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At least 685 records · Page 38Linked to original sources
PubMed1987

Campylobacter pylori, the spiral bacterium associated with human gastritis, is not a true Campylobacter sp.

Comparison of partial 16S rRNA sequences from representative Campylobacter species indicates that the Campylobacter species form a previously undescribed basic eubacterial group, which is related to the other major groups only by very deep branching. This analysis was extended to include the spiral bacterium associated with human gastritis, Campylobacter pylori (formerly Campylobacter pyloridis). The distance between C. pylori and the other Campylobacter species is sufficient to exclude the pyloric organism from the Campylobacter genus. The results indicate that C. pylori is more closely related to Wolinella succinogenes than it is to the other Campylobacter species inspected. Another close relative of the campylobacters was found to be Thiovulum, a sulfide-dependent marine bacterium.

Base Sequence↗
PubMed1990

A trans-unsaturated fatty acid in a psychrophilic bacterium, Vibrio sp. strain ABE-1.

A high level of a trans-unsaturated fatty acid was found in the phospholipids of a psychrophilic bacterium, Vibrio sp. strain ABE-1. This fatty acid was identified as 9-trans-hexadecenoic acid (C16:19t) by gas-liquid chromatography and infrared absorption spectrometry. C16:1(9)t accounted for less than 1% of the total fatty acids in cells grown at 5 degrees C and reached 12% of the total at 20 degrees C. We suggest that the increase in the level of the trans-unsaturated fatty acid is related to the high growth rate of this bacterium at elevated temperatures. Possible biological roles of the trans-unsaturated fatty acid in the adaptation of the microorganism to the ambient temperature are discussed.

Chromatography, Gas↗
PubMed1992

Type II DNA restriction-modification system and an endonuclease from the ruminal bacterium Fibrobacter succinogenes S85.

Fibrobacter succinogenes is an important cellulolytic bacterium found in the rumen and cecum of herbivores. Numerous attempts to introduce foreign DNA into F. succinogenes S85 have failed, suggesting the presence of genetic barriers in this organism. Results from this study clearly demonstrate that F. succinogenes S85 possesses a type II restriction endonuclease, FsuI, which recognizes the sequence 5'-GG(A/T)CC-3'. Analysis of the restriction products on sequencing gels showed that FsuI cleaves between the two deoxyguanosine residues, yielding a 3-base 5' protruding end. These data demonstrate that FsuI is an isoschizomer of AvaII. A methyltransferase activity has been identified in the cell extract of F. succinogenes S85. This activity modified DNA in vitro and protected the DNA from the restriction by FsuI and AvaII. DNA modified in vivo by a cloned methylase gene, which codes for M.Eco47II, also protected the DNA from restriction by FsuI, suggesting that FsuI is inhibited by methylation at one or both deoxycytosine residues of the recognition sequence. The methyltransferase activity in F. succinogenes S85 is likely modifying the same deoxycytosine residues, but the exact site(s) is unknown. A highly active DNase (DNase A) was also isolated from the cell extract of this organism. DNase A is an endonuclease which showed high activity on all forms of DNA (single stranded, double-stranded, linear, and circular) but no activity on RNA. In vitro, the DNase A hydrolyzed F. succinogenes S85 DNA extensively, indicating the lack of protection against hydrolysis by this enzyme. In the presence of Mg2+, DNA was hydrolyzed to fragments of 8 to 10 nucleotides in length. The presence of DNase A and the type II restriction-modification system of F. succinogenes S85 may be the barriers preventing the introduction of foreign DNA into this bacterium.

Base Sequence↗
PubMed1992

Electrogenic malate uptake and improved growth energetics of the malolactic bacterium Leuconostoc oenos grown on glucose-malate mixtures.

