Pseudomonas sp. strain LP1, an organism isolated on the basis of its ability to grow on pyrene, was assayed for its degradative and biosurfactant production potentials when growing on crude, diesel and engine oils. The isolate exhibited specific growth rate and doubling time of 0.304 days -1 and 2.28 days, respectively on crude oil (Escravos Light). The corresponding values on diesel were 0.233 days -1 and 2.97 days, while on engine oil, were 0.122 days -1 and 5.71 days. The organism did not show significant biosurfactant production towards crude oil and diesel, but readily produced biosurfactant on engine oil. The highest Emulsification index (E 24 ) value for the biosurfactant produced by LP1 on engine oil was 80.33 ± 1.20, on day 8 of incubation. Biosurfactant production was growth-associated. The surface-active compound which exhibited zero saline tolerance had its optimal activity at 50°C and pH 2.0.

Samples of soil, water, and sediments from industrial estates in Lagos were collected and analyzed for heavy metals and physicochemical composition. Bacteria that are resistant to elevated concentrations of metals (Cd(2+), Co(2+), Ni(2+), Cr(6+), and Hg(2+)) were isolated from the samples, and they were further screened for antibiotic sensitivity. The minimum tolerance concentrations (MTCs) of the isolates with dual resistance to the metals were determined. The physicochemistry of all the samples indicated were heavily polluted. Twenty-two of the 270 bacterial strains isolated showed dual resistances to antibiotics and heavy metals. The MTCs of isolates to the metals were 14 mM for Cd(2+), 15 mM for Co(2+) and Ni(2+), 17 mM for Cr(6+), and 10 mM for Hg(2+). Five strains (Pseudomonas aeruginosa, Actinomyces turicensis, Acinetobacter junni, Nocardia sp., and Micrococcus sp.) resisted all the 18 antibiotics tested. Whereas Rhodococcus sp. and Micrococcus sp. resisted 15 mM Ni(2+), P. aeruginosa resisted 10 mM Co(2+). To our knowledge, there has not been any report of bacterial strains resisting such high doses of metals coupled with wide range of antibiotics. Therefore, dual expressions of antibiotics and heavy-metal resistance make the isolates, potential seeds for decommissioning of sites polluted with industrial effluents rich in heavy metals, since the bacteria will be able to withstand in situ antibiosis that may prevail in such ecosystems.

Three Pseudomonas species isolated from oil polluted soils in Lagos, Nigeria were studied for their pyrene degradation potentials. These isolates exhibited broad substrate specificities for hydrocarbon substrates including polycyclic aromatic hydrocarbons, petroleum fractions and chlorobenzoates. All three isolates tolerated salt concentrations of more than 3%. They resisted ampicillin, cenfuroxime, but susceptible to ofloxacin and ciprofloxacin. Pseudomonas sp. strain LP1 exhibited growth rates and pyrene degradation rates of 0.018 h -1 and 0.111 mg l -1 h -1 respectively, while P. aeruginosa strains LP5 and LP6 had corresponding values of 0.024, 0.082 and 0.017, 0.067 respectively. The overall respective percentage removal of pyrene obtained for strains LP1, LP5 and LP6 after a 30-day incubation period were 67.79, 66.61 and 47.09. Resting cell assay revealed that strain LP1 had the highest uptake rate. Strains LP1, LP5, and LP6 also used the ortho-cleavage pathway. Enzyme study confirmed activity of catechol 1,2-dioxygenase in all with values 0.6823, 0.9199, and 0.8344 lmol min -1 mg -1 respectively for LP1, LP3 and LP6. To the best of our knowledge, ours is the first report of pyrene-degraders from the sub-Saharan African environment.

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