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At least 19 recordsLinked to original sources

PubMed2002

Secondary (gamma-Proteobacteria) endosymbionts infect the primary (beta-Proteobacteria) endosymbionts of mealybugs multiple times and coevolve with their hosts.

Mealybugs (Hemiptera, Coccoidea, Pseudococcidae) are plant sap-sucking insects that have within their body cavities specialized cells containing prokaryotic primary endosymbionts (P-endosymbionts). The P-endosymbionts have the unusual property of containing within their cytoplasm prokaryotic secondary endosymbionts (S-endosymbionts) [C. D. von Dohlen, S. Kohler, S. T. Alsop, and W. R. McManus, Nature (London) 412:433-436, 2001]. Four-kilobase fragments containing 16S-23S ribosomal DNA (rDNA) were obtained from the P-endosymbionts of 22 mealybug species and the S-endosymbionts of 12 representative species. Phylogenetic analyses of the P-endosymbionts indicated that they have a monophyletic origin and are members of the beta-subdivision of the Proteobacteria; these organisms were subdivided into five different clusters. The S-endosymbionts were members of the gamma-subdivision of the Proteobacteria and were grouped into clusters similar to those observed with the P-endosymbionts. The S-endosymbiont clusters were distinct from each other and from other insect-associated bacteria. The similarity of the clusters formed by the P- and S-endosymbionts suggests that the P-endosymbionts of mealybugs were infected multiple times with different precursors of the S-endosymbionts and once the association was established, the P- and S-endosymbionts were transmitted together. The lineage consisting of the P-endosymbionts of mealybugs was given the designation "Candidatus Tremblaya" gen. nov., with a single species, "Candidatus Tremblaya princeps" sp. nov. The results of phylogenetic analyses of mitochondrial DNA fragments encoding cytochrome oxidase subunits I and II from four representative mealybug species were in agreement with the results of 16S-23S rDNA analyses, suggesting that relationships among strains of "Candidatus T. princeps" are useful in inferring the phylogeny of their mealybug hosts.

Animals↗

PubMed1998

Genome evolution within the alpha Proteobacteria: why do some bacteria not possess plasmids and others exhibit more than one different chromosome?

Animal intracellular Proteobacteria of the alpha subclass without plasmids and containing one or more chromosomes are phylogenetically entwined with opportunistic, plant-associated, chemoautotrophic and photosynthetic alpha Proteobacteria possessing one or more chromosomes and plasmids. Local variations in open environments, such as soil, water, manure, gut systems and the external surfaces of plants and animals, may have selected alpha Proteobacteria with extensive metabolic alternatives, broad genetic diversity, and more flexible and larger genomes with ability for horizontal gene flux. On the contrary, the constant and isolated animal cellular milieu selected heterotrophic alpha Proteobacteria with smaller genomes without plasmids and reduced genetic diversity as compared to their plant-associated and phototrophic relatives. The characteristics and genome sizes in the extant species suggest that a second chromosome could have evolved from megaplasmids which acquired housekeeping genes. Consequently, the genomes of the animal cell-associated Proteobacteria evolved through reductions of the larger genomes of chemoautotrophic ancestors and became rich in adenosine and thymidine, as compared to the genomes of their ancestors. Genome organisation and phylogenetic ancestor-descendent relationships between extant bacteria of closely related genera and within the same monophyletic genus and species suggest that some strains have undergone transition from two chromosomes to a single replicon. It is proposed that as long as the essential information is correctly expressed, the presence of one or more chromosomes within the same genus or species is the result of contingency. Genetic drift in clonal bacteria, such as animal cell-associated alpha Proteobacteria, would depend almost exclusively on mutation and internal genetic rearrangement processes. Alternatively, genomic variations in reticulate bacteria, such as many intestinal and plant cell-associated Proteobacteria, will depend not only on these processes, but also on their genetic interactions with other bacterial strains. Common pathogenic domains necessary for the invasion and survival in association with cells have been preserved in the chromosomes of the animal and plant-associated alpha Proteobacteria. These pathogenic domains have been maintained by vertical inherence, extensively ameliorated to match the chromosome G + C content and evolved within chromosomes of alpha Proteobacteria.

