Showing papers in "Archives of Microbiology in 1996"
TL;DR: Two widespread mechanisms of bacterial resistance do not destroy tetracycline: one is mediated by efflux pumps, the other involves an EF-G-like protein that confers ribosome protection.
Abstract: Tetracyclines probably penetrate bacterial cells by passive diffusion and inhibit bacterial growth by interfering with protein synthesis or by destroying the membrane. A growing number of various bacterial species acquire resistance to the bacteriostatic activity of tetracycline. The two widespread mechanisms of bacterial resistance do not destroy tetracycline: one is mediated by efflux pumps, the other involves an EF-G-like protein that confers ribosome protection. Oxidative destruction of tetracycline has been found in a few species. Several efflux transporters, including multidrug-resistance pumps and tetracycline-specific exporters, confer bacterial resistance against tetracycline. Single amino acids of these carrier proteins important for tetracycline transport and substrate specificity have been identified, allowing the mechanism of tetracycline transport to begin to emerge.
443 citations
TL;DR: On the basis of 16S rRNA sequence analysis, the organism was identified as a species within the genus Desulfitobacterium, which until now only contained the chlorophenol-dechlorinating bacterium, Desulf itobacteria dehalogenans.
Abstract: A strictly anaerobic bacterium, strain PCE1, was isolated from a tetrachloroethene-dechlorinating enrichment culture. Cells of the bacterium were motile curved rods, with approximately four lateral flagella. They possessed a gram-positive type of cell wall and contained cytochrome c. Optimum growth occurred at pH 7.2–7.8 and 34–38° C. The organism grew with l-lactate, pyruvate, butyrate, formate, succinate, or ethanol as electron donors, using either tetrachloroethene, 2-chlorophenol, 2,4,6-trichlorophenol, 3-chloro-4-hydroxy-phenylacetate, sulfite, thiosulfate, or fumarate as electron acceptors. Strain PCE1 also grew fermentatively with pyruvate as the sole substrate. l-Lactate and pyruvate were oxidized to acetate. Tetrachloroethene was reductively dechlorinated to trichloroethene and small amounts (< 5%) of cis-1,2-dichloroethene and trans-1,2-dichloroethene. Chlorinated phenolic compounds were dechlorinated specifically at the ortho-position. On the basis of 16S rRNA sequence analysis, the organism was identified as a species within the genus Desulfitobacterium, which until now only contained the chlorophenol-dechlorinating bacterium, Desulfitobacterium dehalogenans.
305 citations
TL;DR: This review will compare properties of the three toxin prototypes, highlighting the similarities and also the differences in their structure, mode of binding, mechanism of pore formation, and the responses they elicit in target cells.
Abstract: Staphylococcal alpha-toxin, streptolysin-O, and Escherichia coli hemolysin are well-studied prototypes of pore-forming bacterial cytotoxins. Each is produced as a water-soluble single-chain polypeptide that inserts into target membranes to form aqueous transmembrane pores. This review will compare properties of the three toxin prototypes, highlighting the similarities and also the differences in their structure, mode of binding, mechanism of pore formation, and the responses they elicit in target cells. Pore-forming toxins represent the most potent and versatile weapons with which invading microbes damage the host macroorganism.
297 citations
TL;DR: A novel coccoid, anaerobic, Fe2+-oxidizing archaeum was isolated from a shallow submarine hydrothermal system at Vulcano, Italy and represents a novel genus among the Archaeoglobales that is named Ferroglobus.
Abstract: A novel coccoid, anaerobic, Fe2+-oxidizing archaeum was isolated from a shallow submarine hydrothermal system at Vulcano, Italy. In addition to ferrous iron, H2 and sulfide served as electron donors. NO3– was used as electron acceptor. In the presence of H2, also S2O32– could serve as electron acceptor. The isolate was a neutrophilic hyperthermophile that grew between 65° C and 95° C. It represents a novel genus among the Archaeoglobales that we name Ferroglobus. The type species is Ferroglobus placidus (DSM 10642).
293 citations
TL;DR: Strain PD630 utilized β-oxidation and de novo fatty acid biosynthesis for the synthesis of storage lipids and lipid inclusions seemed to have definite structures, probably with membranes at their surfaces, which allow them to maintain their shape, and with some associated proteins, probably involved in the inclusion formation.
