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Microbial diversity in biofilms from corroding heating systems.

Culture-independent investigations of the bacterial diversity and activity in district heating systems with and without corrosion did not make it possible to relate one group of microorganisms with the observed corrosion. Fluorescence in situ hybridization by oligonucleotide probes revealed the dominance of beta-proteobacteria, sulphate reducing prokaryotes and alpha-proteobacteria. Analysis of a clone library from one Danish heating (DH) system showed that the most sequences formed two clusters within the alpha-proteobacteria affiliated to the families Rhizobiaceae and Acetobacteraceae and two clusters within the beta-proteobacteria belonging to the family Comamonadaceae. Functional groups were determined by microautoradiography showing aerobic and anaerobic bacteria (sulphate reducing and methanogenic bacteria). The corrosion study showed that pitting corrosion rates were five to ten times higher than the general corrosion rates, suggesting the presence of biocorrosion. The results indicate that several bacterial groups could be involved in corrosion of DH system piping including sulphate reducing prokaryotes, Acidovorax (within the beta-proteobacteria), methanogenic bacteria and others.

Bacteria↗

Minimizing decompression and warming during deep seawater collection increases abundance and activity of autochthonous bacteria and archaea.

The deep ocean hosts autochthonous pressure-adapted microorganisms that are unique to this environment, as well as allochthonous pressure-sensitive members transported from shallow depths by vertical advection and particle-sinking. However, conventional sampling instruments decompress and warm deep-sea samples during retrieval, potentially altering microbial properties when studied ex situ. Here, we assess this potential sampling bias by comparing seawater microbial communities collected with or without measures aimed at minimizing pressure and temperature effects. When compared to samples collected under pressurized conditions, conventional sampling (using Niskin bottles) was found to affect prokaryotic cells retrieved by reducing their total numbers, diminishing protein synthesis activity (>10%), and also causing overall shifts in the community composition. The most significant compositional change was a >20% decrease in metagenomic archaeal representation (TACK-group/Thaumarchaeota/Nitrososphaerota). Deep-sea bacterial groups had mixed responses to preserving pressure during retrieval, with some groups exhibiting higher representation when samples were maintained pressurized (e.g. members of the family Pelagibacteraceae, unclassified Thiotricales, Thioglobaceae, and Chitinophagaceae), whereas others increased their representation when decompressed (e.g. Burkholderiaceae, Comamonadaceae, and Oxalobacteraceae). This study reveals the existence of bias introduced by the complete decompression of samples retrieved with traditional instrumentation, as well as a decrease in overall bacterial activity when samples are completely decompressed during retrieval. Additionally, incubations lasting for >24 h were shown to transform the original prokaryotic community composition. Precautions addressing these effects are necessary to enhance the reliability of ex situ measurements and improve our understanding of deep-sea microbial ecology and biogeochemistry.

Seawater↗

Transfer of several phytopathogenic Pseudomonas species to Acidovorax as Acidovorax avenae subsp. avenae subsp. nov., comb. nov., Acidovorax avenae subsp. citrulli, Acidovorax avenae subsp. cattleyae, and Acidovorax konjaci.

DNA-rRNA hybridizations, DNA-DNA hybridizations, polyacrylamide gel electrophoresis of whole-cell proteins, and a numerical analysis of carbon assimilation tests were carried out to determine the relationships among the phylogenetically misnamed phytopathogenic taxa Pseudomonas avenae, Pseudomonas rubrilineans, "Pseudomonas setariae," Pseudomonas cattleyae, Pseudomonas pseudoalcaligenes subsp. citrulli, and Pseudomonas pseudoalcaligenes subsp. konjaci. These organisms are all members of the family Comamonadaceae, within which they constitute a separate rRNA branch. Only P. pseudoalcaligenes subsp. konjaci is situated on the lower part of this rRNA branch; all of the other taxa cluster very closely around the type strain of P. avenae. When they are compared phenotypically, all of the members of this rRNA branch can be differentiated from each other, and they are, as a group, most closely related to the genus Acidovorax. DNA-DNA hybridization experiments showed that these organisms constitute two genotypic groups. We propose that the generically misnamed phytopathogenic Pseudomonas species should be transferred to the genus Acidovorax as Acidovorax avenae and Acidovorax konjaci. Within Acidovorax avenae we distinguished the following three subspecies: Acidovorax avenae subsp. avenae, Acidovorax avenae subsp. cattleyae, and Acidovorax avenae subsp. citrulli. Emended descriptions of the new taxa are presented.