Animals↗

PubMed2005

Phylogeny of Proteobacteria and Bacteroidetes from oxic habitats of a tidal flat ecosystem.

Bacteria of the phyla Proteobacteria and Bacteroidetes are known to be the most prominent heterotrophic organisms in marine surface waters. In order to investigate the occurrence of these phyla in a coastal environment, the tidal flat ecosystem German Wadden Sea, we analyzed a clone library of PCR-amplified and sequenced 16S rRNA gene fragments and isolated 46 new strains affiliated with these phyla from the water column with various polymers and complex media as substrates. The phylogenetic affiliation of these strains was analyzed on the basis of sequenced 16S rRNA gene fragments. Subsequently, a comprehensive phylogenetic analysis of Proteobacteria and Bacteroidetes including available sequences from oxic habitats of earlier studies of this ecosystem was performed. Sequences of the earlier studies were derived from isolation approaches and from denaturing gradient gel electrophoresis (DGGE) analyses of environmental samples and high dilution steps of MPN (most probable number) cultures. The majority of the 265 sequences included in this analysis affiliated with alpha-Proteobacteria (45.3%), gamma-Proteobacteria (31.7%), and Bacteroidetes (16.2%). Almost 7% belong to the delta-Proteobacteria and several of these clones affiliated with the Myxococcales, a group comprising obligate aerobic organisms. Within the alpha- and gamma-Proteobacteria specific clusters were identified including isolates from high dilution steps of dilution cultures and/or clones from the clone library or DGGE gels, implying a high abundance of some of these organisms. Within the gamma-Proteobacteria a new cluster is proposed, which consists of marine surface-attached organisms. This SAMMIC (Surface Attached Marine MICrobes) cluster comprises only uncultured phylotypes and exhibits a global distribution. Overall, the analysis indicates that Proteobacteria and Bacteroidetes of the Wadden Sea have a surprisingly high diversity, presumably a result of the signature of this ecosystem as a melting pot at the land-sea interface and comprising a great habitat variety.

Bacteroidetes↗

PubMed2005

Protein signatures distinctive of alpha proteobacteria and its subgroups and a model for alpha-proteobacterial evolution.

Alpha (alpha) proteobacteria comprise a large and metabolically diverse group. No biochemical or molecular feature is presently known that can distinguish these bacteria from other groups. The evolutionary relationships among this group, which includes numerous pathogens and agriculturally important microbes, are also not understood. Shared conserved inserts and deletions (i.e., indels or signatures) in molecular sequences provide a powerful means for identification of different groups in clear terms, and for evolutionary studies (see www.bacterialphylogeny.com). This review describes, for the first time, a large number of conserved indels in broadly distributed proteins that are distinctive and unifying characteristics of either all alpha-proteobacteria, or many of its constituent subgroups (i.e., orders, families, etc.). These signatures were identified by systematic analyses of proteins found in the Rickettsia prowazekii (RP) genome. Conserved indels that are unique to alpha-proteobacteria are present in the following proteins: Cytochrome c oxidase assembly protein Ctag, PurC, DnaB, ATP synthase alpha-subunit, exonuclease VII, prolipoprotein phosphatidylglycerol transferase, RP-400, FtsK, puruvate phosphate dikinase, cytochrome b, MutY, and homoserine dehydrogenase. The signatures in succinyl-CoA synthetase, cytochrome oxidase I, alanyl-tRNA synthetase, and MutS proteins are found in all alpha-proteobacteria, except the Rickettsiales, indicating that this group has diverged prior to the introduction of these signatures. A number of proteins contain conserved indels that are specific for Rickettsiales (XerD integrase and leucine aminopeptidase), Rickettsiaceae (Mfd, ribosomal protein L19, FtsZ, Sigma 70 and exonuclease VII), or Anaplasmataceae (Tgt and RP-314), and they distinguish these groups from all others. Signatures in DnaA, RP-057, and DNA ligase A are commonly shared by various Rhizobiales, Rhodobacterales, and Caulobacter, suggesting that these groups shared a common ancestor exclusive of other alpha-proteobacteria. A specific relationship between Rhodobacterales and Caulobacter is indicated by a large insert in the Asn-Gln amidotransferase. The Rhizobiales group of species are distinguished from others by a large insert in the Trp-tRNA synthetase. Signature sequences in a number of other proteins (viz. oxoglutarate dehydogenase, succinyl-CoA synthase, LytB, DNA gyrase A, LepA, and Ser-tRNA synthetase) serve to distinguish the Rhizobiaceae, Brucellaceae, and Phyllobacteriaceae families from Bradyrhizobiaceae and Methylobacteriaceae. Based on the distribution patterns of these signatures, it is now possible to logically deduce a model for the branching order among alpha-proteobacteria, which is as follows: Rickettsiales --> Rhodospirillales-Sphingomonadales --> Rhodobacterales-Caulobacterales --> Rhizobiales (Rhizobiaceaea-Brucellaceae-Phyllobacteriaceae, and Bradyrhizobiaceae). The deduced branching order is also consistent with the topologies in the 16 rRNA and other phylogenetic trees. Signature sequences in a number of other proteins provide evidence that alpha-proteobacteria is a late branching taxa within Bacteria, which branched after the delta,epsilon-subdivisions but prior to the beta,gamma-proteobacteria. The shared presence of many of these signatures in the mitochondrial (eukaryotic) homologs also provides evidence of the alpha-proteobacterial ancestry of mitochondria.