Abstract: An oleaginous hydrocarbon-degrading Rhodococcus opacus strain (PD630) was isolated from a soil sample. The cells were able to grow on a variety of substrates and to produce large amounts of three different types of intracellular inclusions during growth on alkanes, phenylalkanes, or non-hydrocarbon substrates. Electron microscopy revealed large numbers of electron-transparent inclusions with a sphere-like structure. In addition, electron-dense inclusions representing polyphosphate and electron-transparent inclusions with an elongated disc-shaped morphology occurred in small amounts. The electron-transparent inclusions of alkane- or gluconate-grown cells were composed of neutral lipids (98%, w/w), phospholipids (1.2%, w/w), and protein (0.8%, w/w). The major component of the cellular inclusions was triacylglycerols; minor amounts of diacylglycerols and probably also some free fatty acids were also present. Free fatty acids and/or fatty acids in acylglycerols in cells of R. opacus amounted up to 76 or 87% of the cellular dry weight in gluconate- or olive-oil-grown cells, respectively. The fatty acid composition of the inclusions depended on the substrate used for cultivation. In cells cultivated on n-alkanes, the composition of the fatty acids was related to the substrate, and intermediates of the β-oxidation pathway, such as hexadecanoic or pentadecanoic acid, were among the acylglycerols. Hexadecanoic acid was also the major fatty acid (up 36% of total fatty acids) occurring in the lipid inclusions of gluconate-grown cells. This indicated that strain PD630 utilized β-oxidation and de novo fatty acid biosynthesis for the synthesis of storage lipids. Inclusions isolated from phenyldecane-grown cells contained mainly the non-modified substrate and phenylalkanoic acids derived from the hydrocarbon oxidation, such as phenyldecanoic acid, phenyloctanoic acid, and phenylhexanoic acid, and approximately 5% (w/w) of diacylglycerols. The lipid inclusions seemed to have definite structures, probably with membranes at their surfaces, which allow them to maintain their shape, and with some associated proteins, probably involved in the inclusion formation.
285 citations
TL;DR: This review codifies the nomenclature of the hexose transporter genes and describes the sequence homology and structural similarity of the proteins they encode.
Abstract: Saccharomyces cerevisiae accomplishes high rates of hexose transport. The kinetics of hexose transport are complex. The capacity and kinetic complexity of hexose transport in yeast are reflected in the large number of sugar transporter genes in the genome. Twenty hexose transporter genes exist in S. cerevisiae. Some of these have been found by genetic means; many have been discovered by the comprehensive sequencing of the yeast genome. This review codifies the nomenclature of the hexose transporter genes and describes the sequence homology and structural similarity of the proteins they encode. Information about the expression and function of the transporters is presented. Access to the sequences of the genes and proteins at three sequence databases is provided via the World Wide Web.
245 citations
TL;DR: Evidence suggests that members of this wide-spread protein family can function both at the transcriptional and translational level in vitro, and post-transcriptional regulation seems to play a major role in the induction of CSPs, a process in which the ribosome may be involved.
Abstract: Bacteria respond to an abrupt decrease in temperature with a specific response, in which cold-induced proteins (CIPs) are transiently expressed at a higher level Employing two-dimensional gel electrophoresis, several CIPs have been identified In spite of this, the overall function of the cold shock response is unclear Recently, the main attention has focused on a group of conserved cold shock proteins (CSPs) that have been shown to have the highest induction after cold shock and to play a major regulatory role in the physiology of adaptation to low temperatures CSPs, of which Escherichia coli, Bacillus subtilis, and B cereus possess a family comprising at least 3-7 proteins, are small acidic proteins that share over 45% of sequence identity Recent evidence suggests that members of this wide-spread protein family can function both at the transcriptional and translational level in vitro However, the exact mode of action has yet to be established In addition, post-transcriptional regulation seems to play a major role in the induction of CSPs, a process in which the ribosome may be involved This is in accordance with a model in which the ribosome has been proposed to be the sensor of temperature in bacteria
215 citations
TL;DR: A novel enzyme that catalyzes the disproportionation of chlorite into chloride and oxygen was purified from a gram-negative bacterium, strain GR-1 to homogeneity and displayed maxima for activity at pH 6.0 and 30° C.
Abstract: A novel enzyme that catalyzes the disproportionation of chlorite into chloride and oxygen was purified from a gram-negative bacterium, strain GR-1 to homogeneity. A four-step purification procedure comprising Q-Sepharose, hydroxyapatite, and phenyl-Superose chromatography and ultrafiltration resulted in a 13.7-fold purified enzyme with a final specific activity of 2.0 mmol min-1 (mg protein)-1. The dismutase obeyed Michaelis-Menten kinetics. The Vmax and Km calculated for chlorite were 2,200 U (mg protein)-1 and 170 microM, respectively. Dismutase activity was inhibited by hydroxylamine, cyanide, and azide, but not by 3-amino-1,2,4-triazole. Chlorite dismutase had a molecular mass of 140 kDa and consisted of four 32-kDa subunits. The enzyme was red-colored and had a Soret peak at 392 nm. Per subunit, it contained 0.9 molecule of protoheme IX and 0.7 molecule of iron. Chlorite dismutase displayed maxima for activity at pH 6.0 and 30 degrees C.
212 citations
TL;DR: The methyltetrahydromethanopterin:coenzyme M methyltransferase is a unique, reversible sodium ion pump that couples methyl transfer with the transport of Na+ across the cytoplasmic membrane, and Formylmethanofuran dehydrogenase is an reversible ions pump that catalyzes formylation and deformylation, of methanofuran.
