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Frontiers in Microbiology 2023Bacterial communication is a fundamental process used to synchronize gene expression and collective behavior among the bacterial population. The most studied bacterial...
Bacterial communication is a fundamental process used to synchronize gene expression and collective behavior among the bacterial population. The most studied bacterial communication system is quorum sensing, a cell density system, in which the concentration of inductors increases to a threshold level allowing detection by specific receptors. As a result, bacteria can change their behavior in a coordinated way. While in quorum sensing based on the synthesis of -acyl homoserine lactone molecules is well studied, volatile organic compounds, although considered to be communication signals in the rhizosphere, are understudied. The MFE01 strain has a very active type six secretion system that can kill some competitive bacteria. Furthermore, MFE01 emits numerous volatile organic compounds, including 1-undecene, which contributes to the aerial inhibition of growth. Finally, MFE01 appears to be deprived of -acyl homoserine lactone synthase. The main objective of this study was to explore the role of 1-undecene in the communication of MFE01. We constructed a mutant affected in gene encoding the enzyme responsible for 1-undecene synthesis to provide further insight into the role of 1-undecene in MFE01. First, we studied the impacts of this mutation both on volatile organic compounds emission, using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry and on long-range inhibition. Then, we analyzed influence of 1-undecene on MFE01 coordinated phenotypes, including type six secretion system activity and biofilm formation. Next, to test the ability of MFE01 to synthesize -acyl homoserine lactones in our conditions, we investigated the presence of corresponding genes across the MFE01 genome and we exposed its biofilms to an acyl homoserine lactone-degrading enzyme. Finally, we examined the effects of 1-undecene emission on MFE01 biofilm maturation and aerial communication using an original experimental set-up. This study demonstrated that the Δ mutant is impaired in biofilm maturation. An exposure of the Δ mutant to the volatile compounds emitted by MFE01 during the biofilm development restored the biofilm maturation process. These findings indicate that MFE01 uses 1-undecene emission for aerial communication, reporting for the first time this volatile organic compound as bacterial intraspecific communication signal.
PubMed: 37908545
DOI: 10.3389/fmicb.2023.1264801 -
Pathogens (Basel, Switzerland) Feb 2023Beneficial bacteria with antibacterial properties are attractive alternatives to chemical-based antibacterial or bactericidal agents. Our study sourced such bacteria...
Beneficial bacteria with antibacterial properties are attractive alternatives to chemical-based antibacterial or bactericidal agents. Our study sourced such bacteria from horticultural produce and environments to explore the mechanisms of their antimicrobial properties. Five strains of were studied that possessed antibacterial activity against the pathogen . The vegetative culture of these strains (-PFR46I06, -PFR46H06, -PFR46H07, -PFR46H08 and -PFR46H09) were tested against (n = 31), (n = 1) and (n = 1) isolated from seafood and horticultural sources and from clinical cases (n = 2) using solid media coculture and liquid media coculture. All strains were inhibited by all strains of ; however, -PFR46H07, -PFR46H08 and -PFR46H09 on solid media showed good inhibition, with average zones of inhibition of 14.8 mm, 15.1 mm and 18.2 mm, respectively, and the other two strains and -PFR46H09 had a significantly greater zone of inhibition than the others ( < 0.05). There was no inhibition observed in liquid media coculture or in culture supernatants against spp. by any of the strains. Therefore, we hypothesized that the structural apparatus that causes cell-to-cell contact may play a role in the ejection of ant-listeria molecules on solid media to inhibit isolates, and we investigated the structural protein differences using whole-cell lysate proteomics. We paid special attention to the type VI secretion system (-T6SS) for the transfer of effector proteins or bacteriocins. We found significant differences in the peptide profiles and protein summaries between these isolates' lysates, and PFR46H06 and PFR46H07 possessed the fewest secretion system structural proteins (12 and 11, respectively), while PFR46H08 and PFR46H09 had 18 each. -PFR46H09, which showed the highest antimicrobial effect, had nine -T6SS structural proteins compared to only four in the other three strains.
