Aims: We analyzed thermotolerant bacterial isolates of thermophiles from various regions in South East coasts of India. They were analyzed for Fatty Acid Methyl Ester (FAME) for identification and classification.
Study Design: A total of forty three (9.6%) thermotolerant bacterial isolates of thermophiles were secluded out of 444 isolates obtained from water samples from the Adyar River, Marina coast, Muttu Kadu Backwaters, Kovalam coast (India) and a prawn hatchery. In addition, a novel thermotolerant Gram positive Bacillus type bacterium from the pelletized feed of fish was examined. A total of 18 thermotolerant bacteria were analyzed for Fatty Acid Methyl Ester (FAME).
Results: Amongst 134 isolates that grew on E. coli FAGI agar, 23 (17%) were thermotolerant when tested at 15 psi for 30 min. Of the 72 isolates that grew on Staphylococcus Baird Parker agar 10 (13%) were thermotolerant, whilst among the 128 isolates that grew on Salmonella agar ÖNÖZ 10 (8%) were thermotolerant. In contrast, none of the 110 isolates that grew on TCBS agar (Vibrio sp.) exhibited thermotolerance, although they were isolated from the same regions as the other bacteria. The optimal temperature for the growth of most thermophiles was 45°C, except for 9 isolates. Of the latter, 7 grew at 50°C, one at 52°C and one at 55ºC, respectively.There were some extremely thermotolerant bacterial isolates that exhibited consistency in profuse growth at 15 psi (121°C) for 30 min. Other isolates showed inconsistency in growth after autoclaving the cultures at 15 psi (121°C) for 30 min, and these bacteria showed development of endospores. Isolates of thermotolerant bacteria that grew on Staphylococcus Baird Parker agar and Salmonella agar ÖNÖZ were predominantly antibiotic resistant when compared with those bacterial isolates that grew on E. coli FAGI agar. A major 43 kDa toxin-protein as well as 15 other minor protein subunits was detected in the thermotolerant Bacillus sp. isolate. The proteins were toxic and caused mortality to goldfish Cyprin macrophthalmus. The thermotolerant bacteria were identified as B. cereus, Bacillus subtilis, B. pumilus, B. laevolacticus), B. alcalophilus, Kurthiasibirica, Geobacillus stearothermophilus, Staphylococcus schleiferi and S. gallinarum,
Conclusions: This study documents 43 thermotolerant bacterial isolates from water samples and a Bacillus-type bacterium from fish feed in Chennai region, India and these bacterial isolates offer the potential for exploitation in biotechnological applications.