Search

Infections caused by metallo-β-lactamase (MBL)-producing Enterobacterales and Pseudomonas are increasingly reported worldwide and are usually associated with high mortality rates (>30%). Neither standard therapy nor consensus for the management of these infections exist. Aztreonam, an old β-lactam antibiotic, is not hydrolyzed by MBLs. However, since many MBL-producing strains co-produce enzymes that could hydrolyze aztreonam (e.g., AmpC, ESBL), a robust β-lactamase inhibitor such as avibactam could be given as a partner drug. We performed a systematic review including 35 in vitro and 18 in vivo studies on the combination aztreonam + avibactam for infections sustained by MBL-producing Gram-negatives. In vitro data on 2209 Gram-negatives were available, showing the high antimicrobial activity of aztreonam (MIC ≤ 4 mg/L when combined with avibactam) in 80% of MBL-producing Enterobacterales, 85% of Stenotrophomonas and 6% of MBL-producing Pseudomonas. Clinical data were available for 94 patients: 83% of them had bloodstream infections. Clinical resolution within 30 days was reported in 80% of infected patients. Analyzing only patients with bloodstream infections (64 patients), death occurred in 19% of patients treated with aztreonam + ceftazidime/avibactam. The combination aztreonam + avibactam appears to be a promising option against MBL-producing bacteria (especially Enterobacterales, much less for Pseudomonas) while waiting for new antimicrobials.

Antarctic bacteria are able to survive under extreme environmental conditions and have adapted to exploit some of the most ephemeral nutrient pockets. Importantly, such strains have been often shown to be capable of synthesizing compounds of valuable biotechnological importance. Here we show that Pseudomonas sp. TAE6080, a possibly new bacterium isolated in 1994 during water column samplings near the French Antarctic station Dumont d'Urville, is capable of inhibiting the formation of Staphylococcus epidermidis biofilm, known to be an important opportunistic pathogen in infections associated to medical devices. A better understanding of this bacterium can therefore provide useful insight on new bioactive molecules that could play a role against chronic infections. To this end, the anti-biofilm effect of cell-free supernatant of Pseudomonas sp. TAE6080 was evaluated on S. epidermidis RP62A biofilm formation, demonstrating that it significantly reduced its aggregation. Furthermore, genome sequencing, assembly and mining revealed a plethora of putative biosynthetic gene clusters that might be involved in biofilm disruption. The experimental and genomic data presented here open the venue to further investigations on the molecular basis underlying biofilm inhibition.

One of the biggest environmental problems is related to mining effluents with cyanide, due to its high degree of toxicity, it causes highly significant impacts on the ecosystem in general. Although there are various technologies for its treatment, bioremediation is a potential alternative because it is friendly to the environment. The main objective is to analyze the main microorganisms used to carry out bioremediation processes of mining effluents with cyanide. A review of the different sources of information on cyanide bioremediation microorganisms was carried out. Finding that a wide diversity of microorganisms that can be used as potential biological agents to bioremedy cyanide are reported, among which those of the genus of Pseudomonas and Bacillus stand out; the main factors that must be taken into account to achieve high efficiencies are pH, temperature, nutrients, biomass concentration and cyanide concentration. Bioremediation using microorganisms is increasingly taking a position to remedy contaminants such as cyanide, but even so in Peru there is a lack of further studies at the pilot and plant level to demonstrate its efficiency, which is achieved at the laboratory level. Uno de los mayores problemas ambientales que se tiene es referente a los efluentes mineros con cianuro, por su alto grado de toxicidad ocasiona impactos altamente significativos en el ecosistema en general. A pesar de que existen diversas tecnologías para su tratamiento, la biorremediación es una alternativa potencial por ser amigable con el medio ambiente. Se tiene como objetivo principal analizar los principales microorganismos empleados para llevar acabo procesos de biorremediación de efluentes mineros con cianuro. Se realizó una revisión de las distintas fuentes de información de microorganismos biorremediadores de cianuro. Hallándose que se reportan una amplia diversidad de microorganismos que se pueden emplear como agentes biológicos potenciales para biorremediar el cianuro, entre las que sobresalen las del género de Pseudomonas y Bacillus; los principales factores que se debe tener en cuenta para lograr altas eficiencias son el pH, temperatura, nutrientes, concentración de la biomasa y concentración de cianuro. La biorremediación empleando microorganismos cada vez va tomando mayor posición para remediar contaminantes como el cianuro pero aun así en el Perú faltan mayores estudios a nivel piloto y planta para demostrar su eficiencia que se logra a nivel laboratorio.

Pentachlorophenol (PCP) is a toxic compound, which is widely used as a wood preservative product and general biocide. It is persistent in the environment and has been classified as a persistent organic pollutant to be reclaimed in many countries. Bioremediation is an emerging approach to rehabilitating areas polluted by recalcitrant xenobiotics. In the present study, we evaluated the potential of three strains of Pseudomonas (P. putida S121, P. rhizophila S211, and P. fuscovagiceae S115) as bioremediation agents in depletion and detoxification of PCP in soil microcosms. PCP removal was effectively optimized using a central-composite experimental design and response surface methodology (RSM). The optimum conditions for maximum PCP removal yield (85 ± 5%) were: 500mg/kg PCP concentration, 108 UFC/g soil inoculum size of each strain and 55days incubation period. The bacterial strains, P. putida, P. rhizophila, and P. fuscovagiceae, showed good capability to tolerate and degrade PCP so that they could be successfully used in synergistic effect to treat PCP polluted soils.