DNA, Bacterial↗

Comamonas nitrativorans sp. nov., a novel denitrifier isolated from a denitrifying reactor treating landfill leachate.

A group of Gram-negative denitrifying bacteria has been isolated from a denitrifying reactor treating landfill leachate. The new isolates produced both oxidase and catalase and showed growth on acetate, butyrate, n-caproate, i-butyrate, i-valerate, propionate, n-valerate, lactate, alanine, benzoate, phenylalanine and ethanol. No growth was observed on sugars. The bacteria could perform anoxic reduction of nitrate, nitrite and nitrous oxide to nitrogen, coupled to the oxidation of the same substrates as those used under aerobic conditions, except for aromatic compounds. They were very efficient denitrifiers, as estimated from the specific rate of N2 gas production. All the strains showed the same 16S rDNA restriction profile and one of them, designated 23310T, was selected for phylogenetic analysis. The organism clustered within the family Comamonadaceae, being related to Comamonas terrigena (95.8% sequence similarity). On the basis of the phylogenetic analysis, physiological characterization and the ability to efficiently reduce nitrate to N2, it is proposed that the bacterium be assigned to a new species, Comamonas nitrativorans. The type strain is 23310T (= DSM 13191T = NCCB 100007T = CCT 7062T).

Anaerobiosis↗

Caldimonas manganoxidans gen. nov., sp. nov., a poly(3-hydroxybutyrate)-degrading, manganese-oxidizing thermophile.

A poly(3-hydroxybutyrate) (PHB)-degrading, gram-negative, aerobic bacterium, strain HS(T), was isolated from a hot spring and chemotaxonomically and phylogenetically characterized. The oxidase-positive, weakly catalase-positive, non-pigmented cells (0.6 x 2.6 microm) exhibited a single polar flagellum and accumulated PHB granules. Strain HS(T) was capable of manganese oxidation. Highest growth rate was attained at 50 degrees C. The optimum pH for growth was 7-8. The major respiratory quinone was ubiquinone-8 and major cellular fatty acids were C16:0, C16:1 and C18:1. The G+C content of the DNA was 66.2 mol%. Comparative 16S rDNA analysis indicated that strain HS(T) is related to the Rubrivivax subgroup and the family Comamonadaceae. The nearest phylogenetic relatives were Ideonella dechloratans (92.1% similarity), Leptothrix discophora (93.6%), Roseateles depolymerans (92.4%) and Rubrivivax gelatinosus (92.2%). On the basis of its phylogenetic and phenotypic properties, it is proposed that this isolate be designated Caldimonas manganoxidans gen. nov., sp. nov.; the type strain is HS(T) (= JCM 10698T = IFO 16448T = ATCC BAA-369T).

Bacterial Typing Techniques↗

Alicycliphilus denitrificans gen. nov., sp. nov., a cyclohexanol-degrading, nitrate-reducing beta-proteobacterium.

