A Metagenomic Analysis of Bacterial Microbiota in the Digestive Tract of Triatomines

Abstract

The digestive tract of triatomines (DTT) is an ecological niche favored by microbiota whose enzymatic profile is adapted to the specific substrate availability in this medium. This report describes the molecular enzymatic properties that promote bacterial prominence in the DTT. The microbiota composition was assessed previously based on 16S ribosomal DNA, and whole sequenced genomes of bacteria from the same genera were used to calculate the GC level of rare and prominent bacterial species in the DTT. The enzymatic reactions encoded by coding sequences of both rare and common bacterial species were then compared and revealed key functions explaining why some genera outcompete others in the DTT. Representativeness of DTT microbiota was investigated by shotgun sequencing of DNA extracted from bacteria grown in liquid Luria-Bertani broth (LB) medium. Results showed that GC-rich bacteria outcompete GC-poor bacteria and are the dominant components of the DTT microbiota. In addition, oxidoreductases are the main enzymatic components of these bacteria. In particular, nitrate reductases (anaerobic respiration), oxygenases (catabolism of complex substrates), acetate-CoA ligase (tricarboxylic acid cycle and energy metabolism), and kinase (signaling pathway) were the major enzymatic determinants present together with a large group of minor enzymes including hydrogenases involved in energy and amino acid metabolism. In conclusion, despite their slower growth in liquid LB medium, bacteria from GC-rich genera outcompete the GC-poor bacteria because their specific enzymatic abilities impart a selective advantage in the DTT.

Ontogeny, species identity and environment dominate microbiome dynamics in wild populations of kissing bugs (Triatominae)

“…In our results, Dietzia, a bacterium closely related to Rhodococcus [93], is the dominant bacterium in late instars of T. rubida, T. protracta, and T. lecticularia. Dietzia has been described from other triatomine species [33,35,36,[42][43][44] and other hematophagous insects (Aedes albopictus [94], Glossina pallidipes [95]), suggesting it may be an important mutualist. However, unlike typical primary symbionts, Dietzia does not seem to be transmitted vertically.…”

“…Since 2015, twelve studies have investigated triatomine microbiomes using next-generation sequencing (NGS) tools. Unfortunately, the data lacks methodological consistency, having been retrieved from a wide variety of DNA templates, including pooled or individual bodies, entire abdomens, the distal part of the abdomen, whole guts, midguts, faeces, and cultured bacterial colonies [33][34][35][36][37][38][39][40][41][42][43][44], and often further complicated by other variables (e.g. sex, locality, instar, T. cruzi infection status).…”

“…To date, only a single study [41] has sampled microbiomes from multiple wild populations of any triatomine species. Others have mostly targeted South American vectors in domestic environments or laboratory-reared specimens [34,38,39,43,44], with little consideration for non-urban systems. In this study, we thus focus on wild populations of 5 Triatoma species in southern Texas and Arizona.…”

Ontogeny, species identity, and environment dominate microbiome dynamics in wild populations of kissing bugs (Triatominae)

“…In triatomines, thirteen high throughput sequencing studies published since 2015 have indicated a wide range of factors that potentially influence their microbiomes. However, it remains difficult to derive any consistent cross-species patterns since the studies utilised a wide variety of DNA templates, including pooled or individual bodies, entire abdomens, the distal part of the abdomen, whole guts, midguts, faeces, and cultured bacterial colonies [40][41][42][43][44][45][46][47][48][49][50][51][52], and were often further complicated by other variables (e.g., sex, locality, instar, T. cruzi infection status). Apart from these methodological differences, the disparity among studies could also reflect true biological characteristics of Triatominae.…”

“…To date, only a single study [52] has sampled microbiomes from multiple wild populations of any triatomine species. Others have mostly targeted South American vectors in domestic environments or laboratory-reared specimens [44][45][46][47][48][49], with little consideration for nonurban systems. In this study, we thus focus on wild populations of 5 Triatoma species in southern Texas and Arizona.…”