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At least 379 records · Page 21Linked to original sources
PubMed1965

THE SYNTHESIS OF RIBOSOMES BY A MUTANT OF ESCHERICHIA COLI.

1. When the methionine-requiring mutant 58-161 of Escherichia coli was starved of methionine, ribonucleic acid was made in the absence of protein synthesis. 2. Most of this ribonucleic acid was similar to that found in ribosomes but was contained in particles differing from ribosomes both in sedimentation coefficient and in chromatographic behaviour on diethylaminoethylcellulose. 3. When methionine was added to a starved culture, the ribonucleic acid synthesized during starvation was almost completely undegraded as growth resumed. A transient loss of 5-10% could be largely attributed to breakdown of messenger ribonucleic acid accumulated during starvation. 4. After the addition of methionine, ribosomes were formed from the particles, and during this period preferential synthesis of ribosomal protein took place. 5. It is suggested that under these conditions the direct synthesis of ribosomes from the particles may occur.

Carbon Isotopes↗
PubMed1981

Heterogeneity of RNA polymerase in Bacillus subtilis: evidence for an additional sigma factor in vegetative cells.

Preparations of Bacillus subtilis RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) from vegetatively growing cells contain small amounts of an activity (B. subtilis RNA polymerase holoenzyme II) that shows a unique promoter specificity with T7 bacteriophage DNA as compared with the normal B. subtilis holoenzyme (holoenzyme I) and lacks the normal sigma subunit [Jaehning, J. A., Wiggs, J. L. & Chamberlin, M. J. (1979) Proc. Natl. Acad. Sci. USA 76, 5470-5474]. By heparin-agarose chromatography we have obtained holoenzyme II fractions that have no detectable holoenzyme I activity as judged by their failure to utilize promoter sites for holoenzyme I on any template we have tested. These fractions are far more active with B. subtilis DNA than with T7 DNA or other heterologous templates. This high degree of specificity has allowed identification of plasmids containing cloned fragments of B. subtilis DNA that bear strong promoter sites for holoenzyme II. These promoter sites are not used at all by B. subtilis RNA polymerase holoenzyme I. The specificity of holoenzyme II is dictated by a peptide of Mr 28,000 as judged by copurification of the peptide with specific holoenzyme II activity and by reconstitution of the holoenzyme II promoter specificity when the isolated peptide is added to B. subtilis core polymerase. Hence the 28,000 Mr peptide appears to be a sigma factor that determines a promoter specificity distinct from that of RNA polymerase holoenzyme I and all other known bacterial RNA polymerases.

Bacillus subtilis↗
PubMed2001

A single amidotransferase forms asparaginyl-tRNA and glutaminyl-tRNA in Chlamydia trachomatis.

Aminoacyl-tRNA is generally formed by aminoacyl-tRNA synthetases, a family of 20 enzymes essential for accurate protein synthesis. However, most bacteria generate one of the two amide aminoacyl-tRNAs, Asn-tRNA or Gln-tRNA, by transamidation of mischarged Asp-tRNA(Asn) or Glu-tRNA(Gln) catalyzed by a heterotrimeric amidotransferase (encoded by the gatA, gatB, and gatC genes). The Chlamydia trachomatis genome sequence reveals genes for 18 synthetases, whereas those for asparaginyl-tRNA synthetase and glutaminyl-tRNA synthetase are absent. Yet the genome harbors three gat genes in an operon-like arrangement (gatCAB). We reasoned that Chlamydia uses the gatCAB-encoded amidotransferase to generate both Asn-tRNA and Gln-tRNA. C. trachomatis aspartyl-tRNA synthetase and glutamyl-tRNA synthetase were shown to be non-discriminating synthetases that form the misacylated tRNA(Asn) and tRNA(Gln) species. A preparation of pure heterotrimeric recombinant C. trachomatis amidotransferase converted Asp-tRNA(Asn) and Glu-tRNA(Gln) into Asn-tRNA and Gln-tRNA, respectively. The enzyme used glutamine, asparagine, or ammonia as amide donors in the presence of either ATP or GTP. These results suggest that C. trachomatis employs the dual specificity gatCAB-encoded amidotransferase and 18 aminoacyl-tRNA synthetases to create the complete set of 20 aminoacyl-tRNAs.

