Showing papers in "Archives of Microbiology in 1986"

Pyrococcus furiosus sp. nov. represents a novel genus of marine heterotrophic archaebacteria growing optimally at 100°C

Abstract: Ten strains representing a novel genus of marine thermophilic archaebacteria growing at between 70 and 103°C with an optimal growth temperature of 100°C and a doubling time of only 37 min were isolated from geothermally heated marine sediments at the beach of Porto di Levante, Vulcano, Italy. The organisms are spherical-shaped, 0.8 to 2.5 μm in width and exhibit monopolar polytrichous flagellation. They are strictly anaerobic heterotrophs, growing on starch, maltose, peptone and complex organic substrates. Only CO2 and H2 could be detected as metabolic products, the latter being inhibitory to growth at high concentrations. Hydrogen inhibition can be prevented by the addition of So, whereupon H2S is formed in addition, most likely as the result of a “detoxification” reaction. The GC-content of the DNA of isolate Vc 1 is 38 mol%. The new genus is named Pyrococcus, the “fireball”. Type species and strain is Pyrococcus furiosus Vc 1 (DSM 3638).

Thermotoga maritima sp. nov. represents a new genus of unique extremely thermophilic eubacteria growing up to 90°C

Abstract: A novel type of bacterium has been isolated from various geothermally heated locales on the sea floor. The organisms are strictly anaerobic, rod-shaped, fermentative, extremely thermophilic and grow between 55 and 90°C with an optimum of around 80°C. Cells show a unique sheath-like structure and monotrichous flagellation. By 16S rRNA sequencing they clearly belong to the eubacteria, although no close relationship to any known group could be detected. The majority of their lipids appear to be unique in structure among the eubacteria. Isolate MSB8 is described as Thermotoga maritima, representing the new genus Thermotoga.

Nitrospira marina gen. nov. sp. nov.: a chemolithotrophic nitrite-oxidizing bacterium

Abstract: A new chemolithotrophic nitrite-oxidizing bacterium, for which the name Nitrospira marina is proposed, was isolated from the Gulf of Maine N marina is a Gramnegative curved rod which may form spirals with 1 to 12 turns Cells have a unique periplasmic space and lack intracytoplasmic membranes and carboxysomes N marina is an obligate chemolithotroph, but best growth is obtained in a mixotrophic medium N marina may be one of the most prevalent nitrite-oxidizing bacteria in some oceanic environments Type strain is field with American Type Culture Collection (ATCC 43039)

Acetate oxidation to CO2 in anaerobic bacteria via a novel pathway not involving reactions of the citric acid cycle

Abstract: In several sulfate-reducing bacteria capable of complete oxidation of acetate (or acetyl CoA), the citric acid cycle is not operative. No 2-oxoglutarate dehydrogenase activity was found in these organisms, and the labelling pattern of oxaloacetate excludes its synthesis via 2-oxo-glutarate. These sulfate-reducers contained, however, high activities of the enzymes carbon monoxide dehydrogenase and formate dehydrogenase and catalyzed an isotope exchange between CO2 and the carboxyl group of acetate (or acetyl CoA), showing a direct C-C-cleavage of activated acetic acid. These findings suggest that in the investigated sulfate-reducers acetate is oxidized to CO2 via C1 intermediates. The proposed pathway provides a possible explanation for the reported different fluoroacetate sensitivity of acetate oxidation by anaerobic bacteria, for mini-methane formation, as well as for the postulated anaerobic methane oxidation by special sulfate-reducers.

Metabolism of volatile phenolic compounds from hydroxycinnamic acids by Brettanomyces yeast

Abstract: The formation of 4-ethyl and 4-vinyl derivatives of guaiacol, phenol and syringol from ferulic acid,p-coumaric acid and sinapic acid, respectively, byBrettanomyces sp. in a synthetic medium was studied by gas chromatography-mass spectrometry. Some of these metabolites possess strong spicy, smoke-like, medicinal, clove-like, woody or phenolic odours and their role as spoilage compounds in wine is discussed. Their formation appears to be characteristic of this yeast genus and its sporulating formDekkera, suggesting these yeasts are Pof+. This paper attempts to clarify the distinctive and ‘characteristic’ odours which have long been attributed toBrettanomyces yeast metabolism.