In semiarid regions is important to use native strains best adapted to these environments to optimize plant-PGPR interaction. We aimed to isolate and characterize PGPR from roots and rhizosphere of a tomato crop, as well as studying the effect of its inoculation on tomato seedlings growth. We selected four strains considering their effectiveness of fixing nitrogen, solubilizing phosphate, producing siderophores and indole acetic acid. They belong to the genera Enterobacter, Pseudomonas, Cellulosimicrobium, and Ochrobactrum. In addition, we also analyzed the ability to solubilize Ca3(PO4)2, FePO4 and AlPO4 and the presence of one of the genes encoding the cofactor PQQ in their genome. Enterobacter 64S1 and Pseudomonas 42P4 showed the highest phosphorus solubilizing activity and presence of pqqE gene. Furthermore, in a tomato-based bioassay in speed-bed demonstrated that a sole inoculation at seedling stage with the strains increased dry weight of roots (49–88%) and shoots (39–55%), stem height (8–13%) and diameter (5–8%) and leaf area (22–31%) and were equal or even higher than fertilization treatment. Leaf nitrogen and chlorophyll levels were also increased (50–80% and 26–33%) compared to control. These results suggest that Enterobacter 64S1 and Pseudomonas 42P4 can be used as bio-inoculant in order to realize a nutrient integrated management. Fil: Pérez Rodriguez, María Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Piccoli, Patricia Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Anzuay, María Soledad. Universidad Nacional de Río Cuarto; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Baraldi, Rita. Consiglio Nazionale delle Ricerche; Italia Fil: Neri, Luisa. Consiglio Nazionale delle Ricerche; Italia Fil: Taurian, Tania. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto; Argentina Fil: Lobato Ureche, Miguel Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Segura, Diana María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Cohen, Ana Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina

In this study, the Pseudomonas corrugata strain CFBP 5454 and the P. mediterranea strain CFBP 5447 were shown to produce diffusible compounds that inhibit the in vitro growth of plant pathogenic fungi and bacteria and antifungal volatile compounds. In addition, both bacterial strains were found to produce cyanide. Mutant derivatives in LuxR transcriptional regulators, i.e. P. corrugata GL2 (pcoR mutant) and GLRFIA (rfiA mutant), and P. mediterranea PSMER (pmeR mutant) and PSRFIA (rfiA mutant) impaired in cyclic lipopeptide (CLP) production, showed a diffusible compound-mediated reduced activity, depending on the biocontrol strain, challenge microorganism and culture medium. The volatile compound-mediated activity and cyanide production were not affected in the mutants. Genome analysis of the P. corrugata strain CFBP 5454 led to the identification of putative genes involved in the hydrogen cyanide (HCN) biosynthesis. HCN is a volatile organic compound (VOC), and as in other Pseudomonas, the HCN cluster consisted of three contiguous structural genes, hcnABC, which together encoded a membrane-bound HCN synthase complex, which was sufficient for cyanogenesis. The putative hcnA gene was insertionally inactivated. A genomic mutant was characterized, and the role of this compound in biocontrol activity was investigated. A qualitative test for the detection of HCN production confirmed that in the hcnA mutant strain, metabolite production is completely abolished. In vitro experiments on the phytopathogenic fungus Botrytis cinerea also showed that HCN production is mainly involved in conidia germination inhibition.

The ability of plants to take up phosphorus (P) from soil depends on root morphology and root exudates release and can be modulated by beneficial soil microbes. These microbes can solubilize P, affect root elongation and branching, and lead to a higher uptake of P and other nutrients. However, coordination of these mechanisms is unclear, especially the mechanism for changing the available form of P. We aimed to dissect the effects of two different beneficial microbial taxa (plant growth-promoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF)) on root morphological traits, plant nutrient content, and growth in tomato and corn fertilized with either Gafsa rock phosphate (RP) or triple superphosphate (TSP), which have contrasting solubility levels. Tomato and corn were grown in pots and inoculated with one of three PGPB species or a mix of two AMF species or were not inoculated. Root traits, botanical fractions, and the contents of various mineral nutrients were measured. TSP stimulated tomato biomass accumulation compared to RP but did not stimulate corn biomass accumulation. PGPB improved the growth of both plant species under RP, with limited differences among the strains, whereas AMF only improved tomato growth under TSP. These differences between microbial systems were explained by a bacterial effect on the total root length but not on the mean root diameter and by the ability of AMF to improve the mineral nutrient content. The effects of PGPB were less dependent on the plant species and on P form than the effects of AMF.These results have implications for the improvement of the early plant growth through the management of beneficial microbes.