A facultatively denitrifying bacterium, strain K601T, was isolated at 30 degrees C from a municipal sewage plant on cyclohexanol as sole carbon source and nitrate as electron acceptor. Under aerobic conditions this strain used acetate, fumarate, lactate, pyruvate, crotonate, indole, glucose, vanillate, 4-hydroxybenzoate, m-cresol, o-cresol and p-cresol. Under denitrifying conditions the strain used cyclohexanol, cyclohexanone, 1,3-cyclohexanedione, 2-cyclohexenone, 1,3-cyclohexanediol (cis and trans), monocarboxylic acids (C2-C7), adipate, pimelate, 5-oxocaproate, citrate, 2-oxoglutarate, succinate, malate, crotonate, lactate, pyruvate and fumarate. Cells were short rods, 0.6 microm wide and 1-2 microm long, motile, non-spore-forming, Gram-negative, and catalase- and oxidase-positive. Strain K601T used nitrate, nitrite and oxygen as electron acceptors, but not sulfate, sulfite or fumarate. The DNA G+C content of strain K601T was 66 mol%. Phylogenetic analysis, based on 16S rDNA sequencing, showed that strain K601T represents a separate lineage of the family Comamonadaceae in the beta-subclass of Proteobacteria. Based on the high 16S rDNA sequence divergence and phenotypic characteristics, the name Alicycliphilus denitrificans gen. nov., sp. nov. is proposed for this strain. The type strain is K60IT (=DSM 14773T =CIP 107495T).

Base Composition↗

Acidovorax valerianellae sp. nov., a novel pathogen of lamb's lettuce [Valerianella locusta (L.) Laterr].

Bacterial spot disease of lamb's lettuce [Valerianella locusta (L.) Laterr.] was first observed in fields in 1991. This new bacterial disease is localized in western France in high-technology field production of lamb's lettuce for the preparation of ready-to-use salad. Nineteen strains isolated in 1992 and 1993 from typical black leaf spots of naturally infected lamb's lettuce were characterized and compared with reference strains of Acidovorax and Delftia. The pathogenicity of the 19 strains was confirmed by artificial inoculation. Biochemical and physiological tests, fatty acid profiles, DNA-DNA hybridization and other nucleic acid-based tests were performed. A numerical taxonomic analysis of the 19 lamb's lettuce strains showed a single homogeneous phenon closely related to previously described phytopathogenic taxa of the genus Acidovorax. DNA-DNA hybridization studies showed that the lamb's lettuce strains were 91-100% related to a representative strain, strain CFBP 4730(T), and constituted a discrete DNA hybridization group, indicating that they belong to the same novel species. Results from DNA-rRNA hybridization, 16S rRNA sequence analysis and fatty acid analysis studies confirmed that this novel species belongs to the beta-subclass of the Proteobacteria and, more specifically, to the family Comamonadaceae and the genus Acidovorax. The name Acidovorax valerianellae sp. nov. is proposed for this novel taxon of phytopathogenic bacteria. The type strain is strain CFBP 4730(T) (= NCPPB 4283(T)).

Bacterial Typing Techniques↗

Polaromonas naphthalenivorans sp. nov., a naphthalene-degrading bacterium from naphthalene-contaminated sediment.

Strain CJ2T, capable of growth on naphthalene as a sole carbon and energy source, was isolated from coal-tar-contaminated freshwater sediment. The Gram reaction of strain CJ2T was negative. The cells were non-spore-forming, non-motile cocci (without flagella). The isolate was found to be an aerobic heterotroph capable of utilizing glucose and other simple sugars. Growth was observed between 4 and 25 degrees C (optimum, 20 degrees C) and between pH 6.0 and 9.0 (optimum, pH 7.0-7.5). The G+C content of the genomic DNA was 61.5 mol% and the major quinone was ubiquinone-8. The peptidoglycan of strain CJ2T was determined as belonging to type A1-gamma, meso-diaminopimelic acid. The major fatty acids of strain CJ2T were 16:1omega7c (67.0%), 16:0 (19.6%), 18:1omega7c (approximately 7.9%) and 10:0 3-OH (approximately 2.5%). The polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. Mycolic acid and glycolipids could not be detected. Comparative 16S rDNA analysis indicated that strain CJ2T is related to the family Comamonadaceae and that the nearest phylogenetic relative was Polaromonas vacuolata 34-PT (97.1% similarity). On the basis of the physiological and molecular properties, the naphthalene-degrading isolate was designated Polaromonas naphthalenivorans sp. nov. The type strain is CJ2T (=ATCC BAA-779T=DSM 15660T).

Biodegradation, Environmental↗

Exploring prokaryotic taxonomy.