Anaerobic degradation of phenol and phenol derivatives by Desulfobacterium phenolicum sp. nov.

Abstract: A new sulfate-reducing bacterium was enriched and isolated from marine sediment with phenol as sole electron donor and carbon source. Strain Ph01 grew well in defined media without growth factors. Further aromatic compounds oxidized by strain Ph01 were benzoate, phenylacetate, 2-hydroxybenzoate, 4-hydroxybenzoate, 4-hydroxyphenylacetate, p-cresol, indole, anthranilic acid, and phenylalanine. Various fatty acids, alcohols and dicarboxylic acids were also utilized by strain Ph01. Sulfate and thiosulfate served as electron acceptors and were reduced to H2S. Stoichiometric measurements with strain Ph01 showed complete oxidation of phenol to CO2. Cytochromes and menaquinone MK-7(H2) were present; desulfoviridin could not be detected. Strain Ph01 is described as type strain of the new species Desulfobacterium phenolicum.

Eubacterium oxidoreducens sp. nov. requiring H2 or formate to degrade gallate, pyrogallol, phloroglucinol and quercetin

Abstract: Based on most probable number (MPN) estimates of rumen fluid from a hay-fed steer, 10 mM gallate was decarboxylated by 9.3×106 bacteria per ml. It was decarboxylated and reductively dehydroxylated by 9.3×105 bacteria per ml and was further catabolized to non-aromatic products by 4.3×103 bacteria per ml. Resorcinol was not further degraded and, with 0.1 ml of inoculum, catechol was not degraded. Strain G41 was isolated from a pyrogallolmedium roll tube inoculated with 1 μl of rumen fluid and, with slight modifications of the generic description, was named Eubacterium oxidoreducens sp. nov. It was an anaerobic, nonmotile, curved, Gram-positive, small rod with rounded ends and required H2 or formate to degrade gallate, pyrogallol, phloroglucinol or quercetin to acetate and butyrate and, in the case of quercetin, to 3,4-dihydroxyphenylacetate. Crotonate was catabolized to acetate and butyrate and no electron donor was required. No other compounds were degraded with or without an electron donor or with Desulfovibrio sp. plus sulfate as a possible electron acceptor system. E. oxidoreducens grew well in a chemically-defined culture medium containing usable energy source, minerals, B-vitamins, cysteine and CO2−HCO - 3 -buffer, pH 7.2.

Analogs of the autoinducer of bioluminescence inVibrio fischer

Abstract: The enzymes for luminescence inVibrio fischeri are induced only when a sufficient concentration of a metabolic product (autoinducer) specifically produced by this species accumulates. It has previously been shown that the autoinducer is 3-oxohexanoyl homoserine lactone and that it enters the cells by simple diffusion. To further study the mechanism of induction, we have synthesized several analogs of the autoinducer. The analogs were tested withV. fischeri for their inducing activity and for their ability to inhibit the action of the natural autoinducer. The compounds were found to display various combinations of inducing and inhibiting abilities. None of the compounds tested appeared to have any effect on cells ofV. harveyi strain MAV orPhotobacterium leiognathi strain 721, but several of the compounds decreased light output byP. phosphoreum strain 8265. These studies show that 1) the site of action of the autoinducer is not highly sterically constrained 2) the autoinducers of other species of luminous bacteria are likely to be quite different from that ofV. fischeri and 3) a simple mode in which one autoinducer molecule binds to a single receptor protein site and thus initiates luciferase synthesis is inadequate. The analogs should prove useful in the study of the binding site and mode of action of the autoinducer.

Structural and chemical characterization of S-layers of selected strains of Bacillus stearothermophilus and Desulfotomaculum nigrificans.

