Molecular characterization of gut cellulolytic bacteria isolated from different ecotypes of Brahmina coriacea (Coleoptera: Scarabaeidae) grubs in North-Western Himalaya

Abstract

White grubs are known as the “National pest” of India due to their wide distribution and economic damage. Brahmina coriacea grubs are restricted to Tibet, China and the Himalayan region in Jammu and Kashmir, Himachal Pradesh and Uttarakhand. The grubs of B. coriacea were collected from the soil of Solanum tuberosum, Zea mays, Pisum sativum, Rosa rubiginosa, Phaseolus vulgaris, Malus pumila and Pyrus communis from different ecosystems of eight different locations in Himachal Pradesh, India, by the pit sampling method. The grubs of B. coriacea were identified by examining the raster pattern. There was variation in the morphology and biology among different populations of B. coriacea in Himachal Pradesh. The morphological parameters and biological differences were also recorded, such as fecundity rate and damage potential among different ecotypes of B. coriacea collected from various locations. A total of 102 morphologically distinct bacterial isolates were isolated from the gut of different populations of B. coriacea. The gut microbial diversity and abundance were recorded as maximum in the hind gut, compared to other gut compartments. A total of 11 cellulolytic bacterial isolates were identified using morphological, biochemical and 16S rRNA molecular methods. The cellulolytic index of bacterial strains ranged from 0.33 to 2.0. The 11 gut cellulolytic bacteria were identified by using morphological, biochemical and 16S rRNA gene analysis. Staphylococcus haemolyticus was isolated from the Nauni population of B. coriacea, and it is the first report from the gut of scarabaeids. This is an opportunistic human pathogen but a useful endosymbiont in the grubs of B. coriacea. Bacillus thuringiensis as a biological agent, Staphylococcus cohnii, Ralstonia mannitolilytica and some Bacillus sp. were reported for the first time from B. coriacea grubs in India. The potent cellulose-degrading bacteria can be used in industries for decomposing agricultural waste, in pulp and paper industries and for biofuel production.