Techniques drawn from exploratory data analysis, using tools found in the S-Plus statistical software package, have been used to inspect and maintain the Bergey's Taxonomic Outline and to move towards an automated and community-based means of working on the outline. These techniques can be used to classify sequences from unnamed and uncultured organisms, to visualize errors in the taxonomy or in the curation of the sequences, to suggest emendations to the taxonomy or to the classification of extant species and to complement the visualization of phylogenies based on treeing methods. A dataset of more than 9200 aligned small-subunit rRNA sequences was analysed in the context of the current taxonomic outline. The use of the algorithm in exploring and modifying the taxonomy is illustrated with an example drawn from the family Comamonadaceae.

Bacteria↗

Isolation and characterization of a new poly(3-hydroxybutyrate)-degrading, denitrifying bacterium from activated sludge.

A new denitrifying chemoorganotrophic bacterium capable of aerobic and anaerobic degradation of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) was isolated from activated sludge. A phylogenetic analysis based on 16S rDNA sequences indicated that the new isolate is a member of the beta subclass of the Proteobacteria and represents a distinct line of descent within the family Comamonadaceae. During denitrifying growth with 3-hydroxybutyrate, PHB, or PHBV as the sole carbon source, the isolate reduced nitrate to N2 without appreciable accumulation of nitrite and nitrous oxide as intermediate products. Kinetic analyses of the denitrification with different grades of PHBV indicated that approximately 0.7 g of PHBV was required to reduce 1 g of NO3-. A high denitrification rate (19 mg N-NO3- removed h(-1) x g(-1) dry wt of cells) was found with PHBV as the electron donor.

Anaerobiosis↗

Phylogenetic analysis of the genus Aquaspirillum based on 16S rRNA gene sequences.

Phylogenetic analysis of 15 species of the genus Aquaspirillum based on 16S rRNA gene (rDNA) sequences indicated that the genus Aquaspirillum is phylogenetically heterogeneous and the species could be divided into four groups as follows: Aquaspirillum serpens, the type species of this genus, A. dispar and A. putridiconchylium are situated in the family Neisseriaceae; members of the second group, A. gracile, A. delicatum, A. anulus, A. giesbergeri, A. sinuosum, A. metamorphum and A. psychrophilum, are included in the family Comamonadaceae; the two members of the third group, A. arcticum and A. autotrophicum, are included in the family Oxalobacteriaceae; and members of the fourth group, A. polymorphum, A. peregrinum, and A. itersonii, are included in the alpha-subdivision of Proteobacteria. Thus, phylogenetic studies indicated that all the species excepting A. serpens, the type species, should be transferred to distinct genera.

Fresh Water↗

Identification of bacterial groups preferentially associated with mycorrhizal roots of Medicago truncatula.

The genetic structures of bacterial communities associated with Medicago truncatula Gaertn. cv. Jemalong line J5 (Myc+ Nod+) and its symbiosis-defective mutants TRV48 (Myc+ Nod-) and TRV25 (Myc- Nod-) were compared. Plants were cultivated in a fertile soil (Châteaurenard, France) and in soil from the Mediterranean basin showing a low fertility (Mas d'Imbert, France). Plant growth, root architecture, and the efficiency of root symbiosis of the three plant genotypes were characterized in the two soils. Structures of the bacterial communities were assessed by automated-ribosomal intergenic spacer analysis (A-RISA) fingerprinting from DNA extracted from the rhizosphere soil and root tissues. As expected, the TRV25 mutant did not develop endomycorrhizal symbiosis in any of the soils, whereas mycorrhization of line J5 and the TRV48 mutant occurred in both soils but at a higher intensity in the Mas d'Imbert (low fertility) than in the Châteaurenard soil. However, modifications of plant growth and root architecture, between mycorrhizal (J5 and TRV48) and nonmycorrhizal (TRV25) plants, were recorded only when cultivated in the Mas d'Imbert soil. Similarly, the genetic structures of bacterial communities associated with mycorrhizal and nonmycorrhizal plants differed significantly in the Mas d'Imbert soil but not in the Châteaurenard soil. Multivariate analysis of the patterns allowed the identification of molecular markers, explaining these differences, and markers were further sequenced. Molecular marker analysis allowed the delineation of 211 operational taxonomic units. Some of those belonging to the Comamonadaceae and Oxalobacteraceae (beta-Proteobacteria) families were found to be significantly more represented within bacterial communities associated with the J5 line and the TRV48 mutant than within those associated with the TRV25 mutant, indicating that these bacterial genera were preferentially associated with mycorrhizal roots in the Mas d'Imbert soil.

