Greenhead (Tabanus nigrovittatus) and Its Microbiome: A Preliminary Study.

Endosymbiotic bacteria are known to influence the host physiology, microbiota composition, and dissemination of pathogens. We surveyed a population of Tabanus nigrovittatus, commonly referred to as "greenheads," from Crane Beach (Ipswich, MA, USA) for the presence of the alphaproteobacterial symbiont We studied the COI (mitochondrial cytochrome oxidase) marker gene to evaluate the phylogenetic diversity of the studied specimens. The DNA sequences show strong similarity (between 99.9 and 98%) among the collected specimens but lower similarity to closely related entries in the NCBI database (only between 96.3 and 94.7%), suggesting a more distant relatedness. Low levels of presence necessitated a nested PCR approach, and using 5 markers (, , , , and ), we determined that two recognized "supergroups" of species were represented in the studied specimens, members of clades A and B. Using next-generation sequencing, we also surveyed the insect gut microbiomes of a subset of flies, using Illumina and PacBio 16S rRNA gene sequencing with barcoded primers. The composition of also varied from fly to fly, with components belonging to making up the largest percentage of organisms (30 to 70%) among the microbiome samples. Most of the samples showed the presence of , a member of the phylum , although the frequency of its presence was variable, ranging from 2 to 57%. Another noteworthy bacterial phylum consistently identified was , though the read abundances were typically below 10%. Of interest is an association between presence and higher representation in the microbiomes, suggesting that the presence of affects the host microbiome. Tabanus nigrovittatus greenhead populations contain two supergroups of endosymbionts, members of supergroups A and B. Analysis of the greenhead microbiome using next-generation sequencing revealed that the majority of bacterial species detected belonged to , with most of the samples also showing the presence of , a member of the phylum also known to infect insects. An association between presence and higher Alphaproteobacteria representation in the microbiomes suggests that presence affects the host microbiome composition.