Pseudomonas donghuensis strain SVBP6, an isolate from an agricultural plot in Argentina, displays a broad-spectrum and diffusible antifungal activity, which requires a functional gacS gene but could not be ascribed yet to known secondary metabolites typical of Pseudomonas biocontrol species. Here, we report that Tn5 mutagenesis allowed the identification of a gene cluster involved in both the fungal antagonism and the production of a soluble tropolonoid compound. The ethyl acetate extract from culture supernatant showed a dose-dependent inhibitory effect against the phytopathogenic fungus Macrophomina phaseolina. The main compound present in the organic extract was identified by spectroscopic and X-ray analyses as 7-hydroxytropolone (7HT). Its structure and tautomerism was confirmed by preparing the two key derivatives 2,3-dimethoxy- and 2,7-dimethoxy-tropone. 7HT, but not 2,3- or 2,7-dimethoxy-tropone, mimicked the fungal inhibitory activity of the ethyl acetate extract from culture supernatant. The activity of 7HT, as well as its production, was barely affected by the presence of up to 50 μM added iron (Fe+2). To summarize, P. donghuensis SVBP6 produces 7HT under the positive control of the Gac-Rsm cascade and is the main active metabolite responsible for the broad-spectrum inhibition of different phytopathogenic fungi. Fil: Muzio, Federico Matías. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnologia. Centro de Bioquimica y Microbiologia de Suelos. Laboratorio de Fisiologia, Genetica de Bacterias Para Plantas.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Agaras, Betina Cecilia. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnologia. Centro de Bioquimica y Microbiologia de Suelos. Laboratorio de Fisiologia, Genetica de Bacterias Para Plantas.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Masi, Marco. Università degli Studi di Napoli Federico II; Italia Fil: Tuzi, Angela. Università degli Studi di Napoli Federico II; Italia Fil: Evidente, Antonio. Università degli Studi di Napoli Federico II; Italia Fil: Valverde, Claudio Fabián. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnologia. Centro de Bioquimica y Microbiologia de Suelos. Laboratorio de Fisiologia, Genetica de Bacterias Para Plantas.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

The aim of this study was to investigate the physical, chemical and microbiological contamination of indoor swimming pools.Pool water specimens were collected using a plastic polypropylene sterilized bottle. The physical and chemical qualities of the waters were analyzed in terms of temperature, turbidity, pH, and free residual chlorine, with the standard methods for the examination of water. Bacteriological (routine methods) and parasitological (molecular methods) tests were carried out on pools water.The mean temperature, pH, and residual chlorine of the indoor pools were 31.2 °C, 7.6 and 1.5 mg/L, respectively. Turbidity was not observed in any of the pools. The pH and temperature values were in standard ranges in 92.3% and 15.4% of the waters of swimming pools, respectively. The prevalence rates of bacterial and amoebic contaminations of the water in the swimming pools were 53.8% and 46.2%, respectively. One pool (7.7%) was contaminated with both bacteria and amoeba.In this study, some microorganisms were identified from the water pools. Effective management of swimming pools and proper control of the physical, chemical and microbiological property of water pools can produce the healthy recreational activity.Bu çalışmanın amacı kapalı yüzme havuzlarının fiziksel, kimyasal ve mikrobiyolojik kirlenmelerini araştırmaktır.Havuz suyu örnekleri plastik polipropilen sterilize edilmiş bir şişe kullanılarak toplandı. Suların fiziksel ve kimyasal özellikleri, suyun incelenmesinde kullanılan standart yöntemler ile sıcaklık, bulanıklık, pH ve serbest artık klor açısından analiz edildi. Havuz sularında bakteriyolojik (rutin yöntemler) ve parazitolojik (moleküler yöntemler) çalışmalar yapılmıştır.Kapalı havuzların sıcaklık, pH ve artık klor ortalamaları sırasıyla 31,2 °C, 7,6 ve 1,5 mg/L idi. Havuzların hiçbirinde bulanıklık gözlenmedi. PH ve sıcaklık değerleri yüzme havuzlarının sırasıyla %92,3 ve %15,4’ünde istenilen aralıktaydı. Yüzme havuzlarında suyun bakteriyel ve amipli kirlenme sıklığı sırasıyla %53,8 ve %46,2’dir. Bir havuz (%7,7) hem bakteri hem de amip ile kirlenmiştir.Bu çalışmada, su havuzlarından bazı mikroorganizmalar tanımlanmıştır. Yüzme havuzlarının etkin yönetimi ve su havuzlarının fiziksel, kimyasal ve mikrobiyolojik özelliklerinin uygun şekilde kontrolü sağlıklı rekreasyon aktivitesini sağlayabilir.

Polycyclic aromatic hydrocarbons (PAHs) and heterocyclic derivatives are organic pollutants that pose a serious health risk to human beings. In this study, a newly isolated Pseudomonas brassicacearum strain MPDS could effectively degrade PAHs and heterocyclic derivatives, including naphthalene, fluorene, dibenzofuran (DBF) and dibenzothiophene (DBT). Notably, strain MPDS is able to degrade fluorene, DBF and DBT uniquely via a lateral dioxygenation pathway, while most reported strains degrade fluorene, DBF and DBT via an angular dioxygenation pathway or co-metabolize them via a lateral dioxygenation pathway. Strain MPDS completely degraded 50 mg naphthalene (in 50 mL medium) in 84 h, and OD600 reached 1.0–1.1; while, it stabilized at OD600 0.5–0.6 with 5 mg fluorene or DBF or DBT. Meanwhile, 65.7% DBF and 32.1% DBT were degraded in 96 h, and 40.3% fluorene was degraded in 72 h, respectively. Through genomic and transcriptomic analyses, and comparative genomic analysis with another DBF degradation strain, relevant gene clusters were predicted, and a naphthalene-degrading gene cluster was identified. This study provides understanding of degradation of PAHs and their heterocyclic derivatives, as well as new insights into the lateral dioxygenation pathway of relevant contaminants.

