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Beta-Proteobacteria

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Rudolf Amann – One of the best experts on this subject based on the ideXlab platform.

  • morphological and compositional changes in a planktonic bacterial community in response to enhanced protozoan grazing
    Applied and Environmental Microbiology, 1999
    Co-Authors: Klaus Jurgens, Jakob Pernthaler, Sven Schalla, Rudolf Amann

    Abstract:

    We analyzed changes in bacterioplankton morphology and composition during enhanced protozoan grazing by image analysis and fluorescent in situ hybridization with group-specific rRNA-targeted oligonucleotide probes. Enclosure experiments were conducted in a small, fishless freshwater pond which was dominated by the cladoceran Daphnia magna. The removal of metazooplankton enhanced protozoan grazing pressure and triggered a microbial succession from fast-growing small bacteria to larger grazing-resistant morphotypes. These were mainly different types of filamentous bacteria which correlated in biomass with the population development of heterotrophic nanoflagellates (HNF). Small bacterial rods and cocci, which showed increased proportion after removal of Daphnia and doubling times of 6 to 11 h, belonged nearly exclusively to the beta subdivision of the class Proteobacteria and the Cytophaga-Flavobacterium cluster. The majority of this newly produced bacterial biomass was rapidly consumed by HNF. In contrast, the proportion of bacteria belonging to the gamma and alpha subdivisions of the Proteobacteria increased throughout the experiment. The alpha subdivision consisted mainly of rods that were 3 to 6 μm in length, which probably exceeded the size range of bacteria edible by protozoa. Initially, these organisms accounted for less than 1% of total bacteria, but after 72 h they became the predominant group of the bacterial assemblage. Other types of grazing-resistant, filamentous bacteria were also found within the beta subdivision of Proteobacteria and the Cytophaga-Flavobacterium cluster. We conclude that the predation regimen is a major structuring force for the bacterial community composition in this system. Protozoan grazing resulted in shifts of the morphological as well as the taxonomic composition of the bacterial assemblage. Grazing-resistant filamentous bacteria can develop within different phylogenetic groups of bacteria, and formerly underepresented taxa might become a dominant group when protozoan predation is the major selective pressure.

  • seasonal community and population dynamics of pelagic bacteria and archaea in a high mountain lake
    Applied and Environmental Microbiology, 1998
    Co-Authors: Jakob Pernthaler, Frank Oliver Glöckner, Roland Psenner, Albin Alfreider, Stefanie Unterholzner, Rudolf Amann

    Abstract:

    The seasonal variations in community structure and cell morphology of pelagic procaryotes from a high mountain lake (Gossenkollesee, Austria) were studied by in situ hybridization with rRNA-targeted fluorescent- ly labeled oligonucleotide probes (FISH) and image-analyzed microscopy. Compositional changes and biomass fluctuations within the assemblage were observed both in summer and beneath the winter ice cover and are discussed in the context of physicochemical and biotic parameters. Proteobacteria of the beta subclass (beta- proteobacteria) formed a dominant fraction of the bacterioplankton (annual mean, 24% of the total counts), whereas alpha-proteobacteria were of similar relative importance only during spring (mean, 11%). Bacteria of the Cytophaga-Flavobacterium cluster, although less abundant, constituted the largest fraction of the filamen- tous morphotypes during most of the year, thus contributing significantly to the total microbial biomass. Successive peaks of threadlike and rod-shaped archaea were observed during autumn thermal mixing and the period of ice cover formation, respectively. A set of oligonucleotide probes targeted to single phylotypes was constructed from 16S rRNA-encoding gene clone sequences. Three distinct populations of uncultivated mi- crobes, affiliated with the alpha- and Beta-Proteobacteria, were subsequently monitored by FISH. About one- quarter of all of the Beta-Proteobacteria (range, 6 to 53%) could be assigned to only two phylotypes. The bacterial populations studied were annually recurrent, seasonally variable, and vertically stratified, except dur- ing the periods of lake overturn. Their variability clearly exceeded the fluctuations of the total microbial as- semblage, suggesting that the apparent stability of total bacterioplankton abundances may mask highly dy- namic community fluctuations.

