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At least 19 recordsLinked to original sources

PubMed2002

Members of the family Comamonadaceae as primary poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-degrading denitrifiers in activated sludge as revealed by a polyphasic approach.

The distribution and phylogenetic affiliations of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-degrading denitrifying bacteria in activated sludge were studied by a polyphasic approach including culture-independent biomarker and molecular analyses as well as cultivation methods. A total of 23 strains of PHBV-degrading denitrifiers were isolated from activated sludges from different sewage treatment plants. 16S ribosomal DNA (rDNA) sequence comparisons showed that 20 of the isolates were identified as members of the family Comamonadaceae, a major group of beta-Proteobacteria. When the sludges from different plants were acclimated with PHBV under denitrifying conditions in laboratory scale reactors, the nitrate removal rate increased linearly during the first 4 weeks and reached 20 mg NO(3)(-)-N h(-1) g of dry sludge(-1) at the steady state. The bacterial-community change in the laboratory scale sludges during the acclimation was monitored by rRNA-targeted fluorescence in situ hybridization and quinone profiling. Both approaches showed that the population of beta-Proteobacteria in the laboratory sludges increased sharply during acclimation regardless of their origins. 16S rDNA clone libraries were constructed from two different acclimated sludges, and a total of 37 clones from the libraries were phylogenetically analyzed. Most of the 16S rDNA clones were grouped with members of the family Comamonadaceae. The results of our polyphasic approach indicate that beta-Proteobacteria, especially members of the family Comamonadaceae, are primary PHBV-degrading denitrifiers in activated sludge. Our data provide useful information for the development of a new nitrogen removal system with solid biopolymer as an electron donor.

Acclimatization↗

PubMed1999

Phylogenetic relationships among members of the Comamonadaceae, and description of Delftia acidovorans (den Dooren de Jong 1926 and Tamaoka et al. 1987) gen. nov., comb. nov.

The phylogenetic relationships among members of the family Comamonadaceae and several unclassified strains were studied by direct sequencing of their PCR-amplified 16S rRNA genes. Based on the 16S rRNA gene sequence analysis, members of the family formed a coherent group. The closest relatives are species of the Rubrivivax sub-group: Leptothrix discophora, Ideonella dechloratans and Rubrivivax gelatinosus. The genus Hydrogenophaga formed two subclusters, as did the species of Acidovorax, whereas the five species of the genus [Aquaspirillum] were polyphyletic. Comamonas acidovorans was phylogenetically distant from the type species of Comamonas, Comamonas terrigena. On the basis of this work and previous studies, Comamonas acidovorans is removed from the genus Comamonas and renamed as Delftia acidovorans gen. nov., comb. nov. Descriptions of the new genus Delftia and of the type species Delftia acidovorans, for which the type strain is ATCC 15668T, are presented.

DNA, Bacterial↗

PubMed1992

Rapid identification of bacteria of the Comamonadaceae with amplified ribosomal DNA-restriction analysis (ARDRA).

Ribosomal rRNA gene fragments (rDNA) encompassing the 16S rDNA, the 16S-23S rDNA spacer region and part of the 23S rDNA of 95 strains belonging to 13 well-described taxa of the eubacterial family Comamonadaceae (beta subclass of the Proteobacteria or rRNA superfamily III) were enzymatically amplified using conserved primers. The fragments of approximately 2400 base pairs were subjected to restriction analysis. Restriction fragment length patterns obtained with HinfI enabled us to distinguish 9 of the 13 taxa studied. Restriction with CfoI was necessary to differentiate Acidovorax delafieldii from A. temperans and Hydrogenophaga flava from H. pseudoflava. The results indicate that amplified rDNA restriction analysis is a simple and reliable tool for the identification of bacterial species.

Base Sequence↗

PubMed2001

Genetic diversity among 3-chloroaniline- and aniline-degrading strains of the Comamonadaceae.

