacteria enriched for 48 h in Semi‐selective Medium South Africa (SMSA) broth supplemented with sterilized tomato plant extracts. DNA extracted from the enrichment broth was analysed using a TaqMan test in a duplex format, based on specific egl sequences of RSSC and the use of an extraction and amplification control. The optimized protocol had a detection level of ≤1–10 colony forming units of R. pseudosolanacearum in drain water. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum sensu lato causes bacterial wilt in many agronomic crops and tree species economically important worldwide. It is a species complex that has been divided into phylotypes and sequevars, commonly related to geographic distribution. Knowledge of the phylotype composition and genetic variability in populations of this phytopathogenic bacterium is useful for implementing effective control measures. In a survey conducted in 2019, six bacterial strains were obtained from wilted Eucalyptus urophylla trees in plantations located in the municipality of Dom Eliseu, Pará state, Brazil. Multiplex PCR based on the internal transcribed spacer (ITS) indicated that the bacterial strains belonged to two different species, namely R. pseudosolanacearum (phylotype I) and R. solanacearum (phylotype II). In a phylogenetic analysis, the nucleotide sequence of the endoglucanase (egl) gene from eucalypt strains of phylotype I clustered together with sequevar 18 sequences from GenBank. Separation of the strains into two different species was confirmed by repetitive element palindromic PCR (rep‐PCR). Pathogenicity tests demonstrated that the R. solanacearum and R. pseudosolanacearum strains recovered from E. urophylla cause disease in both tomato and eucalypt plants. Until now, only R. solanacearum (Phylotype II) has been reported causing wilt symptoms on Eucalyptus spp. in Brazil. Therefore, the presence of R. pseudosolanacearum and a need for better understanding of its genetic and aggressiveness variability as well as possible differences between the two species should be considered in breeding programmes aimed at the deployment of host resistance. [ABSTRACT FROM AUTHOR]

Background: The equine conjunctival microbiota has often been reported to be dominated by Gram-positive species such as Staphylococcus sp., Bacillus sp., and Corynebacterium sp. However, traditional culture-based methods can only recover a fraction of the bacterial species present in the sample. Objectives: This pilot study aimed at exploring the diversity of the equine conjunctival microbiota using culture-independent methods. Study design: Eight horses were included in this study, and only eyes with normal ophthalmic examination (n = 15 eyes) were sampled. Methods: Conjunctival biopsies (culture-independent) were collected, and DNA was extracted from the tissues. Bacterial communities in conjunctival biopsies were characterized by next-generation sequencing of the 16S rRNA genes. Individual reads were ascribed to operational taxonomic units (OTUs) using BLASTn and Greengenes databases. Species richness, evenness, and Good's coverage were determined for each conjunctiva-associated microbial community. Results: Culture-independent samples produced a total of 329 bacterial OTUs. The main OTUs identified in the study belonged to the Gram-negative species Ralstonia mannitolilytica (88.0%), Nicoletella semolina (3.3%), and Pseudomonas tolaasii (1.5%). Conclusions: Contrary to previously published data based on culture-dependent methods, the horse eye microbial community was dominated by Gram-negative bacteria of the phylum Proteobacteria. [ABSTRACT FROM AUTHOR]

A series of 1‐aryl‐2,2,2‐trifluoroethanones has been chemically synthesized to later study their bioreduction using stereocomplementary alcohol dehydrogenases (ADHs). Satisfyingly, (R)‐alcohols were obtained in high conversions and selectivities using the ADH from Ralstonia species and the one from Rhodococcus ruber, while the (S)‐enantiomers were independently produced using the ADH from Lactobacillus brevis and the commercially available evo‐1.1.200. In the search for a stereoselective route towards the Odanacatib, an orally bioavailable and selective inhibitor of Cathepsin K, the development of a sequential methodology combining a palladium‐catalyzed cross coupling between 1‐(4‐bromophenyl)‐2,2,2‐trifluoroethanone and 4‐(methylsulfonyl)phenylboronic acid in aqueous medium with the bioreduction of the resulting 2,2,2‐trifluoro‐1‐(4′‐(methylsulfonyl)‐[1,1′‐biphenyl]‐4‐yl)ethanone has been extensively studied. Finally, the desired (R)‐2,2,2‐trifluoro‐1‐(4′‐(methylsulfonyl)‐[1,1′‐biphenyl]‐4‐yl)ethanol was obtained in enantiomerically pure form and 85 % yield with a 128 g L−1 d−1 productivity following a sequential approach. [ABSTRACT FROM AUTHOR]

