Metabolism of methyl bromide and dimethyl sulfide by marine bacteria isolated from coastal and open waters

Abstract

Marine methylotrophic bacteria that consumed methyl bromide (MeBr) and/or dunethyl sulfide (DMS) were isolated: 4 strains from Long Island Sound, USA (LIS) and 1 from the tropical North Atlantic (TNA). Substrates used for enrichment were DMS, trimethylarnine (TMA) or TMA plus MeBr. Attempts to obtain isolates on MeBr as the sole source of carbon and energy were unsuccessful. Three of the isolates used MeBr at rates that were higher than chemical loss, and one of these, isolated from coastal LIS, could use this C,-substrate for biomass production but only when other carbon sources were available simultaneously. Microbial consumption stopped when the MeBr concentration was higher than 0.5 mM and, similarly, when the DMS concentration was higher than 5 mM. The presence of DMS greatly enhanced MeBr consumption in cell suspensions. Inhibitor studies showed that DMS and MeBr were used by the same metabolic pathway in 2 LIS isolates, one of which &splayed hydroxypyruvate reductase activity, ~ndicatlve of the serine pathway of carbon assimilat~on. A third isolate obtained from the TNA that used MeBr did not use DMS, whereas 2 additional LIS strains isolated on DMS did not use MeBr. Therefore, MeBr uthzation is not a common trait of DMS-degrading bacteria. MeBr concentrations in the marine environment are in the pM range and are the highest In coastal waters. This study indicates that growth on MeBr alone is unlikely to support bactenal growth and that removal of MeBr may be a cometabolic phenomenon. However, regardless of growth, consumption by manne bacteria may h u t the flux of MeBr to the atmosphere.

Isolation of Methylophaga spp. from Marine Dimethylsulfide-Degrading Enrichment Cultures and Identification of Polypeptides Induced during Growth on Dimethylsulfide

“…The strains of Methylophaga obtained in this study are the first DMS-degrading isolates of this genus obtained from seawater samples. Strain DMS010 differed in its DMS metabolism from that of Thiobacillus species and unidentified isolates based on inhibition assays (20,53). Strain DMS010 had a low apparent Ks, indicating that it may be able to degrade DMS at typical environmental concentrations (1 to 5 nM) (25) or when DMS concentrations may reach high nM concentrations during the decay of phytoplankton blooms and even M concentrations as observed in coral mucus (5).…”

“…In previous studies, marine bacterial isolates growing on DMS were of undetermined phylogeny (18,20,52), or isolates studied for organosulfur compound transformation were isolated from DMSP enrichments and chosen on the basis of their affiliation with marine Alphaproteobacteria (16). Therefore, Methylophaga DGGE bands and Methylophaga isolates from the same enrichments indicated that the strains represented the populations growing in the enrichment cultures.…”

“…strain DMS010. Inhibition of DMS oxidation by MTBE and by chloroform has been used as a means to differentiate between the operation of the monooxygenase pathway and the methyltransferase pathway of DMS oxidation (20,53). Neither MTBE nor chloroform had an inhibitory effect on DMS oxidation by strain DMS010.…”

“…Unfortunately, isolates were not obtained and so the assumption that the detected populations of Methylophaga were indeed able to grow on DMS could not be substantiated. Previously reported DMS-degrading bacterial isolates from pelagic marine samples that could grow on DMS were not identified by sequencing of 16S rRNA genes (18,20), further highlighting the need to cultivate and identify DMS-degrading bacteria from seawater. …”

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

“…These include methane and ammonia oxidizers (13,24,54,61), dimethyl sulfide and methylamine utilizers (29), and propane oxidizers (62). In addition, several bacteria have been isolated that are able to metabolize CH 3 Br and CH 3 Cl (11,20,39,41,58,59,68).…”