Isolation of a thermophilic bacterium, Geobacillus sp. SH-1, capable of degrading aliphatic hydrocarbons and naphthalene simultaneously, and identification of its naphthalene degrading pathway

A thermophilic naphthalene- and aliphatic hydrocarbon-degrading bacterium SH-1 was isolated from a deep oil well and identified as Geobacillus sp. n-alkanes from C12 to C33 in crude oil and naphthalene were effectively degraded by strain SH-1, and this strain could readily utilize these compounds as its sole carbon and energy resources. During the degradation of naphthalene, strain SH-1 initiated its attack on naphthalene by a monooxygenation at its C-1 to give 1-naphthol and further monooxygenation at C-2 to produce 1,2-dihydroxynaphthalene. The ring of 1,2-dihydroxynaphthalene was cleaved to form trans-o-hydroxybenzylidenepyruvate. Subsequently, trans-o-hydroxybenzylidenepyruvate was transformed to (2E)-3-(2-hydroxyphenyl)prop-2-enal by losing a carboxyl group. Additionally, benzoic acid was identified as an intermediate in the naphthalene degradation pathway of this Geobacillus strain. This study highlights an important potential use of the thermophilic degradative strain SH-1 in the cleanup of environmental contamination by naphthalene and crude oil and presents a mechanism for naphthalene metabolism.