Hemolytic Escherichia coli Inhibits Swarming and Differentiation of Proteus mirabilis

Strain-level screening of human gut microbes identifies Blautia producta as a new anti-hyperlipidemic probiotic

Compelling evidence has tightly linked gut microbiota with host metabolism homeostasis and inspired novel therapeutic potentials against metabolic diseases (e.g., hyperlipidemia). However, the regulatory profile of individual bacterial species and strain on lipid homeostasis remains largely unknown. Herein, we performed a large-scale screening of 2250 human gut bacterial strains (186 species) for the lipid-decreasing activity. Different strains in the same species usually displayed distinct lipid-modulatory actions, showing evident strain-specificity. Among the tested strains, Blautia producta exhibited the most potency to suppress cellular lipid accumulation and effectively ameliorated hyperlipidemia in high fat diet (HFD)-feeding mice. Taking a joint comparative approach of pharmacology, genomics and metabolomics, we identified an anteiso-fatty acid, 12-methylmyristic acid (12-MMA), as the key active metabolite of Bl. Producta. In vivo experiment confirmed that 12-MMA could exert potent hyperlipidemia-ameliorating efficacy and improve glucose metabolism via activating G protein-coupled receptor 120 (GPR120). Altogether, our work reveals a previously unreported large-scale lipid-modulatory profile of gut microbes at the strain level, emphasizes the strain-specific function of gut bacteria, and provides a possibility to develop microbial therapeutics against hyperlipidemia based on Bl. producta and its metabolite.

Into the understanding the multicellular lifestyle of Proteus mirabilis on solid surfaces

Indwelling urinary catheterization can lead to the development of catheter-associated urinary tract infections (CAUTIs), an important type of nosocomial infection, as well as other medical issues among institutionalized adults. Recently, Proteus mirabilis was highlighted as the important cause of CAUTIs. The pathogenicity of P. mirabilis is dependent on two multicellular types of surface colonization: the adherence and swarming motility. Adhesion, mostly mediated by fimbrial and nonfimbrial adhesins, is important for the initiation of biofilm formation. Moreover, the production of urease frequently results in biofilm crystallization, which leads to the blockage of catheters. The heterologous polymeric matrix of the biofilm offers protection against antibiotics and the host immune system. P. mirabilis displays remarkable motility abilities. After contact with solid surfaces, hyper-flagellated cells are able to rapidly migrate. The importance of swarming motility in CAUTIs development remains controversial; however, it was indicated that swarming cells were able to co-express other virulence factors. Furthermore, flagella are strong immunomodulating proteins. On the other hand, both biofilm formation and swarming motility implicates multiple inter- and intraspecies interactions, which might contribute to the pathogenicity.

Inhibitors of Bacterial Swarming Behavior

Bacteria can migrate in groups of flagella-driven cells over semisolid surfaces. This coordinated form of motility is called swarming behavior. Swarming is associated with enhanced virulence and antibiotic resistance of various human pathogens and may be considered as favorable adaptation to the diverse challenges that microbes face in rapidly changing environments. Consequently, the differentiation of motile swarmer cells is tightly regulated and involves multi-layered signaling networks. Controlling swarming behavior is of major interest for the development of novel anti-infective strategies. In addition, compounds that block swarming represent important tools for more detailed insights into the molecular mechanisms of the coordination of bacterial population behavior. Over the past decades, there has been major progress in the discovery of small-molecule modulators and mechanisms that allow selective inhibition of swarming behavior. Herein, an overview of the achievements in the field and future directions and challenges will be presented.