-
MSphere Mar 2021LuxR solos are related to quorum sensing (QS) LuxR family regulators; however, they lack a cognate LuxI family protein. LuxR solos are widespread and almost exclusively...
LuxR solos are related to quorum sensing (QS) LuxR family regulators; however, they lack a cognate LuxI family protein. LuxR solos are widespread and almost exclusively found in proteobacteria. In this study, we investigated the distribution and conservation of LuxR solos in the fluorescent pseudomonads group. Our analysis of more than 600 genomes revealed that the majority of fluorescent spp. carry one or more LuxR solos, occurring considerably more frequently than complete LuxI/LuxR archetypical QS systems. Based on the adjacent gene context and conservation of the primary structure, nine subgroups of LuxR solos have been identified that are likely to be involved in the establishment of communication networks. Modeling analysis revealed that the majority of subgroups shows some substitutions at the invariant amino acids of the ligand-binding pocket of QS LuxRs, raising the possibility of binding to non-acyl-homoserine lactone (AHL) ligands. Several mutants and gene expression studies on some LuxR solos belonging to different subgroups were performed in order to shed light on their response. The commonality of LuxR solos among fluorescent pseudomonads is an indication of their important role in cell-cell signaling. Cell-cell communication in bacteria is being extensively studied in simple settings and uses chemical signals and cognate regulators/receptors. Many Gram-negative proteobacteria use acyl-homoserine lactones (AHLs) synthesized by LuxI family proteins and cognate LuxR-type receptors to regulate their quorum sensing (QS) target loci. AHL-QS circuits are the best studied QS systems; however, many proteobacterial genomes also contain one or more LuxR solos, which are QS-related LuxR proteins which are unpaired to a cognate LuxI. A few LuxR solos have been implicated in intraspecies, interspecies, and interkingdom signaling. Here, we report that LuxR solo homologs occur considerably more frequently than complete LuxI/LuxR QS systems within the group of species and that they are characterized by different genomic organizations and primary structures and can be subdivided into several subgroups. The group consists of more than 50 species, many of which are found in plant-associated environments. The role of LuxR solos in cell-cell signaling in fluorescent pseudomonads is discussed.
Topics: Gene Expression Regulation, Bacterial; Genome, Bacterial; Pseudomonas fluorescens; Quorum Sensing; Repressor Proteins; Signal Transduction; Trans-Activators
PubMed: 33789944
DOI: 10.1128/mSphere.01322-20 -
Frontiers in Microbiology 20232P24 was isolated from soil of natural decay associated with wheat take-all and it can effectively control soil-borne diseases caused by a variety of plant pathogens....
INTRODUCTION
2P24 was isolated from soil of natural decay associated with wheat take-all and it can effectively control soil-borne diseases caused by a variety of plant pathogens. 2,4-diacetylphloroglucinol (2,4-DAPG), is produced by 2P24 and plays an important role in the prevention and control of plant diseases. To understand the resistant mechanism, in this study, we conducted experiments to explore the regulation role of in the synthesis of the antibiotic 2,4-DAPG and regulation of QS system.
METHODS
A random mini-Tn5 mutagenesis procedure was used to screen regulators for transcription in stain PM901, which containing a phlA∷lacZ transcriptional fusion reporter plasmid. We identified 12 insertion mutants could significantly change gene expression. By analyzing the amino acid sequences of the interrupted gene, we obtained a mutant strain Aa4-29 destroyed the gene, which encodes the omiga subunit. We constructed the plasmid of mutant (pBBR-△rpoZ) transformed into competent cells of 2P24 by electro-transformation assay. The strains of 2P24/pBBR, 2P24-△rpoZ/pBBR, 2P24-△rpoZ/pBBR-rpoZ were used to evaluate the regulation role of in 2,4-DAPG production and quorum sensing system.
RESULTS
According to β-galactosidase activity, we found that positively regulated the expression of (a synthesis gene of 2,4-DAPG) and (a synthesis gene of PcoI/PcoR QS signal system) at the transcriptional level. The production of 2,4-DAPG antibiotic and signal molecule AHL was influenced by . Further, was involved in regulating expression. also has a certain regulatory effect on transcription, but no effect on the transcription of , and . According to the biocontrol assay, 2P24 strains with showed obvious antagonism ability against the in cotton, while the mutant strain of lost the biocontrol effect. had a significant effect on the swimming and biofilm formation in 2P24.
