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.
