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When an organism encounters a pathogen, the host innate immune system activates to defend against pathogen colonization and toxic xenobiotics produced. C. elegans employ multiple defense systems to ensure survival when exposed to Pseudomonas aeruginosa including activation of the cytoprotective transcription factor SKN-1/NRF2. Although wildtype C. elegans quickly learn to avoid pathogens, here we describe a peculiar apathy-like behavior towards PA14 in animals with constitutive activation of SKN-1, whereby animals choose not to leave and continue to feed on the pathogen even when a non-pathogenic and healthspan-promoting food option is available. Although lacking the urgency to escape the infectious environment, animals with constitutive SKN-1 activity are not oblivious to the presence of the pathogen and display the typical pathogen-induced intestinal distension and eventual demise. SKN-1 activation, specifically in neurons and intestinal tissues, orchestrates a unique transcriptional program which leads to defects in serotonin signaling that is required from both neurons and non-neuronal tissues. Serotonin depletion from SKN-1 activation limits pathogen defenses capacity, drives the pathogen-associated apathy behaviors and induces a synthetic sensitivity to selective serotonin reuptake inhibitors. Taken together, our work reveals interesting insights into how animals perceive environmental pathogens and subsequently alter behavior and cellular programs to promote survival. Here, Nair et al show that constitutive activation of the cytoprotective transcription factor SKN-1 within the digestive and nervous system of Caenorhabditis elegans impedes serotonin signalling and leads to pathogen-apathy behaviour. [ABSTRACT FROM AUTHOR]

Background: Recurrent respiratory infections are a leading cause of morbidity and mortality in persons with Cystic Fibrosis (pwCF). Recently, the emergence of Nocardia species as a potential pathogen in CF has raised questions about its role and management, as its clinical significance and the optimal patient management remain unclear in current clinical practice. This review explores the clinical implications of Nocardia species in patients with Cystic Fibrosis (pwCF) through a comprehensive literature review. Key objectives include assessing its impact on lung function, identifying colonization risk factors, and evaluating an appropriate treatment. Methods: The literature review, conducted until June 30, 2023, from databases like MEDLINE, PubMed, Embase, and Cochrane, included 16 articles involving 89 pwCF with Nocardia species isolation according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guideline recommendations. Articles reporting Nocardia prevalence and symptoms based on original data in adult and paediatric pwCF were included. All the retrieved studies were observational ones, thus, they were categorized by study type as case report and case series. Results: Overall 89 pwCF and Nocardia species isolation were included: 42 children and 47 adults. Where reported, we found these main following bacterial species: Nocardia asteroides (35%, 23/64), Nocardia farcinica (21%, 14/64), Nocardia tranvalensis (13%, 8/64) and Nocardia cyriacigeorgica (11%, 7/64). A co-infection was reported in 85% of patients (61/72). Of patients whose lung function was reported before and after Nocardia isolation, 23% (16/68) showed a decline in FEV1. Above all, 82 patients were treated at least once after isolation of Nocardia strain. In 93% (77/82) of cases, treatment was started immediately upon isolation. Antibiotic treatment was performed per os or intravenously depending on the clinical condition of the individual patient. Nocardia eradication was attempted in only 32 cases out of 82, and 78% (25/32) of these patients were successfully eradicated after one or more courses of antibiotics. Death was reported in 3 patients, 2 of which were children. Conclusion: In general the isolation of the bacteria does not necessarily imply therapy, but patients need to be monitored closely to assess the possible occurrence of active infection. The treatment seems to be indicated in patients showing lung involvement with the possible appearance of pneumonia, pleural effusion, fever, cough, or a decrease in FEV1, as in the case that we described, or in patients undergoing pulmonary transplantation. Strengths and limitations of this study: • A strength of this study is that it provides an updated systematic review on the management of Nocardia's isolation in patients with Cystic Fibrosis. By synthesising findings across all included studies we propose a therapeutic management algorithm. • This systematic review protocol follows the Joanna Briggs Institute, mixed-method systematic review protocol. • Limitations of the study is the paucity of randomised controlled trials and the heterogeneity among available publications. • There is potential for heterogeneity of published data, which may limit the conclusions that can be drawn from this study. [ABSTRACT FROM AUTHOR]

Although gastroesophageal reflux has been recognized as one of the risk factors of nontuberculous mycobacterial pulmonary disease (NTM-PD) progression, the effect of reflux on the lower respiratory tract microbiota has not been studied in detail. We investigated the composition of the lower respiratory tract microbiota in patients with clinically suspected NTM-PD, comparing them based on the presence of reflux. Forty-seven patients suspected of having NTM-PD were enrolled and assigned according to presence of reflux (n = 22) and non- reflux (n = 25). We performed a pepsin ELISA assay to identify the presence of reflux and 16S ribosomal RNA gene amplicon sequencing to evaluate the microbiota in bronchoalveolar lavage fluid. There were no significant differences in the diversity or composition of the lower respiratory microbiota between the NTM-PD and non-NTM-PD groups. Bacterial richness was observed in the non-reflux group than in the reflux group [P = 0.03] and a cluster in the reflux group was observed. The reflux group showed a predominance for Pseudomonas aeruginosa or Staphylococcus aureus among the NTM-PD group and for P. aeruginosa, Haemophilus influenzae, Klebsiella pneumoniae, or Eikenella species among the non-NTM-PD group. The non-reflux groups presented diverse patterns. A linear discriminant analysis and volcano plot demonstrated that P. aeruginosa, H. haemolyticus, Selenomonas artemidis, and Dolosigranulum pigrum were specifically associated with the NTM-PD reflux group, while P. aeruginosa was specifically associated with the non-NTM-PD reflux group. These observations confirm that the lower respiratory microbiota is consistently altered by reflux but not in NTM-PD. [ABSTRACT FROM AUTHOR]

Respirovirus 3 is a leading cause of severe acute respiratory infections in vulnerable human populations. Entry into host cells is facilitated by the attachment glycoprotein and the fusion glycoprotein (F). Because of its crucial role, F represents an attractive therapeutic target. Here, we identify 13 F-directed heavy-chain-only antibody fragments that neutralize recombinant respirovirus 3. High-resolution cryo-EM structures of antibody fragments bound to the prefusion conformation of F reveal three distinct, previously uncharacterized epitopes. All three antibody fragments bind quaternary epitopes on F, suggesting mechanisms for neutralization that may include stabilization of the prefusion conformation. Studies in cotton rats demonstrate the prophylactic efficacy of these antibody fragments in reducing viral load in the lungs and nasal passages. These data highlight the potential of heavy-chain-only antibody fragments as effective interventions against respirovirus 3 infection and identify neutralizing epitopes that can be targeted for therapeutic development. Respirovirus 3 is a major cause of respiratory infection. Here authors generate and explore heavy-chain antibody fragments that target the fusion protein and test these in vitro and in an animal model. [ABSTRACT FROM AUTHOR]