Betaproteobacteria↗

Initial reactions in the biodegradation of 1-chloro-4-nitrobenzene by a newly isolated bacterium, strain LW1.

Bacterial strain LW1, which belongs to the family Comamonadaceae, utilizes 1-chloro-4-nitrobenzene (1C4NB) as a sole source of carbon, nitrogen, and energy. Suspensions of 1C4NB-grown cells removed 1C4NB from culture fluids, and there was a concomitant release of ammonia and chloride. Under anaerobic conditions LW1 transformed 1C4NB into a product which was identified as 2-amino-5-chlorophenol by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. This transformation indicated that there was partial reduction of the nitro group to the hydroxylamino substituent, followed by Bamberger rearrangement. In the presence of oxygen but in the absence of NAD, fast transformation of 2-amino-5-chlorophenol into a transiently stable yellow product was observed with resting cells and cell extracts. This compound exhibited an absorption maximum at 395 nm and was further converted to a dead-end product with maxima at 226 and 272 nm. The compound formed was subsequently identified by 1H and 13C NMR spectroscopy and mass spectrometry as 5-chloropicolinic acid. In contrast, when NAD was added in the presence of oxygen, only minor amounts of 5-chloropicolinic acid were formed, and a new product, which exhibited an absorption maximum at 306 nm, accumulated.

Aerobiosis↗

Anaerobic mineralization of quaternary carbon atoms: isolation of denitrifying bacteria on pivalic acid (2,2-dimethylpropionic acid).

The degradability of pivalic acid was established by the isolation of several facultative denitrifying strains belonging to Zoogloea resiniphila, to Thauera and Herbaspirillum, and to Comamonadaceae, related to [Aquaspirillum] and Acidovorax, and of a nitrate-reducing bacterium affiliated with Moraxella osloensis. Pivalic acid was completely mineralized to carbon dioxide. The catabolic pathways may involve an oxidation to dimethylmalonate or a carbon skeleton rearrangement, a putative 2,2-dimethylpropionyl coenzyme A mutase.

Anaerobiosis↗

Polyphasic taxonomy, a consensus approach to bacterial systematics.

Over the last 25 years, a much broader range of taxonomic studies of bacteria has gradually replaced the former reliance upon morphological, physiological, and biochemical characterization. This polyphasic taxonomy takes into account all available phenotypic and genotypic data and integrates them in a consensus type of classification, framed in a general phylogeny derived from 16S rRNA sequence analysis. In some cases, the consensus classification is a compromise containing a minimum of contradictions. It is thought that the more parameters that will become available in the future, the more polyphasic classification will gain stability. In this review, the practice of polyphasic taxonomy is discussed for four groups of bacteria chosen for their relevance, complexity, or both: the genera Xanthomonas and Campylobacter, the lactic acid bacteria, and the family Comamonadaceae. An evaluation of our present insights, the conclusions derived from it, and the perspectives of polyphasic taxonomy are discussed, emphasizing the keystone role of the species. Taxonomists did not succeed in standardizing species delimitation by using percent DNA hybridization values. Together with the absence of another "gold standard" for species definition, this has an enormous repercussion on bacterial taxonomy. This problem is faced in polyphasic taxonomy, which does not depend on a theory, a hypothesis, or a set of rules, presenting a pragmatic approach to a consensus type of taxonomy, integrating all available data maximally. In the future, polyphasic taxonomy will have to cope with (i) enormous amounts of data, (ii) large numbers of strains, and (iii) data fusion (data aggregation), which will demand efficient and centralized data storage. In the future, taxonomic studies will require collaborative efforts by specialized laboratories even more than now is the case. Whether these future developments will guarantee a more stable consensus classification remains an open question.