Routine evaluation of the slaughter process is performed by the enumeration of the aerobic colony count, Enterobacteriaceae and Salmonella spp. on the carcass through destructive or non-destructive methods. With non-destructive methods, bacteria are counted from a minimum area of 100 cm2 in different sampling sites on the pork carcasses, and the results of these investigated areas are pooled to one value for the complete carcass evaluation (a total of 400 cm2). However, the composition of the bacterial community present on the different sampling areas remains unknown. The aim of the study was to characterize the microbial population present on four areas (ham, back, jowl and belly) of eight pork carcasses belonging to two different slaughterhouses through culture-dependent (Matrix-assisted laser desorption/ionization time-of-flight Mass Spectrometry MALDI-TOF MS, combined with 16S rRNA gene sequencing) and complementary culture-independent (16S rRNA amplicon sequencing) methods. The presence of Salmonella spp. and Y. enterocolitica was additionally assessed. Using MALDI-TOF MS, Staphylococcus, Pseudomonas, and Escherichia coli were found to dominate the bacterial cultures isolated from the 8 carcasses. Based on the 16S rRNA amplicon sequencing analyses however, no specific genus clearly dominated the bacterial community composition. By using this culture-independent method, the most abundant genera in microbial populations of the ham, back, jowl and belly were found to be similar, but important differences between the two slaughterhouses were observed. Thus, present data suggests that the indigenous bacterial population of individual animals is overruled by the microbial population of the slaughterhouse in which the carcass is handled. Also, our data suggests that sampling of only one carcass area by official authorities may be appropriate for the evaluation of the hygienic status of the carcasses and therefore of the slaughter process.

Pseudomonas ANT_J38B is a Gram-negative bacterium isolated from an Antarctic island. LPS was extracted using the phenol/chloroform/petroleum ether method. A mild acid hydrolysis followed by a gel filtration purification afforded the O-chain. The polysaccharide was characterized by means of chemical analyses and NMR spectroscopy. The O-chain displays a disaccharide repeating unit with the following backbone: →4)-α- l -GulpNAc3OAcAN-(1 →3)-β- d -QuipNAc-(1→ .

PURPOSE: The aim of the present study was to quantitatively assess biofilm growth on the surface of bone cements discs containing different antibiotics, including colistin and linezolid. Biofilms of methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Staphylococcus epidermidis were grown on bone cement discs for 96 h. METHODS: Biofilm amounts were measured by confocal laser microscopy using live/dead staining and dedicated software at different time intervals (48, 72, and 96 h). RESULTS: Bone cement containing vancomycin was not effective at reducing MRSA biofilm formation 96 h following bacterial inoculation. At a comparable time interval, linezolid-, clindamycin-, and aminoglycoside-loaded cement was still active against this biofilm. At the 72- and 96-h observations, S. epidermidis biofilm was present only on tobramycin and gentamicin discs. P. aeruginosa biofilms were present on cement discs loaded with colistin at all time intervals starting from the 48-h observation, whereas no biofilms were detected on tobramycin or gentamicin discs. CONCLUSION: Bone cements containing different antibiotics have variable and time-dependent windows of activity in inhibiting or reducing surface biofilm formation. The effectiveness of bone cement containing vancomycin against MRSA biofilm is questionable. The present study is clinically relevant, because it suggests that adding the right antibiotic to bone cement could be a promising approach to treat periprosthetic infections. Indeed, the antibiofilm activity of different antibiotic-loaded bone cements could be preoperatively assessed using the current methodology in two-stage exchange procedures.

Microbiological, chemical and physical parameters of minimally processed red chicory (Cichorium intybus L.) subjected to two different transformation processes were investigated. A classic ready-to-eat (RTE) process (P1) and a production without cutting (P2) were monitored during refrigerated (4 °C) storage (15 d). Total mesophilic microorganisms, total psychrotrophic microorganisms and pseudomonads were detected at the highest cell densities in all samples. Presumptive Pseudomonas population dominated the cultivable microbial community of RTE red chicory and were characterized genetically. Twenty-two randomly amplified polymorphic DNA (RAPD) types were investigated by 16S rRNA gene sequencing, resulting in members of Rahnella and Pseudomonas. The identification of Pseudomonas species was further determined by sequencing of gyrB, rpoB and rpoD genes resulting in 16 species. A highest visual quality and a lower weight loss and colour variation were registered for P2, while soluble solid, nitrate and ascorbic acid contents were not affected by processing and storage. The integrated microbiological, chemical and physical approach applied in this study demonstrated the longer shelf-life of P2 red chicory.

The importance of the plant microbiome for host fitness has led to the concept of the "plant holobiont". Seeds are reservoirs and vectors for beneficial microbes, which are very intimate partners of higher plants with the potential to connect plant generations. In this study, the endophytic seed microbiota of numerous barley samples, representing different cultivars, geographical sites and harvest years, was investigated. Cultivation-dependent and -independent analyses, microscopy, functional plate assays, greenhouse assays and functional prediction were used, with the aim of assessing the composition, stability and function of the barley seed endophytic bacterial microbiota. Associations were consistently detected in the seed endosphere with Paenibacillus, Pantoea and Pseudomonas spp., which were able to colonize the root with a notable rhizocompetence after seed germination. In greenhouse assays, enrichment with these bacteria promoted barley growth, improved mineral nutrition and induced resistance against the fungal pathogen Blumeria graminis. We demonstrated here that barley, an important crop plant, was consistently associated with beneficial bacteria inside the seeds. The results have relevant implications for plant microbiome ecology and for the holobiont concept, as well as opening up new possibilities for research and application of seed endophytes as bioinoculants in sustainable agriculture.

