The Microbiota of Moon Snail Egg Collars is Shaped by Host-Specific Factors

ABSTRACT Moon Snails lay eggs using a mixture of mucus and sediment to form an egg mass commonly referred to as an egg collar. These collars do not appear to experience micro-biofouling or predation and this observation led us to hypothesize that the egg collars possess a chemically-rich microbiota that protect the egg collars from pathogens. Herein, we sought to gain an understanding of the bacterial composition of the egg collars by amplifying and sequencing the 16S rRNA gene from egg collar and sediment samples collected at four distinct geographical regions in SW Florida. Relative abundance and non-metric multidimensional scaling plots revealed distinct differences in the bacterial composition between the egg collar and sediment samples. In addition, the egg collars had a lower α-diversity than the sediment, with specific genera being significantly enriched in the egg collars. Analysis of microorganisms consistent across two seasons suggests that Flavobacteriaceae make up a large portion of the core microbiota (36 – 58% of 16S sequences). We also investigated the natural product potential of the egg collar microbiota by sequencing a core biosynthetic gene, the adenylation domains (AD), within the gene clusters of non-ribosomal peptide synthetase (NRPS). AD sequences matched multiple modules within known bioactive NRPs biosynthetic gene clusters, suggesting production is possible within the egg collar system and lays the foundation for future studies into the chemical and ecological role of this microbiota. IMPORTANCE Animals commonly partner with microorganisms to accomplish essential tasks, including chemically defending the animal host from predation and/or infections. Understanding animal-microbe partnerships and the molecules used by the microbe to defend the animals from pathogens or predation have the potential to lead to new pharmaceutical agents. However, very few of these systems have been investigated. A particularly interesting system are nutrient rich marine egg collars, which often lack visible protections, and are hypothesized to harbor beneficial microbes that protect the eggs. In this study, we gained an understanding of the bacterial strains that form the core microbiota of Moon Snail egg collars and gained a preliminary understanding of their natural product potential. This work lays the foundation for future work to understand the ecological role of the core microbiome and to study the molecules involved in chemically defending the Moon Snail eggs.