Amino Acid Sequence↗

Description of bacteria able to degrade isoquinoline in pure culture.

Isoquinoline is a nitrogen heterocyclic compound that is associated with coal- and oil-derived wastes. Four strains of bacteria able to degrade isoquinoline in pure culture were isolated from sites known to be contaminated with oil. Isoquinoline was used as the sole source of carbon and nitrogen by these isolates. Isoquinoline was initially transformed to 1-hydroxyisoquinoline, which accumulated in the broth culture, and then disappeared. The four strains isolated were Gram negative, aerobic, rod-shaped bacteria with polar flagella. The strains have been presumptively identified as members of the family Comamonadaceae.

Biodegradation, Environmental↗

Diaphorobacter nitroreducens gen nov, sp nov, a poly(3-hydroxybutyrate)-degrading denitrifying bacterium isolated from activated sludge.

Three denitrifying strains of bacteria capable of degrading poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were isolated from activated sludge and characterized. All of the isolates had almost identical phenotypic characteristics. They were motile gram-negative rods with single polar flagella and grew well with simple organic compounds, as well as with PHB and PHBV, as carbon and energy sources under both aerobic and anaerobic denitrifying conditions. However, none of the sugars tested supported their growth. The cellular fatty acid profiles showed the presence of C16:1omega7cis and C16:0 as the major components and of 3-OH-C10:0 as the sole component of hydroxy fatty acids. Ubiquinone-8 was detected as the major respiratory quinone. A 16S rDNA sequence-based phylogenetic analysis showed that all the isolates belonged to the family Comamonadaceae, a major group of beta-Proteobacteria, but formed no monophyletic cluster with any previously known species of this family. The closest relative to our strains was an unidentified bacterium strain LW1 (=DSM 13225) (99.9% similarity), reported previously as a 1-chloro-4-nitrobenzene degrading bacterium. DNA-DNA hybridization levels among the new isolates were more than 60%, whereas those between our isolates and strain DSM 13225 were less than 50%. The G+C content of genomic DNA of the new strains was 64 to 65 mol%. Based on these results, we concluded that the PHBV-degrading denitrifying isolates should be classified as a new genus and a new species, for which we propose the name Diaphorobacter nitroreducens. The type strain is strain NA10B (=JCM 11421=CIP 107294). We also propose to classify strain DSM 13225 as a genospecies of Diaphorobacter.

Bacterial Typing Techniques↗

[Phylogenetic analysis of bacterial diversity in Pacific Arctic sediments].

Using PCR-DGGE (denaturing gradient gel electrophoresis) methods, bacterial phylogenetic diversity in three Pacific Arctic sediment samples were investigated, taken from different depths in the range of 47 m to 3850 m. DGGE profiles of different layers in the same sediment sample are not completely same. 16S rDNA sequences corresponding to 50 excised bands from three sediment samples were analyzed and fell into seven lineages of the domain Bacteria: alpha- beta-, gamma-, delta-, epsilon- Proteobacteria, the Cytophaga-Flavobacterium-Bacteroides (CFB) group and Actinobacteria. However, the composition of bacterial phylotypes in three sediments is different. Fourteen sequences obtained from sediment B78 collected from the Canadian Basin belong to beta-, gamma- Proteobacteria, Comamonadaceae and Acidobacteria. Bacterial phylotypes in submarine plateau sediment P24 are alpha-, gamma-, delta-Proteobacteria; While seventeen sequences from sediment S11 colleted from continental slop in the Chukchi Sea are grouped into alpha-, gamma-, delta-, epsilon-Proteobacteria, the Cytophaga-Flavobacterium-Bacteroides (CFB) group and Actinobacteria. It is suggested the different characteristics of three sediments may cause the difference in the composition of bacterial phylotypes. 16S rDNA sequences from members of gamma-Proteobacteria dominated three sediments samples. The majority of the sequences were most closely related to uncultured marine environmental sequences, especially marine sediment environmental sequences (88% - 100%).

Arctic Regions↗