Abstract: Methanogenic archaea are strictly anaerobic organisms that derive their metabolic energy from the conversion of a restricted number of substrates to methane. H2+CO2 and formate are converted to CH4 via the CO2-reducing pathway, while methanol and methylamines are metabolized by the methylotrophic pathway. A limited number of methanogenic organisms utilize acetate by the aceticlastic pathway. Redox reactions involved in these processes are partly catalyzed by membrane-bound enzyme systems that generate or, in the case of endergonic reactions, use electrochemical ion gradients. The H2:heterodisulfide oxidoreductase, the F420H2:heterodisulfide oxidoreductase and the CO:heterodisulfide oxidoreductase, are novel systems that generate a proton motive force by redox-potential-driven H+ translocation. The methyltetrahydromethanopterin:coenzyme M methyltransferase is a unique, reversible sodium ion pump that couples methyl transfer with the transport of Na+ across the cytoplasmic membrane. Formylmethanofuran dehydrogenase is a reversible ion pump that catalyzes formylation and deformylation, of methanofuran. In summary, the pathways are coupled to the generation of an electrochemical sodium ion gradient and an electrochemical proton gradient. Both ion gradients are used directly for ATP synthesis via membrane integral ATP synthases. The function of the above-mentioned systems and their components in the metabolism of methanogens are described in detail.
184 citations
TL;DR: Analysis of the 16S rRNA gene sequence of PAL-1 showed that the strain is not related to any of the described metal-reducing bacteria in the Proteobacteria and forms a separate line of descent within the Bacteria.
Abstract: A new, phylogenetically distinct, dissimilatory, Fe(III)-reducing bacterium was isolated from surface sediment of a hydrocarbon-contaminated ditch. The isolate, designated strain PAL-1, was an obligately anaerobic, non-fermentative, motile, gram-negative vibrio. PAL-1 grew in a defined medium with acetate as electron donor and ferric pyrophosphate, ferric oxyhydroxide, ferric citrate, Co(III)-EDTA, or elemental sulfur as sole electron acceptor. PAL-1 also used proline, hydrogen, lactate, propionate, succinate, fumarate, pyruvate, or yeast extract as electron donors for Fe(III) reduction. It is the first bacterium known to couple the oxidation of an amino acid to Fe(III) reduction. PAl-1 did not reduce oxygen, Mn(IV), U(VI), Cr(VI), nitrate, sulfate, sulfite, or thiosulfate with acetate as the electron donor. Cell suspensions of PAL-1 exhibited dithionite-reduced minus air-oxidized difference spectra that were characteristic of c-type cytochromes. Analysis of the 16S rRNA gene sequence of PAL-1 showed that the strain is not related to any of the described metal-reducing bacteria in the Proteobacteria and, together with Flexistipes sinusarabici, forms a separate line of descent within the Bacteria. Phenotypically and phylogenetically, strain PAl-1 differs from all other described bacteria, and represents the type strain of a new genus and species, Geovibrio
ferrireducens.
138 citations
TL;DR: A new strictly anaerobic, gram-negative bacterium was isolated from the sediment of a freshwater lake after enrichment with thiosulfate as the energy source and was shown to be related to, but distinct from members of the genus Desulfobulbus on the basis of physiological characteristics and by comparative sequence analysis of its 16S rDNA.
Abstract: A new strictly anaerobic, gram-negative bacterium was isolated from the sediment of a freshwater lake after enrichment with thiosulfate as the energy source The strain, named Bra2 (DSM 7269), is able to grow by disproportionation of thiosulfate or sulfite to sulfate plus sulfide Elemental sulfur is also disproportionated to sulfate and sulfide, but this only supports growth if free sulfide is chemically removed from the culture, eg, by precipitation with amorphous ferric hydroxide Growth is also possible by coupling the reduction of sulfate to sulfide with the oxidation of ethanol, propanol, or butanol to the corresponding fatty acid The cells are rod-shaped, motile, and have genomic DNA with a mol% G+C content of 507 Cytochromes are present, but desulfoviridin is not The new strain was shown to be related to, but distinct from members of the genus Desulfobulbus on the basis of physiological characteristics and by comparative sequence analysis of its 16S rDNA Strain Bra2 is described as the type strain of a new taxon, Desulfocapsa thiozymogenes gen nov, sp nov
TL;DR: Growth and magnetite formation in Magnetospirillum gryphiswaldense MSR-1 were found close to the maximum at an extracellular iron concentration of 15–20 μM, suggesting a comparatively low-affinity, but high-velocity transport system.
Abstract: Growth and magnetite formation in Magnetospirillum gryphiswaldense MSR-1 were found close to the maximum at an extracellular iron concentration of 15–20 μM. Ferrous iron was incorporated by a slow, diffusion-like process. Several iron chelators including various microbial siderophores were unable to promote transport of iron into the cells. In contrast, spent culture fluids stimulated the uptake of ferric iron in iron-depleted cells at a high rate, whereas fresh medium and transport buffer were unable to promote iron uptake. However, no siderophore-like compound could be detected in spent culture fluids by the Chrome Azurol S assay. Ferric iron uptake followed Michaelis-Menten kinetics with a K
m of 3 μM and a V
max of 0.86 nmol min–1 (mg dry weight)–1, suggesting a comparatively low-affinity, but high-velocity transport system. Iron incorporation was sensitive to 2,4-dinitrophenol and carbonylcyanide-m-chlorophenylhydrazone, indicating an energy-dependent transport process.
