The genus Ammoniphilus is proposed for aerobic endospore-forming Gramvariable rod-shaped bacteria, which are ammonium-dependent, obligately oxa lotrop h ic and haloa I ka I i to lerant, oxidase-and catal ase-pos i t ive, mesop h i I ic and motile b y peritrichous flagella. Cell wall contained two electron-dense layers. The external layer consists of a chain of electron-dense granules morphologically resembling the cellulosomes of CIostridium thermocellum. Two species are described, Ammoniphilus oxalaticus gen. nov., sp. nov. and Ammoniphilus oxalivorans gen. nov., sp. nov. The type strains of these species are strains RAOx-1 (= DSM 11538) and RAOx-FS (= DSM 11537), respectively. Ammoniphilus strains were isolated from the rhizosphere of sorrel (Rumex acetosa) and from decaying wood. The strains require a high concentration of ammonium ions and use oxalate as the sole organic source of carbon and energy for growth; no growth factors were required. Growth occurred a t pH 6-8-9-5. The optimum temperature and pH for growth were 28-30 "C and 80-8.5. All strains grew in a saturated solution of ammonium oxalate, and tolerated 3 O/ O NaCI. Whole-cell hydrolysates contain meso-diaminopimelic acid and glucose. The menaquinone of the strains was MK 7, and the major cellular fatty acids were 12-methyl tetradecanoic, cis-hexadec-9-enoic and hexadecanoic acids. The G+C content of the DNA was 4 5 4 6 mol O/ O for A. oxalaticus and 42 mol O/ O for A. oxalivorans. The almost complete 165 rDNA sequence of three strains of the two species of Ammoniphilus shows that the genus falls into the radiation of the Clostridium-Bacillus subphylum of Grampositive bacteria. The closest phylogenetic neighbour of Ammoniphilus is Oxalophagus oxalicus. The DNA-DNA hybridization value between strains RAOx-1 and RAOx-FS was 3997%.

In cells of Rhodococcus opacus GM-14, GM-29, and 1CP, the contents of branched (10-methyl) fatty acids increased from 3% to 15 to 34% of the total fatty acids when the cells were grown on benzene, phenol, 4-chlorophenol, chlorobenzene, or toluene as the sole source of carbon and energy, in comparison with cells grown on fructose. In addition, the content of trans-hexadecenoic acid increased from 5% to 8 to 18% with phenol or chlorophenol as the carbon source. The 10-methyl branched fatty acid content of R. opacus GM-14 cells increased in a dose-related manner following exposure to phenol or toluene when toluene was not utilized as the growth substrate. The results suggest that 10-methyl branched fatty acids may participate in the adaptation of R. opacus to lipophilic aromatic compounds.

An aerobic mixed bacterial culture (CL-EMC-1) capable of utilizing methyl tert-butyl ether (MTBE) as the sole source of carbon and energy with a growth temperature range of 3 to 30 degrees C and optimum of 18 to 22 degrees C was enriched from activated sludge. Transient accumulation of tert-butanol (TBA) occurred during utilization of MTBE at temperatures from 3 degrees C to 14 degrees C, but TBA did not accumulate above 18 degrees C. The culture utilized MTBE at a concentration of up to 1.5 g l(-1) and TBA of up to 7 g l(-1). The culture grew on MTBE at a pH range of 5 to 9, with an optimum pH of 6.5 to 7.1. The specific growth rate of the CL-EMC-1 culture on 0.1 g l(-1) of MTBE at 22 degrees C and pH 7.1 was 0.012 h(-1), and the growth yield was 0.64 g (dry weight) g(-1). A new MTBE-utilizing bacterium, Variovorax paradoxus strain CL-8, isolated from the mixed culture utilized MTBE, TBA, 2-hydroxy isobutyrate, lactate, methacrylate, and acetate as sole sources of carbon and energy but not 2-propanol, acetone, methanol, formaldehyde, or formate. Two other isolates, Hyphomicrobium facilis strain CL-2 and Methylobacterium extorquens strain CL-4, isolated from the mixed culture were able to grow on C(1) compounds. The combined consortium could thus utilize all of the carbon of MTBE.

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...

No abstract