Amino Acyl-tRNA Synthetases↗
PubMed2000

A study of the method to pick up a selenocysteine tRNA in Bacillus subtilis.

In Bacillus subtilis, selenocysteine tRNA has not been identified in a total genome sequence so far (1). To explore the system of selenocysteine incorporation in B. subtilis, we screened serine-acceptable tRNAs to find an unknown tRNA for selenocysteine by the combined method of specific biotinylation of aa-tRNA (2) and RT-PCR (3). cDNAs obtained from the serine-acceptable tRNA pool were amplified and cloned into plasmid to read its sequence. This procedure gave cDNA library corresponding known serine tRNAs, but no candidate for selenocysteine has been found. Thus, this result, together with the previous data (4), might reveal that there is no selenocysteine tRNA in B. subtilis and/or metabolism of selenium is considerably different from known one as seen in other bacteria.

Bacillus subtilis↗
PubMed1995

"Streptococcus milleri" strains displaying a gliding type of motility.

Isolates belonging to the "Streptococcus milleri" species group that appear to exhibit a gliding type of motility, which is expressed as spreading growth on certain types of agar media, are described. These strains resembled a biotype of "S. milleri" that is usually isolated from genitourinary sources and is notable for its ability to ferment a wide array of carbohydrates. This biotype, which is currently included in the species Streptococcus anginosus, has been implicated in cases of neonatal infection. The "S. milleri" isolates which we studied lacked any observable organelles of motility and gave negative results when they were tested in conventional motility test medium stab cultures. Colonies growing on certain agar media, however, spread over the surfaces of plates and increased in area with increasing time of incubation. Chocolate agar supported maximum spreading, while this characteristic was barely discernible on blood agar. Electron microscopy studies revealed that there was more production of extracellular glycocalyx by motile strains than by a nonmotile isolate having a similar biotype. The results of an analysis of 16S rRNA gene sequences suggested that the motile strains are closely related to S. anginosus and represent a distinct rRNA population within the "S. milleri" species complex.

Base Sequence↗
PubMed1998

An approach to characterizing uncultivated prokaryotes: the Grey Lung agent and proposal of a Candidatus taxon for the organism, 'Candidatus Mycoplasma ravipulmonis'.

An approach to characterizing uncultivated bacteria which combines a PFGE procedure for obtaining purified full-length chromosomes with PCR amplification is described. Isolated chromosomes from uncultivated organisms provide a specifically identifiable source material for hybridization, amplification and cloning. The availability of purified chromosomes for DNA amplification should aid in examining the diversity of microbial populations and should also reduce the possibility of forming hybrid DNA artifact molecules. The approach is illustrated by isolating the chromosome of the uncultivated agent of rodent Grey Lung disease and using the purified chromosomes to amplify and directly sequence the evolutionarily conserved 16S rRNA gene. The Grey Lung agent (GLA) contains a 650 kb chromosome and is shown to be a Mycoplasma sp. located phylogenetically in the hominis group of mycoplasmas. If a simple genomic lesion(s) is responsible for the unculturability of GLA, it is conceivable that complementation with DNA from a close relative could permit growth on artificial media.

Animals↗
PubMed2002

Paenibacillus glycanilyticus sp. nov., a novel species that degrades heteropolysaccharide produced by the cyanobacterium Nostoc commune.

A novel bacterial strain, DS-1T, was isolated that degrades heteropolysaccharide produced by the cyanobacterium Nostoc commune. The isolate was identified by a combination of phenotypic characterization, cellular fatty acid analysis, DNA base composition, DNA-DNA hybridization and 165 rRNA gene sequence analysis. Phylogenetic analysis placed strain DS-1T within the Paenibacillus cluster on a phylogenetic tree and the phenotypic characteristics of this strain appear to be similar to those of Paenibacillus curdlanolyticus IFO 15724T and Paenibacillus kobensis IFO 15729T. The strain was distinguished from P. curdlanolyticus IFO 15724T and P. kobensis IFO 15729T by its ability to degrade the polysaccharide of Nostoc commune, by assimilation of rhamnose, inositol and L-fucose and by its wide range of optimal growth temperature (28-37 degrees C). Like other Paenibacillus species, this strain contains anteiso-C15:0 as a major cellular fatty acid, and it has a DNA G+C content of 50.5 mol %. Based on these results, it is concluded that this isolate should be placed within a novel species of Paenibacillus, Paenibacillus glycanilyticus sp. nov., with the type strain DS-1T (= IFO 16618T = JCM 11221T = NRRL B-23455T).

