ISSN: 0973-7510

E-ISSN: 2581-690X

A. Ramalakshmi
Department of Agricultural Microbiology, Tamil Nadu Agricultural University, Coimbatore – 641 003, India.
J. Pure Appl. Microbiol., 2016, 10 (3): 2439-2442
© The Author(s). 2016
Received: 08/02/2016 | Accepted: 10/03/2016 | Published: 30/09/2016
Abstract

The rhizosphere soil samples were collected during crop growth of black gram, green gram and horse gram at Regional Research Station, Paiyur, Tamil Nadu, India for isolation of B. thuringiensis (Bt). Thirty Bt like colonies based on colony morphology viz.,fried egg colonies were identified from soil samples of Black gram, green gram and horse gram.  Among the 30 fried egg colonies, eleven Bt colonies viz., five from black gram, four from green gram and two from horse gram soil samples were identified based on crystal protein under microscope. All the 11 colonies were plated on 0.5% colloidal chitin agar (CCA) medium and the results revealed that among the 11 Bt colonies, six Bt colonies produced zone of clearance over 0.3cm . Out of six colonies, BG7 produced 0.8cm clearance of zone on CCA plates followed by BG10 (0.72cm). All the six colonies were further screened by chitinase activity and the results showed that among the six Bt colonies, BG7 produced highest level of (2.4 U/ml) chitinase activity followed by BG10 (1.98 U/ml). The growth conditions for isolate, BG7 which showed maximum chitinase activity were optimized under different pH, temperature and incubation time and the result showed that the strain BG7 produced maximum chitinase at pH of 7, temperature of 30 with 0.5 % colloidal chitin. This finding might be applied for the development of new B. thuringiensis formulations against seed and soil borne pathogens along with insecticidal toxins.

Keywords

Bacillus thuringiensis, Chitinase, Rhizosphere soil, Pathogens.

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