Introduction: Ceftolozane/tazobactam (C/T) is a new antibiotic resulting from the combination of a novel cephalosporin, structurally similar to ceftazidime, with tazobactam, a well-known beta-lactamase inhibitor. C/T remains active against extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae and multi-drug resistant (MDR) P. aeruginosa, and has been recently approved for the treatment of complicated intra-abdominal infections (cIAI) and complicated urinary tract infections (cUTI). A trial on hospital-acquired pneumonia is ongoing. Areas covered: The place in therapy of C/T is delineated by addressing the following main topics: (i) antimicrobial properties; (ii) pharmacological properties; (iii) results of clinical studies. Expert commentary: C/T is approved for cIAI and cUTI. However, the drug has a special value for clinicians in any kind of infectious localization for two main reasons. The first is that C/T is especially valuable in suspected or documented severe infections due to MDR P. aeruginosa, which is not a rare occurrence in many countries. The second is that C/T may provide an alternative to carbapenems for the treatment of infections caused by ESBL-producers, thus allowing a carbapenem-sparing strategy. Reporting of off-label use is mandatory to increase the body of evidence and the clinicians’ confidence in using it for indications other than cIAI and cUTI.

Pseudomonas infections are common among hospitalized, immunocompromised, and chronic lung disease patients. These infections are recalcitrant to common antibacterial therapies due to inherent antibiotic resistance. To meet the need of new anti- Pseudomonas drugs, a sensitive, homogenous, and robust assay was developed with the aim of identifying inhibitors of acyl-coenzyme A synthetases (ACSs) from Pseudomonas. Given the importance of fatty acids for in vivo nutrition of Pseudomonas, such inhibitors might have the potential to reduce the bacterial fitness during infection. The assay, based on a coupled reaction between the Pseudomonas spp. ACS and the firefly luciferase, allowed the identification of three classes of inhibitors by screening of a diverse compound collection. These compounds were confirmed to reversibly bind ACS with potencies in the micromolar range. Two classes were found to compete with acyl-coenzyme A, while the third one was competitive with fatty acid binding. Although these compounds inhibit the bacterial ACS in cell-free assays, they show modest or no effect on Pseudomonas growth in vitro.

PubMedID: 25428232 Knowledge of the distribution spectrum of causative organisms and their resistance patterns has become a core requirement for the rational and effective management of urinary tract infections. In the context of a prospective trial on the use of antibiotic prophylaxis in infants with underling kidney malformations, we conducted an online survey among paediatric nephrologists on positive urine cultures (July 2010–June 2012) from both hospitalized and non-hospitalized infants under 24 months of age. We collected 4745 urine cultures (UCs) at 18 units in 10 European countries. Escherichia coli was the most frequent bacterium isolated from UCs; however, in 10/16 hospitals and in 6/15 community settings, E. coli was isolated in less than 50 % of the total positive UCs. Other bacterial strains were Klebsiella, Enterococcus, Proteus and Pseudomonas not only from hospital settings. E. coli showed a high resistance to amoxicillin and trimethoprim and variable to cephalosporin. Nitrofurantoin had a good rate of efficacy, with 11/16 hospitals and 11/14 community settings reporting a resistance lower than 5 %. Conclusion: E. coli is the most common organism causing UTIs in infants; however, other bacterial strains are frequently isolated. As a result, antibiotic prophylaxis should be more elastic and adaptable over time in order to guarantee maximum efficacy. © 2014, Springer-Verlag Berlin Heidelberg.

ABSTRACT: Gallium has a long history as a diagnostic and chemotherapeutic agent. The pharmacological properties of Ga(III) rely on chemical mimicry; when Ga(III) is exogenously supplied to living cells it can replace Fe(III) within target molecules, thereby perturbing bacterial metabolism. Ga(III)-induced metabolic distresses are dramatic in fast-growing cells, like bacterial cells. Interest in the antibacterial properties of Ga(III) has been raised by the compelling need for novel drugs to combat multidrug-resistant bacteria and by the shortage of new antibiotic candidates in the pharmaceutical pipeline. Ga(III) activity has been demonstrated, both in vitro and in animal models of infections, on several bacterial pathogens, also including intracellular and biofilm-forming bacteria. Ga(III) activity is affected by iron availability and the metabolic state of the cell, being maximal in iron-poor media and in respiring cells. Synergism between Ga(III) and antibiotics holds promise as last resort therapy for infections sustained by pandrug-resistant bacteria.

Pseudomonas corrugata and P. mediterranea are soil inhabitant bacteria, generally living as endophytes on symptomless plants and bare soil, but also capable of causing plant diseases. They share a similar genome size and a high proteome similarity. P. corrugata produces many biomolecules which play an important role in bacterial cell survival and fitness. Both species produce different medium-chain-length PHAs (mcl-PHAs) from the bioconversion of glycerol to a transparent film in P. mediterranea and a sticky elastomer in P. corrugata. In this work, using RNA-seq we investigated the transcriptional profiles of both bacteria at the early stationary growth phase with glycerol as the carbon source. Quantitative analysis of P. mediterranea transcripts versus P. corrugata revealed that 1756 genes were differentially expressed. A total of 175 genes were significantly upregulated in P. mediterranea, while 217 were downregulated. The largest group of upregulated genes was related to transport systems and stress response, energy and central metabolism, and carbon metabolism. Expression levels of most genes coding for enzymes related to PHA biosynthesis and central metabolic pathways showed no differences or only slight variations in pyruvate metabolism. The most relevant result was the significantly increased expression in P. mediterranea of genes involved in alginate production, an important exopolysaccharide, which in other Pseudomonas spp. plays a key role as a virulence factor or in stress tolerance and shows many industrial applications. In conclusion, the results provide useful information on the co-production of mcl-PHAs and alginate from glycerol as carbon source by P. mediterranea in the design of new strategies of genetic regulation to improve the yield of bioproducts or bacterial fitness.

