Insight into the surface discharge cold plasma efficient inactivation of Pseudomonas fluorescens in water based on exogenous reactive oxygen and nitrogen species: Synergistic mechanism and energy benefits.

As well known, surface discharge cold plasma has efficient inactivation ability and a variety of RONS are main active particles for inactivation, but their synergistic mechanism is still not clear. Therefore, surface discharge cold plasma system was applied to treat Pseudomonas fluorescens to study bacterial inactivation mechanism and energy benefit. Results showed that energy efficiency was directly proportional to applied voltage and inversely proportional to initial concentration. Cold plasma treatment for 20 min was inactivated by approximately > 4-log10Pseudomonas fluorescens and application of •OH and 1O2 scavengers significantly improved survival rate. In addition, •OH and 1O2 destroyed cell membrane structure and membrane permeability, which promoted diffusion of RONS into cells and affecting energy metabolism and antioxidant capacity, leading to bacterial inactivation. Furthermore, accumulation of intracellular NO and ONOOH was related to infiltration of exogenous RNS, while accumulation of •OH, H2O2, 1O2, O2- was the result of joint action of endogenous and exogenous ROS. Transcriptome analysis revealed that different RONS of cold plasma were responsible for Pseudomonas fluorescens inactivation and related to activation of intracellular antioxidant defense system and regulation of genes expression related to amino acid metabolism and energy metabolism, which promoting cellular process, catalytic activity and other biochemical pathways.

Complete genome sequence of a Pseudomonas fluorescens bacteriophage UNO-G1W1 isolated from freshwater ice in Nebraska.

We provide the complete genome sequence for a novel Pseudomonas fluorescens bacteriophage named UNO-G1W1. This phage was isolated from a single ice cover sampling. The genome was sequenced on the Nanopore MinION, generated with the direct terminal repeat-phage-pipeline and polished with Illumina short reads. Sequence identity classifies the phage as an otagovirus.

The antibacterial and inhibition effect of chitosan grafted gentisate acid derivatives against Pseudomonas fluorescens: Attacking multiple targets on structure, metabolism system, antioxidant system, and biofilm.

This work aimed to investigate the antibacterial ability and potential mechanism of chitosan grafted gentisate acid derivatives (CS-g-GA) against Pseudomonas fluorescens. The results showed that CS-g-GA had a significant suppressive impact on the growth of Pseudomonas fluorescens, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were 0.64 mg/mL and 1.28 mg/mL, respectively. Results of scanning electron microscopy (SEM) and alkaline phosphatase (AKPase) confirmed that CS-g-GA destroyed the cell structure thereby causing the leakage of intracellular components. In addition, 1 × MIC of CS-g-GA could significantly inhibit the formation of biofilms, and 74.78 % mature biofilm and 86.21 % extracellular polysaccharide of Pseudomonas fluorescens were eradicated by CS-g-GA at 2 × MIC. The results on the respiratory energy metabolism system and antioxidant system demonstrated that CS-g-GA caused respiratory disturbance and energy limitation by influencing the key enzyme activities. It could also bind to DNA and affect genetic metabolism. From this, it could be seen that CS-g-GA had the potential to control foodborne contamination of Pseudomonas fluorescens by attacking multiple targets.

Use of Lactoperoxidase Inhibitory Effects to Extend the Shelf Life of Meat and Meat Products.

Lactoperoxidase (LP) is an important enzyme of the salivary and mammary glands. It has been proven to increase the shelf life of raw milk by inhibiting the growth of bacteria, especially Listeria monocytogenes, Escherichia coli, Staphylococcus aureus, and Pseudomonas spp. The aim of this work was to verify the use of LP to extend the shelf life of meat products. In vitro experiments showed inhibitory effects on the selected bacteria (Listeria innocua (ATCC 33090), Staphylococcus saprophyticus (CP054440.1), and Pseudomonas fluorescens (ATCC 13525) due to a prolongation of the lag phase of growth curves. A lower increase in viable counts (p < 0.05) was also found by testing pork cubes' surface treated with LP solution (5%) + L. innocua and stored for 7 days at 15 °C. LP has also been studied at concentrations of 0.25 and 0.50% in meat products (pork ham and pâté) during refrigerated storage (4 °C for 28 days). Lower viable counts were observed throughout the storage experiment, especially for 0.50% LP (p < 0.05). Meat products containing LP also showed lower levels of oxidation (MAD) (p < 0.05). According to these results, LP could extend the shelf life of a wider range of products.