Abstract: The structures, amino acid- and neutral sugar compositions of the crystalline surface layers (S-layers) of four selected strains each ofBacillus stearothermophilus andDesulfotomaculum nigrificans were compared. Among the four strains of each species a remarkable diversity in the molecular weights of the S-layer subunits and in the geometry and constants of the S-layer lattices was apparent. The crystalline arrays included hexagonal (p6), square (p4) and oblique (p2) lattices. In vitro self-assembly of isolated S-layer subunits (or S-layer fragments) led to the formation of flat sheets or open-ended cylindrical assembly products. The amino acid composition of the S-layers exhibited great similarities and was predominantly acidic. With the exception of the S-layers of two strains ofB. stearothermophilus (where only traces of neutral sugars could be detected), all other S-layer proteins seemed to be glycosylated. Among these strains significant differences in the amount and composition of the glycan portions were found. Based on this diversity interesting questions may be asked about the biological significance of the carbohydrate units of glycoproteins in prokaryotic organisms.

The production and release of an extracellular polysaccharide during starvation of a marine Pseudomonas sp. and the effect thereof on adhesion.

Abstract: A marine Pseudomonas sp. S9 produced and released an extracellular polysaccharide during complete energy and nutrient starvation in static conditions. The presence of the polysaccharide on the cell surface, demonstrable by immune transmission electron microscopy, correlated with changes in the degree of adhesion to hydrophobic surfaces. Polysaccharide coated cells showed a lower degree of adhesion than did cells devoid of the polymer. After 10 h of starvation, no ruthenium red stained antibody stabilized polysaccharides could be observed on the cell surface. The polysaccharide was not produced during growth since lysates of mid-log phase cells did not precipitate the antiserum. The relative proportions of sugars in the polysaccharide were 28% glucose, 35% N-acetylglucosamine and 37% N-acetylgalactosamine. The released polysaccharide did not significantly alter the physical parameters of surface tension and viscosity of the starvation regime. Cells starved in agitated conditions did not produce any extracellular polysaccharides and exhibited a different adhesion pattern to hydrophobic surfaces.

Variations in the response of salt-stressed Rhizobium strains to betaines

Abstract: A total of 15 rhizobial strains representing Rhizobium meliloti, Rhizobium japonicum, Rhizobium trifolii, Rhizobium leguminosarum, Rhizobium sp. (Sesbania rostrata) and Rhizobium sp. (Hedysarum coronarium), were studied with regard to growth rate under salt stress in defined liquid media. In the presence of inhibitory concentrations of NaCl, enhancement of growth resulting from added glycine betaine was observed for R. meliloti strains and Rhizobium sp. (Hedysarum coronarium) but not for other Rhizobium species. The concentration of glycine betaine required for maximal growth stimulation was very low (1 mM) in comparison with the osmolarity of the medium. The stimulation was shown to be independent of any specific solutes. Other related compounds like proline betaine, carnitine, choline, γ-butyrobetaine and pipecolate betaine were also effective compounds in restoring the growth rate of cells grown in medium of elevated osmolarity. High rate of glycine betaine uptake was demonstrated in R. meliloti cells grown in media of increased osmotic strength. The intracellular concentration of this solute was found to be 308 mM in 0.3 M NaCl-grown cells and 17 times lower in minimal medium-grown cells. Glycine betaine was used for growth under conditions of low osmolarity but could not serve as sole carbon or nitrogen source in medium of increased osmotic strength. Experiments with [14C]glycine betaine showed that this molecule was not metabolized by cells subjected to osmotic stress, whereas it was rapidly converted to dimethylglycine, sarcosine and glycine in minimal medium-grown cells.