  • Contrasting bacterial strategies to coexist with a flagellate predator in an experimental microbial assemblage.
    Applied and Environmental Microbiology, 1997
    Co-Authors: Jakob Pernthaler, Thomas Posch, Karel Šimek, Jaroslav Vrba, Rudolf Amann, Roland Psenner

    Abstract:

    We studied predator-induced changes within a slowly growing mixed microbial assemblage that was sustained by algal exudates in a continuous cultivation system. In situ hybridization with fluorescent monolabeled oligonucleotide probes was used for a tentative community analysis. This method also allowed us to quantify the proportions of predators with ingested bacteria of different taxonomic groups. In addition, we determined grazing rates on bacteria with fluorescently labelled prey. Bacteria belonging to the alpha and beta subdivisions of the phylum Proteobacteria ((alpha)- and (beta)-Proteobacteria, respectively) showed very different responses to the addition of a bacterivorous flagellate, Bodo saltans. Within one day, filamentous protist-inedible bacteria developed; these belonged to the (beta)-Proteobacteria and constituted between 8.7 and 34% of bacteria from this subgroup. Total abundance of (beta)-Proteobacteria decreased from 3.05 x 10(sup6) to 0.23 x 10(sup6) cells ml(sup-1), and estimated cell division rates were low. Other morphologically inconspicuous protist-edible bacteria belonging to the (alpha)-Proteobacteria were found to respond to predation by an increase in growth rate. Although these bacteria were heavily grazed upon, as on average >85% of flagellate cells had ingested (alpha)-Proteobacteria, they numerically dominated after the addition of B. saltans (mean, 1.35 x 10(sup6) cells ml(sup-1)). It was thus mainly those fast-dividing strains of (alpha)-Proteobacteria that supported the growth of the flagellate population. We conclude that bacteria in mixed assemblages can adopt at least two distinct strategies as a reaction to intense flagellate predation: to outgrow predation pressure or to develop inedible, inactive filaments. Since these strategies occurred within 24 h after the addition of the flagellate, we hypothesize that chemical stimuli released by the predator may have triggered bacterial responses.

Michael Wagner – One of the best experts on this subject based on the ideXlab platform.

  • Obligate bacterial endosymbionts of Acanthamoeba spp. related to the Beta-Proteobacteria: proposal of ‘Candidatus Procabacter acanthamoebae’ gen. nov., sp. nov.
    International Journal of Systematic and Evolutionary Microbiology, 2002
    Co-Authors: Matthias Horn, Thomas R. Fritsche, Tanja Linner, Romesh K. Gautom, Marit D. Harzenetter, Michael Wagner

    Abstract:

    All obligate bacterial endosymbionts of free-living amoebae currently described are affiliated with the alpha-Proteobacteria, the Chlamydiales or the phylum Cytophaga-Flavobacterium-Bacteroides. Here, six rod-shaped gram-negative obligate bacterial endosymbionts of clinical and environmental isolates of Acanthamoeba spp. from the USA and Malaysia are reported. Comparative 16S rDNA sequence analysis demonstrated that these endosymbionts form a novel, monophyletic lineage within the Beta-Proteobacteria, showing less than 90% sequence similarity to all other recognized members of this subclass. 23S rDNA sequence analysis of two symbionts confirmed this affiliation and revealed the presence of uncommon putative intervening sequences of 146 bp within helix-25 that shared no sequence homology to any other bacterial rDNA. In addition, the 23S rRNA of these endosymbionts displayed one polymorphism at the target site of oligonucleotide probe BET42a that is conserved in all other sequenced Beta-Proteobacteria. Intra-cytoplasmatic localization of the endosymbionts within the amoebal host cells was confirmed by electron microscopy and fluorescence in situ hybridization with a specific 16S rRNA-targeted oligonucleotide probe. Based on these findings, the provisional name ‘Candidatus Procabacter acanthamoebae’ is proposed for classification of a representative of the six endosymbionts of Acanthamoeba spp. studied in this report. Comparative 18S rDNA sequence analysis of the Acanthamoeba host cells revealed their membership with either Acanthamoeba 18S rDNA sequence type T5 (Acanthamoeba lenticulata) or sequence type T4, which comprises the majority of all Acanthamoeba isolates.

  • characterization of bacterial communities from activated sludge culture dependent numerical identification versus in situ identification using group and genus specific rrna targeted oligonucleotide probes
    Microbial Ecology, 1996
    Co-Authors: Michael Wagner, Peter Kampfer, R. Erhart, Claudia Beimfohr, Judith Böhringer, Rudolf I. Amann

    Abstract:

