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Molecular Microbiology Feb 2022Many bacteria form mats at the air-liquid interface of static microcosms. These structures typically involve the secretion of exopolysaccharides, the production of which...
Many bacteria form mats at the air-liquid interface of static microcosms. These structures typically involve the secretion of exopolysaccharides, the production of which is often controlled by the secondary messenger c-di-GMP. Mechanisms of mat formation have been particularly well characterized in Pseudomonas fluorescens SBW25; stimuli or mutations that increase c-di-GMP production by diguanylate cyclases (WspR, AwsR, and MwsR) result in the secretion of cellulose and mat formation. Here, we characterize and compare mat formation in two close relatives of SBW25: Pseudomonas simiae PICF7 and P. fluorescens A506. We find that PICF7-the strain more closely related to SBW25-can form mats through mutations affecting the activity of the same three diguanylate cyclases as SBW25. However, instead of cellulose, these mutations activate production of the exopolysaccharide Pel. We also provide evidence for at least two further-as yet uncharacterized-routes to mat formation by PICF7. P. fluorescens A506, while retaining the same mutational routes to mat formation as SBW25 and PICF7, preferentially forms mats by a semi-heritable mechanism that culminates in Psl and Pga over-production. Our results demonstrate a high level of evolutionary flexibility in the molecular and structural routes to mat formation, even among close relatives.
Topics: Biofilms; Biological Evolution; Cyclic GMP; Mutation; Pseudomonas; Pseudomonas aeruginosa; Pseudomonas fluorescens
PubMed: 34856020
DOI: 10.1111/mmi.14855 -
Molecular Microbiology Dec 2011Many bacteria are now believed to produce small signal molecules in order to communicate in a process called quorum sensing (QS), which mediates cooperative traits and a... (Review)
Review
Many bacteria are now believed to produce small signal molecules in order to communicate in a process called quorum sensing (QS), which mediates cooperative traits and a co-ordinated behaviour. Pseudomonads have been extensively studied for their QS response highlighting that it plays a major role in determining their lifestyle. The main QS signal molecules produced by Pseudomonas belong to the family of N-acyl-homoserine lactones (AHLs); these are synthesized by a LuxI-family synthase and sensed by a LuxR-family regulator. Most often in Pseudomonas, repressor genes intergenically located between luxI and luxR form an integral part of QS system. Recent studies have highlighted an important role of these repressors (called RsaL and RsaM) in containing the QS response within cost-effective levels; this is central for pseudomonads as they have very versatile genomes allowing them to live in constantly changing and highly dynamic environments. This review focuses on the role played by RsaL and RsaM repressors and discusses the important implications of this control of the QS response.
Topics: Acyl-Butyrolactones; Gene Expression Regulation, Bacterial; Pseudomonas; Quorum Sensing; Repressor Proteins; Signal Transduction
PubMed: 22060261
DOI: 10.1111/j.1365-2958.2011.07890.x -
Frontiers in Cellular and Infection... 2021and infections frequently co-localize in lungs of immunocompromised patients and individuals with cystic fibrosis (CF). The antifungal activity of has been described...
and infections frequently co-localize in lungs of immunocompromised patients and individuals with cystic fibrosis (CF). The antifungal activity of has been described for its filtrates. Pyoverdine and pyocyanin are the principal antifungal molecules active against biofilm metabolism present in iron-limited or iron-replete planktonic culture filtrates, respectively. Using various laboratory wild-type strains (PA14, PAO1, PAK), we found antifungal activity against colonies on agar. Comparing 36 PA14 and 7 PAO1 mutants, we found that mutants lacking both major siderophores, pyoverdine and pyochelin, display higher antifungal activity on agar than their wild types, while quorum sensing mutants lost antifungal activity. Addition of ferric iron, but not calcium or magnesium, reduced the antifungal effects of on agar, whereas iron-poor agar enhanced antifungal effects. Antifungal activity on agar was mediated by PQS and HHQ, MvfR. Among the MvfR downstream factors, rhamnolipids and elastase were produced in larger quantities by pyoverdine-pyochelin double mutants and showed antifungal activity on agar. In summary, antifungal factors produced by on agar differ from those produced by bacteria grown in liquid cultures, are dependent on quorum sensing, and are downregulated by the availability of ferric iron. Rhamnolipids and elastase seem to be major mediators of ' antifungal activity on a solid surface.