Autotrophic growth and CO2 fixation of Chloroflexus aurantiacus

Abstract: Chlorofluexus aurantiacus OK-70 fl was grown photoautotrophically with hydrogen as the electron source. The lowest doubling time observed was 26 h. The mechanism of CO2 fixation in autotrophically grown cells was studied. The presence of ribulose-1,5-bis-phosphate carboxylase and phosphoribulokinase could not be demonstrated. Carbon isotope fractionation (δ13C) was small, and alanine and aspartate but not 3-phosphoglycerate were the major labelled compounds in short term 14CO2 labelling. Thus CO2 is not fixed by the Calvin cycle. Fluoroacetate (FAc) completely inhibited protein synthesis in cultures and caused a slight citrate accumulation. However, CO2 fixation continued and increased polyglucose formation occurred. Under these conditions added acetate was metabolized to polyglucose, as were glycine, serine, glyoxylate and succinate, but to a lesser extent; little or no formate or CO was utilised. Glyoxylate inhibited CO2 fixation in vivo, indicating that pyruvate is formed from acetyl-CoA and CO2 by pyruvate synthase. Two key enzymes of the reductive TCA cycle, citrate lyase and α-ketoglutarate synthase were not detected in cell free extracts, but pyruvate synthase and phosphoenolpyruvate carboxylase were demonstrated. It is concluded that acetyl-CoA is a central intermediate in the CO2 fixation process, but the mechanism of its synthesis is not clear.

Synthrophomonas sapovorans sp. nov., a new obligately proton reducing anaerobe oxidizing saturated and unsaturated long chain fatty acids

Abstract: An anaerobic obligately syntrophic fatty acid degrading acetogenic bacterium (Strain OM) was isolated on calcium laurate medium from an oleate enrichment. This organism is a short slightly curved Gram-negative rod which can only use protons as electron acceptor. It ferments all linear saturated fatty acids with 4 to 18 carbon atoms in coculture with a hydrogen-utilizing partner. Some mono- and di-unsaturated long chain fatty acids (oleate, elaidate and linolenate) are also oxidized. Calcium is required for batch cultivation of the syntrophic association on fatty acids with a chain length longer than 8 carbon atoms. In spite of some important morphological and nutritional analogies with Syntrophomonas wolfei, the strain OM must be considered as a different species mainly because of its broader substrate range. The description of strain OM as type strain of a new species, Syntrophomonas sapovorans sp. nov., is proposed.

Anaerobic degradation of indolic compounds by sulfate-reducing enrichment cultures, and description of Desulfobacterium indolicum gen. nov., sp. nov.

Abstract: Indole (1.5 mmol/l) added to suflate-rich marine mud or sulfate-free sewage digestor sludge was anaerobically degraded within one week. Enrichments from sludge samples in defined indole-containing media with or without sulfate were selective for sulfate-reducing bacteria or mixed methanogenic associations, respectively. Other enrichments of sulfate-reducing bacteria were obtained with skatole, indoleacetate, indolepropionate, quinoline, and pyridine. From a marine enrichment with indole as sole electron donor and carbon source, an oval to rod-shaped, Gram-negative, nonsporing sulfate-reducing bacterium (strain In04) was isolated. Growth occurred in defined bicarbonate-buffered, sulfide-reduced media supplemented with vitamin B12. Furthen aromatic compounds utilized as electron donors and carbon sources were anthranilic acid and quinoline. Nonaromatic compounds used as substrates were formate, acetate, propionate, ethanol, propanol, butanol, pyruvate, malate, fumarate, and succinate. However, growth with substrates other than indole was rather slow. Thiosulfate served as an alternative electron acceptor. Complete oxidation of indole to CO2 was shown by stoichiometric measurements in batch culture with sulfate as electron acceptor. An average growth yield of 31.3 g cell dry weight was obtained per mol of indole oxidized. Pigment analysis revealed that cytochromes and menaquinone MK-7 (H2) were present. Desulfoviridin could not be detected. Strain In04 is described as new species of the new genus Desulfobacterium indolicum.