PubMed: 36839621
DOI: 10.3390/pathogens12020349 -
Frontiers in Microbiology 2021is a typical spoiler of proteinaceous foods, and it is characterized by high spoilage activity. The sigma factor RpoN is a well-known regulator controlling nitrogen...
is a typical spoiler of proteinaceous foods, and it is characterized by high spoilage activity. The sigma factor RpoN is a well-known regulator controlling nitrogen assimilation and virulence in many pathogens. However, its exact role in regulating the spoilage caused by . is unknown. Here, an in-frame deletion mutation of was constructed to investigate its global regulatory function through phenotypic and RNA-seq analysis. The results of phenotypic assays showed that the mutant was deficient in swimming motility, biofilm formation, and resistance to heat and nine antibiotics, while the mutant increased the resistance to HO. Moreover, the mutant markedly reduced extracellular protease and total volatile basic nitrogen (TVB-N) production in sterilized fish juice at 4°C; meanwhile, the juice with the mutant showed significantly higher sensory scores than that with the wild-type strain. To identify RpoN-controlled genes, RNA-seq-dependent transcriptomics analysis of the wild-type strain and the mutant was performed. A total of 1224 genes were significantly downregulated, and 474 genes were significantly upregulated by at least two folds at the RNA level in the mutant compared with the wild-type strain, revealing the involvement of RpoN in several cellular processes, mainly flagellar mobility, adhesion, polysaccharide metabolism, resistance, and amino acid transport and metabolism; this may contribute to the swimming motility, biofilm formation, stress and antibiotic resistance, and spoilage activities of . . Our results provide insights into the regulatory role of RpoN of . in food spoilage, which can be valuable to ensure food quality and safety.
PubMed: 34135871
DOI: 10.3389/fmicb.2021.641844 -
BMC Microbiology Jul 2020Pseudomonas fluorescens 2P24 is a rhizosphere bacterium that produces 2,4-diacetyphloroglucinol (2,4-DAPG) as the decisive secondary metabolite to suppress soilborne...
BACKGROUND
Pseudomonas fluorescens 2P24 is a rhizosphere bacterium that produces 2,4-diacetyphloroglucinol (2,4-DAPG) as the decisive secondary metabolite to suppress soilborne plant diseases. The biosynthesis of 2,4-DAPG is strictly regulated by the RsmA family proteins RsmA and RsmE. However, mutation of both of rsmA and rsmE genes results in reduced bacterial growth.
RESULTS
In this study, we showed that overproduction of 2,4-DAPG in the rsmA rsmE double mutant influenced the growth of strain 2P24. This delay of growth could be partially reversal when the phlD gene was deleted or overexpression of the phlG gene encoding the 2,4-DAPG hydrolase in the rsmA rsmE double mutant. RNA-seq analysis of the rsmA rsmE double mutant revealed that a substantial portion of the P. fluorescens genome was regulated by RsmA family proteins. These genes are involved in the regulation of 2,4-DAPG production, cell motility, carbon metabolism, and type six secretion system.
CONCLUSIONS
These results suggest that RsmA and RsmE are the important regulators of genes involved in the plant-associated strain 2P24 ecologic fitness and operate a sophisticated mechanism for fine-tuning the concentration of 2,4-DAPG in the cells.
Topics: Bacterial Proteins; Carbon; Gene Deletion; Gene Expression Regulation, Bacterial; Methyltransferases; Mutation; Phloroglucinol; Pseudomonas fluorescens; RNA-Binding Proteins; Sequence Analysis, RNA
PubMed: 32615927
DOI: 10.1186/s12866-020-01880-x -
Food Microbiology Feb 2022In this study, P. fluorescens-infecting phages were isolated, characterized, and evaluated to their potential to control the bacterial counts and, consequently, the...
In this study, P. fluorescens-infecting phages were isolated, characterized, and evaluated to their potential to control the bacterial counts and, consequently, the proteolytic spoilage of raw milk during cold storage. The UFJF_PfDIW6 and UFJF_PfSW6 phages showed titers of 9.7 and 7.6 log PFU/ml; latent period of 115 and 25 min, and burst size of 145 and 25 PFU/infected cell, respectively. They also were highly specific to the host bacterium, morphologically classified as the Podoviridae family, stable at pH 5 to 11 and were not inactivated at 63 °C or 72 °C for 30 min. These phages found to be effective against P. fluorescens, reducing bacterial count throughout the entire exponential growth phase in broth formulated with milk at both 4 °C and 10 °C. This effect on bacteria growth led to inhibition by at least 2 days in proteases production, delaying the degradation of milk proteins. When applied together in raw milk stored at 4 °C, they reduced the total bacteria, psychrotrophic, and Pseudomonas by 3 log CFU/ml. This study's findings indicate that these phages have a great potential to prevent the growth of Pseudomonas and, consequently, to retard proteolytic spoilage of raw milk during chilled storage.