Quorum sensing can induce density-dependent gene expressions that cause various problems. For quorum-sensing inhibition, fundamental solutions such as gene manipulation are required, and acyl-homoserine lactone synthase (AHL synthase), which synthesizes the universal quorum-sensing signal of gram-negative bacteria, can be used as a target. In this study, researchers synthesized His-tagged AHL synthase and its deletion mutant that lacks the active site and compared their biochemical characteristics. His-YpeI, the 6x His-tagged AHL synthase of Serratia fonticola, and His-ΔYpeI, its deletion mutant, were designed, and their property conservation were examined using in silico projection tools. For in vitro synthesis of enzymes, the His-YpeI CFPS template was synthesized by in vitro gene synthesis, and the His-ΔYpeI CFPS template was obtained by deletion PCR. CFPS was performed and the products were purified with the 6x His-tag. The enzymes' properties were compared using an enzymatic assay. The bioinformatic analysis confirmed the conservation of biochemical properties between 6x His-tagged and untagged enzymes, including helix-turn-helix interactions, hydropathy profiles, and tertiary structure between His-YpeI and YpeI and between His-ΔYpeI and ΔYpeI. His-YpeI and His-ΔYpeI synthesized by CFPS were found to have the expected molecular weights and demonstrated distinct differences in enzyme activity. The analyzed enzymatic constants supported a significant decrease in substrate affinity and reaction rate as a result of YpeI's enzyme active site deletion. This result showed that CFPS could be used for in vitro protein synthesis, and quorum sensing could be inhibited at the enzymatic level due to the enzyme active site's deletion mutation. [ABSTRACT FROM AUTHOR]

Background: Quorum sensing (QS) is one of the main regulatory systems which have various effects on populations of microorganisms. This process has been found in a diverse array of microorganisms (various bacterial taxa, microalgae and fungi). QS is required for different activities of microorganisms such as, virulence factor secretion, motility, competence, biofilm and sporulation. There are different molecules as signals in disparate microorganisms. Biofilm formation is one of the significant functions of QS. Biofilms are groups of microorganisms that are tied to a surface (biotic or abiotic). One of the remarkable effects of biofilm formation seems to be the persistence against hostile environmental condistions. Biofilm formation have been widely reported as a pathogenesis strategy in microorganisms. Here we describe QS and biofilm formation in some important microorganisms and describe some of the suggested strategies for eradication of microbial biofilms. Conclusion: Inhibition of biofilms formation can have detectable effects on the treatment of infectous diseases. In this line, multiple approaches have been suggested to inhibit the biofilm formation by microorganisms. [ABSTRACT FROM AUTHOR]

Introduction: Cystic Fibrosis (CF) is the commonest genetically inherited disease (1 in 4,500 newborns) and 70% of people with CF (pwCF) harbour the F508Del mutation, resulting in misfolding and incorrect addressing of the channel CFTR to the epithelial membrane and subsequent dysregulation of fluid homeostasis. Although studies have underscored the importance and over-activation of myeloid cells, and in particular neutrophils in the lungs of people with CF (pwCF), relatively less emphasis has been put on the potential immunological bias in CF blood cells, at homeostasis or following stimulation/infection. Methods: Here, we revisited, in an exhaustive fashion, in pwCF with mild disease (median age of 15, median % FEV1 predicted = 87), whether their PBMCs, unprimed or primed with a 'non specific' stimulus (PMA+ionomycin mix) and a 'specific' one (live P.a =PAO1 strain), were differentially activated, compared to healthy controls (HC) PBMCs. Results: 1) we analysed the lymphocytic and myeloid populations present in CF and Control PBMCs (T cells, NKT, Tgd, ILCs) and their production of the signature cytokines IFN-g, IL-13, IL-17, IL-22. 2) By q-PCR, ELISA and Luminex analysis we showed that CF PBMCs have increased background cytokines and mediators production and a partial functional tolerance phenotype, when restimulated. 3) we showed that CF PBMCs low-density neutrophils release higher levels of granule components (S100A8/A9, lactoferrin, MMP-3, MMP-7, MMP-8, MMP-9, NE), demonstrating enhanced exocytosis of potentially harmful mediators. Discussion: In conclusion, we demonstrated that functional lymphoid tolerance and enhanced myeloid protease activity are key features of cystic fibrosis PBMCs. [ABSTRACT FROM AUTHOR]

Cystic fibrosis-related diabetes (CFRD) affects 40%–50% of adults with CF and is associated with a decline in respiratory health. The microbial flora of the lung is known to change with the development of CF disease, but how CFRD affects the microbiome has not been described. We analyzed the microbiome in sputa from 14 people with CF, 14 with CFRD, and two who were classed as pre-CFRD by extracting DNA and amplifying the variable V3-V4 region of the microbial 16S ribosomal RNA gene by PCR. Sequences were analyzed and sources were identified to genus level. We found that the α-diversity of the microbiome using Shannon’s diversity index was increased in CFRD compared with CF. Bray Curtis dissimilarity analysis showed that there was separation of the microbiomes in CF and CFRD sputa. The most abundant phyla identified in the sputum samples were Firmicutes and Proteobacteria, Actinobacteriota and Bacteroidota, and the ratio of Firmicutes/Bacteroidota was reduced in CFRD compared with CF. Pseudomonas, Azhorizophilus, Porphyromonas, and Actinobacillus were more abundant in CFRD compared with CF, whereas Staphylococcus was less abundant. The relative abundance of these genera did not correlate with age; some correlated with a decline in FEV1/FVC but all correlated with hemoglobin A1C (HbA1c) indicating that development of CFRD mediates further changes to the respiratory microbiome in CF. NEW & NOTEWORTHY Cystic fibrosis-related diabetes (CFRD) is associated with a decline in respiratory health. We show for the first time that there was a change in the sputum microbiome of people with CFRD compared with CF that correlated with markers of raised blood glucose. [ABSTRACT FROM AUTHOR]

Background: Lameness is defined as altered or abnormal gait due to dysfunction of the locomotor system, and is a health issue of feedlot cattle, having major economic, labour, and welfare implications. Digital dermatitis (DD—a lesion of the plantar surface of the foot) and foot rot (FR—affects the interdigital cleft) are common infectious causes of lameness in feedlots. These hoof lesions can occur alone or in combination (DD + FR) in the same hoof. A total of 208 hoof swabs were collected from three commercial feedlots located in southern Alberta. Every lesion sample was matched with a corresponding control skin sample taken from a healthy contralateral foot. Control skin samples were also collected from cattle with no lesion on any feet. Bacterial communities of three types of hoof lesions (DD, DD + FR, FR) and healthy skin were profiled using 16S amplicon sequencing. Results: Alpha diversity analysis revealed a lower bacterial diversity on DD and FR lesions compared to control skin. Beta diversity analysis showed that bacterial communities of DD, FR, and DD + FR lesions were distinct from those of the control skin. While the impact of feedlot was minimal, lesion type contributed to 22% of the variation observed among bacterial communities (PERMANOVA-R = 0.22, P < 0.01). Compared to the corresponding control skin, there were 11, 12, and 3 differentially abundant (DA) bacterial genera in DD, DD + FR, and FR lesions, respectively. Conclusions: The bacterial community description of a DD + FR lesion is a novel finding. Not only did lesions lead to altered bacterial communities when compared to healthy skin, but the composition of those communities also differed depending on the hoof lesion. The 16S amplicon sequencing of surface swabs has significant value as a research tool in separating different hoof lesions and can provide additional insights to the polybacterial etiology of DD and FR in feedlot cattle. [ABSTRACT FROM AUTHOR]