We examined the diversity of the plasmids and of the gene tdnQ, involved in the oxidative deamination of aniline, in five bacterial strains that are able to metabolize both aniline and 3-chloroaniline (3-CA). Three strains have been described and identified previously, i.e., Comamonas testosteroni I2 and Delftia acidovorans CA28 and BN3.1. Strains LME1 and B8c were isolated in this study from linuron-treated soil and from a wastewater treatment plant, respectively, and were both identified as D. acidovorans. Both Delftia and Comamonas belong to the family Comamonadaceae. All five strains possess a large plasmid of ca. 100 kb, but the plasmids from only four strains could be transferred to a recipient strain by selection on aniline or 3-CA as a sole source of carbon and/or nitrogen. Plasmid transfer experiments and Southern hybridization revealed that the plasmid of strain I2 was responsible for total aniline but not 3-CA degradation, while the plasmids of strains LME1 and B8c were responsible only for the oxidative deamination of aniline. Several transconjugant clones that had received the plasmid from strain CA28 showed different degradative capacities: all transconjugants could use aniline as a nitrogen source, while only some of the transconjugants could deaminate 3-CA. For all four plasmids, the IS1071 insertion sequence of Tn5271 was found to be located on a 1.4-kb restriction fragment, which also hybridized with the tdnQ probe. This result suggests the involvement of this insertion sequence element in the dissemination of aniline degradation genes in the environment. By use of specific primers for the tdnQ gene from Pseudomonas putida UCC22, the diversity of the PCR-amplified fragments in the five strains was examined by denaturing gradient gel electrophoresis (DGGE). With DGGE, three different clusters of the tdnQ fragment could be distinguished. Sequencing data showed that the tdnQ sequences of I2, LME1, B8c, and CA28 were very closely related, while the tdnQ sequences of BN3.1 and P. putida UCC22 were only about 83% identical to the other sequences. Northern hybridization revealed that the tdnQ gene is transcribed only in the presence of aniline and not when only 3-CA is present.

Aniline Compounds↗

PubMed2006

Proposal of Giesbergeria voronezhensis gen. nov., sp. nov. and G. kuznetsovii sp. nov. and reclassification of [Aquaspirillum] anulus, [A.] sinuosum and [A.] giesbergeri as Giesbergeria anulus comb. nov., G. sinuosa comb. nov. and G. giesbergeri comb. nov., and [Aquaspirillum] metamorphum and [A.] psychrophilum as Simplicispira metamorpha gen. nov., comb. nov. and S. psychrophila comb. nov.

Five Gram-negative, motile, spiral-shaped strains were isolated from a sulfide spring (D-412T), active sludge of wastewater (D-419T, D-420, D-424) and industrial wastewater (D-416). Comparative 16S rRNA gene sequence analysis showed that the isolates belong to the family Comamonadaceae, within the class Betaproteobacteria, but fall into a distinct cluster. On the basis of phenotypic, chemotaxonomic and phylogenetic data, a new genus, Giesbergeria gen. nov., is proposed, including five species. The type species of the genus is Giesbergeria voronezhensis sp. nov. (type strain D-419T = DSM 12825T = CIP 107340T = VKM B-2350T) and other novel members of the genus are Giesbergeria kuznetsovii sp. nov. (type strain D-412T = DSM 12827T = VKM B-2352T), Giesbergeria giesbergeri comb. nov. (basonym Aquaspirillum giesbergeri), Giesbergeria sinuosa comb. nov. (basonym Aquaspirillum sinuosum) and Giesbergeria anulus comb. nov. (basonym Aquaspirillum anulus). Using the same criteria, isolate D-416 (= DSM 12826) was identified as a strain of [Aquaspirillum] metamorphum. Strain D-416, the type strain of [A.] metamorphum and the type strain of [Aquaspirillum] psychrophilum form a distinct cluster within the family Comamonadaceae (97-97.2% 16S rRNA gene sequence similarity) and share phenotypic and chemotaxonomic properties. Therefore, it is proposed that these strains are reclassified as members of a new genus, Simplicispira gen. nov., as Simplicispira metamorpha comb. nov. (the type species) and Simplicispira psychrophila comb. nov., respectively.

Comamonadaceae↗

PubMed2006

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

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 [(13)C]acetate or [(13)C]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 (13)C-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 (13)C-DNA were affiliated with Methylophilaceae (e.g., Methylophilus, Methylobacillus, and Aminomonas) and Hyphomicrobiaceae. Rarefaction curves for clones retrieved from (13)C-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 (13)C-DNA were clustered in some unidentified groups. On the basis of 16S rRNA gene clone libraries retrieved from (13)C-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).

Acetates↗

PubMed2001

Relationships within the Proteobacteria of plant pathogenic Acidovorax species and subspecies, Burkholderia species, and Herbaspirillum rubrisubalbicans by sequence analysis of 16S rDNA, numerical analysis and determinative tests.