Pseudomonas fluorescens CRBSI outbreak: complying with the standardization of invasive procedures is a step ahead in the fight against antimicrobial resistance.

In the healthcare sector, the implementation of standardized procedures, such as those commonly employed in franchises to ensure consistent quality, remains underprioritized. Within this framework, we focus on the importance of standardized central venous catheter (CVC) insertion procedures to prevent healthcare-associated outbreaks. While antimicrobial resistance (AMR) may still not be the most prevalent problem in some institutions, its increasing significance certainly underlines the urgency of infection prevention.We aim to highlight this issue by describing and discussing an outbreak scenario of carbapenem-resistant (CR) Pseudomonas fluorescens bloodstream infections resulting from a deviation from the standardized CVC insertion procedure. This outbreak led to six episodes of catheter related bloodstream infection (CRBSI) in patients with hematologic malignancies, delaying their primary treatment. Nineteen patients were exposed, leading to an attack rate of 31.6%.

Inclusion of Pseudomonas fluorescens into soil-like fraction from municipal solid waste management park to enhance plastic biodegradation.

Single-use facial masks which are predominantly made out of polypropylene is being used and littered in large quantities during post COVID-19 situation. Extensive researches on bioremediation of plastic pollution on soil led to the identification of numerous plastic degrading microorganisms. These organisms assimilate plastic polymers as their carbon source for synthesizing energy. Pseudomonas fluorescens (PF) is one among such microorganism which is being identified to biodegrade plastic polymers in controlled environment. The natural biodegradation of facial mask in soil-like fraction collected from municipal waste management site, bioaugmentation of the degradation process with Pseudomonas fluorescens, biostimulation of the soil with carbonless nutritional supplements and combined bioaugmentation with biostimulation process were studied in the present work. The study has been conducted both in controlled and in natural condition for a period of 12 months. The efficiency of the degradation was verified through FTIR analyses using carbonyl index, bond energy change, Loss in ignition (LOI) measurement along with CHNS analyses of residual substances. The analysis of results reported that carbonyl index (in terms of transmittance) was reduced to 46% of the control batch through the inclusion of PF in natural condition. The bioaugmented batch maintained in natural condition showed 33% reduction of LOI with respect to the control batch. The unburnt carbon content of the residual matter obtained from the furnace were analysed using CHNS analyser and indicated the lowest carbon content in the same bioaugmented batch. In this study, an attempt is made to verify the feasibility of enhancing biodegradation of single-use facial mask by bioaugmentation of soil-like fraction available in solid waste management park with Pseudomonas fluorescens under natural condition. CHNS and FTIR analysis assures the biodegradation of plastic waste in the soil-like fraction using Pseudomonas fluorescens under both controlled and natural environmental condition.

Thoracic spine infection caused by Pseudomonas fluorescens: A case report and review of literature.

BACKGROUND: The clinical incidence of spinal infection is gradually increasing, and its onset is insidious, easily leading to missed diagnosis and misdiagnosis, which may lead to serious complications such as nervous system dysfunction, spinal instability and/or deformity, and cause a huge burden on society and families. Early identification of the causative agent and precision medicine will greatly reduce the suffering of patients. At present, the main pathogenic bacteria that cause spinal infection are Staphylococcus aureus, Streptococcus, Pneumococcus, Escherichia coli, and Klebsiella. There are no reports of spinal infection caused by Pseudomonas fluorescens. CASE SUMMARY: We report a 32-year-old female patient with spinal infection. She presented with flank pain, initially thought to be bone metastases or bone tuberculosis, and had a family background of tumors. Her clinical features and changes in imaging and laboratory tests led to the suspicion of thoracic spine infection. Histopathology of the lesion showed inflammation, tissue culture of the lesion was negative several times, and the possible pathogen - Pseudomonas fluorescens was found after gene sequencing of the lesion. The patient recovered completely after a full course of antibiotic treatment. CONCLUSION: This report increases the range of pathogens involved in spinal infections, highlights the unique advantages of gene sequencing technology in difficult-to-diagnose diseases, and validates conservative treatment with a full course of antibiotics for spinal infections without complications.

Multiple pathways impact the swarming motility of Pseudomonas fluorescens Pf0-1.