Alphaproteobacteria↗

PubMed2001

Alpha- and beta-Proteobacteria control the consumption and release of amino acids on lake snow aggregates.

We analyzed the composition of aggregate (lake snow)-associated bacterial communities in Lake Constance from 1994 until 1996 between a depth of 25 m and the sediment surface at 110 m by fluorescent in situ hybridization with rRNA-targeted oligonucleotide probes of various specificity. In addition, we experimentally examined the turnover of dissolved amino acids and carbohydrates together with the microbial colonization of aggregates formed in rolling tanks in the lab. Generally, between 40 and more than 80% of the microbes enumerated by DAPI staining (4',6'-diamidino-2-phenylindole) were detected as Bacteria by the probe EUB338. At a depth of 25 m, 10.5% +/- 7.9% and 14.2% +/- 10.2% of the DAPI cell counts were detected by probes specific for alpha- and beta-Proteobacteria. These proportions increased to 12.0% +/- 3.3% and 54.0% +/- 5.9% at a depth of 50 m but decreased again at the sediment surface at 110 m to 2.7% +/- 1.4% and 41.1% +/- 8.4%, indicating a clear dominance of beta-Proteobacteria at depths of 50 and 110 m, where aggregates have an age of 3 to 5 and 8 to 11 days, respectively. From 50 m to the sediment surface, cells detected by a Cytophaga/Flavobacteria-specific probe (CF319a) comprised increasing proportions up to 18% of the DAPI cell counts. gamma-Proteobacteria always comprised minor proportions of the aggregate-associated bacterial community. Using only two probes highly specific for clusters of bacteria closely related to Sphingomonas species and Brevundimonas diminuta, we identified between 16 and 60% of the alpha-Proteobacteria. In addition, with three probes highly specific for close relatives of the beta-Proteobacteria Duganella zoogloeoides (formerly Zoogloea ramigera), Acidovorax facilis, and Hydrogenophaga palleroni, bacteria common in activated sludge, 42 to 70% of the beta-Proteobacteria were identified. In the early phase (<20 h) of 11 of the 15 experimental incubations of aggregates, dissolved amino acids were consumed by the aggregate-associated bacteria from the surrounding water. This stage was followed by a period of 1 to 3 days during which dissolved amino acids were released into the surrounding water, paralleled by an increasing dominance of beta-Proteobacteria. Hence, our results show that lake snow aggregates are inhabited by a community dominated by a limited number of alpha- and beta-Proteobacteria, which undergo a distinct succession. They successively decompose the amino acids bound in the aggregates and release substantial amounts into the surrounding water during aging and sinking.

Alphaproteobacteria↗

PubMed2005

Signature proteins that are distinctive of alpha proteobacteria.