Growth of the malolactic bacterium Leuconostoc oenos was improved with respect to both the specific growth rate and the biomass yield during the fermentation of glucose-malate mixtures as compared with those in media lacking malate. Such a finding indicates that the malolactic reaction contributed to the energy budget of the bacterium, suggesting that growth is energy limited in the absence of malate. An energetic yield (YATP) of 9.5 g of biomass.mol ATP-1 was found during growth on glucose with an ATP production by substrate-level phosphorylation of 1.2 mol of ATP.mol of glucose-1. During the period of mixed-substrate catabolism, an apparent YATP of 17.7 was observed, indicating a mixotrophy-associated ATP production of 2.2 mol of ATP.mol of glucose-1, or more correctly an energy gain of 0.28 mol of ATP.mol of malate-1, representing proton translocation flux from the cytoplasm to the exterior of 0.56 or 0.84 H+.mol of malate-1(depending on the H+/ATP stoichiometry). The growth-stimulating effect of malate was attributed to chemiosmotic transport mechanisms rather than proton consumption by the malolactic enzyme. Lactate efflux was by electroneutral lactate -/H+ symport having a constant stoichiometry, while malate uptake was predominantly by a malate -/H+ symport, though a low-affinity malate- uniport was also implicated. The measured electrical component (delta psi) of the proton motive force was altered, passing from -30 to -60 mV because of this translocation of dissociated organic acids when malolactic fermentation occurred.

Adenosine Triphosphate↗
PubMed1996

Adhesion of the positively charged bacterium Stenotrophomonas (Xanthomonas) maltophilia 70401 to glass and Teflon.

Medical implants are often colonized by bacteria which may cause severe infections. The initial step in the colonization, the adhesion of bacteria to the artificial solid surface, is governed mainly by long-range van der Waals and electrostatic interactions between the solid surface and the bacterial cell. While van der Waals forces are generally attractive, the usually negative charge of bacteria and solid surfaces leads to electrostatic repulsion. We report here on the adhesion of a clinical isolate, Stenotrophomonas maltophilia 70401, which is, at physiological pH, positively charged. S. maltophilia has an electrophoretic mobility of +0.3 x 10(-8) m2 V-1 s-1 at pH 7 and an overall surface isoelectric point at pH 11. The positive charge probably originates from proteins located in the outer membrane. For this bacterium, both long-range forces involved in adhesion are attractive. Consequently, adhesion of S. maltophilia to negatively charged surfaces such as glass and Teflon is much favored compared with the negatively charged bacterium Pseudomonas putida mt2. While adhesion of negatively charged bacteria is impeded in media of low ionic strength because of a thick negatively charged diffuse layer, adhesion of S. maltophilia was particularly favored in dilute medium. The adhesion efficiencies of S. maltophilia at various ionic strengths could be explained in terms of calculated long-range interaction energies between S. maltophilia and glass or Teflon.

Bacterial Adhesion↗
PubMed1997

Genomic organization of the acidophilic chemolithoautotrophic bacterium Thiobacillus ferrooxidans ATCC 21834.

The genomic organization of the acidophilic chemolithoautotrophic bacterium Thiobacillus ferrooxidans ATCC 21834 has been studied by pulsed-field gel electrophoresis (PFGE). Analysis of its intact DNA, as well as the restriction patterns obtained with several endonucleases, allowed the characterization of one circular chromosome of 2.9 Mb and one plasmid of 8.6 kb. The first complete and highly resolved physical map (86 restriction sites) of the chromosome of an acidophilic obligate chemolithoautotrophic bacterium has been constructed by using endonucleases PmeI, SwaI, XbaI, and SpeI. The rRNA and str operons have been located on the chromosomal physical map.

Acidithiobacillus thiooxidans↗
PubMed1999

First evidence for the presence of a hydrogenase in the sulfur-reducing bacterium Desulfuromonas acetoxidans.

Hydrogenases, which are ubiquitous in sulfate-reducing bacteria, were previously thought to be absent from Desulfuromonas acetoxidans. For the first time, a hydrogenase from the strict anaerobic sulfur-respiring bacterium D. acetoxidans, grown on ethanol-malate, was detected and enriched. To assay the role of the hydrogenase in the energetic metabolism of D. acetoxidans, we examined the reactivity of the enzyme with polyheme cytochromes from the same bacterium.

Amino Acid Sequence↗
PubMed1999

Iron reductase for magnetite synthesis in the magnetotactic bacterium Magnetospirillum magnetotacticum.

