The Western Ghats of India is the one of the world's 10 "Hottest biodiversity hotspots" that runs along the western part of India through four states including Tamil Nadu. The only biodiversity reserve in the Western Ghats is the Nilgiri biosphere located in the Tamil Nadu state. In the present study, 525 soil samples were collected from all the 14 different divisions of the Western Ghats in Tamil Nadu state, India. A total of 316 new isolates of Bacillus thuringiensis (Bt) that produce parasporal crystalline inclusions were isolated from 525 soil samples. Seven different types of crystalline inclusions were observed in the 316 new isolates of Bt. Cuboidal inclusion was predominantly present in 26.9% of the Bt isolates when compared to other shapes. Further characterization of 70 of the 316 Bt isolates for crystal protein profile through SDS-PAGE revealed six different types of crystal protein profile viz., 135 and 65, 135, 95, 65, 43, and 30 kDa crystal proteins. Variation in the mass of crystal protein(s) purified from the isolates of Bt revealed molecular diversity of this bacterium prevalent in the Western Ghats of Tamil Nadu, India.

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In this study, potential of the native Bacillus thuringiensis Berliner was investigated against the root knot nematode, Meloidogyne incognita (Kofoid and White) under laboratory and greenhouse conditions. Fourteen out of 50 Bt isolates obtained from root zone of vegetable crops of north western zone of Tamil Nadu, India, were found to be encoded with nematicidal cry genes, confirmed by gene-specific PCR. Nine different Cry protein profiles were obtained from native Bt. Spore-crystal mixtures of 6 isolates out of 14 (at 0.5%) showed 100% inhibition to J2 juveniles emergence from egg masses of M. incognita within 72 h of treatment. Analysis by SEM revealed that fluffy egg masses were observed in untreated samples due to hatching, whereas egg masses were covered by gelatinous matrix, when treated with spore-crystal mixture of nematicidal Bt. Two (BC and BD) of the 6 isolates were selected based on their highest nematicidal activity against J2 of M. incognita with LC50 values of 0.12 and 0.23 μg/ml of protein. The spore-crystal mixtures of isolates BC and BD when applied to tomato plants under greenhouse conditions exhibited the enhanced biocontrol potential by suppressing number of egg masses, reduction of female population and decreased root gall index, when compared to control and chemical treatments.

Biological nitrogen fixation by the microorganisms in the gut of termites is one of the singularly important symbiotic processes, since termites invariably thrive on nitrogen poor diet. Two isolates of free living aerobic and facultative anaerobic N fixing bacteria were obtained from the guts of fungus cultivating termite, Macrotermes sp. Among the total bacterial isolates from termite gut, the per cents of N fixing aerobes viz., Azotobacter and Beijerinckia spp were 49% and 37% from the salivary gland while facultative N fixing anaerobe viz., Klebsiella and Clostridium contributed (51% and 93%). The free living aerobic bacteria were identified as Azotobacter spp (19 x 104 CFU mL‐1) and Beijerinckia (13.2 x 104 CFU mL‐1) from the salivary gland of the termite; interestingly, foregut, mid gut and hind gut registered a low population of these bacteria. The isolates of Azotobacter were smooth, glistening, vicid in nature, rods, gram negative and cyst forming. Isolates of Beijerinckia sp. produced copious slime, tenacious, rods, gram negative with no cyst formations. Both the isolates emitted green fluorescence and produced acid. Facultative N fixing anaerobes were harbored in the hind gut. The isolates were identified as Klebsiella (20 x 104 CFU mL‐1) and Clostridium pasteurianum 39.1 x 104 CFU mL‐1. Klebsiella were straight rods arranged singly or in pairs, non‐motile, gram negative, whereas Clostridium pasteurianum was viscoid, motile with terminal spores. A positive correlation was observed between the extractable polysaccharides of these isolates and soil aggregation. The aggregates formed by the isolates increased soil aeration, porosity, water holding capacity and helped in better plant growth. Thus, the gut microflora of termite, apart from harnessing nitrogen from the atmosphere, also helps improving soil fertility.

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