Isolation and characterization of lead-resistant bacteria from soil collected from Taft Avenue, Manila

Abstract

This study aims to isolate and characterize the lead-resistant bacteria from soil obtained along the major roads of Taft Avenue, Manila. Grab soil samples were collected from each sampling site and suspended in sterile peptone water. Suspensions from dilutions of the soil (10-1 to 10-6) were plated onto Tryptic Soy Agar (TSA) supplemented with 50 ppm PbCl2 and Amphotericin. Isolated colonies were purified and characterized morphologically, microscopically, and through biochemical tests. The presumptive identities of the isolates were determined using the Bergey’s Manual of Determinative Bacteriology (9th edition) and IDENTAX Bacterial Identifier Software (ver. 1.2). A total of 72 lead-resistant bacteria were isolated, of which 21 genera were identified. Brochothrix sp. and Kurthia sp. genera were commonly occurring in all sampling sites. The Cedecea sp., Cellulomonas sp., Citrobacter sp., Enterobacter sp., and Sphingomonas sp. were the least commonly occurring genera of lead-resistant bacteria observed in all sampling sites. Isolates belonging to genera Aeromicrobium sp., Aureobacterium sp., Brochothrix sp, Caryophanon sp., and Cedecea sp., which have no background studies on heavy metal resistance, were able to resist 50 ppm of lead. Several isolates from the genera Jonesia sp., Aeromicrobium sp., Kurthia sp., Cellulomonas sp., Caryophanon sp., Brochothrix sp., Sporosarcina sp., Cedecea sp., Paracoccus sp., Staphylococcus sp., Arthrobacter sp. are found to grow in lead much more effectively relative to other isolates, making them promising candidates for future studies on lead bioremediation and lead biosorption from this study.