Swarming motility in pseudomonads typically requires both a functional flagellum and the production/secretion of a biosurfactant. Published work has shown that the wild-type Pseudomonas fluorescens Pf0-1 is swarming deficient due to a point mutation in the gacA gene, which until recently was thought to inactivate rather than attenuate the Gac/Rsm pathway. As a result, little is known about the underlying mechanisms that regulate swarming motility by P. fluorescens Pf0-1. Here, we demonstrate that a ΔrsmA ΔrsmE ΔrsmI mutant, which phenotypically mimics Gac/Rsm pathway overstimulation, is proficient at swarming motility. RsmA and RsmE appear to play a key role in this regulation. Transposon mutagenesis of the ΔrsmA ΔrsmE ΔrsmI mutant identified multiple factors that impact swarming motility, including pathways involved in flagellar synthesis and biosurfactant production/secretion. We find that loss of genes linked to biosurfactant Gacamide A biosynthesis or secretion impacts swarming motility, as does loss of the alternative sigma factor FliA, which results in a defect in flagellar function. Collectively, these findings provide evidence that P. fluorescens Pf0-1 can swarm if the Gac/Rsm pathway is activated, highlight the regulatory complexity of swarming motility in this strain, and demonstrate that the cyclic lipopeptide Gacamide A is utilized as a biosurfactant for swarming motility.IMPORTANCESwarming motility is a coordinated process that allows communities of bacteria to collectively move across a surface. For P. fluorescens Pf0-1, this phenotype is notably absent in the parental strain, and to date, little is known about the regulation of swarming in this strain. Here, we identify RsmA and RsmE as key repressors of swarming motility via modulating the levels of biosurfactant production/secretion. Using transposon mutagenesis and subsequent genetic analyses, we further identify potential regulatory mechanisms of swarming motility and link Gacamide A biosynthesis and transport machinery to swarming motility.

Local control: a hub-based model for the c-di-GMP network.

The genome of Pseudomonas fluorescens encodes >50 proteins predicted to play a role in bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP)-mediated biofilm formation. We built a network representation of protein-protein interactions and extracted key information via multidimensional scaling (i.e., principal component analysis) of node centrality measures, which measure features of proteins in a network. Proteins of different domain types (diguanylate cyclase, dual domain, phosphodiesterase, PilZ) exhibit unique network behavior and can be accurately classified by their network centrality values (i.e., roles in the network). The predictive power of protein-protein interactions in biofilm formation indicates the possibility of localized pools of c-di-GMP. A regression model showed a statistically significant impact of protein-protein interactions on the extent of biofilm formation in various environments. These results highlight the importance of a localized c-di-GMP signaling, extend our understanding of signaling by this second messenger beyond the current "Bow-tie Model," support a newly proposed "Hub Model," and suggest future avenues of investigation.

Use of systemic biofertilizers in sugarcane results in highly reproducible increments in yield and quality of harvests.

The utilization of a novel (systemic) biofertilizer containing Pseudomonas fluorescens, Azospirillum brasilense, and Bacillus subtilis and possessing the technology to facilitate the entry of bacteria through the stomata, was evaluated at three localities in Mexico (Potrero Nuevo, Veracruz; Ameca, Jalisco; and Champotón, Campeche) in two sugarcane varieties (NCO-310 and Mex 57-473) at different time scales. Inoculation of the systemic biofertilizer was imposed over the local agricultural management of the sugarcane; chemical fertilization of the experimental parcels at Potrero Nuevo was done using 70-20-20 and 120-80-80 at Ameca and Champotón. Three doses of the biofertilizer per hectare were applied during the annual productive cycle of sugarcane at each site; one year at Potrero Nuevo and Champotón; and six years at Ameca. The annual sugarcane yield was evaluated at each site. Additionally, sugar quality (°Brix or sucrose content) was evaluated at the three localities, while different variables of stalk performance were also measured at Ameca and Champotón. Our data provide evidence that this systemic biofertilizer consistently and reliably increased the sugarcane yield at all localities during the time of evaluation, ranging from 73.7 tons ha-1 at Potrero Nuevo (2.5 times increase; P < 0.05) and 77.7 tons ha-1 at Ameca (1.9 times increase; P < 0.05) to 23.8 tons ha-1 at Champotón (1.4 times increase; P < 0.05). This increase in sugarcane biomass was related to increased tillering rather than increased stalk height or diameter. This novel biological product improved the sugarcane quality in terms of °Brix (P < 0.05, 2.6° difference) and sucrose content (P < 0.5, 0.7% difference).

Reconstitution of a biofilm adhesin system from a sulfate-reducing bacterium in Pseudomonas fluorescens.

