Utilization of Halogenated Benzenes, Phenols, and Benzoates by Rhodococcus opacus GM-14

Abstract

Strain GM-14 was isolated by selective enrichment from contaminated soil with chlorobenzene as the sole source of carbon and energy. It utilizes an exceptionally wide spectrum of haloaromatic substrates. It is a gram-positive, weakly acid-fast actinomycete, with a morphological cycle from cocci and short rods to long rods and branched filaments; it grew optimally at 28؇C; and it tolerated 5% NaCl in rich medium. The chemotaxonomic characteristics, the diagnostic biochemical tests, the whole-cell fatty acid composition, and 16S rDNA analysis were consistent with Rhodococcus opacus. R. opacus GM-14 grew on 48 of 117 different aromatic and haloaromatic compounds. It utilized phenol at concentrations up to 1.2 g/liter, 3-and 4-methylphenols up to 0.5 g/liter, 2-and 4-chlorophenols up to 0.25 g/liter, and 3-chlorophenol up to 0.1 g/liter. It grew in saturated aqueous solutions of benzene, chlorobenzene, and 1,3-and 1,4-dichlorobenzene (up to 13, 3, 0.5, and 0.5 g/liter, respectively). The specific growth rate of strain GM-14 on phenol and 3-and 4-chlorophenols in batch culture was 0.27 to 0.29 h ؊1 , and that on benzene and chlorobenzene was similar to the rate on fructose, i.e., 0.2 h ؊1. The growth yield on benzene and on chlorobenzene (<0.4 g liter ؊1) was 40 to 50 g (dry weight) per mol of substrate consumed, equalling 8 g of dry weight biomass per mol of substrate carbon, similar to that obtained on acetate. During growth of strain GM-14 on chlorobenzene, 1,3-dichlorobenzene, and all isomers of monochlorophenol, stoichiometric amounts of chloride were released, and 50% of the stoichiometric amount was released from 1,4-dichlorobenzene. The extensive use of benzene, phenol, and their halogenated derivatives in industrial processes over the past decades has led to widespread pollution of the environment by these toxic compounds (30, 32, 39). Therefore, information on their biodegradation is of great interest. In recent years, much research has focused on the ability of strains able to completely degrade these chemicals (19). Several microorganisms utilizing halogenated benzenes as the sole carbon and energy source are known (9, 22, 29, 34, 37, 38, 42-44, 46, 50). Most investigations have addressed gramnegative bacteria, mainly Pseudomonas and Alcaligenes species. The strains described grew on chlorobenzene (CB) when introduced into the vapor phase but not with the liquid chemical in the culture medium (11, 42). Gram-positive bacteria, mycobacteria, nocardioform actinomycetes, and streptomycete groups are also known as degraders of halogenated aromatic compounds (54). These groups of microorganisms may be attractive for use in biotechnology because of their high biodegradation potential (2, 14-16, 20, 49, 53) and good survival in soil (7, 8, 24). This paper is a comprehensive description of the enrichment, isolation, and characterization of a gram-positive bacterium, strain GM-14, capable of using high concentrations of phenol, benzene, and their halogenated derivatives as the sole sources of carbon and energy; in t...

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Rapid metabolic analysis of Rhodococcus opacus PD630 via parallel 13C‐metabolite fingerprinting

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Effect of Aromatic Compounds on Cellular Fatty Acid Composition of Rhodococcus opacus

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