Topics: Aspergillus; Biofilms; Humans; Pseudomonas; Pseudomonas Infections; Pseudomonas aeruginosa; Pyocyanine; Quorum Sensing
PubMed: 34746024
DOI: 10.3389/fcimb.2021.734296 -
Cellular and Molecular Life Sciences :... Feb 2020Microorganisms acquire energy and nutrients from dynamic environments, where substrates vary in both type and abundance. The regulatory system responsible for... (Review)
Review
Microorganisms acquire energy and nutrients from dynamic environments, where substrates vary in both type and abundance. The regulatory system responsible for prioritizing preferred substrates is known as carbon catabolite repression (CCR). Two broad classes of CCR have been documented in the literature. The best described CCR strategy, referred to here as classic CCR (cCCR), has been experimentally and theoretically studied using model organisms such as Escherichia coli. cCCR phenotypes are often used to generalize universal strategies for fitness, sometimes incorrectly. For instance, extremely competitive microorganisms, such as Pseudomonads, which arguably have broader global distributions than E. coli, have achieved their success using metabolic strategies that are nearly opposite of cCCR. These organisms utilize a CCR strategy termed 'reverse CCR' (rCCR), because the order of preferred substrates is nearly reverse that of cCCR. rCCR phenotypes prefer organic acids over glucose, may or may not select preferred substrates to optimize growth rates, and do not allocate intracellular resources in a manner that produces an overflow metabolism. cCCR and rCCR have traditionally been interpreted from the perspective of monocultures, even though most microorganisms live in consortia. Here, we review the basic tenets of the two CCR strategies and consider these phenotypes from the perspective of resource acquisition in consortia, a scenario that surely influenced the evolution of cCCR and rCCR. For instance, cCCR and rCCR metabolism are near mirror images of each other; when considered from a consortium basis, the complementary properties of the two strategies can mitigate direct competition for energy and nutrients and instead establish cooperative division of labor.
Topics: Carbon; Catabolite Repression; Escherichia coli; Glucose; Humans; Phenotype; Pseudomonadaceae
PubMed: 31768608
DOI: 10.1007/s00018-019-03377-x -
Molecular Plant Pathology Dec 2012Pseudomonas savastanoi pv. savastanoi is the causal agent of olive (Olea europaea) knot disease and an unorthodox member of the P. syringae complex, causing aerial... (Review)
Review
UNLABELLED
Pseudomonas savastanoi pv. savastanoi is the causal agent of olive (Olea europaea) knot disease and an unorthodox member of the P. syringae complex, causing aerial tumours instead of the foliar necroses and cankers characteristic of most members of this complex. Olive knot is present wherever olive is grown; although losses are difficult to assess, it is assumed that olive knot is one of the most important diseases of the olive crop. The last century witnessed a large number of scientific articles describing the biology, epidemiology and control of this pathogen. However, most P. savastanoi pv. savastanoi strains are highly recalcitrant to genetic manipulation, which has effectively prevented the pathogen from benefitting from the scientific progress in molecular biology that has elevated the foliar pathogens of the P. syringae complex to supermodels. A number of studies in recent years have made significant advances in the biology, ecology and genetics of P. savastanoi pv. savastanoi, paving the way for the molecular dissection of its interaction with other nonpathogenic bacteria and their woody hosts. The selection of a genetically pliable model strain was soon followed by the development of rapid methods for virulence assessment with micropropagated olive plants and the analysis of cellular interactions with the plant host. The generation of a draft genome of strain NCPPB 3335 and the closed sequence of its three native plasmids has allowed for functional and comparative genomic analyses for the identification of its pathogenicity gene complement. This includes 34 putative type III effector genes and genomic regions, shared with other pathogens of woody hosts, which encode metabolic pathways associated with the degradation of lignin-derived compounds. Now, the time is right to explore the molecular basis of the P. savastanoi pv. savastanoi-olive interaction and to obtain insights into why some pathovars like it necrotic and why some like it knot.