Microorganisms in insect guts have been recognized as having a great impact on their hosts' nutrition, health, and behavior. Spiders are important natural enemies of pests, and the composition of the gut microbiota of spiders remains unclear. Will the bacterial taxa in spiders be same as the bacterial taxa in insects, and what are the potential functions of the gut bacteria in spiders? To gain insight into the composition of the gut bacteria in spiders and their potential function, we collected three spider species, Pardosa laura, Pardosa astrigera, and Nurscia albofasciata, in the field, and high‐throughput sequencing of the 16S rRNA V3 and V4 regions was used to investigate the diversity of gut microbiota across the three spider species. A total of 23 phyla and 150 families were identified in these three spider species. The dominant bacterial phylum across all samples was Proteobacteria. Burkholderia, Ralstonia, Ochrobactrum, Providencia, Acinetobacter, Proteus, and Rhodoplanes were the dominant genera in the guts of the three spider species. The relative abundances of Wolbachia and Rickettsiella detected in N. albofasciata were significantly higher than those in the other two spider species. The relative abundance of Thermus, Amycolatopsis, Lactococcus, Acinetobacter Microbacterium, and Koribacter detected in spider gut was different among the three spider species. Biomolecular interaction networks indicated that the microbiota in the guts had complex interactions. The results of this study also suggested that at the genus level, some of the gut bacteria taxa in the three spider species were the same as the bacteria in insect guts. [ABSTRACT FROM AUTHOR]

We report a case series of seven patients with nonfermentative Gram‐negative bacteria infections in a single dialysis center; four patients with Ralstonia pickettii and three patients with Stenotrophomonas maltophilia. Two of the seven patients were admitted to hospital for intravenous antibiotic treatment, while the rest were treated with oral antibiotics at home. Both the admitted patients had temporary vascular catheter infections from the aforementioned pathogens. We conclude that the outbreak is due to colonization of treated reverse osmosis water, presumably through contamination via polluted filters and compounded by the usage of reprocessed dialysers in the dialysis center. This is especially relevant because contaminated treated water is directly introduced into the blood compartment of the dialysers during reprocessing. In addition, there seems to be a propensity for both organisms to cause prolonged febrile reactions in patients with temporary vascular catheters, likely through the early development of biofilm. Intensification of general sterilization procedures, servicing and replacement of old decrepit components of the water treatment system and temporary cessation of dialyser reuse practice seem to have halted the outbreak. Due to the virulent nature and difficult resistant profile of nonfermentative Gram‐negative bacteria, we strongly recommend meticulous vigilance in the surveillance of culture isolates in routine microbiological specimens from dialysis centers, especially if there is a senescent water treatment system and a practice of reprocessing dialysers. [ABSTRACT FROM AUTHOR]

A new technological approach to nanoparticle synthesis is using microorganisms, such as bacteria, which have the ability to synthesize nontoxic nanoparticles with high biocompatibility. In addition, bacteria have strict control over size, structure, shape, and dimension of produced nanoparticles. In the present work, Fe (III)‐binding exopolysaccharide (Fe‐EPS) nanoparticles were biosynthesized by Ralstonia pickettii sp. SK03, a bacterium isolated from a mineral spring. 16S rRNA gene sequencing and biochemical tests were done for identification of the isolated bacterium. For the first time, critical biological and physicochemical properties of this iron oxide nanoparticle were characterized using Fourier Transform Infrared (FTIR) Spectroscopy, Transmission Electron Microscopy (TEM), Vibrating Sample Magnetometer (VSM), Dynamic Light Scattering (DLS), Thermogravimetric analysis (TGA), X‐ray crystallography (XRD), Atomic absorption spectroscopy (AAS), and cell viability assays (MTT assay). The characterization results showed that Fe‐EPS nanoparticles were composed of spherical ferrihydrite nanoparticles (with a size range of 1.2–2 nm), trapped in a polysaccharide matrix. The TGA analysis demonstrated that Fe‐EPS nanoparticles contained ∼25.2% polysaccharide. Therefore, this polysaccharide matrix showed a very low magnetic saturation value (0.25 emu/g) and a large negative charge of −93.8 mV. In addition, treatment of hepatocarcinoma cell line (Hep‐G2) with 1–500 µg/mL concentrations of Fe‐EPS nanoparticles caused 40% increase in the cell viability, which indicated that the biosynthesized nanoparticles were nontoxic and biocompatible. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018 © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1167–1176, 2018 [ABSTRACT FROM AUTHOR]