The phenanthrene (PHE) degradation by a halotolerant bacterial consortium enriched from production water of Sercina oilfield in Tunisia was investigated. The consortium PHMM utilized PHE (200 mg/L), as a sole carbon source, in the presence of a wide range of NaCl concentrations, from 1 to 5% (w/v). The maximum growth rate was obtained at 500 mg/L of PHE. A PHE metabolism was assayed by using FTIR, UV and GC–MS analyses. Results revealed that the consortium PHMM metabolized PHE via protochatechuate pathway since intermediates such as naphthalenol and phthalic acid were detected. Phylogenetic analysis showed that the adapted consortium PHMM was composed by two dominant bacterial strains, identified as Pseudomonas sp. (strain PH1) and Staphylococcus sp. (strain PH2). All the results indicated that the microorganisms from the Tunisian oilfield have a promising application in bioremediation of petrochemical contaminated environments and could be potentially useful for the study of PAHs biodegradation.

The siderophore pyoverdine (PVD) is a primary virulence factor of the human pathogenic bacterium Pseudomonas aeruginosa , acting as both an iron carrier and a virulence-related signal molecule. By exploring a number of P. aeruginosa candidate systems for PVD secretion, we identified a tripartite ATP-binding cassette efflux transporter, here named PvdRT-OpmQ, which translocates PVD from the periplasmic space to the extracellular milieu. We show this system to be responsible for recycling of PVD upon internalization by the cognate outer-membrane receptor FpvA, thus making PVD virtually available for new cycles of iron uptake. Our data exclude the involvement of PvdRT-OpmQ in secretion of de novo synthesized PVD, indicating alternative pathways for PVD export and recycling. The PvdRT-OpmQ transporter is one of the few secretion systems for which substrate recognition and extrusion occur in the periplasm. Homologs of the PvdRT-OpmQ system are present in genomes of all fluorescent pseudomonads sequenced so far, suggesting that PVD recycling represents a general energy-saving strategy adopted by natural Pseudomonas populations.

Styrene degradation by Pseudomonas fluorescens ST was determined by analysis of recombinant clones generated. Styrene is degraded via the oxidation of the side chain leading to epoxystyrene, which is subsequently isomerized to phenylacetaldehyde and then oxidized to phenylacetic acid. The acid appears to be activated by phenylacetyl-CoA ligase before hydroxylation to form o-hydroxyphenylacetic acid and then homogentisic acid. The catabolic genes are organized in two operons: the upper pathway genes responsible for the oxidation of styrene to phenylacetic acid, and the lower pathway genes involved in the conversion of the acid into compounds which are then further metabolised in the Krebs cycle.

Pseudomonas flavescens strain B62 (NCPPB 3063) is a recently described bacterium isolated from walnut blight cankers. This strain has been designated as the type strain of a Pseudomonas rRNA group-I species. Strain B62 produced a mixture of two exopolysaccharides, differing in weight average relative molecular mass and composition. Only the most abundant exopolysaccharide (90% by mass), corresponding to the one with the lower molecular mass, was investigated by use of methylation analysis, partial acid hydrolysis, and NMR spectroscopy. The polysaccharide was depolymerised by the action of the cellulase produced by Penicillum funiculosum and the oligosaccharide obtained, corresponding to the repeating unit, was characterised by NMR spectroscopy and ion-spray mass spectrometry. The repeating unit of the B62 exopolysaccharide is [structure in text] where X is glucose (75%) or mannose (25%), and Lac is lactate. The O-acetyl groups are present only on 75% of the repeating units, and they are linked to the C6 of the hexose residues in non-stoichiometric amounts.

Soilborne fungal pathogens are highly persistent and provoke important crop losses. During saprophytic and infectious stages in the soil, these organisms face situations of nutrient limitation and lack of essential elements, such as iron. We investigated the role of the bZIP transcription factor HapX as a central regulator of iron homeostasis and virulence in the vascular wilt fungus Fusarium oxysporum. This root-infecting plant pathogen attacks more than hundred different crops and is an emerging human opportunistic invader. Although iron uptake remains unaffected in a strain lacking HapX, de-repression of genes implicated in iron-consuming processes such as respiration, amino acid metabolism, TCA cycle and heme biosynthesis lead to severely impaired growth under iron-limiting conditions. HapX is required for full virulence of F. oxysporum in tomato plants and essential for infection in immunodepressed mice. Virulence attenuation of the ?hapX strain on tomato plants is more pronounced by co-inoculation of roots with the biocontrol strain Pseudomonas putida KT2440, but not with a mutant deficient in siderophores production. These results demonstrate that HapX is required for iron competition of F. oxysporum in the tomato rhizosphere and establish a conserved role for HapX-mediated iron homeostasis in fungal infection of plants and mammals.

The acidic exopolysaccharides (EPSs) from 63 strains of mushroom production-associated fluorescent pseudomonads which were mucoid on Pseudomonas agar F medium (PAF) were isolated, partially purified, and characterized. The strains were originally isolated from discolored lesion which developed postharvest on mushroom (Agaricus bisporus) caps or from commercial lots of mushroom casing medium. An acidic galactoglucan, previously named marginalan, was produced by mucoid strains of the saprophyte Pseudomonas putida and the majority of mucoid strains of saprophytic P. fluorescens (biovars III and V) isolated from casing medium. One biovar II strain (J1) of P. fluorescens produced alginate, a copolymer of mannuronic and guluronic acids, and one strain (H13) produced an apparently unique EPS containing neutral and amino sugars. Of 10 strains of the pathogen "P. gingeri," the causal agent of mushroom ginger blotch, 8 gave mucoid growth on PAF. The "P. gingeri" EPS also was unique in containing both neutral sugar and glucuronic acid. Mucoid, weakly virulent strains of "P. reactans" produced either alginate or marginalan. All 10 strains of the pathogen P. tolaasii, the causal agent of brown blotch of mushrooms were nonnmucoid on PAF. Production of EPS by these 10 strains plus the 2 nonmucoid strains of "P. gingeri" also was negative on several additional solid media as well as in two broth media tested. The results support our previous studies indicating that fluorescent pseudomonads are a rich source of novel EPSs.

