A Study of Heavy Metal-Resistant, Hydrocarbon-Degrading Bacteria in Lagos and Ologe Lagoons, Nigeria. A Thesis Submitted to University of Lagos School of Postgraduate Studies Phd Thesis and Dissertation, 289pp.
No Thumbnail Available
Date
2014
Authors
Ajani, S.A
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The potential impacts of industrial pollutants, particularly the polycyclic aromatic petroleum hydrocarbons and heavy metals on the ecology of Lagos lagoon are detrimental. The main objective of this work was to isolate indigenous bacterial strains in the Lagos and Ologe lagoon sediments that were able to utilize selected polycyclic aromatic hydrocarbons (PAHs) in the presence of toxic heavy metals. Using a selective, aerobic enrichment procedure with naphthalene, anthracene, phenanthrene, fluorene, fluoranthene, pyrene, chrysene and benz[a]anthracene supplied as sole carbon and energy sources in the presence of a heavy metal mixture (of mercury, chromium, cadmium, lead and nickel), twenty one hydrocarbon- utilizing, heavy metal-resistant bacterial species were isolated from sediment samples collected from the Lagos and Ologe lagoons. The organisms were subsequently phenotypically characterized using Analytical Profile Index (API) test kits. Three of the isolates were selected for further studies owing to their biodegradative potential. Two were identified as Pseudomonas strain K6 and Arthrobacter strain K14 on the basis of their 16S rRNA gene sequences while Alcaligenes xylosoxidans strain K10 was not sequenced. The sequences of strains K6 and K14 have been deposited with GenBank under accession numbers JQ277727 and JQ277728 respectively. The microbial community structures of the sampling points were elucidated with the use of Denaturing Gradient Gel Electrophoresis (DGGE) and a dendrogram was constructed to establish the coefficient of relatedness of the components of the sampling points using NTSYS version 202j. The analysis of the sediment samples demonstrated that members of the Proteobacteria e.g. Burkholderia sp. and Erythrobacter sp. dominated these polluted sediments. Using naphthalene, anthracene, phenanthrene, fluorene, fluoranthene, pyrene, chrysene and benz[a]anthracene as sole sources of carbon and energy, strains K6, K10 and K14 exhibited in batch cultures (25°C, 200 rpm) specific growth rates and doubling times within the range of 0.02-1.575 h-1and 0.44-36.48 h respectively. The EC50 (half maximal effective concentration inhibiting growth) value for resistance to heavy metals in the presence of naphthalene, chrysene and benz[a]anthracene fell within a range of 0.8-15.4mM for the isolates. The biosorption of chromium on the walls of the cells of Arthrobacter strain K14 was established with the aid of scanning and transmission electron microscopy. Protein expression patterns in the presence of cadmium, chromium and lead for the three organisms` using SDS-PAGE revealed a molecular weight between 29KDa and 205KDa. The hydrocarbon utilization potentials and heavy metal resistance of strains K6, K10 and K14 were chromosomally mediated. Microcosm experiments using the sediment samples showed the removal of Cd, Cr, Pb, Hg and Ni by the test organisms. The level of removal of the heavy metals was within a range of 20%-80%. The ability of these strains to utilize polynuclear aromatic hydrocarbons as carbon and energy sources in the presence of mixtures of toxic heavy metals established their potential for bioremediation processes in co-contaminated environments.
Description
A Thesis Submitted to the School of Postgraduate Studies, University of Lagos.
Keywords
Industrial Pollutants , Ecology , Toxic Heavy Metals , Sediment , Research Subject Categories::NATURAL SCIENCES::Biology::Organism biology::Microbiology
Citation
Ajani, S.A (2014), A Study of Heavy Metal-Resistant, Hydrocarbon-Degrading Bacteria in Lagos and Ologe Lagoons, Nigeria.