Summary: Ralstonia solanacearum, the causal agent of bacterial wilt disease, is considered one of the most destructive bacterial pathogens due to its lethality, unusually wide host range, persistence and broad geographical distribution. In spite of the extensive research on plant immunity over the last years, the perception of molecular patterns from R. solanacearum that activate immunity in plants is still poorly understood, which hinders the development of strategies to generate resistance against bacterial wilt disease. The perception of a conserved peptide of bacterial flagellin, flg22, is regarded as paradigm of plant perception of invading bacteria; however, no elicitor activity has been detected for R. solanacearum flg22. Recent reports have shown that other epitopes from flagellin are able to elicit immune responses in specific species from the Solanaceae family, yet our results show that these plants do not perceive any epitope from R. solanacearum flagellin. Searching for elicitor peptides from R. solanacearum, we found several protein sequences similar to the consensus of the elicitor peptide csp22, reported to elicit immunity in specific Solanaceae plants. A R. solanacearum csp22 peptide (csp22Rsol) was indeed able to trigger immune responses in Nicotiana benthamiana and tomato, but not in Arabidopsis thaliana. Additionally, csp22Rsol treatment conferred increased resistance to R. solanacearum in tomato. Transgenic A. thaliana plants expressing the tomato csp22 receptor (SlCORE) gained the ability to respond to csp22Rsol and became more resistant to R. solanacearum infection. Our results shed light on the mechanisms for perception of R. solanacearum by plants, paving the way for improving current approaches to generate resistance against R. solanacearum. [ABSTRACT FROM AUTHOR]

Summary: Phytopathogens translocate effector proteins into plant cells where they sabotage the host cellular machinery to promote infection. An individual pathogen can translocate numerous distinct effectors during the infection process to target an array of host macromolecules (proteins, metabolites, DNA, etc.) and manipulate them using a variety of enzymatic activities. In this review, we have surveyed the literature for effector targets and curated them to convey the range of functions carried out by phytopathogenic proteins inside host cells. In particular, we have curated the locations of effector targets, as well as their biological and molecular functions and compared these properties across diverse phytopathogens. This analysis validates previous observations about effector functions (e.g. immunosuppression), and also highlights some interesting features regarding effector specificity as well as functional diversification of phytopathogen virulence strategies. [ABSTRACT FROM AUTHOR]