SYNONYMS
Pseudomonas syringae pv. savastanoi.
TAXONOMY
Kingdom Bacteria; Phylum Proteobacteria; Class Gammaproteobacteria; Family Pseudomonadaceae; Genus Pseudomonas; included in genomospecies 2 together with at least P. amygdali, P. ficuserectae, P. meliae and 16 other pathovars from the P. syringae complex (aesculi, ciccaronei, dendropanacis, eriobotryae, glycinea, hibisci, mellea, mori, myricae, phaseolicola, photiniae, sesami, tabaci, ulmi and certain strains of lachrymans and morsprunorum); when a formal proposal is made for the unification of these bacteria, the species name P. amygdali would take priority over P. savastanoi.
MICROBIOLOGICAL PROPERTIES
Gram-negative rods, 0.4-0.8 × 1.0-3.0 μm, aerobic. Motile by one to four polar flagella, rather slow growing, optimal temperatures for growth of 25-30 °C; oxidase negative, arginine dihydrolase negative; elicits the hypersensitive response on tobacco; most isolates are fluorescent and levan negative, although some isolates are nonfluorescent and levan positive.
HOST RANGE
P. savastanoi pv. savastanoi causes tumours in cultivated and wild olive and ash (Fraxinus excelsior). Although strains from olive have been reported to infect oleander (Nerium oleander), this is generally not the case; however, strains of P. savastanoi pv. nerii can infect olive. Pathovars fraxini and nerii are differentiated from pathovar savastanoi mostly in their host range, and were not formally recognized until 1996. Literature before about 1996 generally names strains of the three pathovars as P. syringae ssp. savastanoi or P. savastanoi ssp. savastanoi, contributing to confusion on the host range and biological properties.
DISEASE SYMPTOMS
Symptoms of infected trees include hyperplastic growths (tumorous galls or knots) on the stems and branches of the host plant and, occasionally, on leaves and fruits.
EPIDEMIOLOGY
The pathogen can survive and multiply on aerial plant surfaces, as well as in knots, from where it can be dispersed by rain, wind, insects and human activities, entering the plant through wounds. Populations are very unevenly distributed in the plant, and suffer drastic fluctuations throughout the year, with maximum numbers of bacteria occurring during rainy and warm months. Populations of P. savastanoi pv. savastanoi are normally associated with nonpathogenic bacteria, both epiphytically and endophytically, and have been demonstrated to form mutualistic consortia with Erwinia toletana and Pantoea agglomerans, which could result in increased bacterial populations and disease symptoms.
DISEASE CONTROL
Based on preventive measures, mostly sanitary and cultural practices. Integrated control programmes benefit from regular applications of copper formulations, which should be maintained for at least a few years for maximum benefit. Olive cultivars vary in their susceptibility to olive knot, but there are no known cultivars with full resistance to the pathogen.
USEFUL WEBSITES
http://www.pseudomonas-syringae.org/; http://genome.ppws.vt.edu/cgi-bin/MLST/home.pl; ASAP access to the P. savastanoi pv. savastanoi NCPPB 3335 genome sequence https://asap.ahabs.wisc.edu/asap/logon.php.