    The structures of bacterial communities were studied in activated sludge samples obtained from the aerobic and anaerobic zones of a wastewater treatment plant showing enhanced phosphorous removal. Samples were analyzed by in situ hybridization with oligonucleotide probes complementary to selected regions of the 16S and 23S ribosomal RNA (rRNA) characteristic for defined phylogenetic entities (genera and larger groups). The microbial community structures revealed by molecular techniques were compared with the compositions of culturable bacterial communities, obtained from the characterization of 255 isolates from tryptone-soy (TS) agar and R2A agar. These isolates were characterized by 89 physiological tests and their cellular fatty acid patterns, and identified. Culture-dependent techniques indicated the following distribution: different Aeromonas spp. (2.7–8.3% on R2A agar; 45.0–63.7% on TS agar), Acinetobacter spp. (5.4–9.0% on R2A agar; 5.0–9.1% on TS agar), Pseudomonas spp. (up to 10% on R2A agar) and Shewanella putrefaciens (up to 3.0% on R2A agar), all members of the gamma subclass of Proteobacteria, were isolated most frequently. The relatively rare isolates of the beta subclass were identified as Acidovorax spp., Alcaligenes spp., and Comamonas spp., The Gram-positive bacteria (high DNA G+C) were assigned mainly to Arthrobacter spp., Microbacterium spp., and Mycobacterium phlei. In order to assess the in situ abundance of the most frequently isolated genus, Aeromonas, two rRNA-targeted oligonucleotide probes were developed. The two gamma proteobacterial genera Aeromonas and Acinetobacter constituted less than 5% of all bacteria. In situ, Proteobacteria belonging to the beta subclass and high G+C Gram-positive bacteria were dominant. From filamentous bacteria, Sphaerotilus spp. and Leptothrix spp. could be detected occasionally. In addition, one sample contained a high proportion of the morphologically distinct filaments of Microthrix parvicella.

  • Probing Activated Sludge withOligonucleotides Specific for Proteobacteria: Inadequacy ofCulture-Dependent
    , 1993
    Co-Authors: Michael Wagner, H Lemmer, Rudolf Amann, Karl-heinz Schleifer

    Abstract:

    Bacterial community structures inactivated sludge samples fromaeration tanksofatwo-stage system with ahigh-load first stage andalow-load second stage were analyzed witholigonucleotide probes. Theprobes were complementary toconserved regions oftherRNAofthealpha, beta, andgamma subclasses ofproteobacteria andofallbacteria. Group-specific cell counts were determined byinsituhybridization withfluorescent probe derivatives. Contributions oftheproteobacterial subclasses tototal bacterial rRNAwerequantified bydotblot hybridization withdigoxigenin-labeled oligonucleotides. Theactivated sludge samples were dominatedby proteobacteria fromthealpha, beta, or gamma subclass. Theseproteobacteria account forabout80% ofall active bacteria foundintheactivated sludge. Forbothsamples thecommunity structures determined with molecular techniques were compared withthecomposition oftheheterotrophic saprophyte flora isolated on nutrient-rich medium. Probes wereusedtorapidly classify theisolates andtodirectly monitor population shifts innutrient-amended, activated sludge samples. Therichmediumfavoredgrowthofgamma-subclass proteobacteria (e.g., enterobacteria) andselected against beta-subclass proteobacteria. Theculture-dependent community structure analysis ofactivated sludge produced partial andheavily biased results. A more realistic viewwill beobtained byusing insitu techniques. Thetreatment ofwastewater byactivated sludge systems is,intermsofmetabolized matter,probably today’s most important biotechnological process.A lotofeffort hasbeen funneled intoprocess engineering, whereasour current knowledge ofmicrobial community structure-function correlations andconsequently a microbiological understanding

Rudolf I. Amann – One of the best experts on this subject based on the ideXlab platform.

  • Predominance of β‐proteobacteria in summer melt pools on Arctic pack ice
    Limnology and Oceanography, 2004
    Co-Authors: Robin Brinkmeyer, Frank Oliver Glöckner, Elisabeth Helmke, Rudolf I. Amann

    Abstract:

    The diversity and community structure of bacteria in melt pools on Arctic pack ice floes were dominated by bproteobacteria. Thirty-five percent of the pure cultures isolated in 1997 from pack ice floes north of Svalbard and in the Fram Strait were from the b-proteobacteria group. Within this group, there were only two phylotypes clustering within the widespread Beta I cluster, also known as the Comamonadaceae clade. One phylotype, most closely related to Aquaspirillum arcticum(96.0‐97.3% identical), was frequent among cultures isolated from 10 melt pools. A 16S ribosomal RNA (rRNA) gene clone library, constructed from a melt pool that was sampled 2 yr later in the Fram Strait, was also dominated by b-proteobacteria, in particular the same recurrent isolate phylotype designated ‘‘MP-BetaI’’. Fluorescence in situ hybridization of 20 melt pools corroborated the cultivation and cloning data. bProteobacteria were the most abundant bacterial group, constituting ;49% of the bacteria that were stained by 496diamidino-2-phenylindole (DAPI). a- and g-proteobacteria accounted for only 2% each, the Cytophaga‐Flavobacterium group accounted for 9%, and the Actinobacteria spp. accounted for 9%. Approximately 63% of the b-proteobacterial fraction that was found in the melt pools was determined with a newly developed probe to be the recurrent b-proteobacterial MP-BetaI phylotypes, indicating that it is particularly adapted for success in this extreme environment.

