The microbiota of moon snail egg collars is shaped by host-specific factors.

Moon snails (Family: Naticidae) lay eggs using a mixture of mucus and sediment to form an egg mass commonly referred to as an egg collar. These egg 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 egg collars laid by a single species of moon snails, , by amplifying and sequencing the 16S rRNA gene from the egg collar and sediment samples collected at four distinct geographical regions in southwest 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 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 (ADs), within the gene clusters of non-ribosomal peptide synthetase (NRPS). AD sequences matched multiple modules within known NRPS gene clusters, suggesting that these compounds might be produced within the egg collar system. This study lays the foundation for future studies into the ecological role of the moon snail egg collar microbiota.IMPORTANCEAnimals 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 has the potential to lead to new pharmaceutical agents. However, very few of these systems have been investigated. A particularly interesting system is 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 microbiota and to study the molecules involved in chemically defending the moon snail eggs.