Volume 6, Issue 2, April Issue - 2018, Pages:342-351

Authors: Reda Hassan Amasha
Abstract: The microbial diversity within cave ecosystems is largely unknown. This study aimed to studying the microbial communities of the three caves viz Mossy, Hotel and Reda caves which are located approximately 200 km of Riyadh region, between Riyadh and Al Kharj road, Saudi Arabia. These caves have an intricate cave system which developed in the calcareous sandstone and clay. Morphological interpretation revealed that Mossy cave was different from Hotel and Reda caves where it is tall and have a linear cave passage and narrow canyons. Various field studies revealed that many bacteria inhibited in caves and obtained their energy from degradation of inorganic substances, thus they directly interact with the surfaces where they live on. In present study, soil and wall dust samples were collected and cultured on Nutrient agar, starch nitrate agar and PDA plates. During study various Gram positive, Gram negative bacteria, actinomycetes and fungi were isolated from the cave soil and wall. The isolated bacteria were characterized and identified by using culture-dependent methods (morphological and physiological methods). Identifications of the most occurring bacterial genera were confirmed by using 16S rRNA gene amplicon sequencing which revealed the presence of 11 broad taxonomic species of bacteria. Among these, Proteobacteria were dominant in all caves and this was followed by Actinobacteria, Firmicutes and Bacteroidetes. Majority of the true bacterial isolates belong to the genera Alcaligenes, Bacillus, Brevibacterium, Klebsiella, Planomicrobium, Shigella, Pseudomonas and Staphylococcus.  During study, percentage of resistance to some metallic cations, heavy metals and antibiotics were also determined.  Result of study revealed that Bacillus cereus, Klebsiella pneumoniae  and Pseudomonas earuginosa showed the highest resistant percentage to the tested heavy metals while Pseudomonas earuginosa, Klebsiella pneumoniae and Staphylococcus aureus were the highest resistant to the tested antibiotics. In conclusion, present study provide beneficial information about microbial diversity, taxonomic and their resistance to some heavy metals and antimicrobial agents in three uncharacterized caves, located in Alsoman region, north east of Riyadh.
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