BACKGROUND: The alpha (alpha) proteobacteria, a very large and diverse group, are presently characterized solely on the basis of 16S rRNA trees, with no known molecular characteristic that is unique to this group. The genomes of three alpha-proteobacteria, Rickettsia prowazekii (RP), Caulobacter crescentus (CC) and Bartonella quintana (BQ), were analyzed in order to search for proteins that are unique to this group. RESULTS: Blast analyses of protein sequences from the above genomes have led to the identification of 61 proteins which are distinctive characteristics of alpha-proteobacteria and are generally not found in any other bacteria. These alpha-proteobacterial signature proteins are generally of hypothetical functions and they can be classified as follows: (i) Six proteins (CC2102, CC3292, CC3319, CC1887, CC1725 and CC1365) which are uniquely present in most sequenced alpha-proteobacterial genomes; (ii) Ten proteins (CC1211, CC1886, CC2245, CC3470, CC0520, CC0365, CC0366, CC1977, CC3010 and CC0100) which are present in all alpha-proteobacteria except the Rickettsiales; (iii) Five proteins (CC2345, CC3115, CC3401, CC3467 and CC1021) not found in the intracellular bacteria belonging to the order Rickettsiales and the Bartonellaceae family; (iv) Four proteins (CC1652, CC2247, CC3295 and CC1035) that are absent from various Rickettsiales as well as Rhodobacterales; (v) Three proteins (RP104, RP105 and RP106) that are unique to the order Rickettsiales and four proteins (RP766, RP192, RP030 and RP187) which are specific for the Rickettsiaceae family; (vi) Six proteins (BQ00140, BQ00720, BQ03880, BQ12030, BQ07670 and BQ11900) which are specific to the order Rhizobiales; (vii) Four proteins (BQ01660, BQ02450, BQ03770 and BQ13470) which are specific for the order Rhizobiales excluding the family Bradyrhizobiaceae; (viii) Nine proteins (BQ12190, BQ11460, BQ11450, BQ11430, BQ11380, BQ11160, BQ11120, BQ11100 and BQ11030 which are distinctive of the Bartonellaceae family;(ix) Six proteins (CC0189, CC0569, CC0331, CC0349, CC2323 and CC2637) which show sporadic distribution in alpha-proteobacteria, (x) Four proteins (CC2585, CC0226, CC2790 and RP382) in which lateral gene transfers are indicated to have occurred between alpha-proteobacteria and a limited number of other bacteria. CONCLUSION: The identified proteins provide novel means for defining and identifying the alpha-proteobacteria and many of its subgroups in clear molecular terms and in understanding the evolution of this group of species. These signature proteins, together with the large number of alpha-proteobacteria specific indels that have recently been identified http://www.bacterialphylogeny.com, provide evidence that all species from this diverse group share many unifying and distinctive characteristics. Functional studies on these proteins should prove very helpful in the identification of such characteristics.

Alphaproteobacteria↗

PubMed2000

The phylogeny of proteobacteria: relationships to other eubacterial phyla and eukaryotes.

The evolutionary relationships of proteobacteria, which comprise the largest and phenotypically most diverse division among prokaryotes, are examined based on the analyses of available molecular sequence data. Sequence alignments of different proteins have led to the identification of numerous conserved inserts and deletions (referred to as signature sequences), which either are unique characteristics of various proteobacterial species or are shared by only members from certain subdivisions of proteobacteria. These signature sequences provide molecular means to define the proteobacterial phyla and their various subdivisions and to understand their evolutionary relationships to the other groups of eubacteria as well as the eukaryotes. Based on signature sequences that are present in different proteins it is now possible to infer that the various eubacterial phyla evolved from a common ancestor in the following order: low-G+C Gram-positive-->high-G+C Gram-positive-->Deinococcus-Thermus (green nonsulfur bacteria)-->cyanobacteria-->Spirochetes-->Chlamydia-Cytophaga-Aquifex -green sulfur bacteria-->Proteobacteria-1 (epsilon and delta)-->Proteobacteria-2 (alpha)-->Proteobacteria-3 (beta)-->Proteobacteria-4 (gamma). An unexpected but important aspect of the relationship deduced here is that the main eubacterial phyla are related to each other linearly rather than in a tree-like manner, suggesting that the major evolutionary changes within Bacteria have taken place in a directional manner. The identified signatures permit placement of prokaryotes into different groups/divisions and could be used for determinative purposes. These signatures generally support the origin of mitochondria from an alpha-proteobacterium and provide evidence that the nuclear cytosolic homologs of many genes are also derived from proteobacteria.