TL;DR: A new H2/CO2-utilizing acetogenic bacterium was isolated from the feces of a non-methane-excreting human subject and a new species, Ruminococcus hydrogenotrophicus, is proposed based on phenotypic and phylogenetic considerations.
Abstract: A new H2/CO2-utilizing acetogenic bacterium was isolated from the feces of a non-methane-excreting human subject. The two strains S5a33 and S5a36 were strictly anaerobic, gram-positive, non-sporulating coccobacilli. The isolates grew autotrophically by metabolizing H2/CO2 to form acetate as sole metabolite and were also able to grow heterotrophically on a variety of organic compounds. The major end product of glucose and fructose fermentation was acetate; the strains also formed ethanol, lactate and, to a lesser extent, isobutyrate and isovalerate. The G+C content of DNA of strain S5a33 was 45.2 mol%. 16S rRNA gene sequencing demonstrated that the two acetogenic isolates were phylogenetically identical and represent a new subline within Clostridium cluster XIVa. Based on phenotypic and phylogenetic considerations, a new species, Ruminococcus hydrogenotrophicus, is proposed. The type strain of R. hydrogenotrophicus is S5a33 (DSM 10507). Furthermore, H2/CO2 acetogenesis appeared to be a common property of most of the species phylogenetically closely related to strain S5a33 (Clostridium coccoides, Ruminococcus hansenii, and Ruminococcus productus).
TL;DR: It is postulate that a membrane-bound FixGHIS complex might play a role in uptake and metabolism of copper required for the cbb3-type heme-copper oxidase.
Abstract: We report structural and functional analyses of the Bradyrhizobium japonicum fixGHIS genes, which map immediately downstream of the fixNOQP operon for the symbiotically essential cbb3-type heme-copper oxidase complex. Expression of fixGHIS, like that of fixNOQP, is strongly induced in cells grown microaerobically or anaerobically. A fixGHI deletion led to the same prominent phenotypes as those known from a fixNOQP deletion: defective symbiotic nitrogen fixation (Fix-) and decreased cytochrome oxidase activity in cells grown under oxygen deprivation. Only traces, if any, of cytochrome cbb3 subunits were present in membranes isolated from the delta fixGHI strain, as revealed by Western blot analysis with subunit-specific antibodies. This effect was not due to lack of fixNOQP transcription. The results suggested a critical involvement of the fixGHIS gene products in the assembly and/or stability of the cbb3-type heme-copper oxidase. On the basis of sequence similarities between the FixI protein and a Cu-transporting P-type ATPase (CopA) of Enterococcus hirae, and between FixG and a membrane-bound oxidoreductase (RdxA) of Rhodobacter sphaeroides, we postulate that a membrane-bound FixGHIS complex might play a role in uptake and metabolism of copper required for the cbb3-type heme-copper oxidase.
TL;DR: Five Merismopedia-like cyanobacterial strains were collected from microbial mats at Norderney Island, subcultured in the laboratory, and finally grown as unicyanobacterial cultures, and an almost 100% identity of three of the six isolates was determined.
Abstract: Five Merismopedia-like cyanobacterial strains were collected from microbial mats at Norderney Island, subcultured in the laboratory, and finally grown as unicyanobacterial cultures. As a sixth strain, Merismopedia
glauca from the „Sammlung von Algenkulturen“ at Gottingen (SAG) was used for comparisons. According to morphological and physiological characteristics initially observed in the field and during initial subculturing, the five strains were assigned to the species Merismopedia glauca, Merismopedia punctata, or Merismopedia elegans. However, after prolonged maintenance under laboratory conditions, the formation of platelet-like colonies stopped, whereas cell sizes, production of extracellular polymeric substances, and division patterns were stably maintained. These physiological and morphological parameters allowed us to divide the six strains into two clusters. This division was further supported by the profiling of total cell protein and phycobilisomes using SDS-PAGE. The nearly complete 16S rDNA sequence of three of the six isolates was determined. The comparative sequencing analysis revealed an almost 100% identity of these three Merismopedia-like strains. The evolutionary distance dendrogram constructed placed this Merismopedia cluster into a common line of descent with Synechocystis sp. strain PCC6906. Based on the analysis of common stretches of 1,050 nucleotides, the overall similarity between the sequence types of „Merismopedia“ and „Synechocystis“ is 96–97%. The values of the different methods for taxonomic classification of unicyanobacterial strains, the relationship of the cyanobacterial genera Merismopedia, Synechococcus, Synechocystis, and Eucapsis sp., and the functional role of different Merismopedia morphologies within microbial mats are discussed. It is suggested that all analyzed Merismopedia strains be combined into one species, namely Merismopedia
punctata Meyen (1839).
TL;DR: In this paper, the 16S rRNA gene sequences of Ectothiorhodospiraceae were determined from all type strains of the recognized species and from a number of additional strains.
