Predation by Bdellovibrio and like organisms (BALOs) to drive microbiome diversity

• Applicant: Dr. Julia Johnke
• Subject Area: Microbial Ecology and Applied Microbiology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 450059970

Loss of biodiversity is a global threat that affects ecosystem functioning and consequently ecosystem service. Both are directly linked to human health via the productions of goods, the regulation of ecosystem processes, and the provision of nonmaterial benefits. Thus, the link between biodiversity and ecosystem functioning does not only apply to conventional ecosystems, but also to hosts and their associated microbes. Indeed, it has been shown that microbiome dysbiosis is associated with inflammatory bowel disease. Probiotics and faecal transplants have been proposed to restore dysbiotic microbiome diversity, but show only short term and strong individual effects. There is therefore a need for alternatives. Potential allies against the loss of biodiversity are, according to ecological theory, organisms of higher trophic levels (i.e. predators) as they shape communities by reducing the abundance of dominant community members and freeing niches for rarer taxa. One understudied group of predators, the Bdellovibrio and like organisms (BALOs), is in that respect particularly interesting. BALOs are obligate predators of Gram-negative bacteria that can be found in almost all environments. In a pilot study, I was able to show that (i) BALO presence is associated with higher microbiome diversity across distinct host taxa. Additionally, (ii) BALO presence is able to drive microbial diversity over time in mixed liquid cultures containing communities of 12 and 50 members, respectively. This project is now aiming at identifying the effect of BALO presence on host-associated communities, using the well-studied model organism Caenorhabditis elegans as host. Specifically, with this project I aim to (i) understand the effect of BALO activity on microbiome structure (i.e. community composition, diversity, and microbe-microbe interactions) and stability (i.e. community structure after a disturbance) and (ii) understand the resulting consequences on host fitness (i.e. host population growth, brood size, and pathogen resistance), by applying highly controlled laboratory experiments. Lastly, metabolic modelling will be used to understand the functional consequences of a changed community structure. Here, a combination of whole genome and amplicon sequencing data will be used to identify the functional potential of community members at a given time point. This information will allow the inference of direct consequences of the presence or absence of a specific microbe on the community structure and its productivity and ultimately on host health. Together, these aims will help to unravel the probiotic potential of BALOs and the mechanisms behind it.

• DFG Programme: Research Grants