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Lett Appl Microbiol. 2003;36(4):251-7.

Importance of Gram-positive naphthalene-degrading bacteria in oil-contaminated tropical marine sediments.

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1
Environmental Engineering Research Centre, School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798.

Abstract

AIMS:

The aim of this study was to isolate, characterize and evaluate the importance of naphthalene-degrading bacterial strains from oil-contaminated tropical marine sediments.

METHODS AND RESULTS:

Three Gram-positive naphthalene-degrading bacteria were isolated from oil-contaminated tropical intertidal marine sediments by direct isolation or enrichment using naphthalene as the sole source of carbon and energy. Bacillus naphthovorans strain MN-003 can also grow on benzene, toluene, xylene and diesel fuel while Micrococcus sp. str. MN-006 can also grow on benzene. Staphylococcus sp. str. MN-005 can only degrade naphthalene and was not able to use the other aromatic hydrocarbons tested. Strain MN-003 possessed the highest maximal specific growth rate with naphthalene as sole carbon source. An enrichment culture fed with naphthalene as sole carbon source exhibited a significant increase in the relative abundances of the three isolates after 21 days of incubation. The three isolates constituted greater than 69% of the culturable naphthalene-degrading microbial community. Strain MN-003 outcompeted and dominated the other two isolates in competition studies involving batch cultures inoculated with equal cell densities of the three isolates and incubated with between 1 and 10 mg l-1 of naphthalene.

CONCLUSIONS:

Three Gram-positive naphthalene-degrading bacteria were successfully isolated from oil-contaminated tropical marine sediments. Gram-positive bacteria might play an important role in naphthalene degradation in the highly variable environment of oil-contaminated tropical intertidal marine sediments. Among the three isolates, strain MN-003 has the highest maximal specific growth rate when grown on naphthalene, and outgrew the other two isolates in competition experiments.

SIGNIFICANCE AND IMPACT OF THE STUDY:

This research will aid in the development of bioremediation schemes for oil-contaminated marine environments. Strain MN-003 could potentially be exploited in such schemes.

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