Geochemical and mineralogical analysis of Kashmir Cave (SMAST), Buner, Pakistan, and isolation and characterization of bacteria having antibacterial activity

Bacterial strains having the ability to inhibit the growth of other bacteria were isolated from soil samples collected from Kashmir Smast (smast is Pushto for cave), Khyber Pakhtunkhwa, Pakistan. The study includes mineralogical and geochemical analyses of soil sample collected from the cave, so as to describe the habitat from which the microorganisms have been isolated. Total bacterial count of the soil sample was 5.25 × 10⁴ CFU mL⁻¹. Four bacterial isolates having activity against test organisms Micrococcus luteus, Klebsiella sp., Pseudomonas sp., and Staphylococcus aureus were screened out for further study. Two of the isolates were found to be Gram-positive and the other two Gram-negative. The four isolates showing antibacterial activity were identified as Serratia sp. KC1-MRL, Bacillus licheniformis KC2-MRL, Bacillus sp. KC3-MRL, and Stenotrophomonas sp. KC4-MRL on the basis of 16S rRNA sequence analysis. Although all isolates showed antibacterial activity, only Bacillus licheniformis KC2-MRL was selected for further study due to its large zone of inhibition. Antibacterial activity of B. licheniformis KC2-MRL was optimum when grown in nutrient broth adjusted to pH 5 and after 24 hours of incubation at 35 °C. The extracted antibacterial compound was stable at pH 5–7 and 40 uC when incubated for 1 hour. The strain was found resistant against cefotaxime (ctx). Atomic-absorption analysis of the soil sample collected from the cave showed high concentrations of calcium (332.938 mg kg⁻¹) and magnesium (1.2576 mg kg⁻¹) compared to the control soil collected outside the cave. FTIR spectrum of the concentrated protein showed similarity to bacitracin. The antibacterial compound showed activity against both Gram-negative and positive test strains. Mineralogy of Kashmir Smast is diverse and noteworthy. Different geochemical classes identified by X-ray diffraction were nitrates, oxides, phosphates, silicates, and sulfates. Weathered cave limestone contributes notably to the formation of these minerals or compounds. FTIR spectroscopic analysis helped to identify minerals such as quartz, clinochlore, vermiculite, illite, calcite, and biotite.