Screening of Nutritionally Important Gut Bacteria from the Lepidopteran Insects Through Qualitative Enzyme Assays

Abstract

Lepidopteran insects are the most dominant and diversified group among phytophagous pests and economically important insects. Gut bacteria has a continuous and dynamic effect on the host gut. In the present investigation, isolation and enumeration of the bacteria from the gut of three lepidopteran insects viz third instar of Antheraea assamensis, fifth instars of Helicoverpa armigera and Plutella xylostella have been carried out to find out their importance in the nutrition of the host by detecting the cellulolytic, amylolytic and lipolytic activity of these bacterial isolates. Screening with biochemical kit (Enterobacteriaceae™ kit) identified 71 gut bacterial isolates which belonged to Enterobacteriales, a dominant group of bacteria inhabiting intestine of insects. A combination of culture dependent assays and qualitative screening has been deployed to detect nutritionally important gut bacterial isolates in the present study with emphasis on screening of lipase, cellulase, amylase and gelatinase producing bacteria based on enzyme activities. Qualitative assays have detected 52 isolates with cellulase, 46 isolates with lipase, 31 isolates with amylase and 2 isolates with gelatinase activities in A. assamensis. Similarly in case of H. armigera, 12 isolates with cellulase, 12 isolates with lipase and 7 isolates with amylase activity were found. In case of P. xylostella 5 isolates with cellulase, lipase, amylase and one with gelatinase activities were found. The study of the enzymatic activities the gut bacteria constitute a starting point to understand the functional significance of these organisms in the metabolism and physiology of the host insect.