Pseudomonas corrugata was first described as the causal agent of a tomato disease called 'pith necrosis' yet it is considered as a biological resource in various fields such as biocontrol of plant diseases and production of industrially promising microbial biopolymers (mcl-PHA). Here we report the first draft genome sequence of this species. © 2014 Elsevier B.V.

The gram-negative phytopathogen Pseudomonas corrugata has an acyl-homoserine lactone (AHL) quorum-sensing (QS) system called PcoI/PcoR that is involved in virulence on tomato. This work identifies, downstream of pcol, a gene designated rfiA, which we demonstrate is directly linked to QS by cotranscription with pcol. The deduced RfiA protein contains a DNA-binding domain characteristic of the LuxR family but lacks the autoinducer-binding terminus characteristic of the QS LuxR-family proteins. We also identified, downstream of rfiA, an operon designated pcoABC, encoding for the three components of a tripartite resistance nodulation-cell-division (RND) transporter system. The expression of pcoABC is regulated by RfiA. We found that lipodep-sipeptide (LDP) production is cell density dependent and mutants of pcol, pcoR, and rfiA are unable to inhibit the growth of the LDP-sensitive microorganisms Rhodotorula pilimanae and Bacillus megaterium. P. corrugata rfiA mutants were significantly reduced in their ability to cause necrosis development in tomato pith. In addition, it was established that PcoR in the absence of AHL also played a role in virulence on tomato. A model for the role of PcoI, PcoR, and RfiA in tomato pith necrosis is presented. © 2009 The American Phytopathological Society.

Species-specific primers and a multiplex PCR assay were developed for the simultaneous identification and differentiation of Pseudomonas fragi , P. lundensis , and P. putida based on the coamplification of different portions of the small subunit of the carbamoyl phosphate synthase gene ( carA ). The carA multiplex PCR was used to detect the presence of the three Pseudomonas species from beef, chicken, and pork samples and proved to be effective in showing their evolution during the storage of meat.

Pyoverdines are a group of structurally related siderophores produced by fluorescent Pseudomonas species. Recent genomic and biochemical data have shed new light on the complex molecular steps of pyoverdine biogenesis and explained the chemical diversity of these compounds. In the opportunistic pathogen Pseudomonas aeruginosa, pyoverdine is necessary for infection in several different disease models. The occurrence of pyoverdine-defective strains in chronic infections of patients with cystic fibrosis and the extremely high sequence diversity of genes involved in pyoverdine synthesis and uptake indicate that pyoverdine production is subject to high evolutionary pressure. Pyoverdine-dependent iron transport is also crucial for biofilm development, further expanding the importance of these siderophores in Pseudomonas biology.

The biological activities of the lipodepsipeptides (LDP) white line–inducing principle (WLIP), produced by Pseudomonas reactans NCPPB1311, and tolaasin I, produced by P. tolaasii NCPPB2192, were compared. Antimicrobial assays showed that both LDP inhibited the growth of fungi—including the cultivated mushrooms Agaricus bisporus, Lentinus edodes, and Pleurotus spp.—chromista, and gram-positive bacteria. Assays of the two LDP on blocks of Agaricus bisporus showed their capacity to alter the mushrooms’ pseudo-tissues though WLIP was less active than that of tolaasin I. Contrary to previous studies, tolaasin I was found to inhibit the growth of gram-negative bacteria belonging to the genera Escherichia, Erwinia, Agrobacterium, Pseudomonas, and Xanthomonas. The only gram-negative bacterium affected by WLIP was Erwinia carotovora subsp. carotovora. Both WLIP and tolaasin I caused red blood cell lysis through a colloid-osmotic shock mediated by transmembrane pores; however, the haemolytic activity of WLIP was greater than that of tolaasin I. Transmembrane pores, at a concentration corresponding to 1.5 × C50, showed a radius between 1.5 and 1.7 ± 0.1 nm for WLIP and 2.1 ± 0.1 nm for tolaasin I. The antifungal activity of WLIP together with the finding that avirulent morphological variants of P. reactans lack WLIP production suggests that WLIP may play an important role in the interaction of the producing bacterium P. reactans and cultivated mushrooms. Additional keywords: Pseudomonas tolaasii.

Phenol bioconversion by Pseudomonas stutzeri OX1 using either free or immobilized cells was investigated with the aim of searching for optimal operating conditions of a continuous bioconversion process which makes use of microbial cells. The study was developed by analyzing: a) free-cell growth and products of phenol bioconversion by batch cultures of P. stutzeri; b) growth of P. stutzeri cells immobilized on carrier particles; and c) continuous bioconversion of phenol-bearing liquid streams as well as the establishment and growth of an active bacterial biofilm during continuous operation of an internal-loop airlift bioreactor. We have confirmed that free Pseudomonas cultures are able to transform phenol through the classical meta pathway for the degradation of aromatic molecules. Data indicate that bacterial growth is substrate-inhibited, with a limiting phenol concentration of about 600 mg/L. Immobilization tests revealed that a stable bacterial biofilm can be formed on various types of solid carriers (silica sand, tuff, and activated carbon), but not on alumina. Entrapment in alginate beads also proved to be effective for P. stutzeri immobilization. Continuous bioconversion of phenol-bearing liquid streams was successfully obtained in a biofilm reactor operated in the internal-circulation airlift mode. Phenol conversion exceeded 95%. Biofilm formation and growth during continuous operation of the airlift bioreactor were quantitatively and qualitatively assessed by a combination of experimental techniques. The performance of the continuous biofilm reactor was found to be extremely valid in terms of throughput and operability.