The subversion of plant cellular functions is essential for bacterial pathogens to proliferate in host plants and cause disease. Most bacterial plant pathogens employ a type III secretion system to inject type III effector (T3E) proteins inside plant cells, where they contribute to the pathogen-induced alteration of plant physiology. In this work, we found that the Ralstonia solanacearum T3E RipAY suppresses plant immune responses triggered by bacterial elicitors and by the phytohormone salicylic acid. Further biochemical analysis indicated that RipAY associates in planta with thioredoxins from Nicotiana benthamiana and Arabidopsis. Interestingly, RipAY displays γ-glutamyl cyclotransferase (GGCT) activity to degrade glutathione in plant cells, which is required for the reported suppression of immune responses. Given the importance of thioredoxins and glutathione as major redox regulators in eukaryotic cells, RipAY activity may constitute a novel and powerful virulence strategy employed by R. solanacearum to suppress immune responses and potentially alter general redox signalling in host cells. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum sensu lato causes bacterial wilt in many economically important agronomic crops and tree species. Eucalyptus is one of the recorded hosts but, despite the losses to forestry, little is known regarding the disease. The aim of this study was to identify the Ralstonia species that are associated with bacterial wilt of Eucalyptus trees growing in different parts of the world. Phylotyping, sequevar and multilocus sequence analysis were used to identify and determine the genetic diversity of the available isolates. The isolates obtained from Africa and Asia grouped in phylotype I, and those isolates from South America in phylotype II. Following the recent reclassification of R. solanacearum sensu lato, these results show that there are two Ralstonia species associated with bacterial wilt of Eucalyptus, namely, R. solanacearum and R. pseudosolanacearum. The isolates from South America represented R. solanacearum, while those from Africa and Asia were R. pseudosolanacearum. Analysis of the endoglucanase ( egl), transcriptional regulator ( hrpB) and DNA mismatch repair ( mutS) gene regions supported this finding. In addition, one previously unidentified sequevar was identified using partial endoglucanase ( egl) gene sequence analysis of those isolates obtained from Colombia. This study raises questions regarding the aetiology of the two Ralstonia species found on Eucalyptus, their importance relating to quarantine, potential impact and management of the disease with which they are associated. [ABSTRACT FROM AUTHOR]

A strain of Ralstonia sp. FD-1 capable of using 4-fluoroaniline (4-FA) as the sole carbon and nitrogen source was investigated for its ability to utilize 4-FA isomers (2-FA, 3-FA) and homologs (2,4-DFA, 3,4-DFA, and 2,3,4-TFA). Both 4-FA and 3-FA could be mineralized as the sole carbon and nitrogen source by FD-1. 2-FA, 2,4-DFA, 3,4-DFA, and 2,3,4-TFA could not be degraded by FD-1, respectively, and were selected as secondary substrates for cometabolism with 500 mg/L 4-FA as growth substrate. Bacterial growth (OD600), F− concentrations, and fluoroanilines contents were measured to determinate the degradation ability of 4-FA isomers and homologs by FD-1. FD-1 growth was inhibited by 2,4-DFA, 3,4-DFA, and 2,3,4-TFA at higher concentrations (400 mg/L), except for 2-FA. Complete fluoroanilines degradation was achieved while incomplete defluorination was characterized by the stoichiometric fluoride release indicating partial degradation but not total mineralization. When fluoroaniline was supplied to the resting cells of strain FD-1, a relatively effective removal was showed. Strain FD-1 had broadened application prospect of toxicity and low nutrition fluoroanilines wastewater. [ABSTRACT FROM AUTHOR]

A literature review was carried out following concerns about the use of heated, humidified, high-flow nasal cannulae ( HHFNC) in premature infants. Randomised trials following extubation showed that HHFNC was associated with similar or greater reintubation rates than nasal continuous positive airway pressure, but significantly better nasal trauma scores. Infections with Ralstonia bacteria were an issue. Conclusion There is insufficient evidence to support the routine use of HHFNC for premature infants and further research is required. [ABSTRACT FROM AUTHOR]

A series of sulfone derivatives containing 1, 3, 4-oxadiazole moiety were prepared and evaluated for their antibacterial activities by the turbidimeter test. Most compounds inhibited growth of Ralstonia solanacearum ( R. solanacearum) from tomato and tobacco bacterial wilt with high potency, among which compounds 5a and 5b exhibited the most potent inhibition against R. solanacearum from tomato and tobacco bacterial wilts with EC50 values of 19.77 and 8.29 μg/mL, respectively. Our results also demonstrated that 5a, 5b, and a number of other compounds were more potent than commercial bactericides Kocide 3000 and Thiodiazole Copper, which inhibited R. solanacearum from tomato bacterial wilt with EC50 values of 93.59 and 99.80 μg/mL and tobacco bacterial wilt with EC50 values of 45.91 and 216.70 μg/mL, respectively. The structure-activity relationship (SAR) of compounds was studied using three-dimensional quantitative structure-activity relationship (3 D- QSAR) models created by comparative molecular field analysis ( Co MFA) and comparative molecular similarity index analysis ( Co MSIA) based on compound bioactivities against tomato and tobacco bacterial wilts. The 3 D- QSAR models effectively predicted the correlation between inhibitory activity and steric-electrostatic properties of compounds. [ABSTRACT FROM AUTHOR]

