Iron interferes with quorum sensing-mediated cooperation in Pseudomonas aeruginosa by affecting the expression of ppyR and mexT, in addition to rhlR

Effect of LuxS/AI-2-mediated quorum sensing system on bacteriocin production of Lactobacillus plantarum NMD-17

Lactobacillus plantarum NMD-17 separated from koumiss could produce a bacteriocin named plantaricin MX against Gram-positive bacteria and Gram-negative bacteria. The bacteriocin synthesis of L. plantarum NMD-17 was remarkably induced in co-cultivation with Lactobacillus reuteri NMD-86 as the increase of cell numbers and AI-2 activity, and the expressions of luxS encoding signal AI-2 synthetase, plnB encoding histidine protein kinase, plnD encoding response regulator, and plnE and plnF encoding structural genes of bacteriocin were significantly upregulated in co-cultivation, showing that the bacteriocin synthesis of L. plantarum NMD-17 in co-cultivation may be regulated by LuxS/AI-2-mediated quorum sensing system. In order to further demonstrate the role of LuxS/AI-2-mediated quorum sensing system in the bacteriocin synthesis of L. plantarum NMD-17, plasmids pUC18 and pMD18-T simple were used as the skeleton to construct the suicide plasmids pUC18-UF-tet-DF and pMD18-T simple-plnB-tet-plnD for luxS and plnB-plnD gene deletion, respectively. luxS and plnB-plnD gene knockout mutants were successfully obtained by homologous recombination. luxS gene knockout mutant lost its AI-2 synthesis ability, suggesting that LuxS protein encoded by luxS gene is key enzyme for AI-2 synthesis. plnB-plnD gene knockout mutant lost the ability to synthesize bacteriocin against Salmonella typhimurium ATCC14028, indicating that plnB-plnD gene was a necessary gene for bacteriocin synthesis of L. plantarum NMD-17. Bacteriocin synthesis, cell numbers, and AI-2 activity of luxS or plnB-plnD gene knockout mutants in co-cultivation with L. reuteri NMD-86 were obviously lower than those of wild-type strain in co-cultivation at 6-9 h (P < 0.01). The results showed that LuxS/AI-2-mediated quorum sensing system played an important role in the bacteriocin synthesis of L. plantarum NMD-17 in co-cultivation.

PtsN in Pseudomonas aeruginosa Is Phosphorylated by Redundant Upstream Proteins and Impacts Virulence-Related Genes

The bacterial nitrogen-related phosphotransfer (PTSNtr; here, Nitro-PTS) system bears homology to well-known PTS systems that facilitate saccharide import and phosphorylation. The Nitro-PTS comprises an enzyme I (EI), PtsP; an intermediate phosphate carrier, PtsO; and a terminal acceptor, PtsN, which is thought to exert regulatory effects that depend on its phosphostate. For instance, biofilm formation by Pseudomonas aeruginosa can be impacted by the Nitro-PTS, as deletion of either ptsP or ptsO suppresses Pel exopolysaccharide production and additional deletion of ptsN elevates Pel production. However, the phosphorylation state of PtsN in the presence and absence of its upstream phosphotransferases has not been directly assessed, and other targets of PtsN have not been well defined in P. aeruginosa. We show that PtsN phosphorylation via PtsP requires the GAF domain of PtsP and that PtsN is phosphorylated on histidine 68, as in Pseudomonas putida. We also find that FruB, the fructose EI, can substitute for PtsP in PtsN phosphorylation but only in the absence of PtsO, implicating PtsO as a specificity factor. Unphosphorylatable PtsN had a minimal effect on biofilm formation, suggesting that it is necessary but not sufficient for the reduction of Pel in a ptsP deletion. Finally, we use transcriptomics to show that the phosphostate and the presence of PtsN do not appear to alter the transcription of biofilm-related genes but do influence genes involved in type III secretion, potassium transport, and pyoverdine biosynthesis. Thus, the Nitro-PTS influences several P. aeruginosa behaviors, including the production of its signature virulence factors. IMPORTANCE The PtsN protein impacts the physiology of a number of bacterial species, and its control over downstream targets can be altered by its phosphorylation state. Neither its upstream phosphotransferases nor its downstream targets are well understood in Pseudomonas aeruginosa. Here, we examine PtsN phosphorylation and find that the immediate upstream phosphotransferase acts as a gatekeeper, allowing phosphorylation by only one of two potential upstream proteins. We use transcriptomics to discover that PtsN regulates the expression of gene families that are implicated in virulence. One emerging pattern is a repression hierarchy by different forms of PtsN: its phosphorylated state is more repressive than its unphosphorylated state, but the expression of its targets is even higher in its complete absence.

The immune responses to different Uropathogens call individual interventions for bladder infection

Urinary tract infection (UTI) caused by uropathogens is the most common infectious disease and significantly affects all aspects of the quality of life of the patients. However, uropathogens are increasingly becoming antibiotic-resistant, which threatens the only effective treatment option available-antibiotic, resulting in higher medical costs, prolonged hospital stays, and increased mortality. Currently, people are turning their attention to the immune responses, hoping to find effective immunotherapeutic interventions which can be alternatives to the overuse of antibiotic drugs. Bladder infections are caused by the main nine uropathogens and the bladder executes different immune responses depending on the type of uropathogens. It is essential to understand the immune responses to diverse uropathogens in bladder infection for guiding the design and development of immunotherapeutic interventions. This review firstly sorts out and comparatively analyzes the immune responses to the main nine uropathogens in bladder infection, and summarizes their similarities and differences. Based on these immune responses, we innovatively propose that different microbial bladder infections should adopt corresponding immunomodulatory interventions, and the same immunomodulatory intervention can also be applied to diverse microbial infections if they share the same effective therapeutic targets.

Design of Polymeric Thin Films to Direct Microbial Biofilm Growth, Virulence, and Metabolism

Biofilms are ubiquitous in nature, yet strategies to direct biofilm behavior without genetic manipulation are limited. Due to the small selection of materials that have been used to successfully grow biofilms, the availability of functional materials that are able to support growth and program microbial functions remains a critical bottleneck in the design and deployment of functional yet safe microbes. Here, we report the design of insoluble pyridine-rich polymer surfaces synthesized using initiated chemical vapor deposition, which led to modulated biofilm growth and virulence in Pseudomonas aeruginosa (PAO1). A variety of extracellular virulence factors exhibited decreased production in response to the functional polymer, most significantly biomolecules also associated with iron acquisition, validating the material design strategy reported here. This report signifies a rich potential for materials-based strategies to direct the behavior of naturally occurring biofilms, which complement the existing genetic engineering toolkits in advancing microbiology, translational medicine, and biomanufacturing.