Trophic diversification and parasitic invasion as ecological niche
modulators for gut microbiota of a sympatric pair of whitefish
Abstract
The impact of parasites on gut microbiota of the host is well
documented, but the role of the relationship between the parasite and
the host in the formation of the microbiota is poorly understood. Using
16S amplicon sequencing and newly developed methodological approaches,
we characterize the gut microbiota of the sympatric pair of whitefish
Coregonus lavaretus complex and the associated microbiota of cestodes
parasitizing their intestine. The essence of the proposed approaches is,
firstly, to use the method of successive washes of the microbiota from
the cestode’s surfaces to analyze the degree of bacterial association to
the tegument of the parasite. Secondly, to use a method combining the
sampling of intestinal content and mucosa with the wash-out procedure
from the mucosa to understand the real structure of the fish gut
microbiota. Our results demonstrate that the trophic diversification of
a sympatric pair of whitefish predetermines a segregation by ecological
niches of their respective microbial communities within their intestine.
Additional environmental niches for settlement of bacteria in the
intestine are formed by the parasitic helminths that caused the
restructuring of the bacterial community in infected fish compared to
those uninfected. Using the desorption method in Ringer’s solution, we
have demonstrated that Proteocephalus sp. cestodes possess their own
microbial community which is put together from “surface” bacteria
received from the host, bacteria which are weakly and strongly
associated with the tegument, and microbiota obtained after removal of
the tegument from the cestodes.