Ferric iron reductase was purified from magnetotactic bacterium Magnetospirillum (formerly Aquaspirillum) magnetotacticum (ATCC 31632) to an electrophoretically homogeneous state. The enzyme was loosely bound on the cytoplasmic face of the cytoplasmic membrane and was found more frequently in magnetic cells than in nonmagnetic cells. The molecular mass of the purified enzyme was calculated upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be about 36 kDa, almost the same as that calibrated by gel filtration analysis. The enzyme required NADH and flavin mononucleotide (FMN) as optimal electron donor and cofactor, respectively, and the activity was strongly inhibited by Zn2+ acting as a partial mixed-type inhibitor. The Km values for NADH and FMN were 4.3 and 0. 035 microM, respectively, and the Ki values for Zn2+ were 19.2 and 23.9 microM for NADH and FMN, respectively. When the bacterium was grown in the presence of ZnSO4, the magnetosome number in the cells and the ferric iron reductase activity declined in parallel with an increase in the ZnSO4 concentration of the medium, suggesting that the ferric iron reductase purified in the present study may participate in magnetite synthesis.

FMN Reductase↗
PubMed2000

Transcriptional control of expression of genes for photosynthetic reaction center and light-harvesting proteins in the purple bacterium Rhodovulum sulfidophilum.

The purple photosynthetic bacterium Rhodovulum sulfidophilum synthesizes photosynthetic apparatus even under highly aerated conditions in the dark. To understand the oxygen-independent expression of photosynthetic genes, the expression of the puf operon coding for the light-harvesting 1 and reaction center proteins was analyzed. Northern blot hybridization analysis showed that puf mRNA synthesis was not significantly repressed by oxygen in this bacterium. High-resolution 5' mapping of the puf mRNA transcriptional initiation sites and DNA sequence analysis of the puf upstream regulatory region indicated that there are three possible promoters for the puf operon expression, two of which have a high degree of sequence similarity with those of Rhodobacter capsulatus, which shows a high level of oxygen repression of photosystem synthesis. Deletion analysis showed that the third promoter is oxygen independent, but the activity of this promoter was not enough to explain the aerobic level of mRNA. The posttranscriptional puf mRNA degradation is not significantly influenced by oxygen in R. sulfidophilum. From these results, we conclude that puf operon expression in R. sulfidophilum is weakly repressed by oxygen, perhaps as a result of the following: (i) there are three promoters for puf operon transcription, at least one of which is oxygen independent; (ii) readthrough transcripts which may not be affected by oxygen may be significant in maintaining the puf mRNA levels; and (iii) the puf mRNA is fairly stable even under aerobic conditions.

Bacterial Proteins↗
PubMed2001

Promoter cloning in the radioresistant bacterium Deinococcus radiodurans.

Deinococcus radiodurans is a highly radiation-resistant bacterium that is classed in a major subbranch of the bacterial domain. Since very little is known about gene expression in this bacterium, an initial study of promoters was undertaken. In order to isolate promoters and study promoter function, a series of integrative vectors for stable chromosomal insertion in D. radiodurans were developed. These vectors are based on Escherichia coli replicons that are unable to replicate autonomously in D. radiodurans and carry homologous sequences for replacement recombination in the D. radiodurans chromosome. The resulting integration vectors were used to study expression of reporter genes fused to a number of putative promoters that were amplified from the D. radiodurans R1 genome. Further analysis of these and other putative promoters was performed by Northern hybridization and primer extension experiments. In contrast to previous reports, the -10 and -35 regions of these promoters resembled the sigma(70) consensus sequence of E. coli.

Catechol 2,3-Dioxygenase↗
PubMed2001

Genome sequence and comparative analysis of the solvent-producing bacterium Clostridium acetobutylicum.

The genome sequence of the solvent-producing bacterium Clostridium acetobutylicum ATCC 824 has been determined by the shotgun approach. The genome consists of a 3.94-Mb chromosome and a 192-kb megaplasmid that contains the majority of genes responsible for solvent production. Comparison of C. acetobutylicum to Bacillus subtilis reveals significant local conservation of gene order, which has not been seen in comparisons of other genomes with similar, or, in some cases closer, phylogenetic proximity. This conservation allows the prediction of many previously undetected operons in both bacteria. However, the C. acetobutylicum genome also contains a significant number of predicted operons that are shared with distantly related bacteria and archaea but not with B. subtilis. Phylogenetic analysis is compatible with the dissemination of such operons by horizontal transfer. The enzymes of the solventogenesis pathway and of the cellulosome of C. acetobutylicum comprise a new set of metabolic capacities not previously represented in the collection of complete genomes. These enzymes show a complex pattern of evolutionary affinities, emphasizing the role of lateral gene exchange in the evolution of the unique metabolic profile of the bacterium. Many of the sporulation genes identified in B. subtilis are missing in C. acetobutylicum, which suggests major differences in the sporulation process. Thus, comparative analysis reveals both significant conservation of the genome organization and pronounced differences in many systems that reflect unique adaptive strategies of the two gram-positive bacteria.