Sequence data for 16S rDNA of the type strains of Acidovorax avenae subsp. avenae, A. avenae subsp. cattleyae, A. avenae subsp. citrulli, A. konjaci and Herbaspirillum rubrisubalbicans were compared with GenBank library accessions of Burkholderia spp., Comamonas sp., Ralstonia solanacearum and Variovorax sp. Maximum Parsimony analysis produced two clusters: 1. Acidovorax spp., Comamonas sp., and Variovorax sp. (all in the Comamonadaceae), and 2. Burkholderia spp., Ralstonia solanacearum, and Herbaspirillum rubrisubalbicans. Maximum Likelihood analysis produced only one cluster (of the Comamonadaceae). Using nutritional and laboratory tests, all Acidovorax spp., Burkholderia spp., and Herbaspirillum rubrisubalbicans were discriminated in distinct clusters at the species level, and could be identified by selected determinative tests. There were no phenotypic tests constituted as a circumscription of the genera and which permitted the allocation of strains to genera. Strain identification as species allowed allocation to genera only by inference. The nomenclatural implications of these data are discussed.

Base Sequence↗

PubMed2000

Acidovorax anthurii sp. nov., a new phytopathogenic bacterium which causes bacterial leaf-spot of anthurium.

The bacterial leaf-spot of anthurium emerged during the 1980s, in the French West Indies and Trinidad. This new bacterial disease is presently wide spread and constitutes a serious limiting factor for commercial anthurium production. Twenty-nine strains isolated from leaf-spots of naturally infected anthurium were characterized and compared with reference strains belonging to the Comamonadaceae family, the genera Ralstonia and Burkholderia, and representative fluorescent pseudomonads. From artificial inoculations 25 out of 29 strains were pathogenic on anthurium. Biochemical and physiological tests, fatty acid analysis, DNA-DNA hybridization, 16S rRNA gene sequence analysis, DNA-16S RNA hybridization were performed. The 25 pathogenic strains on anthurium were clustered in one phenon closely related to phytopathogenic strains of the genus Acidovorax. Anthurium strains were 79-99% (deltaTm range 0.2-1.6) related to the strain CFBP 3232 and constituted a discrete DNA homology group indicating that they belong to the same species. DNA-rRNA hybridization, 16S rRNA sequence and fatty acid analysis confirmed that this new species belongs to the beta-subclass of Proteobacteria and to rRNA superfamily III, to the family of Comamonadaceae and to the genus Acidovorax. The name Acidovorax anthurii is proposed for this new phytopathogenic bacterium. The type strain has been deposited in the Collection Française des Bactéries Phytopathogènes as CFBP 3232T.

Base Composition↗

PubMed2001

Xenophilus azovorans gen. nov., sp. nov., a soil bacterium that is able to degrade azo dyes of the Orange II type.

The taxonomy of strain KF46FT, which was isolated previously after an aerobic enrichment with the azo compound 1-(4'-carboxyphenylazo)-2-naphthol as the sole source of energy and carbon, was investigated by a polyphasic approach. The organism contained a quinone system with ubiquinone Q-8 and 2-hydroxyputrescine and putrescine as the major polyamines, suggesting that strain KF46FT belonged to the beta-subclass of the Proteobacteria. The polar lipid profile consisted mainly of phosphatidylethanolamine and minor amounts of phosphatidylglycerol and diphosphatidylglycerol. Sequencing of the 16S rRNA gene supported its placement in the family Comamonadaceae, but the sequence similarities to the most closely related species of the genera Hydrogenophaga, Acidovorax, Comamonas and Xylophilus were only in the range 95.0 to 96.1%. Different methods for the construction of phylogenetic trees showed the separate position of strain KF46FT 'between' the genera Hydrogenophaga, Variovorax, Comamonas and Xylophilus. Analysis of the fatty acids revealed an unusual profile, with the presence of 8:0 3-OH, 10:0 3-OH, 16:1 2-OH, 16:0 2-OH and 18:1 2-OH in addition to 17:0 cyclo, which is unique among the previously described genera of the family Comamonadaceae. Thus, a new taxon is proposed for strain KF46FT, with the name Xenophilus azovorans gen. nov., sp. nov.

Azo Compounds↗

PubMed2004

Ottowia thiooxydans gen. nov., sp. nov., a novel facultatively anaerobic, N2O-producing bacterium isolated from activated sludge, and transfer of Aquaspirillum gracile to Hylemonella gracilis gen. nov., comb. nov.

