ABSTRACT
DmoA is a monooxygenase which uses dioxygen (O2) and reduced flavin mononucleotide (FMNH2) to catalyze the oxidation of dimethylsulfide (DMS). Although it has been characterized, the structure of DmoA remains unknown. Here, the crystal structure of DmoA was determined to a resolution of 2.28â Å and was compared with those of its homologues LadA and BdsA. The results showed that their overall structures are similar: they all share a conserved TIM-barrel fold which is composed of eight α-helices and eight ß-strands. In addition, they all have five additional insertions. Detailed comparison showed that the structures have notable differences despite their high sequence similarity. The substrate-binding pocket of DmoA is smaller compared with those of LadA and BdsA.
Subject(s)
Hyphomicrobium/chemistry , Hyphomicrobium/enzymology , Mixed Function Oxygenases/chemistry , Mixed Function Oxygenases/metabolism , Sulfides/chemistry , Amino Acid Sequence , Crystallization , Hyphomicrobium/genetics , Mixed Function Oxygenases/genetics , Protein Structure, Secondary , Protein Structure, TertiaryABSTRACT
Molecular monitoring of bacterial communities can explain and predict the stability of bioprocesses in varying physicochemical conditions. To study methanol-fed denitrification biofilters of municipal wastewater treatment plants, bacterial communities of two full-scale biofilters were compared through fingerprinting and sequencing of the 16S rRNA genes. Additionally, 16S rRNA gene fingerprinting was used for 10-week temporal monitoring of the bacterial community in one of the biofilters. Combining the data with previous study results, the family Methylophilaceae and genus Hyphomicrobium were determined as suitable target groups for monitoring. An increase in the relative abundance of Hyphomicrobium-related biomarkers occurred simultaneously with increases in water flow, NO x- load, and methanol addition, as well as a higher denitrification rate, although the dominating biomarkers linked to Methylophilaceae showed an opposite pattern. The results indicate that during increased loading, stability of the bioprocess is maintained by selection of more efficient denitrifier populations, and this progress can be analyzed using simple molecular fingerprinting.
Subject(s)
Denitrification , Hyphomicrobium/chemistry , Methylophilaceae/chemistry , RNA, Ribosomal, 16S/genetics , Sewage/microbiology , Classification , Filtration , Methanol , Phylogeny , Temperature , Wastewater , Water/chemistryABSTRACT
Hyphomicrobium indicum Johnson and Weisrock 1969 lacks true budding and hyphal branching, and some phenotypic characteristics are in contrast to other true hyphomicrobia. The major quinone system (ubiquinone Q-8), the G+C content of the DNA (40 mol%) and the cellular fatty acid composition (16 : 0, 16 : 1 and 18 : 1 as the major components, and 12 : 0 3-OH and 14 : 0 3-OH as the hydroxy fatty acids) of H. indicum are different from the genus Hyphomicrobium, but similar to the genus Photobacterium. Like the marine bacteria Photobacterium, H. indicum can be tolerant of sea water, while Hyphomicrobium cannot. Phylogenetic analyses of 16S rRNA and gyrB gene sequences revealed that H. indicum is most closely related to the genus Photobacterium of the gamma-Proteobacteria. Based on the phylogenetic, phenotypic and chemotaxonomic evidence, the results indicate that H. indicum should be transferred to the genus Photobacterium, and the name Photobacterium indicum comb. nov. (type strain, NBRC 14233(T)=ATCC 19614(T)) is proposed.
Subject(s)
Hyphomicrobium/classification , Photobacterium/classification , Bacterial Proteins/genetics , Bacterial Typing Techniques , Base Composition , DNA Gyrase/genetics , DNA, Bacterial/chemistry , DNA, Bacterial/isolation & purification , DNA, Ribosomal/chemistry , DNA, Ribosomal/isolation & purification , Fatty Acids/analysis , Fatty Acids/isolation & purification , Genes, rRNA , Hyphomicrobium/chemistry , Hyphomicrobium/physiology , Molecular Sequence Data , Photobacterium/chemistry , Photobacterium/physiology , Phylogeny , Quinones/analysis , Quinones/isolation & purification , RNA, Bacterial/genetics , RNA, Ribosomal, 16S/genetics , Seawater , Sequence Analysis, DNAABSTRACT
The crystal structure of the oxidized cytochrome c(2) from Blastochloris (formerly Rhodopseudomonas) viridis was determined at 1.9 A resolution. Structural comparison with the reduced form revealed significant structural changes according to the oxidation state of the heme iron. Slight perturbation of the polypeptide chain backbone was observed, and the secondary structure and the hydrogen patterns between main-chain atoms were retained. The oxidation state-dependent conformational shifts were localized in the vicinity of the methionine ligand side and the propionate group of the heme. The conserved segment of the polypeptide chain in cytochrome c and cytochrome c(2) exhibited some degree of mobility, interacting with the heme iron atom by the hydrogen bond network. These results indicate that the movement of the internal water molecule conserved in various c-type cytochromes drives the adjustments of side-chain atoms of nearby residue, and the segmental temperature factor changes along the polypeptide chain.
