Abstract:
Compounds present in oil sludge such as polycyclic aromatic hydrocarbons (PAHs) are known to be
cytotoxic, mutagenic and potentially carcinogenic. Microorganisms including bacteria and fungi have been reported
to degrade oil sludge components to innocuous compounds such as carbon dioxide, water and salts. In the present
study, we isolated different bacteria with PAH-degrading capabilities from compost prepared from oil sludge and
animal manures. These bacteria were isolated on a mineral base medium and mineral salt agar plates. A total of 31
morphologically distinct isolates were carefully selected from 5 different compost treatments for identifi cation using
polymerase chain reaction (PCR) of the 16S rRNA gene with specifi c primers (universal forward 16S-P1 PCR and
reverse 16S-P2 PCR). The amplicons were sequenced and sequences were compared with the known nucleotides from
the GenBank. The phylogenetic analyses of the isolates showed that they belong to 3 different clades; Firmicutes,
Proteobacteria and Actinobacteria. These bacteria identifi ed were closely related to the genera Bacillus, Arthrobacter,
Staphylococcus, Brevibacterium, Variovorax, Paenibacillus, Ralstonia and Geobacillus. The results showed that
Bacillus species were predominant in all composts. Based on the results of the degradation of the PAHs in the
composts and results of previous studies on bacterial degradation of hydrocarbons in oil, the characteristics of these
bacterial isolates suggests that they may be responsible for the breakdown of PAHs of different molecular weights in
the composts. Thus, they may be potentially useful for bioremediation of oil sludge during compost bioremediation.