Topics: Animals; Bacteriophages; Cold Temperature; Food Contamination; Food Microbiology; Food Storage; Milk; Peptide Hydrolases; Pseudomonas fluorescens
PubMed: 34579852
DOI: 10.1016/j.fm.2021.103892 -
Scientific Reports Feb 2021Pseudomonas are ubiquitously occurring microorganisms and are known for their ability to produce antimicrobials. An endophytic bacterial strain NP-1, isolated from...
Pseudomonas are ubiquitously occurring microorganisms and are known for their ability to produce antimicrobials. An endophytic bacterial strain NP-1, isolated from Eucalyptus dunnii leaves, exhibits antifungal properties against five tested phytopathogenic fungi. The strain is a Gram-negative rod-shaped bacterium containing a single polar flagellum. It is strictly aerobic, grows at 4-37 °C, 2-5% NaCl, and pH 3-7. The 16S rRNA sequence analysis showed that NP-1 belongs to the Pseudomonas genus. Phylogenetic analysis based on four concatenated partial genes (16S rDNA, gyrB, rpoB and rpoD) and the phylogenomic tree indicated that NP-1 belongs to Pseudomonas fluorescens lineage but is distinct from any known Pseudomonas species. The G + C mol % of NP-1 genome is 63.96, and the differences between NP-1 and related species are larger than 1. The digital DNA-DNA hybridization and tetranucleotide signatures are 23.8 and 0.97, which clearly separates strain NP-1 from its closest neighbours, Pseudomonas coleopterorum and Pseudomonas rhizosphaerae. Its phenotypic and chemotaxonomic features confirmed its differentiation from related taxa. The results from this polyphasic approach support the classification of NP-1 as a novel species of Pseudomonas, and the name of Pseudomonas eucalypticola is thus proposed for this strain, whose type is NP-1 (= CCTCC M2018494 = JCM 33572).
Topics: Antifungal Agents; Base Composition; Eucalyptus; Genome, Bacterial; Humans; Phylogeny; Plant Leaves; Pseudomonas; RNA, Ribosomal, 16S
PubMed: 33542376
DOI: 10.1038/s41598-021-82682-7 -
Frontiers in Microbiology 2023Although the bacterial composition of boar ejaculate has been extensively studied, the bacterial composition of extended boar semen is often overlooked, despite the...
Although the bacterial composition of boar ejaculate has been extensively studied, the bacterial composition of extended boar semen is often overlooked, despite the potential risks these microorganisms may pose to the long-term preservation of extended boar semen at 15-17°C. In this study, we characterized the bacterial community composition of extended semen and discovered that spp. was the dominant flora. The dominant strains were further isolated and identified as a potential new species in the group and named strain, which had adverse effects on sperm quality and was better adapted to growth at 17°C. Antimicrobial susceptibility testing showed that the strain was resistant to all commonly used veterinary antibiotics. Whole-genome sequencing (WGS) and genome annotation revealed the large genetic structure and function [7,253,751 base pairs and 6,790 coding sequences (CDSs)]. Comparative genomic analysis with the closest type strains showed that the strain predicted more diversity of intrinsic and acquired resistance genes to multi-antimicrobial agents. Taken together, our study highlights a problem associated with the long-term storage of extended boar semen caused by a group strain with unique biological characteristics. It is essential to develop a new antibacterial solution for the long-term preservation of boar semen.
PubMed: 37869660
DOI: 10.3389/fmicb.2023.1279630 -
Molecules (Basel, Switzerland) Oct 2022The objective of this study was to investigate the antimicrobial activities of essential oil-based microemulsions in the wash water against Escherichia coli O157:H7 and...
The objective of this study was to investigate the antimicrobial activities of essential oil-based microemulsions in the wash water against Escherichia coli O157:H7 and Pseudomonas fluorescens on Iceberg lettuce. Evaluated wash microemulsions included oregano oil, lemongrass oil, and cinnamon oil, along with a plant-based emulsifier for improved solubility. Iceberg lettuce was inoculated for 2 min with E. coli O157:H7 (6.0 log CFU/g) or P. fluorescens (6.0 log CFU/g) and then dip-treated in a phosphate buffered saline (PBS) control, 50 ppm chlorine, 3% hydrogen peroxide treatment or a 0.1%, 0.3%, or 0.5% microemulsion solution. Treated leaves were stored at 4 °C, and analyzed for surviving bacteria on days 0, 3, 7, 10, 14, 21, and 28. Efficacies of the antimicrobials were concentration and storage-time dependent. There was a 1.26−4.86 log CFU/g reduction in E. coli O157:H7 and significant reductions (0.32−2.35 log CFU/g) in P. fluorescens during storage at days 0−28 (p < 0.05). The 0.1% oregano oil microemulsion resulted in the best visual appeal in Iceberg leaves inoculated with E. coli O157:H7 and showed better improvement in the quality of the Iceberg leaves inoculated with spoilage bacteria P. fluorescens. The results suggest that 0.5% cinnamon and 0.3% oregano oil treatments have the potential to provide natural, eco-friendly, and effective alternatives to chemicals for the decontamination of leafy greens, eliminating E. coli O157:H7 and P. fluorescens.