ATP-Dependent Proteases↗

PubMed2005

Distribution, phylogenetic diversity and physiological characteristics of epsilon-Proteobacteria in a deep-sea hydrothermal field.

Epsilon-Proteobacteria is increasingly recognized as an ecologically significant group of bacteria, particularly in deep-sea hydrothermal environments. In this study, we studied the spatial distribution, diversity and physiological characteristics of the epsilon-Proteobacteria in various microbial habitats in the vicinity of a deep-sea hydrothermal vent occurring in the Iheya North field in the Mid-Okinawa Trough, by using culture-dependent and -independent approaches. The habitats studied were inside and outside hydrothermal plume, and annelid polychaete tubes. In addition, we deployed colonization devices near the vent emission. The polychaete tubes harboured physiologically and phylogenetically diverse microbial community. The in situ samplers were predominantly colonized by epsilon-Proteobacteria. Energy metabolism of epsilon-Proteobacteria isolates was highly versatile. Tree topology generated from the metabolic traits was significantly different (P = 0.000) from that of 16S rRNA tree, indicating current 16S rRNA gene-based analyses do not provide sufficient information to infer the physiological characteristics of epsilon-Proteobacteria. Nevertheless, culturability of epsilon-Proteobacteria in various microbial habitats differed among the phylogenetic subgroups. Members of Sulfurimonas were characterized by the robust culturability, and the other phylogenetic subgroups appeared to lose culturability in seawater, probably because of the sensitivity to oxygen. These results provide new insight into the ecophysiological characteristics of the deep-sea hydrothermal vent epsilon-Proteobacteria, which has never been assessed by comparative analysis of the 16S rRNA genes.

Culture Media↗

PubMed2001

Growth and phylogenetic properties of novel bacteria belonging to the epsilon subdivision of the Proteobacteria enriched from Alvinella pompejana and deep-sea hydrothermal vents.

Recent molecular characterizations of microbial communities from deep-sea hydrothermal sites indicate the predominance of bacteria belonging to the epsilon subdivision of Proteobacteria (epsilon Proteobacteria). Here, we report the first enrichments and characterizations of four epsilon Proteobacteria that are directly associated with Alvinella pompejana, a deep sea hydrothermal vent polychete, or with hydrothermal vent chimney samples. These novel bacteria were moderately thermophilic sulfur-reducing heterotrophs growing on formate as the energy and carbon source. In addition, two of them (Am-H and Ex-18.2) could grow on sulfur lithoautrotrophically using hydrogen as the electron donor. Optimal growth temperatures of the bacteria ranged from 41 to 45 degrees C. Phylogenetic analysis of the small-subunit ribosomal gene of the two heterotrophic bacteria demonstrated 95% similarity to Sulfurospirillum arcachonense, an epsilon Proteobacteria isolated from an oxidized marine surface sediment. The autotrophic bacteria grouped within a deeply branching clade of the epsilon Proteobacteria, to date composed only of uncultured bacteria detected in a sample from a hydrothermal vent along the mid-Atlantic ridge. A molecular survey of various hydrothermal vent environments demonstrated the presence of two of these bacteria (Am-N and Am-H) in more than one geographic location and habitat. These results suggest that certain epsilon Proteobacteria likely fill important niches in the environmental habitats of deep-sea hydrothermal vents, where they contribute to overall carbon and sulfur cycling at moderate thermophilic temperatures.

Animals↗

PubMed2006

Molecular signatures (unique proteins and conserved indels) that are specific for the epsilon proteobacteria (Campylobacterales).