Abstract: Sequences of the 16S rRNA gene were determined from all type strains of the recognized Ectothiorhodospira species and from a number of additional strains. For the first time, these data resolve the phylogenetic relationships of the Ectothiorhodospiraceae in detail, confirm the established species, and improve the classification of strains of uncertain affiliation. Two major groups that are recognized as separate genera were clearly established. The extremely halophilic species were removed from the genus Ectothiorhodospira and reassigned to the new genus Halorhodospira gen. nov., to recognize that the most halophilic eubacteria are species of this genus. These species are Halorhodospira halophila comb. nov., Halorhodospira halochloris comb. nov., and Halorhodospira abdelmalekii comb. nov. Among the slightly halophilic Ectothiorhodospira species, the classification of strains belonging to Ectothiorhodospira mobilis and Ectothiorhodospira shaposhnikovii was improved. Several strains that were tentatively identified as Ectothiorhodospira mobilis form a separate cluster on the basis of their 16S rDNA sequences and are recognized as two new species: Ectothiorhodospira haloalkaliphila sp. nov., which includes the most alkaliphilic strains originating from strongly alkaline soda lakes, and Ectothiorhodospira marina, describing isolates from the marine environment.
TL;DR: One strain, G10, of Namibia origin was equidistantly related to Geodermatophilus obscurus, Frankia alni, Sporichthya polymorpha, and Acidothermus cellulolyticus, and three strains from rock varnish in the Mojave desert, California, were found to be highly related to Arthrobacter (formerly Micrococcus) agilis.
Abstract: In an extended study on the biodiversity of rock-dwelling bacteria, the colony and cell morphology, physiology, protein patterns, and 16S rDNA sequences of 17 bacterial strains isolated from different surfaces of rocks, stones, and monuments and from various geographical locations were characterized. All except one strain, which was found to be a Bacillus, were members of the order Actinomycetales. The majority of the strains either were closely related to Geodermatophilus obscurus, which was also analyzed in this study, or formed a closely related sister taxon. All of these strains were isolated from the surface of marble in Namibia and Greece and from limestone from the Negev desert, Israel. One strain, G10, of Namibia origin was equidistantly related to Geodermatophilus obscurus, Frankia alni, Sporichthya polymorpha, and Acidothermus cellulolyticus. Three strains from rock varnish in the Mojave desert, California, were found to be highly related to Arthrobacter (formerly Micrococcus) agilis. All clusters could be confirmed from results of studies on morphological and physiological properties and from banding patterns of whole cell proteins. Based on the results of tests, four additional strains were assigned to the lineage defined by strain G10.
TL;DR: The dechlorination in cell suspensions rather than in cell extracts was inhibited by the ionophores carbonylcyanide-p-(trifluoromethoxy)-phenylhydrazone (FCCP) and tetrachlorosalicylanilide (TCS), indicating that a membrane potential and/or a pH gradient may be required for the reaction in vivo.
Abstract: Tetrachloroethene (PCE) respiration was studied in the tetrachloroethene-utilizing anaerobe,Dehalospirillum multivorans, with respect to localization of the catabolic enzymes, the electron carriers potentially involved in electron transport, and the response to ionophores and specific inhibitors. Hydrogenase and formate dehydrogenase were recovered in the periplasmic cell fraction and were membrane-associated. Electron-accepting tetrachloroethene dehalogenase was found in the cytoplasmic fraction. In the PCE dehalogenase assay, only artificial electron donors with a standard redox potential of <-360 mV were effective electron donors for PCE reduction. Besides these artificial reductants, ferredoxin isolated fromD. multivorans (E′o=-445 mV) could serve as electron donor for PCE reduction. However, the reaction rate with ferredoxin was only 1% of that with methyl viologen, whereas the pyruvate-ferredoxin oxidoreductase exhibited almost the same reaction rates with methyl viologen and ferredoxin as electron acceptors for pyruvate oxidation. Reduced menadione (2-methyl-1,4-naphthoquinone) did not serve as electron donor in the PCE dehalogenase reaction. 2-Heptyl-4-hydroxyquinoline-N-oxide (HOQNO) had no significant effect on PCE dechlorination in cell suspensions and in crude extracts. Whole cells catalyzed the reductive dechlorination of PCE with H2 or formate as electron donors. The dechlorination in cell suspensions rather than in cell extracts was inhibited by the ionophores carbonylcyanide-p-(trifluoromethoxy)-phenylhydrazone (FCCP) and tetrachlorosalicylanilide (TCS), indicating that a membrane potential and/or a pH gradient may be required for the reaction in vivo.
TL;DR: The enrichment and isolation in pure culture of a bacterium, identified as a strain of Desulfovibrio, able to release and reduce the sulfur of isethionate and other sulfonates to support anaerobic respiratory growth is described.