Quorum sensing is a mechanism of bacterial cell-cell communication that relies on the production and detection of small molecule autoinducers, which facilitate the synchronous expression of genes involved in group behaviors, such as virulence factor production and biofilm formation. The Pseudomonas aeruginosa quorum sensing network consists of multiple interconnected transcriptional regulators, with the transcription factor, RhlR, acting as one of the main drivers of quorum sensing behaviors. RhlR is a LuxR-type transcription factor that regulates its target genes when bound to its cognate autoinducer, C4-homoserine lactone, which is synthesized by RhlI. RhlR function is also regulated by the metallo-β-hydrolase enzyme, PqsE. We recently showed that PqsE binds RhlR to alter its affinity for promoter DNA, a new mechanism of quorum-sensing receptor activation. Here, we perform ChIP-seq analyses of RhlR to map the binding of RhlR across the P. aeruginosa genome, and to determine the impact of C4-homoserine lactone and PqsE on RhlR binding to different sites across the P. aeruginosa genome. We identify 40 RhlR binding sites, all but three of which are associated with genes known to be regulated by RhlR. C4-homoserine lactone is required for maximal binding of RhlR to many of its DNA sites. Moreover, C4-homoserine lactone is required for maximal RhlR-dependent transcription activation from all sites, regardless of whether it impacts RhlR binding to DNA. PqsE is required for maximal binding of RhlR to many DNA sites, with similar effects on RhlR-dependent transcription activation from those sites. However, the effects of PqsE on RhlR specificity are distinct from those of C4-homoserine lactone, and PqsE is sufficient for RhlR binding to some DNA sites in the absence of C4-homoserine lactone. Together, C4-homoserine lactone and PqsE are required for RhlR binding at the large majority of its DNA sites. Thus, our work reveals three distinct modes of activation by RhlR: i) when RhlR is unbound by autoinducer but bound by PqsE, ii) when RhlR is bound by autoinducer but not bound by PqsE, and iii) when RhlR is bound by both autoinducer and PqsE, establishing a stepwise mechanism for the progression of the RhlR-RhlI-PqsE quorum sensing pathway in P. aeruginosa. Author summary: Pseudomonas aeruginosa represents a serious threat to public health in the United States because of its intrinsic mechanisms of antimicrobial resistance. One of the primary drivers of its antimicrobial resistance profile is biofilm formation. Biofilms are multicellular communities that are formed in an ordered mechanism by the collective. In the case of P. aeruginosa, biofilm formation is controlled by a cell-cell communication process called quorum sensing. Quorum sensing underpins transcriptional changes in a bacterium, allowing for the transition from individual, planktonic behaviors to group, sessile behaviors. Group behaviors are behaviors that are only beneficial to engage in once a critical threshold of kin population is reached. The transition to group behaviors is mediated by quorum sensing through an interconnected regulatory system, with the transcription factor receptor RhlR regulating the expression of hundreds of genes. RhlR-dependent transcription relies on the detection of a ligand produced by its partner synthase, RhlI, and an accessory binding protein that alters its affinity for promoter DNA, PqsE, resulting in a dual regulatory mechanism that was not previously observed in quorum sensing. The main goal of this study was to determine the molecular basis for promoter selection by RhlR using bacterial genetics and DNA-based sequencing methods for measuring site-specific protein binding. Our approach established the entirety of the RhlR direct regulon and the contributions of each of the known regulators to RhlR-dependent promoter binding and gene regulation. [ABSTRACT FROM AUTHOR]

The Opuntia ficus-indica (L.) cactus, a crucial crop in Morocco, is threatened by the wild cochineal, Dactylopius opuntiae (Cockerell). The aim of this research was to investigate the efficacy of nine bacterial strains against both D. opuntiae nymphs and adults females applied individually or after black soap in the laboratory, greenhouse, and field conditions. Using the partial 16S ribosomal DNA, the bacterial isolates were identified as Pseudomonas koreensis, Pseudomonas sp., Burkholderia sp. and Bacillus sp. Under laboratory conditions, the insecticidal activity of P. koreensis strain 66Ms.04 showed the level mortality (88%) of adult females' at 108 CFU/mL, 7 days after application. At a concentration of 108 CFU/mL, P. koreensis strain 66Ms.04 and Pseudomonas sp. (strains 37 and 5) caused 100% nymphs mortality rate three days after application. Under greenhouse conditions, the use of P. koreensis strain 66Ms.04 at 108 CFU/mL following the application of black soap (60 g/L) demonstrated the maximum levels of females and nymphs' mortalities with 80 and 91.25%, respectively, after 8 days of treatment. In field conditions, the combined application of the P. koreensis strain 66Ms.04 at 108 CFU/mL with black soap at 60 g/L, for an interval of 7 days, significantly increased the mortality of adult females to 93.33% at 7 days after the second application. These findings showed that the combined treatment of P. koreensis strain 66Ms.04 with black soap can be a potent and eco-friendly pesticide against D. opuntiae. [ABSTRACT FROM AUTHOR]

Carbapenem-resistant Klebsiella pneumoniae (CRKP) causes severe inflammation in various infectious diseases, such as bloodstream infections, respiratory and urinary tract infections, which leads to high mortality. Polydatin (PD), an active ingredient of Yinhuapinggan granule, has attracted worldwide attention for its powerful antioxidant, anti-inflammatory, antitumor, and antibacterial capacity. However, very little is known about the effect of PD on CRKP. In this research, we evaluated the inhibitory effects of PD on both the bacterial level and the bacterial-cell co-culture level on anti-biofilm and efflux pumps and the other was the inhibitory effect on apoptosis, reactive oxygen species (ROS), mitochondrial membrane potential (MMP) after CRKP induction. Additionally, we validated the mechanism of action by qRT-PCR and western blot in human lung epithelial cells. Firstly, PD was observed to have an inhibitory effect on the biofilm of CRKP and the efflux pump AcrAB-TolC. Mechanically, CRKP not only inhibited the activation of Nuclear Factor erythroid 2-Related Factor 2 (Nrf-2) but also increased the level of ROS in cells. These results showed that PD could inhibit ROS and activate Nrf-2 production. Together, our research demonstrated that PD inhibited bacterial biofilm formation and efflux pump AcrAB—TolC expression and inhibited CRKP-induced cell damage by regulating ROS and Nrf-2-regulated antioxidant pathways. [ABSTRACT FROM AUTHOR]