Bacillus↗
PubMed1996

Global regulation in Erwinia species by Erwinia carotovora rsmA, a homologue of Escherichia coli csrA: repression of secondary metabolites, pathogenicity and hypersensitive reaction.

Our previous studies revealed that rsmA of Erwinia carotovora subsp. carotovora strain 71 suppressed the synthesis of the cell density (quorum) sensing signal N-(3-oxohexanoyl)-L-homoserine lactone, the production of extracellular enzymes and tissue macerating ability in soft-rotting Erwinia species and that homologues of this negative regulator gene were present in other Erwinia species. Northern blot data presented here demonstrate that rsmA and rsmA-like genes are also expressed in soft-rotting and non-soft-rotting Erwinia spp. such as E. amylovora, E. carotovora subsp. atroseptica, E. carotovora subsp. betavasculorum, E. carotovora subsp. carotovora, E. chrysanthemi, E. herbicola and E. stewartii. A low-copy plasmid carrying rsmA of E. carotovora subsp. carotovora strain 71 caused suppression of antibiotic production in E. carotovora subsp. betavasculorum, flagellum formation in E. carotovora subsp. carotovora, carotenoid production in E. herbicola and E. stewartii, and indigoidine production in E. chrysanthemi. In E. amylovora, rsmA of E. carotovora subsp. carotovora suppressed the elicitation of the hypersensitive reaction in tobacco leaves and the production of disease symptoms in apple shoots, in addition to repressing motility and extracellular polysaccharide production. We conclude that rsmA homologues function as global regulators of secondary metabolic pathways as well as factors controlling host interaction of Erwinia species.

Anti-Bacterial Agents↗
PubMed2004

Halomonas ventosae sp. nov., a moderately halophilic, denitrifying, exopolysaccharide-producing bacterium.

Halomonas ventosae sp, nov. includes three moderately halophilic, exopolysaccharide-producing strains isolated from saline soils in Jaén (south-eastern Spain). These strains can grow anaerobically using either nitrate or nitrite as terminal electron acceptor and hydrolyse both tyrosine and phenylalanine. Their G+C content varies between 72.6 and 74.3 mol%. The affiliation of the isolates with the genus Halomonas was confirmed by 16S rRNA gene sequence comparison. DNA-DNA hybridization shows 70.4-82.7 % relatedness among the three strains. Nevertheless, their relatedness is less than 43 % compared to related reference strains. The proposed type strain for Halomonas ventosae is strain Al12(T) (=CECT 5797(T)=DSM 15911(T)). It grows best at 8 % (w/v) sea salts and requires the presence of Na(+). Its major fatty acids are 18 : 1 omega7c, 16 : 0, 16 : 1 omega7c, and 15 : 0 iso 2-OH. The predominant respiratory lipoquinone found in strain Al12(T) is ubiquinone with nine isoprene units (Q-9).

Base Composition↗
PubMed2006

Gordonia araii sp. nov. and Gordonia effusa sp. nov., isolated from patients in Japan.

Two bacterial strains, IFM 10211(T) and IFM 10200(T), were isolated from the sputum of two Japanese patients, and were subjected to a polyphasic taxonomic study. The two strains were found to have morphological, physiological and chemotaxonomic properties that were consistent with their assignment to the genus Gordonia, except for a few chemotaxonomic characteristics. Almost complete 16S rRNA gene sequences of the two strains were determined; the data showed that they are related distantly to Gordonia amarae, Gordonia hirsuta, Gordonia hydrophobica and Gordonia sihwensis, showing 16S rRNA gene sequence similarities to the type strains of these species of 96.2-97.9 %. DNA-DNA relatedness data coupled with the combination of genotypic and phenotypic data indicated that the two strains are representatives of two novel, separate species. The names proposed to accommodate these two strains are Gordonia araii sp. nov. (type strain IFM 10211(T)=DSM 44811(T)=NBRC 100433(T)=JCM 12131(T)) and Gordonia effusa sp. nov. (type strain IFM 10200(T)=DSM 44810(T)=NBRC 100432(T)=JCM 12130(T)).