Abstract: The enrichment and isolation in pure culture of a bacterium, identified as a strain of Desulfovibrio, able to release and reduce the sulfur of isethionate (2-hydroxyethanesulfonate) and other sulfonates to support anaerobic respiratory growth, is described. The sulfonate moiety was the source of sulfur that served as the terminal electron acceptor, while the carbon skeleton of isethionate functioned as an accessory electron donor for the reduction of sulfite. Cysteate (alanine-3-sulfonate) and sulfoacetaldehyde (acetaldehyde-2-sulfonate) could also be used for anaerobic respiration, but many other sulfonates could not. A survey of known sulfate-reducing bacteria revealed that some, but not all, strains tested could utilize the sulfur of some sulfonates as terminal electron acceptor. Isethionate-grown cells of Desulfovibrio strain IC1 reduced sulfonate-sulfur in preference to that of sulfate; however, sulfate-grown cells reduced sulfate-sulfur in preference to that of sulfonate.
TL;DR: The sequence similarity among these proteins and the product similarity of cyclic peptides suggests that they might be involved in the biosynthesis or secretion of the peptides.
Abstract: Bacillus subtilis YB8 was found to produce the lipopeptide antibiotics surfactin and plipastatin B1. A gene, lpa-8, required for the production of both lipopeptides was cloned from strain YB8. When this gene was inactivated in strain YB8, neither surfactin nor plipastatin B1 was produced. However, the defective strain transformed with an intact lpa-8 gene had restored ability to produce both peptides. Nucleotide sequence analysis of the region essential for the production of the peptides revealed the presence of a large open reading frame. The deduced amino acid sequence of lpa-8 (224 amino acid residues) showed sequence similarity to that of sfp (from surfactin-producing B. subtilis), lpa-14 (from iturin A- and surfactin-producing B. subtilis), psf-1 (from surfactin-producing Bacillus pumilus), gsp (from gramicidin-S-producing Bacillus brevis), and entD (from siderophore-enterobactin-producing Escherichia coli), which are able to complement a defect in the sfp gene and promote production of the lipopeptide antibiotic surfactin. The sequence similarity among these proteins and the product similarity of cyclic peptides suggests that they might be involved in the biosynthesis or secretion of the peptides.
TL;DR: The phototrophic non-sulfur purple bacterium Rhodobacter capsulatus is able to fix atmospheric dinitrogen either via a conventional molybdenum nitrogenase or via an alternative iron-only nitrogenase, and its regulation is regulated at the transcriptional level and at the post-translational level.
Abstract: The phototrophic non-sulfur purple bacterium Rhodobacter capsulatus is able to fix atmospheric dinitrogen either via a conventional molybdenum nitrogenase or via an alternative iron-only nitrogenase. At least 53 genes are involved in the synthesis and regulation of these two nitrogenase systems, most of which are clustered in four regions widely spread in the genome. Expression of both nitrogenase systems is regulated at the transcriptional level by NifR1 and NifR2, homologues of NtrC and NtrB, respectively. However, this ntr system is only involved in the regulation of the two nitrogenase systems and the high-affinity molybdenum transport system and is not required for utilization of other N sources such as proline and arginine. In contrast to enteric bacteria, the R. capsulatus NtrC homologue does not act in concert with the alternative sigma factor RpoN (σ54). Nitrogen fixation in R. capsulatus is regulated at the transcriptional level and also at the post-translational level. The draTG gene products are responsible for covalent modification of the dinitrogenase reductases of both nitrogenase systems. In addition, mutations in hvrA, a gene previously described as being responsible for low-light activation of the photosynthetic apparatus, also affect regulation of nitrogen fixation.
TL;DR: The organism isolated from a previously described dichloromethane-fermenting, two-component mixed culture represents a new genus and a new species within the phylum of the gram-positive bacteria for which the name Dehalobacterium formicoaceticum is proposed.
Abstract: A strictly anaerobic, dichloromethane-utilizing bacterium was isolated from a previously described dichloromethane-fermenting, two-component mixed culture. In a mineral medium with vitamins, the organism converted 5 mM dichloromethane within 7 days to formate plus acetate in a molar ratio of 2:1 and to biomass and traces of pyruvate. Of 50 potential substrates and combinations of substrates tested, only dichloromethane supported growth. The organism had a DNA G+C content of 42.7 mol%. From its phylogenetic position deduced from 16S rDNA analysis and from its unique substrate range, we conclude that the organism represents a new genus and a new species within the phylum of the gram-positive bacteria for which we propose the name Dehalobacterium formicoaceticum. Cell extracts were found to contain carbon monoxide dehydrogenase, methylene tetrahydrofolate dehydrogenase, formyl tetrahydrofolate synthetase, and hydrogenase activities, whereas activities of methenyl tetrahydrofolate cyclohydrolase and methylene tetrahydrofolate reductase were not detectable. Activity for dehalogenation of dichloromethane was lost on preparation of cell extracts, but was maintained in cell suspensions. Oxygen and reagents that react with thiol groups caused irreversible inhibition, and propyl iodide caused reversible inhibition of dehalogenation. Our observations suggest: 1) conversion of dichloromethane to methylene tetrahydrofolate, which gives rise to both formate and the methyl group of acetate, or 2) conversion of two molecules of dichloromethane to methylene tetrahydrofolate (which is oxidized to formate) and parallel reductive dehalogenation of one dichloromethane to the methyl group of the corrinoid-protein involved in acetate formation.