Quorum sensing is a mechanism of bacterial communication that controls virulence gene expression. Pseudomonas aeruginosa regulates virulence via two synthase/transcription factor receptor pairs: LasI/R and RhlI/R. LasR is considered the master transcriptional regulator of quorum sensing, as it upregulates rhlI/R. However, clinical isolates often have inactivating mutations in lasR, while maintaining Rhl-dependent signaling. We sought to understand how quorum sensing progresses in isolates with lasR mutations, specifically via activation of RhlR. We find that clinical isolates with lasR inactivating mutations often harbor concurrent mutations in rhlI. Using ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry, we discover that strains lacking lasR overproduce the RhlI-synthesized autoinducer and that RhlI variants re-calibrate autoinducer concentrations to wild-type levels, restoring virulent phenotypes. These findings provide a mechanism for the plasticity of quorum sensing progression in an acute infection niche.Simanek et al. discovered variants that arise in the protein responsible for synthesizing a molecule required for bacterial communication, which mediates the progression of virulence in the pathogen Pseudomonas aeruginosa. [ABSTRACT FROM AUTHOR]

Copyright of Saudi Medical Journal is the property of Saudi Medical Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background RNA polymerase (RNAP) is highly conserved and essential for prokaryotic housekeeping activities, making it an important target for the development of new antibiotics. The rpoB gene, encoding a β-subunit of bacterial RNAP, has a well-known association with rifampicin resistance. However, the roles of other RNAP component genes such as rpoA , encoding an α-subunit of RNAP, in antibiotic resistance remain unexplored. Objectives To characterize the antibiotic resistance-related role of RpoA. Methods We measured the expression of the MexEF-OprN efflux pump in an RpoA mutant using a transcriptional reporter. The MICs of various antibiotics for this RpoA mutant were determined. Results We uncover a novel role of antibiotic susceptibility for an RpoA mutant in Pseudomonas aeruginosa. We found that a single amino acid substitution in RpoA resulted in reduced activity of the MexEF-OprN efflux pump, which is responsible for the exportation of various antibiotics, including ciprofloxacin, chloramphenicol, ofloxacin and norfloxacin. This attenuated efflux pump activity, caused by the RpoA mutation, conferred the bacteria further susceptibility to antibiotics regulated by MexEF-OprN. Our work further revealed that certain clinical P. aeruginosa isolates also contained the same RpoA mutation, providing clinical relevance to our findings. Our results elucidate why this new antibiotic-susceptible function of RpoA mutants would have remained undetected in conventional screens for mutants involving antibiotic resistance. Conclusions The discovery of antibiotic susceptibility in an RpoA mutant implicates a new therapeutic approach for treating clinical isolates of P. aeruginosa with RpoA mutations, using specific antibiotics regulated by MexEF-OprN. More generally, our work suggests that RpoA could serve as a promising candidate target for anti-pathogen therapeutic purposes. [ABSTRACT FROM AUTHOR]

Copyright of Advances in Biochemistry / Postepy Biochemii is the property of Polish Biochemical Society / Acta Biochimica Polonica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Mammalian lungs comprise a complex microbial ecosystem that interacts with host physiology. Previous research demonstrates that the environment significantly contributes to bacterial community structure in the upper and lower respiratory tract. However, the influence of host genetics on the makeup of lung microbiota remains ambiguous, largely due to technical difficulties related to sampling, as well as challenges inherent to investigating low biomass communities. Thus, innovative approaches are warranted to clarify host-microbe interactions in the mammalian lung. Results: Here, we aimed to characterize host genomic regions associated with lung bacterial traits in an advanced intercross mouse line (AIL). By performing quantitative microbial profiling (QMP) using the highly precise method of droplet digital PCR (ddPCR), we refined 16S rRNA gene amplicon-based traits to identify and map candidate lung-resident taxa using a QTL mapping approach. In addition, the two abundant core taxa Lactobacillus and Pelomonas were chosen for independent microbial phenotyping using genus-specific primers. In total, this revealed seven significant loci involving eight bacterial traits. The narrow confidence intervals afforded by the AIL population allowed us to identify several promising candidate genes related to immune and inflammatory responses, cell apoptosis, DNA repair, and lung functioning and disease susceptibility. Interestingly, one genomic region associated with Lactobacillus abundance contains the well-known anti-inflammatory cytokine Il10, which we confirmed through the analysis of Il10 knockout mice. Conclusions: Our study provides the first evidence for a role of host genetic variation contributing to variation in the lung microbiota. This was in large part made possible through the careful curation of 16S rRNA gene amplicon data and the incorporation of a QMP-based methods. This approach to evaluating the low biomass lung environment opens new avenues for advancing lung microbiome research using animal models. [ABSTRACT FROM AUTHOR]

Background: Pseudomonas aeruginosa can cause several ocular infections that are associated with adverse outcomes, owing to the production of different virulence factors that are regulated by quorum-sensing (QS) mechanisms. The current study aims to detect different QS dependent virulence factors, antibiotic resistance patterns in P. aeruginosa associated with ocular infections to correlate them with QS genes and to assess their impact on visual outcome. Methods: several ocular specimens were collected for isolation of P. aeruginosa. Antibiotic susceptibility was evaluated. The presence of QS genes (rhlR and lasR) was identified by PCR. The isolates were assessed for their capability to produce virulence factors such as pyocyanin, protease, twitching motility, exopolysaccharides, and biofilm. Results: Out of 55 P. aeruginosa isolates, 38.2% were MDR, 29.1% were XDR, and 12.7% were PDR. The highest sensitivity was to meropenem 67.3% while the lowest sensitivity was to ceftazidime18.2%. The frequency of studied virulence factors, exopolysaccharides production, biofilm formation, twitching motility, protease, and pyocyanin production was 94.5%, 89.1%, 83.6%, 81.8%, and 78.2% respectively. Quorumsensing genes lasR and rhlR were identified in 89% and 81.8% of the isolates respectively. The assessed virulence factors and antibiotic resistance pattern were significantly correlated with the presence of QS system. Conclusion: This study emphasized the importance of the QS system in regulating the formation of virulence factors and antimicrobial resistance in P. aeruginosa. Consequently, anti-QS and antivirulence therapy can be a promising substitute to antibiotic therapy currently available. [ABSTRACT FROM AUTHOR]

Many plant pathogenic bacteria suppress host defenses by secreting small molecule toxins or immune-suppressing proteins into host cells, processes that likely require close physical contact between pathogen and host. Yet, in most cases, little is known about whether phytopathogenic bacteria physically attach to host surfaces during infection. Here we report that Pseudomonas syringae pv. tomato strain DC3000, a Gram-negative bacterial pathogen of tomato and Arabidopsis, attaches to polystyrene and glass surfaces in response to chemical signals exuded from Arabidopsis seedlings and tomato leaves. We characterized the molecular nature of these attachment-inducing signals and discovered that multiple hydrophilic metabolites found in plant exudates, including citric acid, glutamic acid, and aspartic acid, are potent inducers of surface attachment. These same compounds were previously identified as inducers of P. syringae genes encoding a type III secretion system (T3SS), indicating that both attachment and T3SS deployment are induced by the same plant signals. To test if surface attachment and T3SS are regulated by the same signaling pathways, we assessed the attachment phenotypes of several previously characterized DC3000 mutants, and found that the T3SS master regulator HrpL was partially required for maximal levels of surface attachment, whereas the response regulator GacA, a negative regulator of T3SS, negatively regulated DC3000 surface attachment. Together, our data indicate that T3SS deployment and surface attachment by P. syringae may be co-regulated by the same host signals during infection, possibly to ensure close contact necessary to facilitate delivery of T3SS effectors into host cells. [ABSTRACT FROM AUTHOR]

