Structure, and culture of the gut microbiome of the Mormon cricket Anabrus simplex

Authors: SMITH, CHAD - University Of Texas At Austin; Srygley, Robert; HEALY, FRANK - Trinity University; SWAMINATH, KARTHIKEYAN - University Of Texas At Austin; MUELLER, ULRICH - University Of Texas At Austin

Submitted to: bioRxiv
Publication Type: Research Notes
Publication Acceptance Date: 1/23/2017
Publication Date: 1/23/2017
Citation: Smith, C.C., Srygley, R.B., Healy, F., Swaminath, K., Mueller, U.G. 2017. Structure, and culture of the gut microbiome of the Mormon cricket Anabrus simplex. bioRxiv. doi: https://doi.org/10.1101/080846.

Interpretive Summary: We investigated the guts of female Mormon crickets to determine the compartmentalization of their microbial communities. Although most of the 11 dominant bacterial types were common in all gut regions, we found lactic-acid bacteria were more common in the foregut and midgut, whereas enteric bacteria were more common in the hindgut. Previously we showed that mated female Mormon crickets maintain three Pediococcus phylotypes for which the abundances are greatly reduced in unmated females. These were found to be of highest abundance in the midgut and hindgut relative to the foregut. Lactic acid bacteria are known for their beneficial effects on insects, and prevalence of Pediococcus in the midgut might offset the insect’s vulnerability to pathogen invasion in this gut region relative to other regions. Pantoea agglomerans were abundant in the hindgut. In the desert locust, Pantoea produces a component of the aggregation pheromone and reduces susceptibility to pathogens. Low levels of divergence of the gut bacteria from those in plants and other insects suggest that the Mormon crickets frequently exchange bacteria with their environment.

Technical Abstract: The gut microbiome of insects plays an important role in their ecology and evolution, participating in nutrient acquisition, immunity, and behavior. Microbial community structure within the gut is heavily influenced by differences among gut regions in morphology and physiology, which determine the niches available for microbes to colonize. We present a high-resolution analysis of the structure of the gut microbiome in the Mormon cricket Anabrus simplex, an insect known for its periodic outbreaks in the Western United States and nutrition-dependent mating system. The Mormon cricket microbiome was dominated by eleven bacterial phylotypes from the Lactobacillaceae, Enterobacteriaceae, and Streptococcaeae. While most of these were represented in all gut regions, there were marked differences in their relative abundance, with lactic-acid bacteria (Lactobacillaceae) more common in the foregut and midgut and enteric (Enterobacteriaceae) bacteria more common in the hindgut. Differences in community structure were driven by variation in the relative prevalence of three groups: a Lactobacillus phylotype in the foregut, Pediococcus lactic-acid bacteria in the midgut, and Pantoea agglomerans, an enteric bacterium, in the hindgut. These taxa have been shown to have beneficial effects on their hosts in insects and other animals by improving nutrition, increasing resistance to pathogens, and modulating social behavior. Phylogenetic analysis of 16s rRNA sequences from cultured isolates indicated low levels of divergence from sequences derived from plants and other insects, suggesting that these bacteria are likely to be exchanged between Mormon crickets and the environment. Our study provides the foundation for future work on an economically important insect and emerging model for the study of how social interaction influence host-microbe symbiosis.