Syntrophococcus sucromutans sp.nov.gen.nov. uses carbohydrates as electron donors and formate, methoxymonobenzenoids or Methanobrevibacter as electron acceptor systems

Abstract: Most probable number (MPN) estimates indicated that a mean of 4.3×107 and 5×106 bacteria per ml of rumen fluid from a predominantly alfalfa hay-fed steer demethoxylated ferulate and syringate, respectively. After further enrichment from an MPN tube of the highest dilution showing demethoxylation of syringate, strain S195 was isolated using roll tubes with syringate as an added energy source. S195 was an anaerobic, Gram-negative, nonmotile coccus, 1 to 1.3 μm in diameter, and was unique in using various carbohydrates as electron donor with acetate as the sole organic product. One of the following electron acceptor systems allowed growth (organic products in parentheses): Methanobrevibacter simithii (CH4), formate (acetate), 3,4,5-trimethoxybenzoate and syringate (acetate and gallate), vanillate (acetate and protocatechuate), vanillin (acetate, protocatechuic aldehyde and protocatechuate), ferulate (acetate, caffeate and hydrocaffeate), caffeate (hydrocaffeate). Strain S195 required 30% (v/v) rumen fluid in the medium for good growth. S195 was placed in a new genus and species, Syntrophococcus sucromutans, of the family Veillonellaceae.

Growth yields of Desulfotomaculum orientis with hydrogen in chemostat culture

Abstract: Desulfotomaculum orientis (strain Singapore 1) was grown autotrophically with H2+CO2 and sulfate, thiosulfate or sulfite as electron acceptor in sulfide- and pH-controlled continuous culture. Under sulfate-limiting conditions real growth yields of up to 9.7 g cell dry mass per mol sulfate were obtained. Electron acceptor limitation resulted in the excretion of up to 14.5 mmol acetate per liter, formed by reduction of CO2 with H2. Acetate production was not coupled to an increase of growth yields: under hydrogen-limiting conditions only 1.6 mmol acetate per liter was produced, and even higher growth yields of up to 12,4 g cell dry mass per mol sulfate were obtained. With thiosulfate or sulfite as electron acceptor growth yields increased up to 17.9 g cell dry mass per mol electron acceptor. Growth yields were not simply correlated with the growth rate, and did not allow the determination of maintenance coefficients and the extrapolation to maximal yields at infinite growth rate (Ymax). The maximal growth rates (μmax) with sulfate and thiosulfate were 0.090 and 0.109 h-1, respectively, if cells were grown continuously in sulfidostat culture under nonlimiting conditions.

Chemolithotrophic growth ofDesulfovibrio desulfuricans with hydrogen coupled to ammonification of nitrate or nitrite

Abstract: Two of nine sulfate reducing bacteria tested,Desulfobulbus propionicus andDesulfovibrio desulfuricans (strain Essex 6), were able to grow with nitrate as terminal electron acceptor, which was reduced to ammonia.

A xylanase gene from Bacillus subtilis: nucleotide sequence and comparison with B. pumilus gene

Abstract: A gene coding for xylanase (endo-1,4-β-d-xylan xylanohydrolase, EC 3.2.1.8) from Bacillus subtilis PAP115 has been isolated and its complete nucleotide sequence determined. Starting from an ATG initiator codon, an open reading frame coding for 213 amino acids was found. The N terminus of the processed enzyme as expressed in Escherichia coli was located by amino acid sequence analysis. The amino acid analysis and apparent molecular weight (22,000) of the expressed enzyme were consistent with the translated nucleotide sequence. A proposed 28-residue signal sequence of the enzyme shows features comparable with other Bacillus signal sequences, namely a negatively charged region close to methionine followed by a long hydrophobic string. The coding sequence is preceded by a possible ribosome binding site and, further upstream, by potential transcription initiation signals. When the xylanase amino acid sequence was compared to a xylanase from B. pumilus, strong evidence for homology was found, with over 50% identities in the processed enzymes.

