Phenotypic characterization of facultative methylotrophic bacteria isolated from toxic waste-contaminated soil of mine tailings in Zambales

A total of forty (40) facultative (pigmented/non-pigmented) methylotrophic bacterial isolates were obtained from the toxic waste - contaminated soil of two (2) different mine tailings located at Sta. Cruz, Zambales. The two mine tailings utilized for the research were DMCI mine tail and Acoje mine tail. A total of forty (40) tests were performed in order to characterize the isolates phenotypically. The bacterial isolates grew on Ammonium Mineral Salt (AMS) agar with 0.5% methanol. Methanol served as their sole carbon source. It was also observed that the bacteria were able to thrive on Glycerol Peptone agar and Nutrient agar. Facultative methylotrophic bacteria, based on microscopic observations, were found to be gram variable, non-capsule, and non-endospore forming. Biochemical tests employed on the samples showed that they were catalase, oxidase, and urease positive. These bacteria were capable to grow at an environment with temperatures ranging from 300 C - 370 C and with salt concentrations ranging from 3% - 9%. Additionally, isolates were phenotypically identified using the Analytical Profile Index (API) 20 NE System by Biomerieux. After 48 hours of incubation on the API strips, four (4) different species were identified out of the 40 samples, namely: Ochrobactrum anthropi, Sphingomonas paucimobilis, Moraxella sp., and Pseudomonas putida. Further scientific research was performed in order to verify if the identified bacterial isolates were facultative methylotrophic and the result was affirmative. Moreover, based on growth at AMS + 0.5% methanol, nutrient and glycerol peptone agar, 3 out of the 4 bacterial species were non-pigmented and the only pink-pigmented strain was Ochrobactrum anthropi. With the successful isolation, phenotypic characterization and identification of the 40 bacterial isolates, it could then be said that there were facultative methylotrophic bacteria which were able to thrive on toxic-waste contaminated soil in mine tailings. Hence, it was recommended that studies be set for bioremedi