Strain K11T was isolated from activated sludge of a municipal wastewater-treatment plant. Phylogenetic analysis of the 16S rRNA gene sequence revealed that it represents a distinct line of descent within the Comamonadaceae. The novel strain was a Gram-negative, catalase- and oxidase-positive, non-motile, straight to slightly curved rod. Polyhydroxyalkanoate granules were stored intracellularly as reserve material. Colonies on agar plates were small, regular and characterized by a water-insoluble yellow pigment. Unbranched fatty acids 16:1omega7c, 16:0 and 18:1omega7c dominated the cellular fatty acid pattern and ubiquinone-8 (Q-8) was the major component of the respiratory lipoquinones, both traits typical of members of the Comamonadaceae. A distinguishing characteristic was the presence of the two hydroxy fatty acids 10:0 3-OH and 12:0 2-OH, each in significant amounts. The G+C content of the DNA was 59 mol%. Strain K11T was capable of aerobic chemolithoheterotrophic growth using thiosulfate as an additional substrate, but could not grow autotrophically with thiosulfate or hydrogen. Facultative anaerobic growth was possible with nitrate and nitrite as electron acceptors, but not with ferric iron, sulfate or by fermentation. The sole end product of denitrification was N2O; nitrite accumulated only transiently in small amounts. Based upon phylogenetic and phenotypic evidence, it is proposed to establish the novel taxon Ottowia thiooxydans gen. nov., sp. nov., represented by the type strain K11T (=DSM 14619T=JCM 11629T). Aquaspirillum gracile was among the phylogenetically most closely related species to strain K11T. This species has been wrongly classified, and it is proposed to reclassify it as Hylemonella gracilis gen. nov., comb. nov. The type strain is ATCC 19624T (=DSM 9158T).

Betaproteobacteria↗

PubMed2006

Microbial community succession in an unvegetated, recently deglaciated soil.

Primary succession is a fundamental process in macroecosystems; however, if and how soil development influences microbial community structure is poorly understood. Thus, we investigated changes in the bacterial community along a chronosequence of three unvegetated, early successional soils ( approximately 20-year age gradient) from a receding glacier in southeastern Peru using molecular phylogenetic techniques. We found that evenness, phylogenetic diversity, and the number of phylotypes were lowest in the youngest soils, increased in the intermediate aged soils, and plateaued in the oldest soils. This increase in diversity was commensurate with an increase in the number of sequences related to common soil bacteria in the older soils, including members of the divisions Acidobacteria, Bacteroidetes, and Verrucomicrobia. Sequences related to the Comamonadaceae clade of the Betaproteobacteria were dominant in the youngest soil, decreased in abundance in the intermediate age soil, and were not detected in the oldest soil. These sequences are closely related to culturable heterotrophs from rock and ice environments, suggesting that they originated from organisms living within or below the glacier. Sequences related to a variety of nitrogen (N)-fixing clades within the Cyanobacteria were abundant along the chronosequence, comprising 6-40% of phylotypes along the age gradient. Although there was no obvious change in the overall abundance of cyanobacterial sequences along the chronosequence, there was a dramatic shift in the abundance of specific cyanobacterial phylotypes, with the intermediate aged soils containing the greatest diversity of these sequences. Most soil biogeochemical characteristics showed little change along this approximately 20-year soil age gradient; however, soil N pools significantly increased with soil age, perhaps as a result of the activity of the N-fixing Cyanobacteria. Our results suggest that, like macrobial communities, soil microbial communities are structured by substrate age, and that they, too, undergo predictable changes through time.

Bacteria↗

PubMed2005

Hydrogenophaga defluvii sp. nov. and Hydrogenophaga atypica sp. nov., isolated from activated sludge.

Two Gram-negative, oxidase-positive rods (strains BSB 9.5T and BSB 41.8T) isolated from wastewater were studied using a polyphasic approach. 16S rRNA gene sequence comparisons demonstrated that both strains cluster phylogenetically within the family Comamonadaceae: the two strains shared 99.9 % 16S rRNA gene sequence similarity and were most closely related to the type strains of Hydrogenophaga palleronii (98.5 %) and Hydrogenophaga taeniospiralis (98.0 %). The fatty acid patterns and substrate-utilization profiles displayed similarity to the those of the five Hydrogenophaga species with validly published names, although clear differentiating characteristics were also observed. The two strains showed DNA-DNA hybridization values of 51 % with respect to each other. No close similarities to any other Hydrogenophaga species were detected in hybridization experiments with the genomic DNAs. On the basis of these results, two novel Hydrogenophaga species, Hydrogenophaga defluvii sp. nov. and Hydrogenophaga atypica sp. nov. are proposed, with BSB 9.5T (=DSM 15341T=CIP 108119T) and BSB 41.8T (=DSM 15342T=CIP 108118T) as the respective type strains.

