Machine learning-based motion tracking reveals an inverse correlation between adhesivity and surface motility of the leptospirosis spirochete

Colonization Mediated by T6SS-ClpV Disrupts Host Gut Microbiota and Enhances Virulence of Salmonella enterica serovar Typhimurium

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a common foodborne enteric pathogen that infects humans or mammals and colonizes the intestinal tract primarily by invading the host following ingestion. Meanwhile, ClpV is a core secreted protein of the bacterial type VI secretion system (T6SS). Because elucidating ClpV's role in the pathogenesis of T6SS is pivotal for revealing the virulence mechanism of Salmonella, in our study, clpV gene deletion mutants were constructed using a λ-red-based recombination system, and the effect of clpV mutation on SL1344's pathogenicity was examined in terms of stress resistance, motility, cytokine secretion, gut microbiota, and a BALB/c mouse model. Among the results, ClpV affected SL1344's motility and was also involved in cell invasion, adhesion, and intracellular survival in the MDBK cell model but did not affect invasion or intracellular survival in the RAW264.7 cell model. Moreover, clpV gene deletion significantly reduced the transcription levels of GBP2b, IFNB1, IL-6, NLRP3, NOS2, and TNF-α proinflammatory factor levels but significantly increased transcription levels of IL-4 and IL-10 anti-inflammatory factors. Last, ClpV appeared to closely relate to the pathogenicity of S. Typhimurium in vivo, which can change the gut environment and cause dysbiosis of gut microbiota. Our findings elucidate the functions of ClpV in S. Typhimurium and illustrating interactions between T6SS and gut microbiota help to clarify the mechanisms of the pathogenesis of foodborne diseases.

It's not all about flagella - sticky invasion by pathogenic spirochetes

Pathogenic spirochetes cause a range of serious human diseases such as Lyme disease (LD), syphilis, leptospirosis, relapsing fever (RF), and periodontal disease. Motility is a critical virulence factor for spirochetes. From the mechanical perspective of the infection, it has been widely believed that flagella are the sole key players governing the migration and dissemination of these pathogens in the host. Here, we highlight the important contribution of spirochetal surface-exposed adhesive molecules and their dynamic interactions with host molecules in the process of infection, specifically in spirochetal swimming and crawling migration. We believe that these recent findings overturn the prevailing view depicting the spirochetal body to be just an inert elastic bag, which does not affect spirochetal cell locomotion.