CONCLUSION
Our data showed that was an important regulator of QS system, 2,4-DAPG in 2P24. This may imply that has evolved different regulatory features to adapt to different environmental threats.
PubMed: 37250031
DOI: 10.3389/fmicb.2023.1160913 -
Applied Microbiology and Biotechnology Oct 2023Early blight of tomato caused by Alternaria solani results in significant crop losses. In this study, Bacillus subtilis J3 and Pseudomonas fluorescens J8 were...
Early blight of tomato caused by Alternaria solani results in significant crop losses. In this study, Bacillus subtilis J3 and Pseudomonas fluorescens J8 were co-cultured as a synthetic microbial community (BCA) for synergistic biocontrol of A. solani, and the inhibition mechanism was investigated. BCA presented an inhibition ration against A. solani at 94.91%, which lowered the disease incidence by 38.26-42.87%; reduced peroxidase, catalase, superoxide dismutase activity of tomatoes by 73.11-90.22%; and promoted the biomass by 66.91-489.21%. With BCA protection, the relative expression of tomato resistance genes (including gPAL2, SWRKY, PR-10, and CHI) in roots and leaves was 12.83-90.70% lower than without protection. BCA also significantly altered the rhizosphere and phyllosphere microbial community. The abundance of potentially beneficial bacteria, including Bacillus, Pseudomonas, Arthrobacter, Lysobacter, and Rhizobium, elevated by 6.58-192.77%. They were negatively correlated with resistance gene expression, indicating their vital involvement in disease control. These results provided essential information on the synergistic biocontrol mechanism of bacteria against pathogens, which could contribute to developing novel biocontrol strategies. KEY POINTS: • Bacillus and Pseudomonas present a synergistic biocontrol effect against A. solani. • Biocontrol prevents pathogen damage and improves tomato growth and systemic resistance. • Beneficial bacteria thrive in the rhizosphere is the key to microbial regulation.
Topics: Pseudomonas fluorescens; Bacillus subtilis; Solanum lycopersicum; Pseudomonas; Bacillus; Plant Diseases
PubMed: 37540249
DOI: 10.1007/s00253-023-12642-w -
Microorganisms Jan 2022The present study evaluates the antimicrobial susceptibility of persister cells of and after their regrowth in suspension and as biofilms. Two conventional...
The present study evaluates the antimicrobial susceptibility of persister cells of and after their regrowth in suspension and as biofilms. Two conventional (benzalkonium chloride-BAC and peracetic acid-PAA) and two emerging biocides (glycolic acid-GA and glyoxal-GO) were selected for this study. Persister cells resulted from biofilms subjected to a critical treatment using the selected biocides. All biocide treatments developed persister cells, except PAA that effectively reduced the levels of vegetative cells and endospores. persister cells comprise viable and viable but non-culturable cells. Afterwards, persister cells were regrown in suspension and in biofilms and were subjected to a second biocide treatment. In general, planktonic cultures of regrown persister cells in suspension lost their antimicrobial tolerance, for both bacteria. Regrown biofilms of persister cells had antimicrobial susceptibility close to those regrown biofilms of biocide-untreated cells, except for regrown biofilms of persister after BAC treatment, which demonstrated increased antimicrobial tolerance. The most active biocide against persister cells was PAA, which did not promote changes in susceptibility after their regrowth. In conclusion, persister cells are ubiquitous within biofilms and survive after critical biocide treatment. The descendant planktonic and biofilms populations showed similar properties as the original ones.
PubMed: 35056610
DOI: 10.3390/microorganisms10010160 -
Annual Review of Microbiology Sep 2020Biofilms are the dominant bacterial lifestyle. The regulation of the formation and dispersal of bacterial biofilms has been the subject of study in many organisms. Over... (Review)
Review
Biofilms are the dominant bacterial lifestyle. The regulation of the formation and dispersal of bacterial biofilms has been the subject of study in many organisms. Over the last two decades, the mechanisms of biofilm formation and regulation have emerged as among the best understood of any bacterial biofilm system. Biofilm formation by occurs through the localization of an adhesin, LapA, to the outer membrane via a variant of the classical type I secretion system. The decision between biofilm formation and dispersal is mediated by LapD, a c-di-GMP receptor, and LapG, a periplasmic protease, which together control whether LapA is retained or released from the cell surface. LapA localization is also controlled by a complex network of c-di-GMP-metabolizing enzymes. This review describes the current understanding of LapA-mediated biofilm formation by and discusses several emerging models for the regulation and function of this adhesin.