Amino Acid Sequence↗
PubMed2002

The PhlA hemolysin from the entomopathogenic bacterium Photorhabdus luminescens belongs to the two-partner secretion family of hemolysins.

Photorhabdus is an entomopathogenic bacterium symbiotically associated with nematodes of the family Heterorhabditidae. Bacterial hemolysins found in numerous pathogenic bacteria are often virulence factors. We describe here the nucleotide sequence and the molecular characterization of the Photorhabdus luminescens phlBA operon, a locus encoding a hemolysin which shows similarities to the Serratia type of hemolysins. It belongs to the two-partner secretion (TPS) family of proteins. In low-iron conditions, a transcriptional induction of the phlBA operon was observed by using the chloramphenicol acetyltransferase reporter gene, causing an increase in PhlA hemolytic activity compared to iron-rich media. A spontaneous phase variant of P. luminescens was deregulated in phlBA transcription. The phlA mutant constructed by allelic exchange remained highly pathogenic after injection in the lepidopteran Spodoptera littoralis, indicating that PhlA hemolysin is not a major virulence determinant. Using the gene encoding green fluorescent protein as a reporter, phlBA transcription was observed in hemolymph before insect death. We therefore discuss the possible role of PhlA hemolytic activity in the bacterium-nematode-insect interactions.

Amino Acid Sequence↗
PubMed2002

Chloride, a new environmental signal molecule involved in gene regulation in a moderately halophilic bacterium, Halobacillus halophilus.

The gram-positive, aerobic, moderately halophilic bacterium Halobacillus halophilus is challenged in its environment by frequently changing salt (NaCl) concentrations. Recently, H. halophilus was shown to be the first prokaryote that is dependent on Cl(-) for growth. In a search for the biological function of Cl(-) in this prokaryote, we identified different Cl(-)-dependent processes, which suggests a more general role for Cl(-) in the metabolism of H. halophilus. To analyze the effect of Cl(-) in more detail, we concentrated on one model system, the Cl(-)-dependent production of flagella, and aimed to identify the molecular basis for the Cl(-) dependence of flagellum production. Here, we report that synthesis of the major subunit of the flagellum, FliC, is dependent on the Cl(-) concentration of the medium, as determined by Western blot analyses. The gene encoding FliC was cloned and sequenced, and Northern blot as well as reverse transcriptase PCR analyses revealed that expression of fliC is Cl(-) dependent. FliC is the first protein of known function demonstrated to be synthesized in a Cl(-)-dependent manner in a prokaryote. Two-dimensional gel electrophoresis of cells grown under different conditions revealed five more Cl(-)-induced proteins; these were identified by N-terminal sequencing and database searches to be orthologs of proteins involved in stress response in Bacillus subtilis. The data indicate that Cl(-) is an important environmental signal in this moderate halophile and regulates protein synthesis and gene expression. Furthermore, the data may suggest that Cl(-) plays a role in the signal transduction involved in salt perception by this bacterium.

Amino Acid Sequence↗
PubMed2004

A cambialistic superoxide dismutase in the thermophilic photosynthetic bacterium Chloroflexus aurantiacus.

Superoxide dismutase from the thermophilic anoxygenic photosynthetic bacterium Chloroflexus aurantiacus was cloned, purified, and characterized. This protein is in the manganese- and iron-containing family of superoxide dismutases and is able to use both manganese and iron catalytically. This appears to be the only soluble superoxide dismutase in C. aurantiacus. Iron and manganese cofactors were identified by using electron paramagnetic resonance spectroscopy and were quantified by atomic absorption spectroscopy. By metal enrichment of growth media and by performing metal fidelity studies, the enzyme was found to be most efficient with manganese incorporated, yet up to 30% of the activity was retained with iron. Assimilation of iron or manganese ions into superoxide dismutase was also found to be affected by the growth conditions. This enzyme was also found to be remarkably thermostable and was resistant to H2O2 at concentrations up to 80 mM. Reactive oxygen defense mechanisms have not been previously characterized in the organisms belonging to the phylum Chloroflexi. These systems are of interest in C. aurantiacus since this bacterium lives in a hyperoxic environment and is subject to high UV radiation fluxes.