The increasing incidence and rapid spread of bacterial resistance to conventional antibiotics are a serious global threat to public health, highlighting the need to develop new antimicrobial alternatives. Antimicrobial peptides (AMPs) represent a class of promising natural antibiotic candidates due to their broad-spectrum activity and low tendency to induce resistance. However, the development of AMPs for medical use is hampered by several obstacles, such as moderate activity, lability to proteolytic degradation, and low bioavailability. To date, many researchers have focussed on the optimization or design of novel artificial AMPs with desired properties. Unnatural amino acids (UAAs) are valuable building blocks in the manufacture of a variety of pharmaceuticals, and have been used to develop artificial AMPs with specific structural and physicochemical properties. Rational incorporation of UAAs has become a very promising approach to endow AMPs with strong and long-lasting activity but no toxicity. This review aims to summarize key approaches that have been used to incorporate UAAs to develop novel AMPs with improved properties and better performance. It is anticipated that this review will guide future design considerations for UAA-based antimicrobial applications. [ABSTRACT FROM AUTHOR]

Beyond their role in horizontal gene transfer, conjugative plasmids commonly encode homologues of bacterial regulators. Known plasmid regulator homologues have highly targeted effects upon the transcription of specific bacterial traits. Here, we characterise a plasmid translational regulator, RsmQ, capable of taking global regulatory control in Pseudomonas fluorescens and causing a behavioural switch from motile to sessile lifestyle. RsmQ acts as a global regulator, controlling the host proteome through direct interaction with host mRNAs and interference with the host's translational regulatory network. This mRNA interference leads to large-scale proteomic changes in metabolic genes, key regulators, and genes involved in chemotaxis, thus controlling bacterial metabolism and motility. Moreover, comparative analyses found RsmQ to be encoded on a large number of divergent plasmids isolated from multiple bacterial host taxa, suggesting the widespread importance of RsmQ for manipulating bacterial behaviour across clinical, environmental, and agricultural niches. RsmQ is a widespread plasmid global translational regulator primarily evolved for host chromosomal control to manipulate bacterial behaviour and lifestyle. Plasmids contain homologs of bacterial signaling proteins and use them to manipulate host cells to their benefit. This study describes a widespread plasmid-borne translational regulator that subverts ecological traits in soil bacteria, inducing community organization and promoting plasmid transmission. [ABSTRACT FROM AUTHOR]

Natural products largely produced by Pseudomonads-like soil-dwelling microorganisms are a consistent source of antimicrobial metabolites and pesticides. Herein we report the isolation of Pseudomonas mosselii strain 923 from rice rhizosphere soils of paddy fields, which specifically inhibit the growth of plant bacterial pathogens Xanthomonas species and the fungal pathogen Magnaporthe oryzae. The antimicrobial compound is purified and identified as pseudoiodinine using high-resolution mass spectra, nuclear magnetic resonance and single-crystal X-ray diffraction. Genome-wide random mutagenesis, transcriptome analysis and biochemical assays define the pseudoiodinine biosynthetic cluster as psdABCDEFG. Pseudoiodinine biosynthesis is proposed to initiate from guanosine triphosphate and 1,6-didesmethyltoxoflavin is a biosynthetic intermediate. Transposon mutagenesis indicate that GacA is the global regulator. Furthermore, two noncoding small RNAs, rsmY and rsmZ, positively regulate pseudoiodinine transcription, and the carbon storage regulators CsrA2 and CsrA3, which negatively regulate the expression of psdA. A 22.4-fold increase in pseudoiodinine production is achieved by optimizing the media used for fermentation, overexpressing the biosynthetic operon, and removing the CsrA binding sites. Both of the strain 923 and purified pseudoiodinine in planta inhibit the pathogens without affecting the rice host, suggesting that pseudoiodinine can be used to control plant diseases. Natural antimicrobial metabolites produced by soil microorganisms can be used as green pesticides. Here, the authors isolated a Pseudomonas mosselii strain 923 from rice rhizosphere soils and identify the compound pyrazolotriazine pseudoiodinine inhibits the growth of plant bacterial and fungal pathogens. [ABSTRACT FROM AUTHOR]

A new mixed-ligand oxidovanadium (IV) complex, [VO(DFX)(1,10-phen)], in which DFX = Deferasirox and 1,10-phen = 1,10-phenanthroline, was synthesized using the reflux method and characterized by Fourier transform infrared spectroscopy (FT-IR), UV–Vis spectroscopy and field emission scanning electron microscopy (FE-SEM). Distorted octahedral geometry is suggested for the complex. The DFX ligand is coordinated to the central atom by two phenolate oxygen atoms and one triazole nitrogen atom. Two nitrogen atoms of the 1,10-phen ligand and the oxo group occupy three other positions around the central atom. The in vitro antibacterial activity of the synthesized complex, metal precursor (VO(acac)2) and parent ligands was evaluated against Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Pseudomonas aeruginosa bacterial strains. Furthermore, the antibiofilm activity of these compounds was investigated against S. aureus and P. aeruginosa bacteria. Based on the obtained results, the [VO(DFX)(1,10-phen)] complex exhibited higher antibacterial and antibiofilm activities in comparison to VO(acac)2, DFX and 1,10-phen. [ABSTRACT FROM AUTHOR]

Background: Pulmonary tuberculosis is a chronic infectious disease of the respiratory system. It is still one of the leading causes of death from a single infectious disease, but it has been stuck in the study of a single pathogen. Recent studies have shown that many diseases are associated with disruption of the native microbiota. In this study we investigated the occurrence of tuberculosis and the correlation between drug resistance and respiratory flora. High-throughput 16 S rRNA gene sequencing was used to characterize the respiratory microbiota composition of 30 tuberculosis (TB) affected patients and compared with 30 healthy (H) controls. According to their Gene Xpert results, 30 pulmonary tuberculosis patients were divided into 12 persons in the drug-sensitive group (DS0) and 18 persons in the drug-resistant group (DR0). The microbial flora of the two were compared with the H group. Results: The data generated by sequencing showed that Firmicutes, Proteus, Bacteroides, Actinomyces and Fusobacterium were the five main bacterial phyla detected, and they constituted more than 96% of the microbial community. The relative abundances of Fusobacterium, Haemophilus, Porphyromonas, Neisseria, TM7, Spirochetes, SR1, and Tenericutes in the TB group was lower than that of the H group, and Granulicatella was higher than the H group. The PcoA diagrams of the two groups had obvious clustering differences. The Alpha diversity of the TB group was lower than that of the H group, and the Beta diversity was higher than that of the H group (P < 0.05). The relative abundance of Streptococcus in the DS0 group was significantly higher than that in the DR0 group (P < 0.05). Conclusion: Pulmonary tuberculosis can cause disorders of the respiratory tract microbial flora, in which the relative abundance of Streptococcus was significantly different between rifampicin-sensitive and rifampicin-resistant patients. [ABSTRACT FROM AUTHOR]

