Are you what you eat? A highly transient and prey-influenced gut microbiome in the grey house spider Badumna longinqua

Stable core microbial communities have been described in numerous animal
species and are commonly associated with fitness benefits for their hosts.
Recent research, however, highlights examples of species whose microbiota
are transient and environmentally derived. Here, we test the effect of
diet on gut microbial community assembly in the spider Badumna longinqua.
Using 16S rRNA gene amplicon sequencing combined with quantitative PCR, we
analyze diversity and abundance of the spider’s gut microbes, and
simultaneously characterize its prey communities using nuclear rRNA
markers. We find a clear correlation between community similarity of the
spider’s insect prey and gut microbial DNA, suggesting that microbiome
assembly is primarily diet-driven . This assumption is supported by a
feeding experiment, in which two types of prey – crickets and fruit flies
– both substantially altered microbial diversity and community similarity
between spiders, but did so in different ways. After cricket consumption,
numerous cricket-derived microbes appeared in the spider’s gut, resulting
in a rapid homogenization of microbial communities among spiders. In
contrast, few prey-associated bacteria were detected after consumption of
fruit flies; instead, the microbial community was remodeled by
environmentally sourced microbes, or abundance shifts of rare taxa in the
spider’s gut. The reshaping of the microbiota by both prey taxa mimicked a
stable core microbiome in the spiders for several weeks post feeding. Our
results suggest that the spider’s gut microbiome undergoes pronounced
temporal fluctuations, that its assembly is dictated by the consumed prey,
and that different prey taxa may remodel the microbiota in drastically
different ways.