Thauera

About: Thauera is a research topic. Over the lifetime, 175 publications have been published within this topic receiving 6522 citations. The topic is also known as: P. butanovorae.

Taxonomic position of aromatic-degrading denitrifying pseudomonad strains K 172 and KB 740 and their description as new members of the genera Thauera, as Thauera aromatica sp. nov., and Azoarcus, as Azoarcus evansii sp. nov., respectively, members of the beta subclass of the Proteobacteria

Abstract: In the past workers have isolated several pseudomonad strains which have been used for studies of anaerobic aromatic metabolism. The best studied of these strains are strains KB 740T(T = type strain) and K172T. The taxonomic positions of these two organisms were determined by classical methods, including experiments to determine substrate spectrum, quinone type, and total fatty acid composition. Our results clearly excluded these strains from the authentic genus Pseudomonas, which belongs to the gamma subclass of the Proteobacteria. Instead, the properties of these organisms indicated that they belong to the beta subclass of the Proteobacteria. The sequences of the 16S ribosomal DNA genes confirmed this conclusion and indicated that strain K 172Trepresents a new species of the genus Thauera, Thauera aromatica, and that strain KB 740Trepresents a new species of the genus Azoarcus, Azoarcus evansii.

Phylogenetic and metabolic diversity of bacteria degrading aromatic compounds under denitrifying conditions, and description of Thauera phenylacetica sp. nov., Thauera aminoaromatica sp. nov., and Azoarcus buckelii sp. nov.

Abstract: Six strains of denitrifying bacteria isolated from various oxic and anoxic habitats on different monocyclic aromatic substrates were characterized by sequencing 16S rRNA genes, determining physiological and morphological traits, and DNA-DNA hybridization. According to these criteria, strains S100, SP and LG356 were identified as members of Thauera aromatica. Strains B5–1 and B5–2 were tentatively affiliated to the species Azoarcus tolulyticus. Strains B4P and S2 were only distantly related to each other and to other described Thauera species. These two strains are proposed as the type strains of two new species, Thauera phenylacetica sp. nov. and Thauera aminoaromatica sp. nov., respectively. By 16S rRNA gene analysis, strain U120 was highly related to the type strains of Azoarcus evansii and Azoarcus anaerobius, whereas corresponding DNA-DNA reassociation values indicated only a low degree of genomic relatedness. Based upon a low DNA similarity value and the presence of distinguishing physiological properties, strain U120 is proposed as the type strain of a new species, Azoarcus buckelii sp. nov. Almost all of the new isolates were obtained with different substrates. The highly varied substrate spectra of the isolates indicates that an even higher diversity of denitrifying bacteria degrading aromatic compounds would be discovered in the different habitats by using a larger spectrum of aromatic substrates for enrichment and isolation.

Aerobic and anaerobic toluene degradation by a newly isolated denitrifying bacterium, Thauera sp. strain DNT-1.

Abstract: A newly isolated denitrifying bacterium, Thauera sp. strain DNT-1, grew on toluene as the sole carbon and energy source under both aerobic and anaerobic conditions. When this strain was cultivated under oxygen-limiting conditions with nitrate, first toluene was degraded as oxygen was consumed, while later toluene was degraded as nitrate was reduced. Biochemical observations indicated that initial degradation of toluene occurred through a dioxygenase-mediated pathway and the benzylsuccinate pathway under aerobic and denitrifying conditions, respectively. Homologous genes for toluene dioxygenase (tod) and benzylsuccinate synthase (bss), which are the key enzymes in aerobic and anaerobic toluene degradation, respectively, were cloned from genomic DNA of strain DNT-1. The results of Northern blot analyses and real-time quantitative reverse transcriptase PCR suggested that transcription of both sets of genes was induced by toluene. In addition, the tod genes were induced under aerobic conditions, whereas the bss genes were induced under both aerobic and anaerobic conditions. On the basis of these results, it is concluded that strain DNT-1 modulates the expression of two different initial pathways of toluene degradation according to the availability of oxygen in the environment.

Strains in the genus Thauera exhibit remarkably different denitrification regulatory phenotypes

Abstract: Denitrifiers differ in how they handle the transition from oxic to anoxic respiration, with consequences for NO and N2O emissions. To enable stringent comparisons we defined parameters to describe denitrification regulatory phenotype (DRP) based on accumulation of NO2(-) , NO and N2O, oxic/anoxic growth and transcription of functional genes. Eight Thauera strains were divided into two distinct DRP types. Four strains were characterized by a rapid, complete onset (RCO) of all denitrification genes and no detectable nitrite accumulation. The others showed progressive onset (PO) of the different denitrification genes. The PO group accumulated nitrite, and no transcription of nirS (encoding nitrite reductase) was detected until all available nitrate (2 mM) was consumed. Addition of a new portion of nitrate to an actively denitrifying culture of a PO strain (T. terpenica) resulted in a transient halt in nitrite reduction, indicating that the electron flow was redirected to nitrate reductase. All eight strains controlled NO at nano-molar concentrations, possibly reflecting the importance of strict control for survival. Transient N2O accumulation differed by two orders of magnitude between strains, indicating that control of N2O is less essential. No correlation was seen between phylogeny (based on 16S rRNA and functional genes) and DRP.

Identification of acetate- or methanol-assimilating bacteria under nitrate-reducing conditions by stable-isotope probing.

Abstract: Stable-isotope probing (SIP) was used to identify acetate- or methanol-assimilating bacteria under nitrate-reducing conditions in activated sludge. A sludge sample obtained from wastewater treatment systems was incubated in a denitrifying batch reactor fed with synthetic wastewater containing [13C]acetate or [13C]methanol as the main carbon source and nitrate as the electron acceptor. We analyzed how growth of bacterial populations was stimulated by acetate or methanol as the external carbon source in nitrogen-removal systems. Most of the acetate- or methanol-assimilating bacteria identified by SIP have been known as denitrifiers in wastewater treatment systems. When acetate was used as the carbon source, 16S rRNA gene sequences retrieved from 13C-labeled DNA were closely related to the 16S rRNA genes of Comamonadaceae (e.g., Comamonas and Acidovorax) and Rhodocyclaceae (e.g., Thauera and Dechloromonas) of the Betaproteobacteria, and Rhodobacteraceae (e.g., Paracoccus and Rhodobacter) of the Alphaproteobacteria. When methanol was used as the carbon source, 16S rRNA gene sequences retrieved from 13C-DNA were affiliated with Methylophilaceae (e.g., Methylophilus, Methylobacillus, and Aminomonas) and Hyphomicrobiaceae. Rarefaction curves for clones retrieved from 13C-DNA showed that the diversity levels for methanol-assimilating bacteria were considerably lower than those for acetate-assimilating bacteria. Furthermore, we characterized nitrite reductase genes (nirS and nirK) as functional marker genes for denitrifier communities in acetate- or methanol-assimilating populations and detected the nirS or nirK sequence related to that of some known pure cultures, such as Alcaligenes, Hyphomicrobium, and Thauera. However, most of the nirS or nirK sequences retrieved from 13C-DNA were clustered in some unidentified groups. On the basis of 16S rRNA gene clone libraries retrieved from 13C-DNA, these unidentified nir sequences might be identified by examining the nir gene in candidates for true denitrifiers (e.g., the families Comamonadaceae, Hyphomicrobiaceae, Methylophilaceae, and Rhodobacteraceae).