Biofilms of sulfate-reducing bacterium (SRB) like Desulfovibrio vulgaris Hildenborough (DvH) can facilitate metal corrosion in various industrial and environmental settings leading to substantial economic losses. Although the mechanisms of biofilm formation by DvH are not yet well understood, recent studies indicate the large adhesin, DvhA, is a key determinant of biofilm formation. The dvhA gene neighborhood resembles the biofilm-regulating Lap system of Pseudomonas fluorescens but is curiously missing the c-di-GMP-binding regulator LapD. Instead, DvH encodes an evolutionarily unrelated c-di-GMP-binding protein (DVU1020) that we hypothesized is functionally analogous to LapD. To study this unusual Lap system and overcome experimental limitations with the slow-growing anaerobe DvH, we reconstituted its predicted SRB Lap system in a P. fluorescens strain lacking its native Lap regulatory components (ΔlapGΔlapD). Our data support the model that DvhA is a cell surface-associated LapA-like adhesin with a N-terminal "retention module" and that DvhA is released from the cell surface upon cleavage by the LapG-like protease DvhG. Further, we demonstrate DVU1020 (named here DvhD) represents a distinct class of c-di-GMP-binding, biofilm-regulating proteins that regulates DvhG activity in response to intracellular levels of this second messenger. This study provides insight into the key players responsible for biofilm formation by DvH, thereby expanding our understanding of Lap-like systems.

Differential Immunogenicity and Lung Disease-Inducing Potential of Mycobacterium immunogenum Genotypes and Impact of Co-Exposure with Pseudomonas: Optimizing a Mouse Model of Chronic Hypersensitivity Pneumonitis.

Mycobacterium immunogenum (MI) colonizing metalworking fluids (MWFs) has been associated with chronic hypersensitivity pneumonitis (HP) in machinists. However, it is etiologically unclear why only certain mycobacteria-contaminated fluids induce this interstitial lung disease. We hypothesized that this may be due to differential immunogenicity and the HP-inducing potential of MI strains/genotypes as well as the confounding effect of co-inhaled endotoxin-producers. To test this hypothesis, we optimized a chronic HP mouse model in terms of MI antigen dose, timepoint of sacrifice, and form of antigen (cell lysates vs. live cells) and compared six different field-isolated MI strains. Overall, MJY10 was identified as the most immunogenic and MJY4 (or MJY13) as the least immunogenic genotype based on lung pathoimmunological changes as well as Th1 cellular response (IFN-γ release). Infection with MI live cells induced a more severe phenotype than MI cell lysate. Co-exposure with Pseudomonas fluorescens caused a greater degree of lung innate immune response and granuloma formation but a diminished adaptive (Th1) immune response (IFN-γ) in the lung and spleen. In summary, this study led to the first demonstration of differential immunogenicity and the disease-inducing potential of field strains of MI and an interfering effect of the co-contaminating Pseudomonas. The improved chronic MI-HP mouse model and the identified polar pair of MI strains will facilitate future diagnostic and therapeutic research on this poorly understood environmental lung disease.

A phenylalanine-free recombinant nutritional protein for the dietary management of phenylketonuria.

Phenylketonuria (PKU) is a congenital metabolic disorder that causes the systemic elevation of phenylalanine (Phe), which is neurotoxic and teratogenic. PKU is currently incurable, and management involves lifelong adherence to an unpalatable protein-restricted diet based on Phe-free amino acid mixtures. Seeking a palatable dietary alternative, we identified a Bacillus subtilis protein (GSP16O) with a well-balanced but low-Phe amino acid profile. We optimized the sequence and expressed a modified Phe-free version (GSP105) in Pseudomonas fluorescens, achieving yields of 20 g/L. The purified GSP105 protein has a neutral taste and smell, is highly soluble, and remains stable up to 80°C. Homozygous enu2 mice, a model of human PKU, were fed with diets containing either GSP105 or normal protein. The GSP105 diet led to normalization of blood Phe levels and brain monoamine neurotransmitter metabolites, and prevented maternal PKU. The GSP105 diet thus provides an alternative and efficacious dietary management strategy for PKU.

Characterization of soybean chitinase genes induced by rhizobacteria involved in the defense against Fusarium oxysporum.

