Targeted Manipulation of Interspecies Competition of gut microbes: Campylobacter jejuni v/s. Lactobacillus johnsonii

Ghosh, Aditya (2022) Targeted Manipulation of Interspecies Competition of gut microbes: Campylobacter jejuni v/s. Lactobacillus johnsonii. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Aditya Ghosh (18MS045)) Thesis_18MS045.pdf - Submitted Version Restricted to Repository staff only Download (2MB)

Abstract

Campylobacter jejuni is one of the most common causes of foodborne illnesses, such as gastroenteritis and acute diarrhoea in humans. The avians, particularly chickens, are the natural host for C. jejuni and remain a primary source for human transmission through contaminated food and water. Like other Gram-negative gut pathogens, C. jejuni utilises various toxin secretion systems for host pathogenesis and competitive advantages in the complex gut environment. Among them, the recently characterised Type-VI Secretion System (T6SS) has been found to facilitate bacterial self-survival and prey killing to drive gut dysbiosis leading to the disruption of gut homeostasis. Recently it was shown that targeted manipulation of T6SS activity could cause “self-destruction” under environmental stress and the presence of prey bacteria, such as E. coli. Therefore, we expect that a similar strategy, if utilised under a carefully regulated gut environment, bacterial predation cost can be an effective strategy in mitigating gut colonisation of potentially harmful pathogens. To this end, the present study investigated whether the unique functional attributes of C. jejuni T6SS can be utilized for improvising gut health. We employed non-pathogenic but beneficial gut microbes (probiotics), Lactobacillus johnsonii, as interacting “prey” bacteria to explore the T6SS-dependent interspecies interactions. Here, we showed under altered growth conditions, co-culture of C. jejuni and L. johnsonii can lead to the perturbation of C. jejuni growth and proliferation. Further, we confirmed that in the presence of L. johnsonii, T6SS functionality could drive marked intracellular accumulation of bile salt leading to DNA damage and enhanced ROS generation in C. jejuni. Moreover, as a gut-friendly bacteria, selective use of L. johnsonii as an interacting bacterium, can have additional advantages in exhibiting bacteriocin-mediated antibacterial effects on C. jejuni. Together the data presented in this study suggest that targeted manipulation of T6SS-dependent functionality has great potential in the pervasiveness of host-microbes or microbes-microbes competition in the gut.

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