Cultivation-Independent Methods Reveal Differences among Bacterial Gut Microbiota in Triatomine Vectors of Chagas Disease

Abstract

BackgroundChagas disease is a trypanosomiasis whose agent is the protozoan parasite Trypanosoma cruzi, which is transmitted to humans by hematophagous bugs known as triatomines. Even though insecticide treatments allow effective control of these bugs in most Latin American countries where Chagas disease is endemic, the disease still affects a large proportion of the population of South America. The features of the disease in humans have been extensively studied, and the genome of the parasite has been sequenced, but no effective drug is yet available to treat Chagas disease. The digestive tract of the insect vectors in which T. cruzi develops has been much less well investigated than blood from its human hosts and constitutes a dynamic environment with very different conditions. Thus, we investigated the composition of the predominant bacterial species of the microbiota in insect vectors from Rhodnius, Triatoma, Panstrongylus and Dipetalogaster genera.Methodology/Principal FindingsMicrobiota of triatomine guts were investigated using cultivation-independent methods, i.e., phylogenetic analysis of 16s rDNA using denaturing gradient gel electrophoresis (DGGE) and cloned-based sequencing. The Chao index showed that the diversity of bacterial species in triatomine guts is low, comprising fewer than 20 predominant species, and that these species vary between insect species. The analyses showed that Serratia predominates in Rhodnius, Arsenophonus predominates in Triatoma and Panstrongylus, while Candidatus Rohrkolberia predominates in Dipetalogaster.Conclusions/SignificanceThe microbiota of triatomine guts represents one of the factors that may interfere with T. cruzi transmission and virulence in humans. The knowledge of its composition according to insect species is important for designing measures of biological control for T. cruzi. We found that the predominant species of the bacterial microbiota in triatomines form a group of low complexity whose structure differs according to the vector genus.

Triatomine bugs, their microbiota and Trypanosoma cruzi: asymmetric responses of bacteria to an infected blood meal

“…Some differences in the taxonomic composition of triatomine gut bacterial communities were found in our study, in comparison with previous results obtained with non-culture- [19, 20] and culture-based methods (reviewed in great extension by Vallejo et al [32]). A significant absence in our samples is Serratia , a genus of bacteria that have trypanolytic activity on specific T. cruzi strains [12].…”

“…Moreover, the ability of some T. cruzi strains to develop in certain vector species depends on the intrinsic qualities of either the parasite or the insect vector, as well as the resident host gut microbiota [18]. Previous studies using non-culturing based methods [19, 20] identified some triatomine gut microbiota characteristics: first, its diversity within each host is low with only one or few genera being dominant; secondly, some bacterial genera appear to be specific to certain triatomine hosts, i.e. Rhodococcus to Rhodnius and Arsenophonus to Triatoma ; finally, lab-reared insects lose part of the original microbiota diversity but conserve most of the bacterial groups found in their wild counterparts.…”

Cultivable Bacterial Diversity in the Gut of the Chagas Disease Vector Triatoma dimidiata: Identification of Possible Bacterial Candidates for a Paratransgenesis Approach

“…These results are also in accordance with a study by da Mota et al in 2012 that reported the characterization of the bacterial symbionts found in four triatomine genera, including two species of the Triatoma genus that inhabit South America (Triatoma infestans and T. vitticeps) (da Mota et al, 2012).…”

“…Previous studies have reported a low diversity of bacteria associated with the microbiota of triatomine insects in comparison to other insect groups (Vallejo et al, 2009;da Mota et al, 2012;Gumiel et al, 2015). Our results agree with this observation since we found only 14 different 16S rRNA sequences among all field collecting sites, laboratory specimens, and life stages of the insects.…”

Diverse Applications of Environmental DNA Methods in Parasitology

“…eDNA methods are more recently being applied to other hosts for example mammals [90], plants [91], and invertebrates. Examples of the latter include the use of 16S rDNA denaturing gradient gel electrophoresis (DGGE) and clone sequencing to suggest that vector gut microbiota may influence transmission and virulence of Trypanosoma cruzi [92], similar methods used for understanding gut microbiota assembly in the western corn rootworm (Coleoptera) and their potential as pathogen vectors [93], variation in bumble bee gut bacteriome between related species and how this varies with pathogen infections [94], and the suggestion via metatranscriptome sequencing that shifts in honey bee gut bacteria/community may be a marker of CCD [86]. Pathogens in the microbiotic environment in which organisms live are also important for health and as selective agents: metabarcoding of bacterial communities local to European minnow populations has shown that host-parasite interactions drive local adaptation of the major histocompatibility complex (MHC) class IIB loci, in relation to local pathogen diversities [95].…”