Bacteria from the genus Providencia are ubiquitous Gram-negative opportunistic pathogens, causing "travelers' diarrhea", urinary tract, and other nosocomial infections in humans. Some Providencia strains have also been isolated as natural pathogens of Drosophila melanogaster. Despite clinical relevance and extensive use in Drosophila immunity research, little is known about Providencia virulence mechanisms and the corresponding insect host defenses. To close this knowledge gap, we investigated the virulence factors of a representative Providencia species—P. alcalifaciens which is highly virulent to fruit flies and amenable to genetic manipulations. We generated a P. alcalifaciens transposon mutant library and performed an unbiased forward genetics screen in vivo for attenuated mutants. Our screen uncovered 23 mutants with reduced virulence. The vast majority of them had disrupted genes linked to lipopolysaccharide (LPS) synthesis or modifications. These LPS mutants were sensitive to cationic antimicrobial peptides (AMPs) in vitro and their virulence was restored in Drosophila mutants lacking most AMPs. Thus, LPS-mediated resistance to host AMPs is one of the virulence strategies of P. alcalifaciens. Another subset of P. alcalifaciens attenuated mutants exhibited increased susceptibility to reactive oxygen species (ROS) in vitro and their virulence was rescued by chemical scavenging of ROS in flies prior to infection. Using genetic analysis, we found that the enzyme Duox specifically in hemocytes is the source of bactericidal ROS targeting P. alcalifaciens. Consistently, the virulence of ROS-sensitive P. alcalifaciens mutants was rescued in flies with Duox knockdown in hemocytes. Therefore, these genes function as virulence factors by helping bacteria to counteract the ROS immune response. Our reciprocal analysis of host-pathogen interactions between D. melanogaster and P. alcalifaciens identified that AMPs and hemocyte-derived ROS are the major defense mechanisms against P. alcalifaciens, while the ability of the pathogen to resist these host immune responses is its major virulence mechanism. Thus, our work revealed a host-pathogen conflict mediated by ROS and AMPs. Author summary: Pathogens express special molecules or structures called virulence factors to successfully infect a host. By identifying these factors, we can learn how hosts fight and how pathogens cause infections. Here, we identified virulence factors of the human and fruit fly pathogen Providencia alcalifaciens, by infecting flies with a series of mutants of this pathogen. In this way, we detected 23 mutants that were less virulent. Some of these less virulent mutants were hypersensitive to fruit fly immune defense molecules called antimicrobial peptides (AMPs), while others were sensitive to reactive oxygen species (ROS) produced by the immune cells. Notably, AMPs-sensitive mutants remained virulent in a Drosophila mutant that lacks AMPs, while pathogens sensitive to oxidative stress retained their virulence in a fruit fly mutant devoid of oxidative species. These results suggest that the ability of P. alcalifaciens to resist two major host immune molecules, namely AMPs and ROS, is the major virulence mechanism. Overall, our systematic analysis of P. alcalifaciens virulence factors has identified the major defense mechanisms of the fruit fly against this pathogen and the bacterial mechanisms to combat these immune responses. [ABSTRACT FROM AUTHOR]

Cystic fibrosis (CF) pulmonary exacerbations (PEx) are clinical events that commonly result in increased treatment burden, decreased quality of life, and accelerated lung disease progression. CF PEx have historically been approached as though dealing with acute infections, and antibiotic treatments have been associated with improved outcomes. In this review, we discuss data supporting a causal role of CF airway infection in PEx as well studies that highlight our knowledge gaps in regard to PEx definitions, pathophysiology, and optimal treatment approaches. In the era of highly effective cystic fibrosis transmembrane conductance regulator modulator therapy, and the continually increasing health and longevity of persons with CF, a better understanding of PEx and further optimization of PEx antibiotic treatment approaches are needed. [ABSTRACT FROM AUTHOR]

Chronic lower respiratory tract infections are a leading contributor to morbidity and mortality in persons with cystic fibrosis (pwCF). Traditional respiratory tract surveillance culturing has focused on a limited range of classic pathogens; however, comprehensive culture and culture-independent molecular approaches have demonstrated complex communities highly unique to each individual. Microbial community structure evolves through the lifetime of pwCF and is associated with baseline disease state and rates of disease progression including occurrence of pulmonary exacerbations. While molecular analysis of the airway microbiome has provided insight into these dynamics, challenges remain including discerning not only "who is there" but "what they are doing" in relation to disease progression. Moreover, the microbiome can be leveraged as a multi-modal biomarker for both disease activity and prognostication. In this article, we review our evolving understanding of the role these communities play in pwCF and identify challenges in translating microbiome data to clinical practice. [ABSTRACT FROM AUTHOR]

The last decade of research has revolutionized our understanding of respiratory microbiology, revealing that the lungs and airways contain diverse and dynamic microbial communities in health and disease. This "respiratory ecosystem"-a densely interconnected environment of microbial and host interactions-represents a tremendous and under-appreciated source of biological and clinical heterogeneity across patients with acute and chronic lung disease. Unlike other major sources of heterogeneity, such as comorbidities and host genetics, the respiratory microbiome is readily modifiable by clinical interventions, and therefore represents an untapped opportunity for therapeutic manipulation. As a potential "treatable trait" in efforts to subphenotype patients and deliver precision medicine, the respiratory microbiome is a promising therapeutic target. In this Pulmonary Perspective, we identify and discuss multiple challenges, both conceptual and practical, that must be overcome before the respiratory microbiome can be effectively modulated as a therapeutic target. Barriers include: 1) the need to identify specific microbiologic and ecologic "targets" for therapeutic modulation; 2) the need for an improved understanding of the efficacy and persistence of response to respiratory microbiome-modulating interventions; 3) the need for clinicians to be able to access, understand and utilize microbiome data for sub-phenotyping patients, and 4) specific concerns in special populations (including children, patients with chronic lung disease, and critically ill patients). By delineating these barriers, we identify opportunities for prospective research to advance our understanding of the respiratory microbiome, its role in human respiratory disease, and its genuine potential as a therapeutic target. [ABSTRACT FROM AUTHOR]