Chemolithotrophic potential of a Hyphomicrobium species, capable of growth on methylated sulphur compounds

Abstract: The yield of Hyphomicrobium EG on dimethyl sulphoxide, dimethyl sulphide and methylamine, considering the metabolic pathways of these compounds, suggested that the organism gained energy from the oxidation of the sulphur moiety of the former compounds. Indeed, a comparison of chemostat cultures of Hyphomicrobium EG grown on methylamine in the presence and absence of sulphide or thiosulphate proved this obligate methylotroph to be a chemolithoheterotroph. The apparent Ysulphide and Ythiosulphate were comparable, being 8–10 g dry weight/mol. In batch cultures thiosulphate concentrations up to 10 mM had a stimulatory effect on the growth rate of Hyphomicrobium EG, whereas higher concentrations increased the organisms doubling time. Enzyme- and respiration data showed that the organism had constitutive enzymes for the breakdown of dimethyl sulphoxide although they were clearly regulated to need. Addition of sulphide or thiosulphate to methylamine-limited chemostat cultures of Hyphomicrobium EG not only resulted in the induction of enzymes necessary for their breakdown, but also caused the enzymes for dimethyl sulphoxide metabolism, especially methyl mercaptan oxidase, to be induced. The formation of H2O2, a product of the latter enzyme, was reflected in the relatively high catalase activities during growth on dimethyl sulphoxide and in the organisms inability to grow on this compound in the presence of a catalase inhibitor.

Chemical composition of the peptidoglycan-free cell envelopes of budding bacteria of the Pirella/Planctomyces group

Abstract: Cell envelopes were prepared from freeze-dried cells of 8 strains of budding bacteria belonging to the Pirella/Planctomyces group. Treatment with 10% sodium dodecylsulfate (SDS) (30 min, 100°C) allowed the isolation of stable cell sacculi which still maintained the original cell shape. The chemical analysis showed, as the main component, protein which was unusually rich in proline and cystine. Except for Planctomyces maris IFAM 1317 (where this protein comprised 62.6% of the total envelope dry weight) the corresponding values for the other strains varied from 75 to 82%. Amino sugars and neutral sugars were present only in small amounts and uronic acids were not found. The ash content varied from 5 to 10% of the dry weight, except for IFAM 1317 which had 19% ash. The high content of cystine indicated a high degree of crosslinking of the cell envelopes through disulfide bonds. Our data show that bacteria of the Pirella/Planctomyces group possess a similar cell wall composition.

Pyruvate decarboxylase from Zymomonas mobilis. Isolation and partial characterization

Abstract: Pyruvate decarboxylase (EC 4.1.1.1) from the ethanol producing bacterium Zymomonas mobilis was purified to homogeneity. This enzyme is an acidic protein with an isoelectric point of 4.87 and has an apparent molecular weight of 200,000±10,000. The enzyme showed a single band in sodium dodecylsulfate gel electrophoresis with a molecular weight of 56,500±4,000 which indicated that the enzyme consists of four probably identical subunits. The dissociation of the cofactors Mg2+ and thiamine pyrophosphate at pH 8.9 resulted in a total loss of enzyme activity which could be restored to 99.5% at pH 6.0 in the presence of both cofactors. For the apoenzyme the apparent Km values for Mg2+ and thiamine pyrophosphate were determined to be 24 μM and 1.28 μM. The apparent Km value for the substrate pyruvate was 0.4 mM. Antiserum prepared against this purified pyruvate decarboxylase failed to crossreact with cell extracts of the reportedly pyruvate decarboxylase positive bacteria Sarcina ventriculi, Erwinia amylovora, or Gluconobacter oxydans, or with cell extracts of Saccharomyces cerevisiae.

Isolation and characterization of Methanoplanus endosymbiosus sp. nov., an endosymbiont of the marine sapropelic ciliate Metopus contortus quennerstedt

Abstract: Epifluorescence microscopy revealed the presence of a methanogenic bacterium as an endosymbiont in the sapropelic marine ciliate Metopus contortus. The in situ methanogenic activity of the symbiont could be demonstrated. The isolated endosymbiont was an irregular, disc-shaped bacterium with a diameter of 1.6–3.4 μm. It had a generation time of 7 or 12 hours on growth on H2/CO2 or formate, respectively. The temperature range for growth was between 16 and 36°C with an optimum at 32°C. The optimal pH range for growth was 6.8 to 7.3. Salts, with an optimum concentration of 0.25 M, and tungsten were required for growth. The mol% G+C was 38.7%. The cell envelope consisted of proteins and a glycoprotein with an apparent molecular weight of 110,000. Morphology, antigenic relationship and the G+C content established the isolate MC1 as a new species of the genus Methanoplanus, and the name Methanoplanus endosymbiosus is proposed.

