Isolation of Thermophilic Bacteria from Sri Lankan Hot Water Springs

Abstract

Thermophilic bacteria have gained significant attention in the biotechnological industry due to their capacity to produce enzymes that can withstand high temperatures. Geothermal springs are considered a promising source of industrially important thermophilic bacteria. This study investigated thermophiles in Sri Lankan geothermal springs to analyse their industrial potential. Water samples were collected aseptically into vacuum flasks from selected geothermal springs such as Madunagala, Gomarankadawala, Kanniya, and Nelumwewa where the water temperatures ranged from 39°C to 55°C and brought to the laboratory for culturing and isolation of thermophiles. In parallel, at the collection sites, water samples were introduced aseptically into nutrient broth media. Sessile thermophilic bacteria were obtained using sterile cotton swabs and subsequently introduced onto nutrient agar plates. The heat tolerance screening of isolated bacteria was conducted by gradually increasing incubation temperatures starting from the temperature at the sites of collection to 60°C. Selected heat-tolerance bacterial isolates were differentiated based on morphological and microscopical methods. Overall, 15 morphologically different isolates (Eight Gram-positive bacteria and seven Gram-negative bacteria) that can grow at 50°C were identified from all sites. However, only nine out of 15 exhibited growths at temperatures above 50°C. Among those, two isolates (Gram positive rod and gram-negative coccus) from the Madunagala hot water spring showed a growth at 55°C. From the Kanniya hot water springs, a single strain (Gram-positive long rod) capable of thriving at 55°C was isolated. Furthermore, Nelumwewa springs yielded six isolates that exhibited growth at 55°C, while three of them (Gram-positive filamentous strain, Gram-negative rod, Gram negative tiny rods) displayed exceptional heat tolerance at 60°C. The variations observed within these isolates emphasize the necessity of molecular-based identifications. This study paves the way for future biotechnological research and practical applications of Sri Lankan thermophiles.