TL;DR: The isolate is described as the type strain of the new species and genus, Desulforhopalus vacuolatus, which was isolated from reduced mud obtained from a temperate estuary with thiosulfate and lactate as substrates and grew heterotrophically only with hydrogen as electron donor.
Abstract: A new type of gas-vacuolated, sulfate-reducing bacterium was isolated at 10° C from reduced mud (E0 < 0) obtained from a temperate estuary with thiosulfate and lactate as substrates. The strain was moderately psychrophilic with optimum growth at 18–19° C and a maximum growth temperature of 24° C. Propionate, lactate, and alcohols served as electron donors and carbon sources. The organism grew heterotrophically only with hydrogen as electron donor. Propionate and lactate were incompletely oxidized to acetate; traces of lactate were fermented to propionate, CO2, and possibly acetate in the presence of sulfate. Pyruvate was utilized both with and without an electron acceptor present. The strain did not contain desulfoviridin. The G+C content was 48.4 mol%. The differences in the 16S rRNA sequence of the isolate compared with that of its closest phylogenetic neighbors, bacteria of the genus Desulfobulbus, support the assignment of the isolate to a new genus. The isolate is described as the type strain of the new species and genus, Desulforhopalus vacuolatus.
TL;DR: From anoxic intertidal sediment, a dimethylsulfoniopropionate-cleaving anaerobe (strain W218) was isolated that reduced the acrylate formed to propionate and was assigned to a new Desulfovibrio species for which the name DesulfOVibrio acrylicus is proposed.
Abstract: From anoxic intertidal sediment, a dimethylsul- foniopropionate (DMSP)-cleaving anaerobe (strain W218) was isolated that reduced the acrylate formed to propionate. The bacterium was vibrio- to rod-shaped and motile by means of multiple polar flagella. It reduced sulfate, thio- sulfate, and acrylate, and used lactate, fumarate, succinate, malate, pyruvate, ethanol, propanol, glycerol, glycine, ser- ine, alanine, cysteine, hydrogen, and formate as electron donors. Sulfate and acrylate were reduced simultaneously; growth with sulfate was faster than with acrylate. Extracts of cells grown in the presence of DMSP contained high DMSP lyase activities (9.8 U/mg protein). The DNA mol% G+C was 45.1. On the basis of its characteristics and the 16S rRNA gene sequence, strain W218 was assigned to a new Desulfovibrio species for which the name Desulfovib- rio acrylicus is proposed. A variety of other sulfate-reduc- ing bacteria (eight of them originating from a marine or saline environment and five from other environments) did not reduce acrylate.
TL;DR: Characterization of the oleate-induced β-oxidation pathway showed the presence of the two enzyme activities involved in the first step of this catabolic system: acyl-CoA oxidase and acyl -CoA dehydrogenase.
Abstract: Aspergillus nidulans is able to grow on oleic acid as sole carbon source. Characterization of the oleate-induced β-oxidation pathway showed the presence of the two enzyme activities involved in the first step of this catabolic system: acyl-CoA oxidase and acyl-CoA dehydrogenase. After isopicnic centrifugation in a linear sucrose gradient, microbodies (peroxisomes) housing the β-oxidation enzymes, isocitrate lyase and catalase were clearly resolved from the mitochondrial fraction, which contained fumarase. Growth on oleic acid was associated with the development of many microbodies that were scattered throughout the cytoplasm of the cells. These microbodies (peroxisomes) were round to elongated, made up 6% of the cytoplasmic volume, and were characterized by the presence of catalase. The β-oxidation pathway was also induced in acetate-grown cells, although at lower levels; these cells lacked acyl-CoA oxidase activity. Nevertheless, growth on acetate did not cause a massive proliferation of microbodies in A. nidulans.
TL;DR: This is the first report of thermogenic composts as habitats of thermophilic sulfur- and hydrogen-oxidizing bacteria, which to date have been known only from geothermal manifestations, and contrasts with the generally held belief that thermogenic decomposition support only a very low diversity of obligatory heterotrophic thermophiles related to Bacillus stearothermophilus.
Abstract: A variety of autotrophic, sulfur- and hydrogen-oxidizing thermophilic bacteria were isolated from thermogenic composts at temperatures of 60–80° C. All were penicillin G sensitive, which proves that they belong to the Bacteria domain. The obligately autotrophic, non-spore-forming strains were gram-negative rods growing at 60–80°C, with an optimum at 70–75°C, but only under microaerophilic conditions (5 kPa oxygen). These strains had similar DNA G+C content (34.7–37.6 mol%) and showed a high DNA:DNA homology (70–87%) with Hydrogenobacter strains isolated from geothermal areas. The facultatively autotrophic strains isolated from hot composts were gram-variable rods that formed spherical and terminal endospores, except for one strain. The strains grew at 55–75° C, with an optimum at 65–70° C. These bacteria were able to grow heterotrophically, or autotrophically with hydrogen; however, they oxidized thiosulfate under mixotrophic growth conditions (e.g. pyruvate or hydrogen plus thiosulfate). These strains had similar DNA G+C content (60–64 mol%) to and high DNA:DNA homology (> 75%) with the reference strain of Bacillus schlegelii. This is the first report of thermogenic composts as habitats of thermophilic sulfur- and hydrogen-oxidizing bacteria, which to date have been known only from geothermal manifestations. This contrasts with the generally held belief that thermogenic composts at temperatures above 60° C support only a very low diversity of obligatory heterotrophic thermophiles related to Bacillus stearothermophilus.