Most bacterial strains accumulate intracellular polyhydroxybutyrate (PHB) granules as an energy reservoir, in response to fluctuations in their microenvironment. Flow cytometry was applied for the analysis of single cells of Ralstonia pickettii AR1 in response to changes in the culture conditions. Two parameters, the PHB production-related FL2 and side scatter (SSC) parameters, were used to monitor, distinguish and characterize different subpopulations in the growth and PHB production phases. A high SSC level was observed in the mid-log exponential growth phase. When the nitrogen source reached a limiting level, the SSC started to decrease, in contrast to the intracellular PHB granules-related FL2 parameter. The results show that ammonium limitation is a critical and important factor for the accumulation of reserve compounds. Four subpopulations were observed and distinguished upon entrance of the cells into the exponential growth phase. When the cells entered the late exponential growth or early stationary phase, two subpopulations had disappeared and only two, different subpopulations were dominant. One of the subpopulations with changed SSC and PHB production activity switched to another subpopulation that was only active in PHB production in the stationary phase. The whole cells of R. pickettii AR1 tended to form a homogeneous population at the end of the stationary phase. In fact, the changes in the subpopulations of a single strain are related to different physiological states of the cells. The observation of different subpopulations suggests that each subpopulation shows a specific response to changes in the surrounding microenvironment, nutrients and limiting factors. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Summary A two-hybrid approach was applied to screen for proteins with the ability to interact with PHB synthase (PhaC1) of Ralstonia eutropha. The H16_A0141 gene ( phaM) was identified in the majority of positive clones. PhaM (26.6 kDa) strongly interacted with PhaC1 and with phasin PhaP5 but not with PhaP1 or other PHB granule-associated proteins. A Δ phaM mutant accumulated only one or two large PHB granules instead of three to six medium-sized PHB granules of the wild type, and distribution of granules to daughter cells was disordered. All three phenotypes (number, size and distribution of PHB granules) were reversed by reintroduction of phaM. Purified PhaM revealed DNA-binding properties in gel mobility shift experiments. Expression of a fusion of the yellow fluorescent protein (eYfp) with PhaM resulted in formation of many small fluorescent granules that were bound to the nucleoid region. Remarkably, an eYfp-PhaP5 fusion localized at the cell poles in a PHB-negative background and overexpression of eYfp-PhaP5 in the wild type conferred binding of PHB granules to the cell poles. In conclusion, subcellular localization of PHB granules in R. eutropha depends on a concerted expression of at least three PHB granule-associated proteins, namely PhaM, PhaP5 and PHB synthase PhaC1. [ABSTRACT FROM AUTHOR]

Cyanobacterial NAD(P)+-reducing reversible hydrogenases comprise five subunits. Four of them (HoxF, HoxU, HoxY, and HoxH) are also found in the well-described related enzyme from Ralstonia eutropha. The fifth one (HoxE) is not encoded in the R. eutropha genome, but shares homology with the N-terminal part of R. eutropha HoxF. However, in cyanobacteria, HoxE contains a 2Fe-2S cluster-binding motif that is not found in the related R. eutropha sequence. In order to obtain some insights into the role of HoxE in cyanobacteria, we deleted this subunit in Synechocystis PCC6803. Three types of interaction of the cyanobacterial hydrogenase with pyridine nucleotides were tested: (a) reductive activation of the NiFe site, for which NADPH was found to be more efficient than NADH; (b) H2 production, for which NADH appeared to be a more efficient electron donor than NADPH; and (c) H2 oxidation, for which NAD+ was a much better electron acceptor than NADP+. Upon hoxE deletion, the Synechocystis hydrogenase active site remained functional with artificial electron donors or acceptors, but the enzyme became unable to catalyze H2 production or uptake with NADH/NAD+. However, activation of the electron transfer-independent H/D exchange reaction by NADPH was still observed in the absence of HoxE, whereas activation of this reaction by NADH was lost. These data suggest different mechanisms for diaphorase-mediated electron donation and catalytic site activation in cyanobacterial hydrogenase. [ABSTRACT FROM AUTHOR]

