Study of a Putative Niche Adapting Operon in Microbes Inhabiting the Gut of Blood Digesting Animals

The sialic acid utilization (SAU) operon is a horizontally acquired gene set that allows bacteria to utilize sialic acid as an alternate source of carbon and nitrogen in the guts of blood eating animals. Sialic acid often occurs as a terminal sugar in complex glycoproteins. It functions in cell signaling and adhesion. Sialic acid is an important component of the cellular envelope of animals. Some microorganisms have evolved to decorate their own surface with sialic acid to evade the host’s immune response (molecular mimicry). The SAU operon encodes enzymes that hydrolyze sialic acid from glycoproteins, transport sialic acid into the bacterial cytoplasm, and metabolize it into N-acetylglucosamine phosphate. This work provides an example for the role and evolution of niche adapting genes, illuminates the role of within and between species transfers of genomic islands, and illustrates that at least in some instances genes themselves are adapted to an ecological niche rather than the whole species. In contrast to reports from the literature, ongoing work on the vampire bat microbiome revealed a paucity of Aeromonads in the vampire bat gut microbiome and suggests Paraclostria as carriers of the SAU operon