BACKGROUND: The epsilon proteobacteria, which include many important human pathogens, are presently recognized solely on the basis of their branching in rRNA trees. No unique molecular or biochemical characteristics specific for this group are known. RESULTS: Comparative analyses of proteins in the genomes of Wolinella succinogenes DSM 1740 and Campylobacter jejuni RM1221 against all available sequences have identified a large number of proteins that are unique to various epsilon proteobacteria (Campylobacterales), but whose homologs are not detected in other organisms. Of these proteins, 49 are uniquely found in nearly all sequenced epsilon-proteobacteria (viz. Helicobacter pylori (26695 and J99), H. hepaticus, C. jejuni (NCTC 11168, RM1221, HB93-13, 84-25, CF93-6, 260.94, 11168 and 81-176), C. lari, C. coli, C. upsaliensis, C. fetus, W. succinogenes DSM 1740 and Thiomicrospira denitrificans ATCC 33889), 11 are unique for the Wolinella and Helicobacter species (i.e. Helicobacteraceae family) and many others are specific for either some or all of the species within the Campylobacter genus. The primary sequences of many of these proteins are highly conserved and provide novel resources for diagnostics and therapeutics. We also report four conserved indels (i.e. inserts or deletions) in widely distributed proteins (viz. B subunit of exinuclease ABC, phenylalanyl-tRNA synthetase, RNA polymerase beta '-subunit and FtsH protein) that are specific for either all epsilon proteobacteria or different subgroups. In addition, a rare genetic event that caused fusion of the genes for the largest subunits of RNA polymerase (rpoB and rpoC) in Wolinella and Helicobacter is also described. The inter-relationships amongst Campylobacterales as deduced from these molecular signatures are in accordance with the phylogenetic trees based on the 16S rRNA and concatenated sequences for nine conserved proteins. CONCLUSION: These molecular signatures provide novel tools for identifying and circumscribing species from the Campylobacterales order and its subgroups in molecular terms. Although sequence information for these signatures is presently limited to Campylobacterales species, it is likely that many of them will also be found in other epsilon proteobacteria. Functional studies on these proteins and conserved indels should reveal novel biochemical or physiological characteristics that are unique to these groups of epsilon proteobacteria.

Bacterial Proteins↗

PubMed2002

Succinate:quinone oxidoreductases from epsilon-proteobacteria.

The epsilon-proteobacteria form a subdivision of the Proteobacteria including the genera Wolinella, Campylobacter, Helicobacter, Sulfurospirillum, Arcobacter and Dehalospirillum. The majority of these bacteria are oxidase-positive microaerophiles indicating an electron transport chain with molecular oxygen as terminal electron acceptor. However, numerous members of the epsilon-proteobacteria also grow in the absence of oxygen. The common presence of menaquinone and fumarate reduction activity suggests anaerobic fumarate respiration which was demonstrated for the rumen bacterium Wolinella succinogenes as well as for Sulfurospirillum deleyianum, Campylobacter fetus, Campylobacter rectus and Dehalospirillum multivorans. To date, complete genome sequences of Helicobacter pylori and Campylobacter jejuni are available. These bacteria and W. succinogenes contain the genes frdC, A and B encoding highly similar heterotrimeric enzyme complexes belonging to the family of succinate:quinone oxidoreductases. The crystal structure of the W. succinogenes quinol:fumarate reductase complex (FrdCAB) was solved recently, thus providing a model of succinate:quinone oxidoreductases from epsilon-proteobacteria. Succinate:quinone oxidoreductases are being discussed as possible therapeutic targets in the treatment of several pathogenic epsilon-proteobacteria.

Citric Acid Cycle↗

PubMed2026

Accessing Underexplored Biosynthetic Potential by Initiation Unit Engineering of Nonribosomal Peptide Synthetases in Proteobacteria.