Rationale: The pathobiology of Staphylococcus aureus in non-cystic fibrosis bronchiectasis (nCFB) is poorly defined. When present at high density or "inoculum," some methicillin-sensitive S. aureus (MSSA) can inefficiently degrade antistaphylococcal β-lactam antibiotics via BlaZ penicillinases (termed the "inoculum effect" [IE]). Given the high burden of organisms in bronchiectatic airways, this is particularly relevant. Objectives: Drawing from a prospectively collected biobank, we sought to understand the prevalence, natural history, potential for transmission, and antibiotic resistance profiles among nCFB-derived MSSA isolates. Methods: All individuals attending a regional consultancy nCFB clinic with sputum collected between 1981 and 2017 were considered, and those with one or more S. aureus-positive cultures composed the cohort. Each individual's most recent biobank isolate was subjected to whole-genome sequencing (including the blaZ gene), antibacterial susceptibility testing, and comparative β-lactam testing at standard (5 × 105 colony-forming unit [cfu]/ml) and high (5 × 107 cfu/ml) inocula to assess for the IE and pronounced IE. Results: Seventy-four (35.4%) of 209 individuals had one or more sputum samples with S. aureus (68 MSSA, 6 methicillin-resistant S. aureus). Those with S. aureus infection were more likely to be female. Among 60 of 74 MSSA isolates subjected to whole-genome sequencing, no evidence of transmission was identified, although specific multilocus sequence typing types were prevalent, including ST-1, ST-15, ST-30, and ST-45. Antibiotic resistance was uncommon, except for macrolides (∼20%). Among the 60 MSSA samples, the prevalence of IE and pronounced IE was observed to be drug specific: meropenem (0% and 0%, respectively), cefepime (3% and 5%, respectively), ceftazidime (8% and 0%, respectively), cloxacillin (12% and 0%, respectively), cefazolin (23% and 0%, respectively), and piperacillin-tazobactam (37% and 17%, respectively). The cefazolin IE was associated with blaZ type A (P < 0.01) and ST-30 (P < 0.01), whereas the piperacillin-tazobactam IE was associated with type C blaZ (P < 0.001) and ST-15 (P < 0.05). Conclusions:S. aureus infection was common, although no evidence of transmission was apparent in our nCFB cohort. Although routine susceptibility testing did not identify significant resistance, inoculum-related resistance was found to be relevant for commonly used nCFB antibiotics, including cefazolin and piperacillin-tazobactam. Given previous associations between IEs and negative patient outcomes, further work is warranted to understand how this phenotype impacts nCFB disease progression. [ABSTRACT FROM AUTHOR]

Carbapenems are the most effective agents for treating clinical P. aeruginosa (PsA) infections. During an infection, a quorum-sensing (QS) system and its regulating virulence genes have a great role. The aim of the study was to detect the presence of a las and rhl QS system and related virulence genes, biofilm formation and a class 1 (Cls1) integron. A total of 52 carbapenem-resistant PsA (CRPsA) isolates obtained from Kastamonu, Turkey was analyzed. For the isolation and identification of CRPsA isolates, a conventional culture method, an automated VITEK-2 compact system, and oprL gene-based molecular technique were applied. The two QS system genes were detected in 51 (98.1%), and co-existed of four two QS system genes (lasI/R and rhIl/R genes) were determined in 41 (78.8%) of the isolates. algD, lasB, toxA and aprA genes were detected in between 46.1 and 88.5%, and co-existence of four two QS system genes with four virulence genes were detected in 40.4% of the isolates. Biofilm formation using microtiter plate assay and slime production using Congo Red Agar and Cls1 integron were determined in 84.6%, 67.3% and 51.9% of the isolates, respectively. According to statistical analyses results, there was a significant positive correlation (p <.10) between the las and the rhl systems and a strongly and positive correlation (p <.01 or p <.05) between the rhl system—three virulence genes and slime production—and among some virulence genes. In conclusion, the CRPsA isolates tested in the study are highly virulent and QS systems have a significant role in pathogenesis. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa is an important pathogen that is frequently associated with nosocomial infections. The goal of this work was to determine the relationship between the quorum sensing system (QS) and the production of virulence factors in P. aeruginosa. A number of 100 P. aeruginosa isolates were collected from various clinical sources from different Mansoura university hospitals in the period from April 2018 till April 2019. PCR screening of QS genes in the isolates was carried out including lasI, lasR, rhlI and rhlR. Thereafter, assay of the production of different virulence factors in the isolates was established including biofilm formation, pyocyanin production, protease production, lipase production, hemolysin production as well as swimming motility. Finally, statistical analysis of the data was performed to confirm the relationship between the QS and the production of virulence factors. Out of the 100 P. aeruginosa isolates, 27 clinical isolates were QS deficient. PCR analysis revealed that 8 isolates lacked lasR gene, 15 isolates lacked lasR and rhlR genes, 1 isolate lacked lasR and lasI genes, 2 isolates lacked lasR, lasI and rhlR genes and 1 isolate lacked rhlR, rhlI and lasR genes. There was a significant decrease observed in the production of pyocyanin, protease, lipase, hemolysin and biofilm formation as well as swimming motility in P. aeruginosa QS deficient isolates in comparison to non-QS deficient ones. There was a clear association between QS and virulence factors production in P. aeruginosa. This could open the door for novel promising targets for developing new therapeutic strategies against infections caused by this pathogen. [ABSTRACT FROM AUTHOR]

The development of resistome analysis, i.e. the comprehensive analysis of antibiotic-resistance genes (ARGs), is enabling a better understanding of the mechanisms of antibiotic-resistance emergence. The respiratory microbiome is a dynamic and interactive network of bacteria, with a set of ARGs that could influence the response to antibiotics. Viruses such as bacteriophages, potential carriers of ARGs, may also form part of this respiratory resistome. Chronic respiratory diseases (CRDs) such as cystic fibrosis, severe asthma, chronic obstructive pulmonary disease and bronchiectasis, managed with long-term antibiotic therapies, lead to multidrug resistance. Antibiotic susceptibility testing provides a partial view of the bacterial response to antibiotics in the complex lung environment. Assessing the ARG network would allow personalised, targeted therapeutic strategies and suitable antibiotic stewardship in CRDs, depending on individual resistome and microbiome signatures. This review summarises the influence of pulmonary antibiotic protocols on the respiratory microbiome, detailing the variable consequences according to antibiotic class and duration of treatment. The different resistome-profiling methods are explained to clarify their respective place in antibiotic-resistance analysis in the lungs. Finally, this review details current knowledge on the respiratory resistome related to therapeutic strategies and provides insight into the application of resistome analysis to counter the emergence of multidrug-resistant respiratory pathogens. [ABSTRACT FROM AUTHOR]

Microbial growth is widely responsible for shortened shelf life of cold water-living fish products. So, it seems that current chemical-based food packaging has no acceptable efficacy, and food industrialists tend to the usage of more novel approaches like active food packaging. Among them, there is a great research interest in nanotechnology-emerging approaches. This study aimed to investigate the anti-microbial efficacies of Polyethylene/CuNP/nanoclay nanocomposites to enhance the shelf life and physiochemical features of rainbow trout. Three main nanocomposites with various concentrations of Cu and clay nanoparticles were examined. SEM, XRD, and EDX (as physiochemical analysis), disk diffusion (as antimicrobial assays), total volatile nitrogen (TVB-N), and peroxide value (PV) (as biochemical parameters) were measured. Based on the results, nanocomposites could reduce the microorganism growth rate by reducing the number of colonies (33.3%), inhibitory activities against both gram-positive (8 mm) and gram-negative bacteria (10 mm), maintenance of TVB-N (42% reduction), and PV (44% reduction) below the standard range. To sum up, these new nanocomposites can be a good candidate to enhance the shelf life of Rainbow Trout. [ABSTRACT FROM AUTHOR]

