Abstract:
Polycyclic Aromatic Hydrocarbons (PAHs) are persistent in the environment
and are toxic pollutants which have carcinogenic and mutagenic properties.
They are composed of two or more fused benzene rings. Bacteria present in
soil are capable of degrading these compounds via anaerobic and aerobic
respiration. However, heavy metals such as tin have the ability to hinder the
degradation capabilities of bacteria. The goal of this study is to isolate and
identify soil bacteria capable of degrading Naphthalene and Phenanthrene in
the presence of heavy metals. Soil samples were collected from 4 different
locations in Sri Lanka: Colombo, Galle and Jaffna, as they are highly polluted
areas according to previous literature and Meemure, as it had the lowest PAH
pollution according to studies and were serially diluted and plated.
Morphologically different strains were identified and starved on Bushnell
Haas Agar. Primary screening was performed using Naphthalene and
phenanthrene spiked plates. Five bacterial strains: RUSHJ08, RUSHC09,
RUSHMO6, RUSHG02, and RUSHG04, were able to degrade these PAHs
were identified and were a subjected to second screening using methyl blue.
UV- Spectrophotometric analysis revealed that these bacteria can degrade
over 40% of the PAHs under optimum conditions. RJO8 (Accession number
PV942241) and RJO2 (Accession number PV942264) were identified as best
PAH degraders. Gram staining was performed to identify Gram-negative and
Gram-positive bacteria, and antagonistic assay was performed to identify the
capability of the strains to exist as a consortium. Atomic Absorption
Spectroscopy was performed to evaluate the presence of heavy metals in the
Colombo soil sample, and the concentration of tin was 2.22mg/kg. The
results of this experiment support the development of a bioremediation
technique in tin-stressed environments, which provides a solution to
environmentalpollution.