  • Characterization of bacterial communities from activated sludge: Culture-dependent numerical identification versus in situ identification using group- and genus-specific rRNA-targeted oligonucleotide probes
    Microbial Ecology, 1996
    Co-Authors: Peter Kampfer, R. Erhart, Claudia Beimfohr, Judith Böhringer, M. Wagner, Rudolf I. Amann

    Abstract:

    The structures of bacterial communities were studied in activated sludge samples obtained from the aerobic and anaerobic zones of a wastewater treatment plant showing enhanced phosphorous removal. Samples were analyzed by in situ hybridization with oligonucleotide probes complementary to selected regions of the 16S and 23S ribosomal RNA (rRNA) characteristic for defined phylogenetic entities (genera and larger groups). The microbial community structures revealed by molecular techniques were compared with the compositions of culturable bacterial communities, obtained from the characterization of 255 isolates from tryptone-soy (TS) agar and R2A agar. These isolates were characterized by 89 physiological tests and their cellular fatty acid patterns, and identified. Culture-dependent techniques indicated the following distribution: different Aeromonas spp. (2.7–8.3% on R2A agar; 45.0–63.7% on TS agar), Acinetobacter spp. (5.4–9.0% on R2A agar; 5.0–9.1% on TS agar), Pseudomonas spp. (up to 10% on R2A agar) and Shewanella putrefaciens (up to 3.0% on R2A agar), all members of the gamma subclass of Proteobacteria, were isolated most frequently. The relatively rare isolates of the beta subclass were identified as Acidovorax spp., Alcaligenes spp., and Comamonas spp., The Gram-positive bacteria (high DNA G+C) were assigned mainly to Arthrobacter spp., Microbacterium spp., and Mycobacterium phlei . In order to assess the in situ abundance of the most frequently isolated genus, Aeromonas , two rRNA-targeted oligonucleotide probes were developed. The two gamma proteobacterial genera Aeromonas and Acinetobacter constituted less than 5% of all bacteria. In situ, Proteobacteria belonging to the beta subclass and high G+C Gram-positive bacteria were dominant. From filamentous bacteria, Sphaerotilus spp. and Leptothrix spp. could be detected occasionally. In addition, one sample contained a high proportion of the morphologically distinct filaments of Microthrix parvicella . As for the genus Acinetobacter , the relative abundance of the most frequently gamma-proteobacterial genus Aeromonas was overestimated by the intrinsic selectivity of cultivation. Cultivation on nutrient-rich medium (TS-agar) especially supported an enhanced isolation of bacteria belonging to these two genera.

  • characterization of bacterial communities from activated sludge culture dependent numerical identification versus in situ identification using group and genus specific rrna targeted oligonucleotide probes
    Microbial Ecology, 1996
    Co-Authors: Michael Wagner, Peter Kampfer, R. Erhart, Claudia Beimfohr, Judith Böhringer, Rudolf I. Amann

    Abstract:

    The structures of bacterial communities were studied in activated sludge samples obtained from the aerobic and anaerobic zones of a wastewater treatment plant showing enhanced phosphorous removal. Samples were analyzed by in situ hybridization with oligonucleotide probes complementary to selected regions of the 16S and 23S ribosomal RNA (rRNA) characteristic for defined phylogenetic entities (genera and larger groups). The microbial community structures revealed by molecular techniques were compared with the compositions of culturable bacterial communities, obtained from the characterization of 255 isolates from tryptone-soy (TS) agar and R2A agar. These isolates were characterized by 89 physiological tests and their cellular fatty acid patterns, and identified. Culture-dependent techniques indicated the following distribution: different Aeromonas spp. (2.7–8.3% on R2A agar; 45.0–63.7% on TS agar), Acinetobacter spp. (5.4–9.0% on R2A agar; 5.0–9.1% on TS agar), Pseudomonas spp. (up to 10% on R2A agar) and Shewanella putrefaciens (up to 3.0% on R2A agar), all members of the gamma subclass of Proteobacteria, were isolated most frequently. The relatively rare isolates of the beta subclass were identified as Acidovorax spp., Alcaligenes spp., and Comamonas spp., The Gram-positive bacteria (high DNA G+C) were assigned mainly to Arthrobacter spp., Microbacterium spp., and Mycobacterium phlei. In order to assess the in situ abundance of the most frequently isolated genus, Aeromonas, two rRNA-targeted oligonucleotide probes were developed. The two gamma proteobacterial genera Aeromonas and Acinetobacter constituted less than 5% of all bacteria. In situ, Proteobacteria belonging to the beta subclass and high G+C Gram-positive bacteria were dominant. From filamentous bacteria, Sphaerotilus spp. and Leptothrix spp. could be detected occasionally. In addition, one sample contained a high proportion of the morphologically distinct filaments of Microthrix parvicella.