Metabolism of γ-hexachlorocyclohexane by Arthrobacter citreus strain BI-100: Identification of metabolites

Growth characteristics of the aerobic bacterial strain Arthrobacter citreus BI-100 in mineral salts medium with gamma-hexachlorocyclohexane (gamma-HCH) as the sole source of carbon and degradation of gamma-HCH by the strain are reported. The highest yield of the bacteria is observed at a gamma-HCH concentration of 100 mg/L. At this concentration, the bacteria entered the exponential phase of growth without any lag. At 8 h of growth, no residual HCH, but its metabolites, was detectable in the medium. The bacterium attained its stationary phase at 48 h and at 72 h; no metabolite of gamma-HCH could be detected by gas chromatography. Six metabolic intermediates of gamma-HCH produced by A. citreus BI-100 at different periods of growth were characterized by using gas chromatography-mass spectrometry and high-performance liquid chromatography, which furnished evidence for the presence of gamma-1,3,4,5,6-pentachlorocyclohexene, tetrachlorocyclohexene, trichlorocyclohexa-diene, 2-chlorophenol, phenol, and catechol, among others.