Amino Acid Sequence↗
PubMed1963

Temperature-sensitive formic hydrogenlyase in a psychrophilic bacterium.

Upadhyay, J. (Washington State University, Pullman) and J. L. Stokes. Temperature-sensitive formic hydrogenlyase in a psychrophilic bacterium. J. Bacteriol. 85:177-185. 1963.-A temperature-sensitive formic hydrogenlyase has been found in a psychrophilic bacterium, strain 82. The enzyme was most active at 30 C, but completely inactive at 45 C. In contrast, formic hydrogenlyase in mesophilic Escherichia coli was most active at 45 C, and completely inactivated only at 70 C. The hydrogenlyase-forming system in psychrophile strain 82 also was unusually heat-sensitive. It was inactivated at temperatures above 20 C; whereas, in mesophilic E. coli, Proteus vulgaris, and Salmonella oranienburg, hydrogenlyase was formed even at 45 C. This heat sensitivity of the enzyme-forming system accounted fully for the inability of strain 82 to produce gas from carbohydrates above 20 C. Psychrophile hydrogenlyase resembled the mesophilic variety in several respects. It was most active at pH 5.0. It was not formed by cells grown aerobically. It could be induced in resting-cell suspensions by use of glucose, formate, and casein hydrolysate as supplements, although several times as much glucose was required as for enzyme induction in strains of E. coli and Salmonella. The enzyme was formed best at pH 7.5, which was somewhat higher than the pH of 6 to 7 for mesophile hydrogenlyase, and by cells taken from the beginning of the stationary phase of growth.

Bacteria↗
PubMed1963

IDENTIFICATION OF COLEMAN'S SULFATE-REDUCING BACTERIUM AS A MESOPHILIC RELATIVE OF CLOSTRIDIUM NIGRIFICANS.

Postgate, John R. (University of Illinois, Urbana) and L. Leon Campbell. Identification of Coleman's sulfate-reducing bacterium as a mesophilic relative of Clostridium nigrificans. J. Bacteriol. 86:274-279. 1963.-Coleman's sulfate-reducing bacterium is immunologically and morphologically similar to Clostridium nigrificans and unlike Desulfovibrio species. It is not thermophilic and does not acquire the thermophilic habit; it is thus the first naturally occurring mesophilic member of this group to be described.

Bacteria↗
PubMed1964

Lysis and dissolution of cells and envelopes of an extremely halophilic bacterium.

Kushner, D. J. (National Research Council, Ottawa, Ontario, Canada). Lysis and dissolution of cells and envelopes of an extremely halophilic bacterium. J. Bacteriol. 87:1147-1156. 1964.-Envelopes of the extremely halophilic bacterium, Halobacterium cutirubrum, disintegrate in the absence of salt to form much smaller particles. Extensive proteolytic breakdown to compounds of low molecular weight is not involved in this process or in the lysis of cells in the absence of salt. NaCl is much more effective than KCl or NH(4)Cl in preserving the integrity of intact cells, but is only slightly more effective in preserving the integrity of mechanically prepared envelopes, of cells made permeable by treatment with acid, and of cells made permeable by formalin fixation followed by exposure to water. MgCl(2) is much more effective in preserving the integrity of these preparations than of intact cells. The results suggest that the exterior cell surface has sites specifically requiring Na(+) to maintain their integrity, whereas the interior surface has sites whose integrity is maintained at least as well by K(+) or NH(4) (+) as by Na(+).

Ammonium Chloride↗
PubMed1966

Effect of light intensity on the formation of the photochemical apparatus in the green bacterium Chloropseudomonas ethylicum.

Holt, Stanley C. (Dartmouth Medical School, Hanover, N.H.), S. F. Conti, and R. C. Fuller. Effect of light intensity on the formation of the photochemical apparatus in the green bacterium Chloropseudomonas ethylicum. J. Bacteriol. 91:349-355. 1966.-When the green bacterium Chloropseudomonas ethylicum was grown at various light intensities, the formation of the photosynthetic vesicles was found to be an inverse function of the light intensity at which the cells were grown. The specific chlorophyll content of isolated vesicles varied as the light intensity was changed over a wide range. Thus, the regulation of chlorophyll content in C. ethylicum in response to a change in light intensity is achieved both by a change in the number of vesicles that are formed and by a change in the specific chlorophyll content of these vesicles.

Bacteria↗