Summary The tetralin biodegradation genes of Sphingomonas macrogolitabida strain TFA are repressed by catabolite. Insertion mutants in which thn genes are transcribed in the presence of a preferential carbon source and tetralin, bear the insertion in phaC, encoding a poly(3-hydroxybutyrate) (PHB) synthase, a key enzyme in PHB synthesis. Mutant complementation with phaC genes from either Ralstonia euthropha or TFA restored PHB accumulation and the wild-type regulatory pattern of thn genes, thus indicating that this accumulation is a signal for carbon sufficient conditions that prevents expression of thn catabolic genes in this α-proteobacteria. [ABSTRACT FROM AUTHOR]

Chitinase from the moderately thermophilic bacterium Ralstonia sp. A-471 (Ra-ChiC) is divided into two domains: a chitin-binding domain (residues 36-80) and a catalytic domain (residues 103-252). Although the catalytic domain of Ra-ChiC has homology to goose-type lysozyme, Ra-ChiC does not show lysozyme activity but does show chitinase activity. The catalytic domain with part of an interdomain loop (Ra-ChiC89-252) was crystallized under several different conditions using polyethylene glycol as a precipitant. The crystals diffracted to 1.85 Å resolution and belonged to space group P6122 or P6522, with unit-cell parameters a = b = 100, c = 243 Å. The calculated Matthews coefficient was approximately 3.2, 2.4 or 1.9 Å3 Da−1 assuming the presence of three, four or five Ra-ChiC89-252 molecules in the asymmetric unit, respectively. [ABSTRACT FROM AUTHOR]

LysR -type transcriptional regulators (LTTRs) constitute the largest family of regulators in prokaryotes. The full-length structures of the LTTR TsaR from C omamonas testosteroni T-2 and its complex with the natural inducer para-toluensulfonate have been characterized by X-ray diffraction. Both ligand-free and complexed forms reveal a dramatically different quaternary structure from that of CbnR from Ralstonia eutropha, or a putative LysR- type regulator from Pseudomonas aeruginosa, the only other determined full-length structures of tetrameric LTTRs. Although all three show a head-to-head tetrameric ring, TsaR displays an open conformation, whereas CbnR and PA01-PR present additional contacts in opposing C-terminal domains that close the ring. Such large differences may be due to a broader structural versatility than previously assumed or either, reflect the intrinsic flexibility of tetrameric LTTRs. On the grounds of the sliding dimer hypothesis of LTTR activation, we propose a structural model in which the closed structures could reflect the conformation of a ligand-free LTTR, whereas inducer binding would bring about local changes to disrupt the interface linking the two compact C-terminal domains. This could lead to a TsaR-like, open structure, where the pairs of recognition helices are closer to each other by more than 10 Å. [ABSTRACT FROM AUTHOR]

The diversity of 40 strains of Ralstonia solanacearum causing bacterial wilt of potato in the major potato-growing areas of Iran was assessed. Based on rep-PCR genomic fingerprinting, strains fell into two distinct groups. The first group contained 37 of the 40 strains and the second consisted of three strains from a narrow tropical region in Iran. The three strains from the narrow tropical region were found to be phenotypically and genotypically most similar to R. solanacearum biovar 2T strains, whereas all other strains were phenotypically and genotypically identified as being R. solanacearum biovar 2/race 3. Phylogenetic analysis of endoglucanase gene sequence information of two of the strains from the tropical region revealed that they belonged to phylotype II of the R. solanacearum species complex and had 100% sequence similarity to a biovar 2T strain from potato in Peru. This is the first report of the presence of R. solanacearum phylotype II/biovar 2T in Iran and the first report of the existence of this group of R. solanacearum outside South America. [ABSTRACT FROM AUTHOR]