Topics: Anti-Bacterial Agents; Anti-Infective Agents; Chlorine; Colony Count, Microbial; Escherichia coli O157; Food Contamination; Food Handling; Food Microbiology; Hydrogen Peroxide; Lactuca; Oils, Volatile; Phosphates; Water
PubMed: 36235235
DOI: 10.3390/molecules27196699 -
Italian Journal of Food Safety Jun 2022Bacteria belonging to the genus are ubiquitous and characterized by a high adaptation capability to different environmental conditions and wide range of temperatures....
Bacteria belonging to the genus are ubiquitous and characterized by a high adaptation capability to different environmental conditions and wide range of temperatures. They may colonize food, sometimes causing alteration. Quite recently, a blue pigmentation due to has been widely reported in mozzarella cheese. In this report, we describe a blue coloration occurred on rabbit meat stored in the refrigeration cell of a slaughterhouse. The alteration was observed after about 72 hours of storage at 4-6°C. Bacteriological analyses were performed, and a microorganism included in the group was identified. The experimental contamination was planned, using a bacterial suspension with 1×10 UFC/ml load to spread on rabbit carcasses. The blue pigmentation appeared after 24 hours of storage in a cell with the same conditions of temperature. The bacterium was reisolated and identified as responsible for the alteration on meat. These findings highlight the importance of considering the members of the genus and, more specifically, of the group when the microbiological quality of food is to be ascertained. In fact, even if these bacteria are not considered a public health problem, their presence should be monitored by food industry operators in self-control plans because they may cause alteration in food. In fact, any altered product should be withdrawn from the market in agreement with Regulation (EC) No 178/2002 of the European Parliament and of the Council.
PubMed: 35795461
DOI: 10.4081/ijfs.2022.9998 -
International Journal of Molecular... Nov 2020Biofilms consist of a complex microbial community adhering to biotic or abiotic surfaces and enclosed within a protein/polysaccharide self-produced matrix. The formation...
Biofilms consist of a complex microbial community adhering to biotic or abiotic surfaces and enclosed within a protein/polysaccharide self-produced matrix. The formation of this structure represents the most important adaptive mechanism that leads to antibacterial resistance, and therefore, closely connected to pathogenicity. Antimicrobial peptides (AMPs) could represent attractive candidates for the design of new antibiotics because of their specific characteristics. AMPs show a broad activity spectrum, a relative selectivity towards their targets (microbial membranes), the ability to act on both proliferative and quiescent cells, a rapid mechanism of action, and above all, a low propensity for developing resistance. This article investigates the effect at subMIC concentrations of Temporin-L (TL) on biofilm formation in () both in static and dynamic conditions, showing that TL displays antibiofilm properties. Biofilm formation in static conditions was analyzed by the Crystal Violet assay. Investigation of biofilms in dynamic conditions was performed in a commercial microfluidic device consisting of a microflow chamber to simulate real flow conditions in the human body. Biofilm morphology was examined using Confocal Laser Scanning Microscopy and quantified via image analysis. The investigation of TL effects on showed that when subMIC concentrations of this peptide were added during bacterial growth, TL exerted antibiofilm activity, impairing biofilm formation both in static and dynamic conditions. Moreover, TL also affects mature biofilm as confocal microscopy analyses showed that a large portion of preformed biofilm architecture was clearly perturbed by the peptide addition with a significative decrease of all the biofilm surface properties and the overall biomass. Finally, in these conditions, TL did not affect bacterial cells as the live/dead cell ratio remained unchanged without any increase in damaged cells, confirming an actual antibiofilm activity of the peptide.
Topics: Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Bacterial Adhesion; Biofilms; Biomass; Drug Resistance, Bacterial; Microbial Sensitivity Tests; Microfluidics; Microscopy, Confocal; Polymers; Polysaccharides, Bacterial; Pseudomonas fluorescens; Shear Strength; Stress, Mechanical; Surface Properties
PubMed: 33198325
DOI: 10.3390/ijms21228526