Description of Toluene Inhibition of Methyl Bromide Biodegradation in Seawater and Isolation of a Marine Toluene Oxidizer That Degrades Methyl Bromide

Abstract

Methyl bromide (CH 3 Br) and methyl chloride (CH 3 Cl) are important precursors for destruction of stratospheric ozone, and oceanic uptake is an important component of the biogeochemical cycle of these methyl halides. In an effort to identify and characterize the organisms mediating halocarbon biodegradation, we surveyed the effect of potential cometabolic substrates on CH 3 Br biodegradation using a 13 CH 3 Br incubation technique. Toluene (160 to 200 nM) clearly inhibited CH 3 Br and CH 3 Cl degradation in seawater samples from the North Atlantic, North Pacific, and Southern Oceans. Furthermore, a marine bacterium able to co-oxidize CH 3 Br while growing on toluene was isolated from subtropical Western Atlantic seawater. The bacterium, Oxy6, was also able to oxidize o-xylene and the xylene monooxygenase (XMO) pathway intermediate 3-methylcatechol. Patterns of substrate oxidation, lack of acetylene inhibition, and the inability of the toluene 4-monooxygenase (T4MO)-containing bacterium Pseudomonas mendocina KR1 to degrade CH 3 Br ruled out participation of the T4MO pathway in Oxy6. Oxy6 also oxidized a variety of toluene (TOL) pathway intermediates such as benzyl alcohol, benzylaldehyde, benzoate, and catechol, but the inability of Pseudomonas putida mt-2 to degrade CH 3 Br suggested that the TOL pathway might not be responsible for CH 3 Br biodegradation. Molecular phylogenetic analysis identified Oxy6 to be a member of the family Sphingomonadaceae related to species within the Porphyrobacter genus. Although some Sphingomonadaceae can degrade a variety of xenobiotic compounds, this appears to be the first report of CH 3 Br degradation for this class of organism. The widespread inhibitory effect of toluene on natural seawater samples and the metabolic capabilities of Oxy6 indicate a possible link between aromatic hydrocarbon utilization and the biogeochemical cycle of methyl halides.Methyl bromide (CH 3 Br) and methyl chloride (CH 3 Cl) are significant components of the tropospheric halogen burden. When transported into the stratosphere these gases are photolysed, releasing halogen atoms that contribute to catalytic ozone depletion. The global sources and sinks of these ozonedepleting substances are not well known, and their atmospheric budgets remain unbalanced (35, 76). Methyl bromide is produced anthropogenically for use as a fumigant, and it is a natural algal product (2, 38, 56, 57). The sources of CH 3 Cl are primarily natural with some anthropogenic contributions, particularly from man-made fires (5, 25). The net global flux to the ocean reflects a balance between uptake of atmospheric CH 3 Br and CH 3 Cl and internal cycling (production and consumption) in the ocean distributed over large geographic regions. The ocean is a net sink for atmospheric CH 3 Br (33), where it is degraded by chemical (17, 32) and biological (19, 34, 65) processes. Methyl chloride is also produced and destroyed in the oceans, although the oceans represent a net source in the atmospheric budget (46,47,77). Oceanic uptake of me...

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Novel Pathway for the Degradation of 2-Chloro-4-Nitrobenzoic Acid by Acinetobacter sp. Strain RKJ12

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“…1 H nuclear magnetic resonance ( 1 H-NMR) and 13 C-NMR spectroscopy were performed using a Bruker Avance DRX500 spectrometer (Bruker, Germany), operating at 500 and 125 MHz for Fourier transform infrared (FT-IR) spectra were obtained in the range of 4,000 to 450 cm Ϫ1 by using a Perkin-Elmer Paragon 500 FT-IR spectrophotometer. Solid samples dispersed in KBr pellets were used for FT-IR analysis.…”

“…The morphological features were determined and conventional biochemical tests performed using standard methods as described by Smibert and Krieg (39). The 16S rRNA gene was amplified using universal bacterium-specific primers 27F and 1492R as described by Goodwin et al (13), and the reaction product was analyzed on an ABI PRISM 377 automated DNA sequencer (Perkin-Elmer Applied Biosystems). The 16S rRNA gene sequence of the new isolate was compared to those in the EMBL, GenBank, and DDBJ databases using BLAST version 2.2.12 from the National Center for Biotechnology Information (NCBI) (1).…”

Microbial Removal of Atmospheric Carbon Tetrachloride in Bulk Aerobic Soils

“…Separate triplicate or duplicate syringes were used for each treatment. Glass syringes were kept gas tight by the standard method of storing them immersed in water in order to maintain a film of water between the plunger and barrel to prevent air/gas leakage (21,23,24).…”