The mechanisms and rates of mercury methylation in the Florida Everglades are of great concern because of potential adverse impacts on human and wildlife health through mercury accumulation in aquatic food webs. We developed a new PCR primer set targeting hgcA, a gene encoding a corrinoid protein essential for Hg methylation across broad phylogenetic boundaries, and used this primer set to study the distribution of hgcA sequences in soils collected from three sites along a gradient in sulfate and nutrient concentrations in the northern Everglades. The sequences obtained were distributed in diverse phyla, including Proteobacteria, Chloroflexi, Firmicutes, and Methanomicrobia; however, hgcA clone libraries from all sites were dominated by sequences clustering within the order Syntrophobacterales of the Deltaproteobacteria (49 to 65% of total sequences). dsrB mRNA sequences, representing active sulfate-reducing prokaryotes at the time of sampling, obtained from these sites were also dominated by Syntrophobacterales (75 to 89%). Laboratory incubations with soils taken from the site low in sulfate concentrations also suggested that Hg methylation activities were primarily mediated by members of the order Syntrophobacterales, with some contribution by methanogens, Chloroflexi, iron-reducing Geobacter, and non-sulfate-reducing Firmicutes inhabiting the sites. This suggests that prokaryotes distributed within clades defined by syntrophs are the predominant group controlling methylation of Hg in low-sulfate areas of the Everglades. Any strategy for managing mercury methylation in the Everglades should consider that net mercury methylation is not limited to the action of sulfate reduction.

The taxonomic positions of Lysobacter species with validly published names and a novel strain Ko07T , which was newly isolated from an upflow anaerobic sludge blanket reactor treating wastewater from a brewery, were (re)estimated on the basis of results obtained by using a polyphasic taxonomy approach. Phylogenetic inference based on 16S rRNA gene sequences showed that strain Ko07 T and all Lysobacter species with validly published names clustered together in a phylogenetic branch within the class 'Gammaproteobacteria'. The sequence similarity of strain Ko07 T to the type strains of established Lysobacter species was in the range 94?9-96?7 %. Ubiquinone Q-8 and branched fatty acids, C 11 : 0 iso, C 15 : 0 iso, C 16 : 0 iso, iso C 17 : 1 v9c and C 11 : 0 iso 3OH, predominantly appeared in strain Ko07 T as well as in all type strains of the recognized Lysobacter species. The DNA-DNA hybridization values of strain Ko07 T with those of recognized Lysobacter species were estimated to be 2-20 %.

The aerobic and anaerobic degradation of trimethylamine by a newly isolated denitrifying bacterium from an enrichment culture with trimethylamine inoculated with activated sludge was studied. Based on 16S rDNA analysis, this strain was identified as a Paracoccus sp. The isolate, strain T231, aerobically degraded trimethylamine, dimethylamine and methylamine and released a stoichiometric amount of ammonium ion into the culture fluid as a metabolic product, indicating that these methylated amines were completely degraded to formaldehyde and ammonia. The strain degraded trimethylamine also under denitrifying conditions and consumed a stoichiometric amount of nitrate, demonstrating that complete degradation of trimethylamine was coupled with nitrate reduction. Cell-free extract prepared from cells grown aerobically on trimethylamine exhibited activities of trimethylamine mono-oxygenase, trimethylamine N-oxide demethylase, dimethylamine mono-oxygenase, and methylamine mono-oxygenase. Cell-free extract from cells grown anaerobically on trimethylamine and nitrate exhibited activities of trimethylamine dehydrogenase and dimethylamine dehydrogenase. These results indicate that strain T231 had two different pathways for aerobic and anaerobic degradation of trimethylamine. This is a new feature for trimethylamine metabolism in denitrifying bacteria.

A polyphasic study was carried out to determine the taxonomic position of two aerobic, cyanide-degrading bacterial strains, designated L61 T and L22, which had been isolated from a bioreactor for the treatment of nickel-complexed cyanide. The two isolates exhibited almost identical taxonomic characteristics. Phylogenetic analysis inferred from comparative 16S rRNA gene sequences indicated that the isolates fall in a sublineage of the genus Rhizobium comprising the type strains of Rhizobium giardinii, Rhizobium radiobacter, Rhizobium rubi, Rhizobium larrymoorei, Rhizobium vitis, Rhizobium undicola, Rhizobium loessense, Rhizobium galegae and Rhizobium huautlense. Cells of the two isolates are Gram-negative, aerobic, motile and non-spore-forming rods (0?6-0?761?1-1?3 mm), with peritrichous flagella. The DNA G+C content is 60?1-60?9 mol%. Cellular fatty acids are C 16 : 0 (2?2-3?3 %), C 18 : 0 (2?1-3?2 %), C 19 : 0 cyclo v8c (9?9-16?8 %), C 20 : 3 v6,9,12c (2?7-3?3 %), summed feature 3 (7?2-7?7 %) and summed feature 7 (67?8-73?7 %). The strains formed nodules on a legume plant, Medicago sativa. A nifH gene encoding denitrogenase reductase, the key component of the nitrogenase enzyme complex, was detected in L61 T by PCR amplification by using a nifH-specific primer system. Strains L61 T and L22 were distinguished from the type strains of recognized Rhizobium species in the same sublineage based on low DNA-DNA hybridization values (2-4 %) and/or a 16S rRNA gene sequence similarity value of less than 96 %. Moreover, some phenotypic properties with respect to substrate utilization as a carbon or nitrogen source, antibiotic resistance and growth conditions could be used to discriminate L61 T and L22 from Rhizobium species in the same sublineage. Based on the results obtained in this study, L61 T and L22 are considered to be representatives of a novel species of Rhizobium, for which the name Rhizobium daejeonense sp. nov. is proposed. The type strain is L61 T (=KCTC 12121 T =IAM 15042 T =CCBAU 10050 T ).Since the first description of the genus Rhizobium for rootand/or stem-nodule bacteria by Frank (1889), a number of revisions and additions of novel species into this genus have been made. Currently, the genus Rhizobium includes 20 recognized species: Rhizobium galegae, R. huautlense, R. vitis, R. undicola, R. rubi, R. radiobacter, R. loessense, R. larrymoorei, R. mongolense, R. sullae, R. hainanense, R. leguminosarum, R. etli, R. tropici, R. rhizogenes, R. giardinii, R. gallicum, R. indigoferae, R. lupini and R. phaseoli.Cyanides have been regarded as toxic pollutants because of their inhibitory effect on cytochrome oxidase in respiratory electron transport chains; therefore, most countries request the complete removal of cyanide from wastewater effluent before discharge. Toxic cyanides have been known to be oxidized by various species of bacteria, fungi, yeast and plants. Isolations were made here of the cyanide-degrading bacterial population found in a bioreactor. Comparative The GenBank/EMBL/DDBJ accession numbers for...