Presence of Bdellovibrio bacteriovorus increases lifespan in C. elegans nematodes by altering microbiota dynamics

In most ecosystems, a diverse microbiota contributes to stability - a principle applicable to host organisms. This is grounded in the enhanced functional redundancy associated with diversity, providing support during disturbances and mitigating dysbiosis risks. Predators like Bdellovibrio bacteriovorus influence community dynamics by creating niches. Indeed, B. bacteriovorus presence is associated with higher microbiota diversity of various hosts¹. However, identifying a causal relationship between predator presence, community dynamics, and host fitness requires controlled laboratory experiments using a suitable host, such as the nematode Caenorhabditis elegans.

This study aims to assess the probiotic potential of two B. bacteriovorus strains to influence microbiota diversity and composition using a C. elegans reference microbiota (CeMbio)².

Exposure to B. bacteriovorus induces changes in CeMbio structure, in both the nematode"s gut and the surrounding medium. Moreover, B. bacteriovorus MYbb2 (broad prey range), but not MYbb4 (narrow prey range), presence significantly increases C. elegans" mean lifespan. Interestingly, the microbiota of nematodes exposed to MYbb2 demonstrates increased relative abundances of Pseudomonas and Ochrobactrum. Members of these genera may benefit the nematode by providing bacterial vitamin B12 according to whole genome predictions³ and the results of a Pacdh-1p::gfp nematode reporter strain screen. Additionally, B12-supplementation of nematodes exposed to non-B12-producing CeMbio strains caused a significant increase in C. elegans longevity.

These findings underscore the intricate, context-dependent relationship between B. bacteriovorus, microbiota structure, and C. elegans' life-history traits, urging further analyses for a deeper understanding of these interactions and the impact of prey specificity in B. bacteriovorus.

¹ Johnke J. et al., Microb Ecol (2020)

² Dirksen P. et al., BMC Biol (2016)

³ Zimmerman J. et al., ISME (2020)