Abstract
BackgroundThe native gut microbiota of Anopheles mosquitoes is known to play a key role in the physiological function of its host. Interestingly, this microbiota can also influence the development of Plasmodium in its host mosquitoes. In recent years, much interest has been shown in the employment of gut symbionts derived from vectors in the control of vector-borne disease transmission. In this study, the midgut microbial diversity has been characterized among laboratory-reared adult Anopheles stephensi mosquitoes, from the colony created by rearing progeny of wild-caught mosquitoes (obtained from three different locations in southern India) for multiple generations, using 16S ribosomal RNA (rRNA) gene sequencing approach. Further, the influence of native midgut microbiota of mosquitoes on the development of rodent malaria parasite Plasmodium berghei in its host has been studied.MethodsThe microbial diversity associated with the midgut of An. stephensi mosquitoes was studied by sequencing V3 region of 16S ribosomal RNA (rRNA) gene. The influence of native midgut microbiota of An. stephensi mosquitoes on the susceptibility of the mosquitoes to rodent malaria parasite P. berghei was studied by comparing the intensity and prevalence of P. berghei infection among the antibiotic treated and untreated cohorts of mosquitoes.ResultsThe analysis of bacterial diversity from the midguts of An. stephensi showed Proteobacteria as the most dominant population among the three laboratory-reared strains of An. stephensi studied. Major genera identified among these mosquito strains were Acinetobacter, Pseudomonas, Prevotella, Corynebacterium, Veillonella, and Bacillus. The mosquito infectivity studies carried out to determine the implication of total midgut microbiota on P. berghei infection showed that mosquitoes whose native microbiota cleared with antibiotics had increased susceptibility to P. berghei infection compared to the antibiotic untreated mosquitoes with its natural native microbiota.ConclusionsThe use of microbial symbiont to reduce the competence of vectors involved in disease transmission has gained much importance in recent years as an emerging alternative approach towards disease control. In this context, the present study was aimed to identify the midgut microbiota composition of An. stephensi, and its effect on the development of P. berghei. Interestingly, the analysis of midgut microbiota from An. stephensi revealed the presence of genus Veillonella in Anopheles species for the first time. Importantly, the study also revealed the negative influence of total midgut microbiota on the development of P. berghei in three laboratory strains of An. stephensi, emphasizing the importance of understanding the gut microbiota in malaria vectors, and its relationship with parasite development in designing strategies to control malaria transmission.
Highlights
The native gut microbiota of Anopheles mosquitoes is known to play a key role in the physiological function of its host
Anopheles identification The mosquitoes collected from three cities of southern India, Bengaluru, Chennai and Mangaluru were identified as An. stephensi type form based on their morphological characteristics and egg ridge numbers [16,17,18]
Antibiotic treatments for mosquitoes Single cohort of 2–3 days old female An. stephensi were fed with combination of antibiotics (15 μg/ml gentamicin, and 100 units penicillin, 100 units streptomycin combination) in sterile 10% glucose solution containing 0.05% para-aminobenzoic acid for 3 days to clear the endogenous bacteria present in mosquitoes [14, 21]
Summary
The native gut microbiota of Anopheles mosquitoes is known to play a key role in the physiological function of its host. This microbiota can influence the development of Plasmodium in its host mosquitoes. The influence of native midgut microbiota of mosquitoes on the development of rodent malaria parasite Plasmodium berghei in its host has been studied. Prior to successful transmission of infective sporozoites to the vertebrate host, the parasite has to undergo a series of developmental transitions within the mosquito [3]. Various physiological and environmental factors, together with the presence of xanthurenic acid, trigger gametogenesis, where the male gametocytes undergo the process of exflagellation producing microgametes and female gametocytes to form macrogametes, and both are fused to form a fertilized zygote. The presence of microbiota in the gut of mosquitoes has gained increased attention in recent years for their ability to modulate Plasmodium infection in Anopheles mosquitoes [7, 12, 14]
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