Comamonadaceae↗

PubMed2005

Malikia granosa gen. nov., sp. nov., a novel polyhydroxyalkanoate- and polyphosphate-accumulating bacterium isolated from activated sludge, and reclassification of Pseudomonas spinosa as Malikia spinosa comb. nov.

A Gram-negative, motile, rod-shaped bacterium, designated strain P1(T), was isolated from activated sludge of a municipal wastewater treatment plant. Phylogenetic analysis of its 16S rRNA gene sequence placed the novel isolate among representatives of the family Comamonadaceae. The closest relatives in reconstructed phylogenetic trees were Pseudomonas spinosa, Macromonas bipunctata and Hydrogenophaga species. Strain P1(T) was not able to grow anaerobically or autotrophically, reduced nitrate to nitrite and required vitamins for growth. Ubiquinone 8 (Q8) and 3-hydroxy-substituted fatty acids were present, but 2-hydroxy fatty acids were absent. The G+C content of the DNA was 67 mol%. Phenotypic characteristics allowed a clear differentiation of strain P1(T) from representatives of the genera Hydrogenophaga and Macromonas, whereas DNA-DNA hybridization experiments revealed that strain P1(T) did not belong to the species P. spinosa. As a peculiarity, cells of strain P1(T) and P. spinosa ATCC 14606(T) were able to accumulate large amounts of polyhydroxyalkanoates and polyphosphate in the form of large intracellular granules. Apparently in both strains nitrogen limitation stimulates the production of polyhydroxyalkanoates, whereas carbon starvation induces the formation of polyphosphates. Based upon phylogenetic and phenotypic evidence, it is proposed to establish the novel taxon Malikia granosa gen. nov., sp. nov., represented by the type strain P1(T) (=DSM 15619(T)=JCM 12706(T)=CIP 108194(T)). The most closely related species of strain P1(T) was P. spinosa. This species has been misclassified, and it is proposed to transfer it to the new genus Malikia as Malikia spinosa gen. nov., comb. nov. The type strain is ATCC 14606(T) (=DSM 15801(T)).

Comamonadaceae↗

PubMed2005

Molecular characterization of the nonphotosynthetic partner bacterium in the consortium "Chlorochromatium aggregatum".

Phototrophic consortia represent valuable model systems for the study of signal transduction and coevolution between different bacteria. The phototrophic consortium "Chlorochromatium aggregatum" consists of a colorless central rod-shaped bacterium surrounded by about 20 green-pigmented epibionts. Although the epibiont was identified as a member of the green sulfur bacteria, and recently isolated and characterized in pure culture, the central colorless bacterium has been identified as a member of the beta-Proteobacteria but so far could not be characterized further. In the present study, "C. aggregatum" was enriched chemotactically, and the 16S rRNA gene sequence of the central bacterium was elucidated. Based on the sequence information, fluorescence in situ hybridization probes targeting four different regions of the 16S rRNA were designed and shown to hybridize exclusively to cells of the central bacterium. Phylogenetic analyses of the 1,437-bp-long sequence revealed that the central bacterium of "C. aggregatum" represents a so far isolated phylogenetic lineage related to Rhodoferax spp., Polaromonas vacuolata, and Variovorax paradoxus within the family Comamonadaceae. The majority of relatives of this lineage are not yet cultured and were found in low-temperature aquatic environments or aquatic environments containing xenobiotica or hydrocarbons. In CsCl-bisbenzimidazole equilibrium density gradients, genomic DNA of the central bacterium of "Chlorochromatium aggregatum" formed a distinct band which could be detected by quantitative PCR using specific primers. Using this method, the G+C content of the central bacterium was determined to be 55.6 mol%.

Base Composition↗

PubMed2005

Investigation of an acetate-fed denitrifying microbial community by stable isotope probing, full-cycle rRNA analysis, and fluorescent in situ hybridization-microautoradiography.

