Exploration of the microbial diversity of caves in the Philippines and its biotechnological potential: bacterial biofilm formation of Bulalon and Mapanghe caves in the Polilio Island, Quezon Province [Philippines]

Cave microbiology and its possible contribution to microbial diversity in the Philippines have not been given favorable attention at present and are almost neglected. It has been recognized that microbial contribution to cave ecology, mineral formation and ecosystem bioenergetics are some of the salient information that might be drawn from the taxonomic studies of microbial communities specifically from caves in the Philippines. Hence, preliminary assessment on the bacterial diversity of caves in the Philippines was conducted based on the samples collected from Bulalon and Mapanghe Caves in the Municipality of Burdeos, Polillo Island, Quezon Province. Standing water from streams and underwater passages as well as dripping water and cave wall and rock surface swabs were collected and analyzed following standard collection and isolation procedures. Representative bacterial isolates were then purified and characterized using the conventional methods. Cultural, morphological, physiological and biochemical tests revealed significant presence of Escherichia coli, Salmonella sp., Serratia marcescens, Pseudomonas aeruginosa, Bacillus subtilis, Micrococcus luteus and unknown strains of sulfur-reducing bacteria. All isoalted and purified strains of Serratea marcescens, Bacillus subtilis and Pseudomonas aeruginosa also gave positive results in the production of biofilms. These resources will be further use in the study of biofilms produced by microorganisms inside caves and how this biofilm influences or aid in cave formation as has been reported in several studies of cave abroad. Furthermore, results suggest that the water inside the cave is highly contaminated with these microorganisms either indigenous (resident) or transient from fecal wastes of common cave inhabitants, bats and birds as well as those of human origin. Though they are common water-borne bacteria, their growth and adaptation in a subterranean environment of extreme and/or near-starvation conditions are indeed interesting facets of microbial diversity. Thus characterization of bacterial strains is currently being further performed to explore taxonomic and biotechnological significance.