Dicarboxylic acid transport in Rhizobium meliloti : isolation of mutants and cloning of dicarboxylic acid transport genes

Abstract: The role of the dicarboxylic acid transport (dct) system in the Rhizobium meliloti-Alfalfa symbiosis was investigated. Mutants of R. meliloti CM2 unable to grow on medium containing succinate as the sole carbon source were isolated following chemical and transposon mutagenesis. These mutants were also unable to utilize malate or fumarate as the sole source of carbon. Transport studies with 14C-labelled succinate showed that the mutants were specifically defective in succinate transport. Revertants of both chemical and transposon mutants were obtained at a frequency of 10-5–10-6. The R. meliloti dct mutants were able to nodulate Alfalfa plants but the nodules formed were unable to fix nitrogen. Revertants of the mutants were fully effective on plants. The mutants unable to transport succinate were used to isolate dct genes from a R. meliloti gene bank. Two plasmids containing a common 26.5 Mdal insert were found to complement some of the mutants. The presence of this DNA insert in the complementing mutant strains restored their effectivenss of plants. This DNA fragment encoding succinate transport function(s) was used to produce genetically engineered R. meliloti strains with an increased rate of succinate uptake.

Growth the Wolinella succinogenes on H2S plus fumarate and on formate plus sulfur as energy sources

Abstract: Wolinella succinogenes was found to grow on H2S plus fumarate with the formation of elemental sulfur and succinate. The growth rate was 0.18 h-1 (t d=3.8 h) and the growth yield was estimated to be 6.0 g per mol fumarate used. Growth also occurred on formate plus elemental sulfur; the products formed were H2S and CO2. The growth rate and estimated growth yield were 0.58 h-1 (t d=1.2 h) and 3.5 g per mol formate used, respectively. These results suggest that certain chemotrophic anaerobes may be involved in both the formation and reduction of sulfur.

Cloning and expression of the structural gene for pyruvate decarboxylase of Zymomonas mobilis in Escherichia coli

Abstract: A genomic library of Zymomonas mobilis DNA was constructed in Escherichia coli using cosmid vector pHC79. Immunological screening of 483 individual E. coli strains revealed two clones expressing pyruvate decarboxylase, the key enzyme for efficient ethanol production of Z. mobilis. The two plasmids, pZM1 and pZM2, isolated from both E. coli strains were found to be related and to exhibit a common 4.6 kb SphI fragment on which the gene coding for pyruvate decarboxylase, pdc, was located. The pdc gene was similarily well expressed in both aerobically and anaerobically grown E. coli cells, and exerted a considerable effect on the amount of fermentation products formed. During fermentative growth on 25 mM glucose, plasmid-free E. coli lacking a pdc gene produced 6.5 mM ethanol, 8.2 mM acetate, 6.5 mM lactate, 0.5 mM succinate, and about 1 mM formate leaving 10.4 mM residual glucose. In contrast, recombinant E. coli harbouring a cloned pdc gene from Z. mobilis completely converted 25 mM glucose to up to 41.5 mM ethanol while almost no acids were formed.

Production, by filamentous, nitrogen-fixing cyanobacteria, of a bacteriocin and of other antibiotics that kill related strains.

Abstract: Colonies of sixty-five filamentous cyanobacteria were screened for the production of temperate phages and/or antibiotics on solid medium. None of them was observed to release phages. However, seven N2-fixing strains were found to produce antibiotics very active against other cyanobacteria. The antibiotic produced by Nostoc sp. 78-11A-E represents a bacteriocin of low molecular weight. Nostoc sp. ATCC 29132 appears to secrete, together with an antibiotic, a protein that inhibits its action.