Topics: Adaptation, Physiological; Genome, Bacterial; Host-Pathogen Interactions; Humans; Olea; Plant Diseases; Pseudomonas
PubMed: 22805238
DOI: 10.1111/j.1364-3703.2012.00816.x -
Microbial Biotechnology May 2018Bacteria of the genus Pseudomonas are widespread in nature. In the last decades, members of this genus, especially Pseudomonas aeruginosa and Pseudomonas putida, have... (Comparative Study)
Comparative Study Review
Bacteria of the genus Pseudomonas are widespread in nature. In the last decades, members of this genus, especially Pseudomonas aeruginosa and Pseudomonas putida, have acquired great interest because of their interactions with higher organisms. Pseudomonas aeruginosa is an opportunistic pathogen that colonizes the lung of cystic fibrosis patients, while P. putida is a soil bacterium able to establish a positive interaction with the plant rhizosphere. Members of Pseudomonas genus have a robust metabolism for amino acids and organic acids as well as aromatic compounds; however, these microbes metabolize a very limited number of sugars. Interestingly, they have three-pronged metabolic system to generate 6-phosphogluconate from glucose suggesting an adaptation to efficiently consume this sugar. This review focuses on the description of the regulatory network of glucose utilization in Pseudomonas, highlighting the differences between P. putida and P. aeruginosa. Most interestingly, It is highlighted a functional link between glucose assimilation and exotoxin A production in P. aeruginosa. The physiological relevance of this connection remains unclear, and it needs to be established whether a similar relationship is also found in other bacteria.
Topics: Gene Expression Regulation, Bacterial; Glucose; Metabolic Networks and Pathways; Pseudomonas aeruginosa; Pseudomonas putida; Transcription Factors
PubMed: 29607620
DOI: 10.1111/1751-7915.13263 -
Respiratory Medicine Oct 2017Altered composition of airway microbiota has been reported in subjects suffering from asthma but its relation to eosinophilic phenotype is unclear.
BACKGROUND
Altered composition of airway microbiota has been reported in subjects suffering from asthma but its relation to eosinophilic phenotype is unclear.
OBJECTIVE
To examine the relationship between sputum microbiota, asthma severity and inflammatory type in asthmatic subjects from Guangzhou, China.
METHODS
Induced sputum samples were obtained from 49 non-smoking asthma patients, 25 severe and 24 non-severe, and 15 healthy subjects. Total DNA was amplified using primers specific for the V3-V5 hypervariable region of bacterial 16s rRNA and sequenced using the 454 GS FLX sequencer. Sequences were assigned to bacterial taxa by comparing them with 16s rRNA sequences in the Ribosomal Database Project.
RESULTS
Sputum eosinophil counts were higher and FEV (% predicted) was lower in severe compared to non-severe asthmatics. There were no significant differences in operational taxonomic unit (OTU) numbers at the phylum level and in diversity scores between non-severe asthmatics and severe asthmatics, and healthy subjects. At the family level, Porphyromonadaceae was most abundant in healthy subjects whereas Pseudomonadaceae and Enterobacteriaceae were higher in severe asthmatics compared to non-severe asthmatics (p < 0.05). Actinomycetaceae was particularly abundant in eosinophilic asthma patients compared to non-eosinophilic asthma (p = 0.011). Bacteroidaceae was positively correlated with FEV in all subjects (r = 0.335, p < 0.01), whereas body mass index was negatively associated with the number of species observed (r = -0.3, p < 0.05). Principal component analysis confirmed the positive association of Actinomycetaceae and Enterobacteriaceae abundance with eosinophilic asthma.
CONCLUSION
Patients with asthma have an altered airway microbiota, with specific bacteria associated with severe asthma and the eosinophilic inflammatory phenotype.
Topics: Actinomycetaceae; Adult; Asthma; Bacteroidaceae; Case-Control Studies; China; Enterobacteriaceae; Eosinophils; Female; Forced Expiratory Volume; Humans; Inflammation; Leukocyte Count; Male; Microbiota; Middle Aged; Phenotype; Porphyromonas; Principal Component Analysis; Pseudomonadaceae; Pulmonary Eosinophilia; RNA, Ribosomal, 16S; Severity of Illness Index; Sputum
PubMed: 28947029
DOI: 10.1016/j.rmed.2017.08.016 -
Frontiers in Cellular and Infection... 2021Bacterial biofilms are important medically, environmentally and industrially and there is a need to understand the processes that govern functional synergy and dynamics...
