Date Published: September 30, 2019
Publisher: Public Library of Science
Author(s): Suresh J. Gawande, Sivalingam Anandhan, Ashish Ingle, Praveen Roylawar, Kiran Khandagale, Tushar Gawai, Alana Jacobson, Ramasamy Asokan, Major Singh, Ulrich Melcher.
The gut microbial community structure of adult Thrips tabaci collected from 10 different agro-climatically diverse locations of India was characterized by using the Illumina MiSeq platform to amplify the V3 region of the 16S rRNA gene of bacteria present in the sampled insects. Analyses were performed to study the bacterial communities associated with Thrips tabaci in India. The complete bacterial metagenome of T. tabaci was comprised of 1662 OTUs of which 62.25% belong to known and 37.7% of unidentified/unknown bacteria. These OTUs constituted 21 bacterial phyla of 276 identified genera. Phylum Proteobacteria was predominant, followed by Actinobacteria, Firmicutes, Bacteroidetes and Cyanobacteria. Additionally, the occurrence of the reproductive endosymbiont, Wolbachia was detected at two locations (0.56%) of the total known OTUs. There is high variation in diversity and species richness among the different locations. Alpha-diversity metrics indicated the higher gut bacterial diversity at Bangalore and lowest at Rahuri whereas higher bacterial species richness at T. tabaci samples from Imphal and lowest at Jhalawar. Beta diversity analyses comparing bacterial communities between the samples showed distinct differences in bacterial community composition of T. tabaci samples from different locations. This paper also constitutes the first record of detailed bacterial communities associated with T. tabaci. The location-wise variation in microbial metagenome profile of T. tabaci suggests that bacterial diversity might be governed by its population genetic structure, environment and habitat.
Bacterial communities in insects play an important role in their growth, development, immunological, physiological and morphological functioning. The majority of insects are believed to harbour heritable bacterial symbionts  that can be pathogenic, mutualist, or commensal, with some required for survival while others are not. Across Insecta, microorganisms have been reported to positively influence many functions, including the production of essential amino acids from nutrient poor diets , protection against toxic agents [3–5], aide in the production of honey , protection against parasitoids , virus transmission , insecticide resistance , degradation of phytotoxins and pesticides . Conversely, some are reported to negatively impact insects by causing sterility and distorting sex ratios [11,12]. Despite their influence on important metabolic processes in the host, they have not been accurately profiled due to the difficulty in isolating and culturing many of the symbionts. Identification of symbionts has been improved with the availability of next generation sequencing technology, which, bypasses the need of isolating and culturing, can detect microbes present in very low amounts, and facilitates the study of the microbial community in its natural habitat with accurate taxonomic identification and their relative abundances . Characterizing the diversity of symbionts is an important first step towards understanding their importance in the life history of organisms.
Microorganisms exhibit a variety of interactions with their hosts and most of the time these interactions are beneficial to the insect . Despite being an economically important pest, the information on insect-microbe interactions of T. tabaci is very limited. Recently, NGS has become the method of choice for insect microbiome analyses due to the ability to detect both culturable and non-culturable bacteria. The present study constitutes the first detailed examination of bacterial communities in T. tabaci using sequencing methods. In this study phyla Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes together constituted more than 90% of the total T. tabaci identified microbiome. These phyla are also reported to be the predominant in the microbiomes of other thrips species [16,41,42], several insects [43,44,45], and amphibians .
This paper described the microbiome of T. tabaci collected from the different geographical locations of India using NGS approach. Findings of the present study increased understanding of microbiome of T. tabaci as well as its variation with respect to geography and climatic conditions. Though it is first report of its kind in T. tabaci, for more in depth study of T. tabaci microbiome needs to be done at different developmental stages for better understanding of its role in development and growth of T. tabaci.