Nonribosomal peptide synthetases (NRPSs) represent a valuable yet underexplored resource for producing bioactive natural products. However, most NRPSs remain silenced potentially due to factors such as dysfunction of the initiation unit. The starter condensation (Cs) domain of the initiation unit catalyzes the lipoinitiation of nonribosomal peptides via the incorporation of an N-terminal fatty acyl chain. The concept of initiation unit engineering introduced herein encompasses the replacement of the native initiation unit of NRPSs with a foreign and well-characterized Cs domain-containing initiation unit to activate the NRPS and optimize its expression. This strategy was employed herein to successfully access three of the six previously silent NRPS pathways in Mycetohabitans rhizoxinica HKI 454, a bacterium of the class β-proteobacteria, resulting in the identification of three classes of lipopeptides. This strategy was then extended to access two NRPS pathways in Pseudomonas syringae (γ-proteobacteria) and obtain novel lipopeptides, thereby establishing a feasible complement to existing genome mining strategies for natural product discovery. Furthermore, change of the initiation regions of biosynthetic pathways of nonlipidated chitinimide (β-proteobacteria) and pseudotetraivprolide (γ-proteobacteria) with heterologous Cs-containing initiation units enabled the successful incorporation of fatty acyl chains into the N-terminus of both peptide backbones, launching a workable approach to create artificial lipopeptides. Overall, this study provides a practical strategy for the rational recovery of silent BGCs and introduction of fatty acyl chains into nonribosomal peptides, at least in Proteobacteria, thereby enriching genome mining and combinatorial biosynthesis approaches for accessing the underexplored biosynthetic potential of NRPSs from various bacteria.

Proteobacteria↗

PubMed1993

Probing activated sludge with oligonucleotides specific for proteobacteria: inadequacy of culture-dependent methods for describing microbial community structure.

Bacterial community structures in activated sludge samples from aeration tanks of a two-stage system with a high-load first stage and a low-load second stage were analyzed with oligonucleotide probes. The probes were complementary to conserved regions of the rRNA of the alpha, beta, and gamma subclasses of proteobacteria and of all bacteria. Group-specific cell counts were determined by in situ hybridization with fluorescent probe derivatives. Contributions of the proteobacterial subclasses to total bacterial rRNA were quantified by dot blot hybridization with digoxigenin-labeled oligonucleotides. The activated sludge samples were dominated by proteobacteria from the alpha, beta, or gamma subclass. These proteobacteria account for about 80% of all active bacteria found in the activated sludge. For both samples the community structures determined with molecular techniques were compared with the composition of the heterotrophic saprophyte flora isolated on nutrient-rich medium. Probes were used to rapidly classify the isolates and to directly monitor population shifts in nutrient-amended, activated sludge samples. The rich medium favored growth of gamma-subclass proteobacteria (e.g., enterobacteria) and selected against beta-subclass proteobacteria. The culture-dependent community structure analysis of activated sludge produced partial and heavily biased results. A more realistic view will be obtained by using in situ techniques.

Bacteria↗

PubMed2000

Selected chitinase genes in cultured and uncultured marine bacteria in the alpha- and gamma-subclasses of the proteobacteria.

PCR primers were patterned after chitinase genes in four gamma-proteobacteria in the families Alteromonadaceae and Enterobacteriaceae (group I chitinases) and used to explore the occurrence and diversity of these chitinase genes in cultured and uncultured marine bacteria. The PCR results from 104 bacterial strains indicated that this type of chitinase gene occurs in two major groups of marine bacteria, alpha- and gamma-proteobacteria, but not the Cytophaga-Flavobacter group. Group I chitinase genes also occur in some viruses infecting arthropods. Phylogenetic analysis indicated that similar group I chitinase genes occur in taxonomically related bacteria. However, the overall phylogeny of chitinase genes did not correspond to the phylogeny of 16S rRNA genes, possibly due to lateral transfer of chitinase genes between groups of bacteria, but other mechanisms, such as gene duplication, cannot be ruled out. Clone libraries of chitinase gene fragments amplified from coastal Pacific Ocean and estuarine Delaware Bay bacterioplankton revealed similarities and differences between cultured and uncultured bacteria. We had hypothesized that cultured and uncultured chitin-degrading bacteria would be very different, but in fact, clones having nucleotide sequences identical to those of chitinase genes of cultured alpha-proteobacteria dominated both libraries. The other clones were similar but not identical to genes in cultured gamma-proteobacteria, including vibrios and alteromonads. Our results suggest that a closer examination of chitin degradation by alpha-proteobacteria will lead to a better understanding of chitin degradation in the ocean.

