Abstract
Background/MethodologyTriatomine bugs are the vectors of Trypanosoma cruzi, the agent of Chagas disease. Vector control has for decades relied upon insecticide spraying, but insecticide resistance has recently emerged in several triatomine populations. One alternative strategy to reduce T. cruzi transmission is paratransgenesis, whereby symbiotic bacteria are genetically engineered to produce T. cruzi-killing proteins in the vector’s gut. This approach requires in-depth knowledge of the vectors’ natural gut microbiota. Here, we use metagenomics (16S rRNA 454 pyrosequencing) to describe the gut microbiota of field-caught Triatoma sordida–likely the most common peridomestic triatomine in Brazil. For large nymphs (4th and 5th stage) and adults, we also studied separately the three main digestive-tract segments–anterior midgut, posterior midgut, and hindgut.Principal findingsBacteria of four phyla (12 genera) were present in both nymphs (all five stages) and adults, thus defining T. sordida’s ‘bacterial core’: Actinobacteria (Brevibacterium, Corynebacterium, Dietzia, Gordonia, Nitriliruptor, Nocardia, Nocardiopsis, Rhodococcus, and Williamsia), Proteobacteria (Pseudomonas and Sphingobium), and Firmicutes (Staphylococcus). We found some clear differences in bacterial composition and relative abundance among development stages; overall, Firmicutes and Proteobacteria increased, but Actinobacteria decreased, through development. Finally, the bacterial microbiotas of the bugs’ anterior midgut, posterior midgut, and hindgut were sharply distinct.Conclusions/SignificanceOur results identify the ‘bacterial core set’ of T. sordida and reveal important gut microbiota differences among development stages–particularly between 1st–3rd stage nymphs and adults. Further, we show that, within any given development stage, the vectors’ gut cannot be regarded as a single homogeneous environment. Cultivable, non-pathogenic ‘core’ bacterial species may now be tested as candidates for paratransgenic control of T. cruzi transmission by T. sordida.
Highlights
Chagas disease is a potentially life-threatening illness caused by the protozoan Trypanosoma cruzi
Sequences were clustered into 52 bacterial Operational taxonomic units (OTUs) representing 49 genera in 38 families and four phyla
We found no clear differences in bacterial OTU diversity across intestinal segments in the development stages we studied (Table 3)
Summary
Chagas disease is a potentially life-threatening illness caused by the protozoan Trypanosoma cruzi. T. cruzi is a parasite of mammals primarily transmitted through the feces of infected vectors–blood-sucking bugs of the subfamily Triatominae. As all stages feed on vertebrate blood, they are all prone to acquiring and transmitting T. cruzi [2]. Once the parasite arrives at the triatomine’s midgut with a blood meal, it comes into contact with the local microbiota. In the anterior midgut the parasite differentiates from the blood-borne trypomastigote to a spheromastigote, and to the epimastigote replicative form. Elongated epimastigotes attach to the waxy cuticle of the hindgut wall, multiply by binary fission, and change into the infective metacyclic trypomastigote form, which is excreted with the feces from the rectum, ready to begin a new infective cycle [4]
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