Bio-characterizations of some marine bacterial strains isolated from mangrove sediment samples of four major cities of Saudi Arabia

Aim: To isolate, purify and bio-characterize native antibiotic-producing bacterial strains present in the mangrove sediment samples sourced from the coastal areas of four major cities, i.e, Jeddah, Yanbu, Dammam and Jubail of Saudi Arabia. Methodology: The mangrove sediment samples were collected and processed according to the reported standard techniques. Selective Millipore® filter technique was followed to isolate bioactive marine organisms. Isolates were identified by the next-generation 16S rRNA sequencing method. The isolated strains were screened for their antimicrobial activity by spot inoculation method. The effects of pH, temperature, and salt concentrations on the growth of isolated bacterial strains were also recorded. Results: Out of four mangrove sediment samples, eight bioactive bacterial strains namely, Bacillus pumilus NCTC 10337, Bacillus cereus strain JEM-2, Bacillus cereus FRI-35, Bacillus safensis strain KCTC 12796BP, Bacillus pumilus strain W3, Escherichia coli 0157 strain FDAAR GOS_293, Klebsiella oxytoca strain AR-0147, and Bacillus pumilus strain NJ-V2 were isolated. The optimum growth of bacteria was observed between pH 6.5-7.5 at a temperature range of 35-45°C, and salt (NaCl) concentration of 2.0-3.5 %, except for Klebsiella oxytoca strain AR-0147, which grew well at 25°C temperature. Interpretation: The emulation of marine-linked mangrove ecosystem, salty and heated sandy-soil inhabitant environment favored these strains. The best bacterial growth nearly biomimicked with the natural environment of optimum local temperature, bearable-salinity, and soil pH.