Rhizobacteria are capable of inducing defense responses via the expression of pathogenesis-related proteins (PR-proteins) such as chitinases, and many studies have validated the functions of plant chitinases in defense responses. Soybean (Glycine max) is an economically important crop worldwide, but the functional validation of soybean chitinase in defense responses remains limited. In this study, genome-wide characterization of soybean chitinases was conducted, and the defense contribution of three chitinases (GmChi01, GmChi02, or GmChi16) was validated in Arabidopsis transgenic lines against the soil-borne pathogen Fusarium oxysporum. Compared to the Arabidopsis Col-0 and empty vector controls, the transgenic lines with GmChi02 or GmChi16 exhibited fewer chlorosis symptoms and wilting. While GmChi02 and GmChi16 enhanced defense to F. oxysporum, GmChi02 was the only one significantly induced by Burkholderia ambifaria. The observation indicated that plant chitinases may be induced by different rhizobacteria for defense responses. The survey of 37 soybean chitinase gene expressions in response to six rhizobacteria observed diverse inducibility, where only 10 genes were significantly upregulated by at least one rhizobacterium and 9 genes did not respond to any of the rhizobacteria. Motif analysis on soybean promoters further identified not only consensus but also rhizobacterium-specific transcription factor-binding sites for the inducible chitinase genes. Collectively, these results confirmed the involvement of GmChi02 and GmChi16 in defense enhancement and highlighted the diverse inducibility of 37 soybean chitinases encountering F. oxysporum and six rhizobacteria.

Chitosan-encapsulated microbial biofertilizer: A breakthrough for enhanced tomato crop productivity.

Encapsulation technology protects the beneficial microorganisms, which are the sources of Nitrogen (N), Phosphorus (P), and Potassium (K), with a carrier material and improves the nutrient uptake from the soil. Pseudomonas fluorescens, gram-negative bacteria, was selected as the microorganism for encapsulation. A chitosan carrier (3 %), a polysaccharide, was chosen for the encapsulation of the bacterial strain to use as biofertilizers by standardization with two carriers, sodium alginate and chitosan. P. fluorescens encapsulated with chitosan showed a higher shelf life than sodium alginate. The shelf life of the encapsulated culture (7 × 1010 CFU/mL) was maintained for ten months. Studies were performed with the encapsulated P. fluorescens to analyze its nature and characteristics. The pot and field studies were conducted with the encapsulated P. fluorescens for the tomato crop. The difference between the treated and control plants was observed based on biometric parameters like shoot length and root length, fruit weight, and number of branches and fruits per plant. This study reveals that encapsulated P. fluorescens improved the yield of the crops. In addition, soil health and fertility were also enhanced. Thus, encapsulated P. fluorescens could be a superior solution for promoting soil health and crop productivity for sustainable agriculture.

Adaptive laboratory evolution reveals regulators involved in repressing biofilm development as key players in Bacillus subtilis root colonization.

Root-associated microorganisms play an important role in plant health, such as plant growth-promoting rhizobacteria (PGPR) from the Bacillus and Pseudomonas genera. Although bacterial consortia including these two genera would represent a promising avenue to efficient biofertilizer formulation, we observed that Bacillus subtilis root colonization is decreased by the presence of Pseudomonas fluorescens and Pseudomonas protegens. To determine if B. subtilis can adapt to the inhibitory effect of Pseudomonas on roots, we conducted adaptative laboratory evolution experiments with B. subtilis in mono-association or co-cultured with P. fluorescens on tomato plant roots. Evolved isolates with various colony morphology and stronger colonization capacity of both tomato plant and Arabidopsis thaliana roots emerged rapidly from the two evolution experiments. Certain evolved isolates also had better fitness on the root in the presence of other Pseudomonas species. In all independent lineages, whole-genome resequencing revealed non-synonymous mutations in genes ywcC or sinR encoding regulators involved in repressing biofilm development, suggesting their involvement in enhanced root colonization. These findings provide insights into the molecular mechanisms underlying B. subtilis adaptation to root colonization and highlight the potential of directed evolution to enhance the beneficial traits of PGPR.IMPORTANCEIn this study, we aimed to enhance the abilities of the plant-beneficial bacterium Bacillus subtilis to colonize plant roots in the presence of competing Pseudomonas bacteria. To achieve this, we conducted adaptive laboratory experiments, allowing Bacillus to evolve in a defined environment. We successfully obtained strains of Bacillus that were more effective at colonizing plant roots than the ancestor strain. To identify the genetic changes driving this improvement, we sequenced the genomes of these evolved strains. Interestingly, mutations that facilitated the formation of robust biofilms on roots were predominant. Many of these evolved Bacillus isolates also displayed the remarkable ability to outcompete Pseudomonas species. Our research sheds light on the mutational paths selected in Bacillus subtilis to thrive in root environments and offers exciting prospects for improving beneficial traits in plant growth-promoting microorganisms. Ultimately, this could pave the way for the development of more effective biofertilizers and sustainable agricultural practices.