TL;DR: It is concluded that a modified 3-hydroxypropionate pathway operates in Acidianus brierleyi, a facultatively anaerobic thermoacidophilic archaebacterium, and that the reductive tricarboxylic acid cycle operates in this bacterium.
Abstract: The autotrophic CO2 fixation pathway inAcidianus brierleyi, a facultatively anaerobic thermoacidophilic archaebacterium, was investigated by measuring enzymatic activities from autotrophic, mixotrophic, and heterotrophic cultures. Contrary to the published report that the reductive tricarboxylic acid cycle operates inA. brierleyi, the enzymatic activity of ATP:citrate lyase, the key enzyme of the cycle, was not detected. Instead, activities of acetyl-CoA carboxylase and propionyl-CoA carboxylase, key enzymes of the 3-hydroxypropionate cycle, were detected only whenA. brierleyi was growing autotrophically. We conclude that a modified 3-hydroxypropionate pathway operates inA. brierleyi.
TL;DR: Experiments indicate that the cbb regulon in Rhodobacter is controlled by a global two-component signal transduction system that also regulates other metabolic processes in this organism.
Abstract: In phototrophic and chemoautotrophic proteobacteria, genes encoding enzymes of the Calvin-Benson-Bassham pathway of CO2 fixation are often found in clusters that are transcribed from a single promoter under control of the LysR-type transcriptional activator, CbbR Mutations affecting CbbR prevent induction of cbb genes Gel-retardation assays have demonstrated CbbR binding to putative regulatory regions of cbb operons, and in two cases, footprinting experiments have delimited the nucleotide sequence protected by CbbR Fusion of cbb control sequences to reporter genes has allowed the regions required for promoter activity to be defined, and recent experiments indicate that the cbb regulon in Rhodobacter is controlled by a global two-component signal transduction system that also regulates other metabolic processes in this organism Different ways of regulating CBB cycle enzymes that also have roles in heterotrophic metabolism have recently been discovered In cyanobacteria, the genes of the CBB pathway are organized and regulated differently, and these oxygen-evolving phototrophic bacteria have evolved different strategies to control the assimilation of CO2
TL;DR: Although the acquired thermotolerance was inhibited markedly by chloramphenicol, the other NaCl-induced cross-tolerances seemed not to be correlated with de novo protein synthesis.
Abstract: Enterococcus faecalis was strongly resistant to high osmotic pressure in complex medium; however, when it was subjected to a moderate osmotic stress [6.5% (w/v) NaCl or 52% (w/v) sucrose] for 2 h, it showed cross-protection against ethanol (22%), detergents stresses [bile sales (0.3%) and SDS (0.017%)], hydrogen peroxide challenge (45 mM), and to a minor extent against lethal temperature (62 degrees C). In response to salt stress [6.5% (w/v) NaCl], E. faecalis induced a large number of stress proteins. In addition, NaCl strongly induced the synthesis of many proteins more than tenfold. Although the acquired thermotolerance was inhibited markedly by chloramphenicol, the other NaCl-induced cross-tolerances seemed not to be correlated with de novo protein synthesis. The relationship between the stress protein synthesis and the induction of different types of cross-protection is discussed.
TL;DR: Yeast growth under acid stress changed the pattern of gene expression observed at optimal pH, and the PMA2 promoter at the optimal pH was up to eightfold more efficient in cells grown at pH 2.5, although it remained several hundred times less efficient than that of the PM a1 gene.
Abstract: Cells of Saccharomyces cerevisiae grown in media with an initial pH of 2.5–6.0, acidified with a strong acid (HCl), exhibited the highest plasma membrane H+-ATPase-specific activity at an initial pH of 6.0. At a lower pH (above pH 2.5) ATPase activity (62–83% of the maximum level) still allowed optimal growth. At pH 2.5, ATPase activity was about 30% of the maximum value and growth was impaired. Quantitative immunoassays showed that the content of ATPase protein in the plasma membrane was similar across the entire pH range tested, although slightly lower at pH 2.5. The decrease of plasma membrane ATPase activity in cells grown at low pH was partially accounted for by its in vitro stability, which decreased sharply at pH below 5.5, although the reduction of activity was far below the values expected from in vitro measurements. Yeast growth under acid stress changed the pattern of gene expression observed at optimal pH. The level of mRNA from the essential plasma-membrane-ATPase-encoding gene PMA1 was reduced by 50% in cells grown at pH 2.5 as compared with cells grown at the optimal pH 5.0, although the content of ATPase in the plasma membrane was only modestly reduced. As observed in response to other kinds of stress, the PMA2 promoter at the optimal pH was up to eightfold more efficient in cells grown at pH 2.5, although it remained several hundred times less efficient than that of the PMA1 gene.