Isolation and characterization of thermophilic bacteria from different habitats and their assessment for antagonism against soil-borne fungal plant pathogens

Abstract

S., G. Three different biomaterials viz., boiled cow milk, compost manure and tomato rhizospheric soil were found as habitats of the thermophilic antagonistic bacteria. The isolated bacteria were able to grow satisfactorily at thermophilic temperature range (>55C). Based on morphological, biochemical and physiological characters, the bacterial isolates were identified as Bacillus licheniformis (boiled cow milk), and Bacillus stearothermophilus (compost manure and tomato rhizospheric soil). All the three thermophilic bacterial isolates exhibited strong antagonism against tested soil-borne fungal plant pathogens in order of B. licheniformis (inhibition zone of 67.67 mm against R. bataticola) > B. stearothermophilus from compost manure (51.67 mm against R. solani) > B. stearothermophilus from tomato rhizospheric soil (38.33 mm against P. aphanidermatum). The ability to tolerate high temperature (>55°C), pH (6-8) and salt concentrations (up to 8%), and antibiotic resistance properties of the antagonistic thermophilic Bacillus isolates may hold them as potential biocontrol candidates, especially under stressed rhizosphere environments where other biocontrol agents fail. However, the results need further confirmation under field conditions where these bioagents will be applied in a formulated form.