Magic spot synthetases are emerging targets to overcome persistence caused by stringent response. The 'stringent response' is a bacterial stress survival mechanism, which results in the accumulation of alarmones (also called Magic spots) leading to the formation of dormant persister cells. These 'sleeper cells' evade antibiotic treatment and could result in relapse of infection. This review broadly investigates the phenomenon of stringent response and persistence, and specifically discusses the distribution, classification, and nomenclature of proteins such as Rel/SpoT homologs (RSH), responsible for alarmone synthesis. The authors further explain the relevance of RSH as potential drug targets to break the dormancy of persister cells commonly seen in biofilms. One of the significant factors that initiate alarmone synthesis is nutrient deficiency. In a starved condition, ribosome-associated RSH detects deacylated tRNA and initiates alarmone synthesis. Accumulation of alarmones has a considerable effect on bacterial physiology, virulence, biofilm formation, and persister cell formation. Preventing alarmone synthesis by inhibiting RSH responsible for alarmone synthesis will prevent or reduce persister cells' formation. Magic spot synthetases are thus potential targets that could be explored to overcome persistence seen in biofilms. [ABSTRACT FROM AUTHOR]

Azotobacter vinelandii is a motile bacterium that possesses an unusual pattern of peritrichous flagellation for members of the Pseudomonadaceae family. Unlike what has been reported for Pseudomonas spp. FleQ is not the master regulator of motility in A. vinelandii, this role is performed by FlhDC. Other factors involved in the regulation of motility are AlgU (σE) and CydR which act as negative regulators. In some members of the Enterobacteriaceae and Pseudomonadaceae families, the GacS/A-Rsm pathway is another important factor regulating motility. In the present study, the involvement of the GacS/A-Rsm pathway in regulating the motility of A. vinelandii was explored; we found that contrary to what has been reported for most of the strains studied of Pseudomonas species, GacS/A, through the Rsm system, positively controlled swimming motility. We show that the target of this regulation is the synthesis of flagella, which most likely occurs in an FlhDC-independent manner. [ABSTRACT FROM AUTHOR]

Trp is unique among the amino acids since it is involved in many different types of noncovalent interactions such as electrostatic and hydrophobic ones, but also in π-π, π-cation, π-anion and π-ion pair interactions. In membranotropic peptides and proteins, Trp locates preferentially at the water-membrane interface. In antimicrobial or cell-penetrating peptides (AMPs and CPPs respectively), Trp is well-known for its strong role in the capacity of these peptides to interact and affect the membrane organisation of both bacteria and animal cells at the level of the lipid bilayer. This essential amino acid can however be involved in other types of interactions, not only with lipids, but also with other membrane partners, that are crucial to understand the functional roles of membranotropic peptides. This review is focused on this latter less known role of Trp and describes in details, both in qualitative and quantitative ways: (i) the physico-chemical properties of Trp; (ii) its effect in CPP internalisation; (iii) its importance in AMP activity; (iv) its role in the interaction of AMPs with glycoconjugates or lipids in bacteria membranes and the consequences on the activity of the peptides; (v) its role in the interaction of CPPs with negatively charged polysaccharides or lipids of animal membranes and the consequences on the activity of the peptides. We intend to bring highlights of the physico-chemical properties of Trp and describe its extensive possibilities of interactions, not only at the well-known level of the lipid bilayer, but with other less considered cell membrane components, such as carbohydrates and the extracellular matrix. The focus on these interactions will allow the reader to reevaluate reported studies. Altogether, our review gathers dedicated studies to show how unique are Trp properties, which should be taken into account to design future membranotropic peptides with expected antimicrobial or cell-penetrating activity. [ABSTRACT FROM AUTHOR]

How biodiversity arises and can be maintained in asexual microbial populations growing on a single resource remains unclear. Many models presume that beneficial genotypes will outgrow others and purge variation via selective sweeps. Environmental structure like that found in biofilms, which are associated with persistence during infection and other stressful conditions, may oppose this process and preserve variation. We tested this hypothesis by evolving Pseudomonas aeruginosa populations in biofilm-promoting arginine media for 3 months, using both a bead model of the biofilm life cycle and planktonic serial transfer. Surprisingly, adaptation and diversification were mostly uninterrupted by fixation events that eliminate diversity, with hundreds of mutations maintained at intermediate frequencies. The exceptions included genotypes with mutator alleles that also accelerated genetic diversification. Despite the rarity of hard sweeps, a remarkable 40 genes acquired parallel mutations in both treatments and often among competing genotypes within a population. These incomplete soft sweeps include several transporters (including pitA, pntB, nosD , and pchF) suggesting adaptation to the growth media that becomes highly alkaline during growth. Further, genes involved in signal transduction (including gacS , aer2, bdlA , and PA14_71750) reflect likely adaptations to biofilm-inducing conditions. Contrary to evolution experiments that select mutations in a few genes, these results suggest that some environments may expose a larger fraction of the genome and select for many adaptations at once. Thus, even growth on a sole carbon source can lead to persistent genetic and phenotypic variation despite strong selection that would normally purge diversity. [ABSTRACT FROM AUTHOR]

Recently, green nanotechnology is considered a more suitable and safer tool for medical applications due to its nature reductants with low toxicity and low eco-hazard. The micro-algal biomass was used for the nanoparticles biosynthesis, depending on using whole algal cell cultivation. During the current study, cyanobacteria Oscillatoria sp. and Spirulina platensis exhibited their ability to synthesize silver oxide (Ag2O|AgO-NPs) and gold nanoparticles (Au-NPs), respectively. The characterization results confirmed the formation of Oscillatoria sp.-mediated silver oxide nanoparticles (O.Ag2O|AgO-NPs) and S. platensis-mediated gold nanoparticles (S.Au-NPs). Three different methods had been examined, (i) culture-free cells (secondary metabolites), (ii) algal aqueous extract, and (iii) whole cells cultivation (in vivo). UV–Vis spectroscopy confirmed the biosynthesized O.Ag-NPs at 438 nm, while S.Au-NPs reached 545 nm by whole cells cultivation technique. TEM scanning indicated the formation of spherical-shaped O.Ag2O|AgO-NPs with an average size ranged between 10.49 and 45.81 nm. S.Au-NPs also were detected in triangular, pentagonal, and slightly spherical shapes with an average size of 15.49–55.08 nm. Both O.Ag2O|AgO-NPs, and S.Au-NPs demonstrated antibacterial and antifungal properties against Gram-positive and Gram-negative bacteria. S.Au-NPs were more effective than O.Ag2O|AgO-NPs, which recorded high significant MIC results against Bacillus subtilis ATCC 19659 (1.95 μg/ml), Salmonella typhi ATCC14028 (3.90 μg/ml), and Candida tropicalis ATCC 1380 (1.1 μg/ml) after 24 h treatment, comparing with the control. It is concluded that O.Ag2O|AgO-NPs and S.Au-NPs have efficient antibacterial and antifungal activities. [ABSTRACT FROM AUTHOR]