Bacterial biofilms are important medically, environmentally and industrially and there is a need to understand the processes that govern functional synergy and dynamics of species within biofilm communities. Here, we have used a model, mixed-species biofilm community comprised of PAO1, Pf-5 and KP1. This biofilm community displays higher biomass and increased resilience to antimicrobial stress conditions such as sodium dodecyl sulfate and tobramycin, compared to monospecies biofilm populations. is present at low proportions in the community and yet, it plays a critical role in community function, suggesting it acts as a keystone species in this community. To determine the factors that regulate community composition, we focused on because of its pronounced impact on community structure and function. Specifically, we evaluated the role of the N-acyl homoserine lactone (AHL) dependent quorum sensing (QS) system of PAO1, which regulates group behaviors including biofilm formation and the production of effector molecules. We found that mixed species biofilms containing QS mutants had significantly altered proportions of and populations compared to mixed species biofilms with the wild type . Similarly, inactivation of QS effector genes, e.g. and , also governed the relative species proportions. While the absence of QS did not alter the proportions of the two species in dual species biofilms of and , it resulted in significantly lower proportions of in dual species biofilms with . These observations suggest that QS plays an important role in modulating community biofilm structure and physiology and affects interspecific interactions.
Topics: Acyl-Butyrolactones; Biofilms; Pseudomonas; Pseudomonas aeruginosa; Quorum Sensing
PubMed: 33869078
DOI: 10.3389/fcimb.2021.646991 -
FEMS Immunology and Medical Microbiology Aug 2010We review the recent advances in the understanding of the Pseudomonas aeruginosa biofilm lifestyle from studies using in vitro laboratory setups such as flow chambers... (Review)
Review
We review the recent advances in the understanding of the Pseudomonas aeruginosa biofilm lifestyle from studies using in vitro laboratory setups such as flow chambers and microtiter trays. Recent work sheds light on the role of nutrients, motility, and quorum sensing in structure formation in P. aeruginosa biofilms. The second messenger, c-di-GMP, is established as an important regulator of the synthesis of polysaccharide and protein components of the biofilm matrix. Extracellular DNA is shown to be an essential component of the biofilm matrix. It has become apparent that biofilm formation involves interactions between different subpopulations. The molecular mechanisms underlying the tolerance of biofilm bacteria to antimicrobial agents are beginning to be unraveled, and new knowledge has been obtained regarding the environmental cues and regulatory mechanisms involved in biofilm dispersal.
Topics: Anti-Bacterial Agents; Biofilms; DNA, Bacterial; Polysaccharides, Bacterial; Pseudomonas aeruginosa
PubMed: 20497222
DOI: 10.1111/j.1574-695X.2010.00690.x -
Microbiology (Reading, England) Mar 2019Pseudomonas syringae is best known as a plant pathogenic bacterium that causes diseases in a multitude of hosts, and it has been used as a model organism to understand...
Pseudomonas syringae is best known as a plant pathogenic bacterium that causes diseases in a multitude of hosts, and it has been used as a model organism to understand the biology of plant disease. Pathogenic and non-pathogenic isolates of P. syringae are also commonly found living as epiphytes and in the wider environment, including water sources such as rivers and precipitation. Ice-nucleating strains of P. syringae are associated with frost damage to crops. The genomes of numerous strains of P. syringae have been sequenced and molecular genetic studies have elucidated many aspects of this pathogen's interaction with its host plants.
Topics: Genome, Bacterial; Host-Pathogen Interactions; Phylogeny; Plant Diseases; Pseudomonas syringae; Water Microbiology
PubMed: 30427303
DOI: 10.1099/mic.0.000715