The acetate-utilizing microbial consortium in a full-scale activated sludge process was investigated without prior enrichment using stable isotope probing (SIP). [13C]acetate was used in SIP to label the DNA of the denitrifiers. The [13C]DNA fraction that was extracted was subjected to a full-cycle rRNA analysis. The dominant 16S rRNA gene phylotypes in the 13C library were closely related to the bacterial families Comamonadaceae and Rhodocyclaceae in the class Betaproteobacteria. Seven oligonucleotide probes for use in fluorescent in situ hybridization (FISH) were designed to specifically target these clones. Application of these probes to the sludge of a continuously fed denitrifying sequencing batch reactor (CFDSBR) operated for 16 days revealed that there was a significant positive correlation between the CFDSBR denitrification rate and the relative abundance of all probe-targeted bacteria in the CFDSBR community. FISH-microautoradiography demonstrated that the DEN581 and DEN124 probe-targeted cells that dominated the CFDSBR were capable of taking up [14C]acetate under anoxic conditions. Initially, DEN444 and DEN1454 probe-targeted bacteria also dominated the CFDSBR biomass, but eventually DEN581 and DEN124 probe-targeted bacteria were the dominant bacterial groups. All probe-targeted bacteria assessed in this study were denitrifiers capable of utilizing acetate as a source of carbon. The rapid increase in the number of organisms positively correlated with the immediate increase in denitrification rates observed by plant operators when acetate is used as an external source of carbon to enhance denitrification. We suggest that the impact of bacteria on activated sludge subjected to intermittent acetate supplementation should be assessed prior to the widespread use of acetate in the wastewater industry to enhance denitrification.

Acetates↗

PubMed2003

Application of polyhydroxyalkanoates for denitrification in water and wastewater treatment.

Application of polyhydroxyalkanoates (PHAs) and related biodegradable polymers has gained momentum in various areas of biotechnology. A promising application that started appearing in the past decade is the use of PHAs as the solid substrate for denitrification of water and wastewater. This type of denitrification, termed here "solid-phase denitrification", has several advantages over the conventional system supplemented with liquid organic substrate. PHAs serve not only as constant sources of reducing power for denitrification but also as solid matrices favorable for development of microbial films. In addition, in contrast to conventional processes, the use of PHAs has no potential risk of release of dissolved organic carbon with the resultant deterioration of effluent water quality. If the production cost of PHAs can be brought down, its application to the denitrification process will become economically more promising. A number of PHA-degrading denitrifying bacteria have been isolated and characterized from activated sludge and continuous flow-bed reactors for denitrification with PHAs. Most of these isolates have been assigned phylogenetically to members of beta-Proteobacteria, especially those of the family Comamonadaceae. The metabolic and regulatory relationships between PHA degradation and denitrification, and the interactive relationship between PHA-degrading cells and the solid surface structure are important subjects awaiting future studies, which would provide a new insight into our comprehensive understanding of the solid-phase denitrification process.

Betaproteobacteria↗

PubMed2004

High phylogenetic diversity of transconjugants carrying plasmid pJP4 in an activated sludge-derived microbial community.

Transconjugants of plasmid pJP4, originating from an agar plate mating of a Pseudomonas putida donor with an activated sludge-derived microbial community, were isolated and identified by partial 16S rDNA sequencing. The transconjugant strains belonged to a variety of genera of the alpha-, beta-, gamabeta- and gamma-classes of the Proteobacteria, mostly to the families Rhizobiaceae and Comamonadaceae and the genus Stenotrophomonas. Only P. putida and Delftia spp. strains were able to grow on 2,4-D as the sole carbon source.

Conjugation, Genetic↗

PubMed2000

Polyphasic characterization of poly-3-hydroxybutyrate-co-3-hydroxyvalerate (p(HB-co-HV)) metabolizing and denitrifying Acidovorax sp. strains.

For the purpose of denitrification in small drinking water plants, a bacterial mixed population was isolated from a packed bed column bioreactor with poly-3-hydroxybutyrate-co-3-hydroxyvalerate (P(HB-co-HV)) as a substrate for the denitrification of ground water (10 degrees C). Isolates 2nIII from the mixed culture, with the ability to denitrify and metabolize P(HB-co-HV), were used as starter cultures for the elimination of nitrate in ground water. The strains were characterized by diverse techniques. Classical phenotypic studies lead to rRNA group III of the genus Pseudomonas. Results obtained by molecular techniques demonstrated that the 2nIII strains are members of the Comamonadaceae and shows similarities to the genus Acidovorax. However, an integration of the 2nIII isolates within one of the known Acidovorax species is not possible for the moment. The 2nIII starter cultures clustered close to Av. temperans according to their whole cell proteins and fatty acids, whereas in DNA/DNA hybridization no significant DNA binding (< 25%) was found. In contrast a significant but low degree of DNA/DNA hybridization was found between the 2nIII strains and Av. facilis and Av. delafieldii. Our polyphasic results lead to the conclusion that the 2nIII strains may constitute a separate Acicdovorax species.

Bacterial Typing Techniques↗