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Subject: Biotechnology and Molecular Biology × End date: 2017 × Start date: 2010 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    METAGENOMIC ANALYSIS OF GUT MICROFLORA OF FIELD AND LAB POPULATION OF TOBACCO CUTWORM (Spodoptera litura)
    (University of Agricultural Sciences, Dharwad, 2015-06) MANMOHAN KUMAR, D; PRASHANTHI, S.K.
    The insect gut harbors a variety of microorganisms that probably exceed the number of cells in insects themselves. These microorganisms can live and multiply in the insect, contributing to digestion, nutrition, and development of their host. Our study compared the bacterial communities in the larval gut of field and laboratory population of a polyphagous pest, tobacco caterpillar (Spodoptera litura) using denaturant gradient gel electrophoresis (DGGE) of amplified 16S rDNA gene sequence and by using Illumina MiSeq sequencing platform. The microbial composition of guts differed substantially among larvae collected from field and lab reared. Analysis of resulting sequence revealed that laboratory larval population harboured a relatively simple gut microflora as compared to field larval population consisting mostly Firmicutes (96.90%) and Proteabacteria (2.30%), whereas field population was diverse with having Proteobacteria (31.80%), Firmicutes (21.30%), Bacteriodetes (13.70%) and Acidobacteria (7.80%) as major genera. The lab-reared sample was rich in gram-positive species while the field sample harbors mainly Gram-negative species. DGGE results also revealed that higher bacterial diversity in the field population of larvae compared to laboratory population, interpreting the Shannon diversity index (Field H' = 2.55; Laboratory H' = 1.96) value. The simplicity of the gut bacteria community may reflect the narrower range of food available to laboratory-reared insects or other environmental factors that differ between the field and laboratory populations. Our attempts to elucidate role of gut bacteria towards suceptibilty to Bacillus thuringiensis did not give satisfactory result since the late instars of Spodoptera litura were insensitive to activity of cry toxins. Thus, understanding the composition and functional role of these gut microflora in insect growth and development will allow us to develop innovative strategies for pest management.