Comparison of fatty acid content and DNA homology of the filamentous gliding bacteriaVitreoscilla, Flexibacter, Filibacter

Abstract: DNA hybridization experiments showed that there was a high degree of homology amongVitreoscilla strains but not with DNA fromFilibacter limicola. Flexibacter spp were much more heterogeneous indicating a low genetic similarity. These results were also reflected in the membrane fatty acids of the bacteria. TheVitreoscilla strains were very similar with the 16:1ω7c fatty acid being dominant. The membrane fatty acids ofF. limicola were dominated by a15:0 and a17:0 components which provided additional support for its relatedness to the genusBacillus. There was much greater diversity in the fatty acid patterns of theFlexibacter spp.F. aurantiacus, F. ruber andF. elegans shared the common dominant fatty acids 16:1ω7c with theVitreoscilla strains, but this was replaced by the 16:1ω6c acid inF. flexilis. F. ruber was distinguished by the absence of branched odd-chain monounsaturated fatty acids andF. elegans by the dominance of the β-OH i15:0 acid. Precise determination of fatty acid double bond positions and geometry are essential for correct interpretation of increasingly complex ecological and taxonomic data sets.

Isolation and characterization of alkene-utilizing Xanthobacter spp.

Abstract: Yellow-pigmented bacteria showing typical characteristics of Xanthobacter spp were isolated from enrichments with propene and 1-butene, using classical techniques The generation time for growth on propene and 1-butene of these bacteria ranged from 5 to 7h A NADH-dependent mono-oxygenase was identified in cell-free extract of Xanthobacter Py2 This mono-oxygenase was not influenced by potential inhibitors tested indicating that propene mono-oxygenase is different from other hydrocarbon mono-oxygenases described until now Nitrogenase activity could be measured using the acetylene reduction assay with propene as energy source, because acetylene did not inhibit the mono-oxygenase activity

Specificity of cellulase and β-xylanase induction in Trichoderma reesei QM 9414

Abstract: Cellulose- and xylan-degrading enzymes of Trichoderma reesei QM 9414 induced by, sophorose, xylobiose, cellulose and xylan were analyzed by isoelectric focusing. The sophorose-induced enzyme system contained two types of endo-1,4-β-glucanases (EC 3.2.1.4), one specific for cellulose and the other non-specific, hydrolyzing both cellulose and xylan, and exo-1,4-β-glucanases (cellobiohydrolases I, EC 3.2.1.91), i.e. all types of glucanases that are produced during growth on cellulose. Specific endo-1,4-β-xylanases (EC 3.2.1.8) present in the cellulose-containing medium were less abundant in the sophorose-induced enzyme system. Xylobiose and xylan induced only specific endo-1,4-β-xylanases. It is concluded that syntheses of cellulases and β-xylanases in T. reesei QM 9414 are under separate control and that the non-specific endo-1,4-β-glucanases are constituents of the cellulose-degrading enzyme system.

Distribution and regulation of nitrate and nitrite reduction by Desulfovibrio and Desulfotomaculum species

Abstract: Rates of nitrate and nitrite reduction by cultures and washed suspensions of both natural isolates and culture collection strains of sulphate-reducing bacteria have been determined. Neither activity was detected in the Desulfotomaculum strains, but all Desulfovibrio strains reduced nitrite. Only the Desulfovibrio natural isolate FBA 20a was also able to reduce nitrate. Nitrate reduction by washed suspensions of strain FBA 20a was far more rapid than previously reported rates for sulphate-reducing bacteria [6.6 μmol NO 3 - reduced h-1 (mg dry weight)-1] and was regulated by nitrate induction and sulphate repression: it was insensitive to the product of nitrate reduction, ammonium ions. Cell yields from sulphate-limited cultures were proportional to the concentration of nitrate added with a yield coefficient of 28.0 g bacterial dry weight per mol of nitrate reduced. These results indicate that although the ability of strain FBA 20a to reduce nitrate is a physiologically significant process, it is a specialized property of only a few strains of Desulfovibrio isolates.