Topics: Adhesins, Bacterial; Bacterial Proteins; Biofilms; Cyclic GMP; Gene Expression Regulation, Bacterial; Pseudomonas fluorescens
PubMed: 32689917
DOI: 10.1146/annurev-micro-011520-094214 -
Foods (Basel, Switzerland) Dec 2022Background: Mozzarella cheese possesses a high moisture content (50−60%) and a relatively high pH (around 5.5) and is therefore considered a perishable food product...
Background: Mozzarella cheese possesses a high moisture content (50−60%) and a relatively high pH (around 5.5) and is therefore considered a perishable food product characterized by high quality deterioration and the potential risk of microbial contamination. Moreover, it can be spoiled by Pseudomonas spp. and coliform bacteria, which may be involved in different negative phenomena, such as proteolysis, discolorations, pigmentation, and off-flavors. To prevent these, different methods were investigated. In this context, the present study aims to assess the antimicrobial effect of cellobiose oxidase on Pseudomonas fluorescens (5026) and Escherichia coli (k88, k99) in mozzarella cheese during refrigerated shelf life. Methods: microbiological challenge tests were designed by contaminating the mozzarella covering liquid containing different cellobiose oxidase concentrations with P. fluorescens (5026) and E. coli (k88, k99). The behavior of these microorganisms and the variation of hydrogen peroxide concentrations were then tested under refrigerated conditions for 20 days to simulate the mozzarella cheese shelf life. Results and Conclusions: The data obtained demonstrated the effect of cellobiose oxidase on microbial growth. In particular, E. coli (k88, k99) was inhibited over the entire shelf life, while P. fluorescens (5026) was only partially affected after a few days of refrigerated storage.
PubMed: 36613361
DOI: 10.3390/foods12010145 -
Biotechnologia 2021Endophytes are an important constituent of sustainable agriculture because of their ability to produce a large number of agriculturally important metabolites. A...
Endophytes are an important constituent of sustainable agriculture because of their ability to produce a large number of agriculturally important metabolites. A salt-tolerant fluorescent green pigment-producing endophytic bacterium was isolated on 2.5% NaCl-supplemented nutrient agar from the leaf samples of Roxb. The isolate Z1B4 was identified as based on morphological features, fatty acid methyl ester analysis, biochemical tests, and 16S rRNA gene sequencing. Z1B4 showed positive results for tricalcium phosphate solubilization; 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity; and production of auxins, siderophores, hydrogen cyanide, and ammonia. Z1B4 also showed strong antagonistic activity against (MTCC 283), (MTCC 3322), and (MTCC 1362) and exhibited stress tolerance to a wide range of temperature and pH and concentrations of NaCl and calcium salts. Under natural conditions, following inoculation with the isolate Z1B4, a significant increase in the growth of pea and maize test plants in pots was observed compared to that of uninoculated control plants. The rifampicin-resistant mutant Z1B4 was recovered from the roots, shoots, and leaves of the test plants, indicating that the isolated endophytic bacterium can grow well within different plant tissues. The present study indicated that the endophytic bacterium Z1B4 can be used as a bacterial inoculant in stressed environments for sustainable agriculture.
PubMed: 36606150
DOI: 10.5114/bta.2021.108725 -
World Journal of Microbiology &... Nov 2022Phosphate (Pi) is essential for life as it is an integral part of the universal chemical energy adenosine triphosphate (ATP), and macromolecules such as, DNA, RNA...
Phosphate (Pi) is essential for life as it is an integral part of the universal chemical energy adenosine triphosphate (ATP), and macromolecules such as, DNA, RNA proteins and lipids. Despite the core roles and the need of this nutrient in living cells, some bacteria can grow in environments that are poor in Pi. The metabolic mechanisms that enable bacteria to proliferate in a low phosphate environment are not fully understood. In this study, the soil microbe Pseudomonas (P.) fluorescens was cultured in a control and a low Pi (stress) medium in order to delineate how energy homeostasis is maintained. Although there was no significant variation in biomass yield in these cultures, metabolites like isocitrate, oxaloacetate, pyruvate and phosphoenolpyruvate (PEP) were markedly increased in the phosphate-starved condition. Components of the glycolytic, glyoxylate and tricarboxylic acid cycles operated in tandem to generate ATP by substrate level phosphorylation (SLP) as NADH-producing enzymes were impeded. The α-ketoglutarate (KG) produced when glutamine, the sole carbon nutrient was transformed into phosphoenol pyruvate (PEP) and succinyl-CoA (SC), two high energy moieties. The metabolic reprogramming orchestrated by isocitrate lyase (ICL), phosphoenolpyruvate synthase (PEPS), pyruvate phosphate dikinase (PPDK), and succinyl-CoA synthetase fulfilled the ATP budget. Cell free extract experiments confirmed ATP synthesis in the presence of such substrates as PEP, oxaloacetate and isocitrate respectively. Gene expression profiling revealed elevated transcripts associated with numerous enzymes including ICL, PEPS, and succinyl-CoA synthetase (SCS). This microbial adaptation will be critical in promoting biological activity in Pi-poor ecosystems.