Alphaproteobacteria↗

PubMed2002

Detection of Proteobacteria from the rumen by PCR using methanotroph-specific primers.

AIMS: To detect Proteobacteria, including methanotrophs, from the rumen fluid and the bacteria inhabiting the rumen epithelium. METHODS AND RESULTS: Proteobacteria inhabiting the rumen were detected by PCR using methanotroph-specific primers. The detected Proteobacteria were divided into clusters A, B, and C in addition to one clone, which was distinct from the clusters and closely related to Nitrosomonas sp. The clusters A, B, and C were close to Succinivibrio dextrinosolvens, Enterobacter cloacae, and Actinobacillus minor, respectively. The clones obtained from the rumen fluid each belonged to cluster A or B. The clones obtained from the rumen epithelium belonged to cluster B or C or to Nitrosomonas sp. CONCLUSIONS: It has been assumed that the rumen fluid and the rumen epithelium host different populations of Proteobacteria. Moreover, detection of Nitrosomonas from the rumen epithelium would indicate the possibility that the bacterium oxidizes ammonia and methane on the rumen surface. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings suggest that the rumen fluid and the epithelium support different microbial populations, which would play specific roles in rumen function. Future study should focus on the relationship between these communities and physiological functions in the rumen.

Animals↗

PubMed2004

Differences in LexA regulon structure among Proteobacteria through in vivo assisted comparative genomics.

The LexA regulon encompasses an ensemble of genes involved in preserving cell viability under massive DNA damage and is present in most bacterial phyla. Up to date, however, the scope of this network had only been assessed in the Gamma Proteobacteria. Here, we report the structure of the LexA regulon in the Alpha Proteobacteria, using a combined approach that makes use of in vitro and in vivo techniques to assist and validate the comparative genomics in silico methodology. This leads to the first experimentally validated description of the LexA regulon in the Alpha Proteobacteria, and comparison of regulon core structures in both classes suggests that a least common multiple set of genes (recA, ssb, uvrA and ruvCAB) might be a defining property of the Proteobacteria LexA network.

Algorithms↗

PubMed2000

Proposal for the reclassification of Thiobacillus novellus as Starkeya novella gen. nov., comb. nov., in the alpha-subclass of the Proteobacteria.

Thiobacillus novellus is a facultatively chemolithoautotrophic and methylotrophic, Gram-negative, rod-shaped sulfur bacterium, shown by 16S rRNA gene sequence analysis to be a member of the alpha-2 subclass of the Proteobacteria. As such, it must be excluded from the genus Thiobacillus, whose species are members of the beta-Proteobacteria. It closest phylogenetic neighbour appears to be Ancylobacter, from which it is distinct morphologically and in some physiological characteristics. It is distinct physiologically and biochemically in a number of diagnostic features from Paracoccus versutus, in the alpha-3 subclass of the Proteobacteria and does not appear to be sufficiently closely related to any other genus of the alpha-Proteobacteria to be reassigned to a known genus. The new genus and species name Starkeya novella is proposed for T. novellus. The type strain is ATCC 8093T (= NCIMB 10456T = NCIMB 9113T = DSM 506T = IAM 12100T = IFO 12443T = CCM 1077T).

Alphaproteobacteria↗

PubMed1995

Phylogenetic analysis of a novel sulfate-reducing magnetic bacterium, RS-1, demonstrates its membership of the delta-Proteobacteria.

Most of the 16S ribosomal RNA gene of a sulfate-reducing magnetic bacterium, RS-1, was sequenced, and phylogenetic analysis was carried out. The results suggest that RS-1 is a member of the delta-Proteobacteria, and it appears to represent a new genus. RS-1 is the first bacterium reported outside the alpha-Proteobacteria that contains magnetite inclusions. RS-1 therefore disrupts the correlation between the alpha-Proteobacteria and possession of magnetite inclusions, and that between the delta-Proteobacteria and possession of greigite inclusions. The existence of RS-1 also suggests that intracellular magnetite biomineralization is of multiple evolutionary origins.

Bacteria↗