A recombinant lipase cloned from Pseudomonas fragi strain IFO 3458 (PFL) was found to retain significant activity at low temperature. In an attempt to elucidate the structural basis of this behaviour, a model of its three-dimensional structure was built by homology and compared with homologous mesophilic lipases, i.e. the Pseudomonas aeruginosa lipase (45% sequence identity) and Burkholderia cepacia lipase (38%). In this model, features common to all known lipases have been identified, such as the catalytic triad (S83, D238 and H260) and the oxyanion hole (L17, Q84). Structural modifications recurrent in cold-adaptation, i.e. a large amount of charged residues exposed at the protein surface, have been detected. Noteworthy is the lack of a disulphide bridge conserved in homologous Pseudomonas lipases that may contribute to increased conformational flexibility of the cold-active enzyme.

Pseudomonas syringae pv. syringae strain B359 secreted two main lipodepsipeptides (LDPs), syringomycin E (SRE) and syringopeptin 25A (SP25A), together with at least four types of cell wall—degrading enzymes (CWDEs). In antifungal bioassays, the purified toxins SRE and SP25A interacted synergistically with chitinolytic and glucanolytic enzymes purified from the same bacterial strain or from the biocontrol fungus Trichoderma atroviride strain P1. The synergism between LDPs and CWDEs occurred against all seven different fungal species tested and P. syringae itself, with a level dependent on the enzyme used to permeabilize the microbial cell wall. The antifungal activity of SP25A was much more increased by the CWDE action than was that of the smaller SRE, suggesting a stronger antifungal role for SP25A. In vivo biocontrol assays were performed by using P. syringae alone or in combination with T. atroviride, including a Trichoderma endochitinase knock-out mutant in place of the wild type and a chitinase-specific enzyme inhibitor. These experiments clearly indicate that the synergistic interaction LDPs—CWDEs is involved in the antagonistic mechanism of P. syringae, and they support the concept that a more effective disease control is given by the combined action of the two agents.

A gene cluster isolated from Pseudomonas stutzeri OX1 genomic DNA and containing six ORFs codes for toluene/o-xylene-monooxygenase. The putative regulatory D subunit was expressed in Escherichia coli and purified. Its protein sequence was verified by mass spectrometry mapping and found to be identical to the sequence predicted on the basis of the DNA sequence. The surface topology of subunit D in solution was probed by limited proteolysis carried out under strictly controlled conditions using several proteases as proteolytic probes. The same experiments were carried out on the homologous P2 component of the multicomponent phenol hydroxylase from Pseudomonas putida CF600. The proteolytic fragments released from both proteins in their native state were analyzed by electrospray mass spectrometry, and the preferential cleavage sites were assessed. The results indicated that despite the relatively high similarity between the sequences of the two proteins, some differences in the distribution of preferential proteolytic cleavages were detected, and a much higher conformational flexibility of subunit D was inferred. Moreover, automatic modeling of subunit D was attempted, based on the known three-dimensional structure of P2. Our results indicate that, at least in this case, standard modeling procedures based on automatic alignment on the structure of P2 fail to produce a model consistent with limited proteolysis experimental data. Thus, it is our opinion that reliable techniques such as limited proteolysis can be employed to test three-dimensional models and highlight problems in automatic model building.

Pseudomonas strains have long been proven to be effective in aromatic pollutant conversion. Typically, Pseudomonas strains growth on aromatic species is characterized by substrate inhibition and the kinetic parameters are assessed working out results of batch tests. On the other hand, continuous cultures operated under steady state conditions most closely reflect realistic operational conditions and are, as such, better suited for reliable assessment of kinetic parameters. The peculiar growth kinetics makes the chemostat intrinsically unstable, so that properly tuned control systems are required to counterbalance the inherent process instability. Turbidostats and nutristats have been reported in the literature as possible configurations of controlled chemostat to accomplish continuously operated cultures. However, it may be difficult to continuously measure state variables like biomass or carbon-source concentrations as compared with dissolved oxygen concentration. The present study addresses the characterization of the kinetics of Pseudomonas sp. OX1 growth using phenol as carbon and energy source. Tests were carried out in a chemostat equipped with a dilution rate control unit. The dissolved oxygen concentration was adopted as the controlled variable and an ad-hoc proportional-integral control loop was developed. A test procedure was purposely adopted in which the control system forced the chemostat to operate steadily under conditions that would otherwise be inherently unstable. Tests demonstrated that the control strategy was successful in stabilizing steady state continuous cultures at phenol concentration characterized by unstable behaviour. The unstable branch of the growth kinetics was characterized. Moreover, phenol degradation under starving conditions was investigated. The specific growth rate () as a function of pH are well fitted by the Haldane model, data regression yielding max = 0.26 h-1, KM = 0.005 g/L and KI = 0.2 g/L. Phenol to biomass fractional yield increases with  according to the Pirt model, with a maintenance contribution of 0.017 g/(g ·h) and a theoretical fractional yield of 1.3 g/g.