Pseudomonas fluorescens pneumonia.

Pseudomonas fluorescens (P. fluorescens) is not generally considered a bacterial pathogen in humans; however, multiple culture-based and culture-independent studies have identified it in the indigenous microbiota of multiple body sites. We herein report a rare case of pneumonia caused by P. fluorescens. A man in his 80 s with chronic obstructive pulmonary disease and diabetes mellitus was diagnosed with stage II rectal cancer. He underwent laparoscopic surgery, and on the 6th postoperative day, he developed a high fever. Chest computed tomography revealed infiltration in the left lower lung. Gram staining of the sputum showed Gram-negative rods phagocytosed by neutrophils, suggesting postoperative nosocomial pneumonia. The patient was started on tazobactam/piperacillin, and his pneumonia quickly improved. Later, only P. fluorescens was detected in a sputum culture. It was susceptible to common antipseudomonal agents. Gram staining of P. fluorescens appears to show a slightly thicker and larger morphology in comparison to Pseudomonas aeruginosa. Although there have been reports of opportunistic infections caused by P. fluorescens in immunosuppressed patients, including those with advanced cancer, most have been bloodstream infections, with very few reports of pneumonia alone. Clinicians should be aware that patients, who are not necessarily immunosuppressed, may develop pneumonia caused by P. fluorescens.

Safety evaluation of the food enzyme phosphoinositide phospholipase C from the genetically modified Pseudomonas fluorescens strain PIC.

The food enzyme phosphoinositide phospholipase C (1-phosphatidyl-1D-myo-inositol-4,5-bisphosphate inositoltrisphosphohydrolase EC 3.1.4.11.) is produced with the genetically modified Pseudomonas fluorescens strain PIC by DSM Food specialties B.V. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and its DNA. It is intended to be used in the processing of fats and oils for the production of refined edible fats and oils by degumming. Since residual amounts of the total organic solids are removed by the washing and purification steps applied during degumming, dietary exposure estimation and toxicity testing were considered unnecessary. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and no matches were found. The Panel considered that the risk of allergic reactions by dietary exposure cannot be excluded, but the likelihood for this to occur is low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Transcriptome Reveals Regulation of Quorum Sensing of Hafnia alvei H4 on the Coculture System of Hafnia alvei H4 and Pseudomonas fluorescens ATCC13525.

In the food industry, foodborne spoilage bacteria often live in mixed species and attach to each other, leading to changes in spoilage characteristics. Quorum sensing (QS) has been reported to be a regulating mechanism for food spoiling by certain kinds of bacteria. Here, the contents of biofilm, extracellular polysaccharides, and biogenic amines in the coculture system of Hafnia alvei H4 and Pseudomonas fluorescens ATCC13525 were significantly reduced when the QS element of H. alvei H4 was deleted, confirming that QS of H. alvei H4 is involved in the dual-species interactions. Then, transcriptomics was used to explore the regulatory mechanism at the mRNA molecular level. The deletion of the QS element decreased the transcript levels of genes related to chemotaxis, flagellar assembly, and the two-component system pathway of H. alvei H4 in the coculture system. Furthermore, a total of 732 DEGs of P. fluorescens ATCC13525 were regulated in the dual species, which were primarily concerned with biofilm formation, ATP-binding cassette transporters, and amino acid metabolism. Taken together, the absence of the QS element of H. alvei H4 weakened the mutual cooperation of the two bacteria in the coculture system, making it a good target for managing infection with H. alvei and P. fluorescens.

An inhibitor of the adaptability of Pseudomonas fluorescens in a high-salt environment. Phenomenon and mechanism of inhibition.

Pseudomonas fluorescens is a spoilage bacterium in food that has the ability to maintain growth and reproduction in high-salt environments. It acts as a defence mechanism through the exclusion of ions and the formation of biofilms. Hence, disrupting this defence mechanism may be a good way to control food spoilage. In this study, a specific flavonoid small molecule baicalin was found, which was able to dismantle the defence mechanism of the bacteria at a lower concentration (400 µM) of treatment. In synergy with salt, baicalin showed a significant inhibitory effect on the growth, c-di-gmp synthetics and biofilm formation of Pseudomonas fluorescens Pf08. Through transcriptomics, we also found that baicalein interfered with bacterial transport and polysaccharide production functions. Through molecular docking and QPCR, we found that baicalin is able to binding with the RpoS protein through hydrogen bonding and thus interfere with its function.