Topics: Pseudomonas fluorescens; Adenosine Triphosphate; Isocitrates; Phosphates; Ecosystem; Phosphoenolpyruvate; Homeostasis; Pyruvic Acid; Oxaloacetates; Ligases
PubMed: 36319705
DOI: 10.1007/s11274-022-03432-z -
Scientific Reports Mar 2021The genome of Pseudomonas fluorescens F113, a model rhizobacterium and a plant growth-promoting agent, encodes three putative type VI secretion systems (T6SSs); F1-, F2-...
The genome of Pseudomonas fluorescens F113, a model rhizobacterium and a plant growth-promoting agent, encodes three putative type VI secretion systems (T6SSs); F1-, F2- and F3-T6SS. Bioinformatic analysis of the F113 T6SSs has revealed that they belong to group 3, group 1.1, and group 4a, respectively, similar to those previously described in Pseudomonas aeruginosa. In addition, in silico analyses allowed us to identify genes encoding a total of five orphan VgrG proteins and eight putative effectors (Tfe), some with their cognate immunity protein (Tfi) pairs. Genes encoding Tfe and Tfi are found in the proximity of P. fluorescens F113 vgrG, hcp, eagR and tap genes. RNA-Seq analyses in liquid culture and rhizosphere have revealed that F1- and F3-T6SS are expressed under all conditions, indicating that they are active systems, while F2-T6SS did not show any relevant expression under the tested conditions. The analysis of structural mutants in the three T6SSs has shown that the active F1- and F3-T6SSs are involved in interbacterial killing while F2 is not active in these conditions and its role is still unknown.. A rhizosphere colonization analysis of the double mutant affected in the F1- and F3-T6SS clusters showed that the double mutant was severely impaired in persistence in the rhizosphere microbiome, revealing the importance of these two systems for rhizosphere adaption.
Topics: Adaptation, Physiological; Gene Expression Regulation, Bacterial; Microbial Viability; Microbiota; Multigene Family; Phylogeny; Protein Domains; Pseudomonas fluorescens; Rhizosphere; Type VI Secretion Systems
PubMed: 33707614
DOI: 10.1038/s41598-021-85218-1 -
International Journal of Environmental... Sep 2020Bioremediation technology is one of the most profitable and sustainable strategies for remediating soils contaminated with hydrocarbons. This study focuses on assessing...
Bioremediation technology is one of the most profitable and sustainable strategies for remediating soils contaminated with hydrocarbons. This study focuses on assessing the influence of biostimulation and bioaugmentation with to contribute to the removal of total petroleum hydrocarbons (TPHs) of a soil. Laboratory studies were carried out (measurements of emitted CO, surface tension, and residual TPH) to select the best bioaugmentation and biostimulation treatment. The sources of C, N, and P were glucose-yeast extract, NHCl-NaNO, and KHPO-KPO, respectively. The effect of culture conditions on the reduction of TPH and respiratory activity was evaluated through a factorial design, 2, in a solid culture system. After 80 days of incubation, it was observed that treatments of yeast extract-NHCl-KHPO (Y4) and glucose-NaNO-KPO (Y5) presented a higher level of TPH removal (20.91% and 20.00% degradation of TPH, respectively). Biostimulation favors the production of biosurfactants, indirectly measured by the change in surface tension in the soil extracts. The treatments Y4 and Y5 showed a lower change value of the surface tension (23.15 and 23.30 mN·m at 25 °C). A positive correlation was determined between the change in surface tension and the removal of TPH; hence there was a contribution of the biosurfactants produced to the removal of hydrocarbons.
Topics: Biodegradation, Environmental; Biological Availability; Environmental Restoration and Remediation; Humans; Hydrocarbons; Nutrients; Petroleum; Pseudomonas fluorescens; Soil; Soil Microbiology; Soil Pollutants
PubMed: 32977570
DOI: 10.3390/ijerph17196959