Aged↗
PubMed2006

Bacteraemic pneumonia caused by Neisseria lactamica with reduced susceptibility to penicillin and ciprofloxacin in an adult with liver cirrhosis.

This report presents a case of bacteraemic pneumonia caused by Neisseria lactamica in an adult patient with liver cirrhosis who was successfully treated with ceftriaxone. The isolate was confirmed as N. lactamica by analysis of a partial sequence of the 16S rRNA gene; it had reduced susceptibilities to penicillin (MIC 0.75 microg ml(-1)) and ciprofloxacin (MIC > or =0.5 mg l(-1)).

Adult↗
PubMed2004

Temperature-dependent processing of the cspA mRNA in Rhodobacter capsulatus.

The expression of genes for cold-shock proteins is proposed to be regulated primarily at the post-transcriptional level by increase of mRNA stability after transition to low temperatures. Destabilization of the Escherichia coli cold-induced cspA transcript at 37 degrees C as well as stabilization upon cold shock is known to depend on the unusually long (159 nt) 5'-untranslated region. Determination of the cspA mRNA 5'-end from Rhodobacter capsulatus revealed a shorter distance between the start of transcription and the start codon for translation. The cspA mRNA of R. capsulatus was shown to be stabilized at low temperatures to a greater extent than other investigated transcripts. To address the mechanism of decay of the cspA transcript, it was incubated with purified degradosome of R. capsulatus. Endoribonucleolytic in vitro cleavage in the 5'-untranslated region as reported for the cspA transcript of E. coli in vivo was not observed. Instead, the data indicated that the cspA mRNA decay in R. capsulatus is mediated by endoribonucleolytic cleavages within the cspA coding region.

5' Untranslated Regions↗
PubMed2006

Tryptophanase in sRNA control of the Escherichia coli cell cycle.

The field of gene regulation underwent a major revolution with the discovery of small non-coding RNAs (sRNAs) and the various roles they play in organisms from bacteria to man. Escherichia coli has more than 60 sRNAs that are transcribed primarily from intergenic regions. They usually target the leader region of mRNAs and prevent their translation. Protein targets are relatively rare. In this issue of Molecular Microbiology, Chant and Summers provide an example of a totally unexpected protein target. They show that dimers of plasmid ColE1 make an sRNA that interacts directly with the enzyme tryptophanase and enhances its affinity for its substrate, tryptophan. A breakdown product, indole, then arrests cell division until the dimers are resolved to monomers. The monomerization helps to prevent plasmid loss. Targeting a catabolic enzyme to buy time for recombination is an amazing example of adaptation, which illustrates the power of a selfish element (a plasmid in this case) to exploit the host cell machinery to its advantage.

Escherichia coli↗
PubMed2007

The Sinorhizobium meliloti ExoR protein is required for the downregulation of lpsS transcription and succinoglycan biosynthesis in response to divalent cations.

The Sinorhizobium meliloti lpsS gene encodes a sulfotransferase that modifies lipopolysaccharide. Mutants lacking lpsS display no defect in lipopolysaccharide sulfation when assayed under laboratory conditions, but exhibit an abnormal symbiosis with alfalfa. These results suggest that lpsS is transcriptionally repressed under laboratory conditions, but upregulated during symbiosis. Here, it is shown that lpsS, as well as exo genes required for the biosynthesis of succinoglycan, are transcriptionally repressed in laboratory media containing divalent cations. Furthermore, the divalent cation-dependent transcriptional downregulation of lpsS is dependent on the exoR gene, which encodes a global regulator of transcription.

Artificial Gene Fusion↗