Anaerobic Degradation of the Benzene Nucleus by a Facultatively Anaerobic Microorganism

A bacterium was isolated by elective culture with p-hydroxybenzoate as substrate and nitrate as electron acceptor. It grew either aerobically or anaerobically, by nitrate respiration, on a range of aromatic compounds. The organism was identified as a pseudomonad and was given the trivial name Pseudomonas PN-1. Benzoate and p-hydroxybenzoate were metabolized aerobically via protocatechuate, followed by meta cleavage catalyzed by protocatechuic acid-4,5-oxygenase, to yield alpha-hydroxy-gamma-carboxymuconic semialdehyde. Pseudomonas PN-1 grew rapidly on p-hydroxybenzoate under strictly anaerobic conditions, provided nitrate was present, even though protocatechuic acid-4,5-oxygenase was repressed. Suspensions of cells grown anaerobically on p-hydroxybenzoate oxidized benzoate with nitrate and produced 4 to 5 mumoles of CO(2) per mumole of benzoate added; these cells did not oxidize benzoate aerobically. The patterns of the oxidation of aromatic substrates with oxygen or nitrate by cells grown aerobically or anaerobically on different aromatic compounds indicated that benzoate rather than protocatechuate was a key intermediate in the early stages of anaerobic metabolism. It was concluded that the pathway for the anaerobic breakdown of the aromatic ring is different and quite distinct from the aerobic pathway. Mechanisms for the anaerobic degradation of the benzene nucleus by Pseudomonas PN-1 are discussed.     

Sulfurospirillum tamanensis sp. nov., a Facultatively Anaerobic Alkaliphilic Bacterium from a Terrestrial Mud Volcano

Microbiology - An alkaliphilic, facultatively anaerobic bacterium (strain T05bT) was isolated from a terrestrial mud volcano on the Taman Peninsula, Russia. The cells of the isolate were motile...     

Spirochaeta aurantia, a Pigmented, Facultatively Anaerobic Spirochete

A strain of Spirochaeta aurantia was isolated from mud by a procedure involving migration of the organisms through cellulose ester filter discs (0.3-mum pore diameter) onto the surface of culture plates. The helical cells measured 0.3 by 10 to 20 mum during exponential growth. Electron microscopy showed the presence of two subterminally inserted axial fibrils partially overlapping in a 1-2-1 arrangement. An outer envelope, exhibiting a polygonal substructure, was observed. The spirochete grew either aerobically or anaerobically, with aerobic yields of 9.8 x 10(8) cells per ml and anaerobic yields of 3.0 x 10(8) cells per ml. The organism used carbohydrates, but not amino acids, as energy sources. Amino acids served as sole nitrogen sources, whereas inorganic ammonium salts did not. The presence of biotin and thiamine in the medium was required for growth. Growing cells fermented maltose mainly to carbon dioxide, hydrogen, ethyl alcohol, and acetic acid. Small amounts of formic and lactic acids, acetoin, and diacetyl were produced. Cells of S. aurantia growing aerobically produced a yellow-orange pigment. Chemical analysis indicated that the pigment was carotenoid in nature, its main component being lycopene or a similar compound. S. aurantia is not closely related to the leptospires, since it lacks both the hemolytic antigen and the hooked ends typical of the latter organisms. Furthermore, the guanine plus cytosine content in the deoxyribonucleic acid of S. aurantia (66.8 moles%) differs drastically from that of leptospires.     

Draft Genome Sequence of Amphibacillus jilinensis Y1T,a Facultatively Anaerobic,Alkaliphilic and Halotolerant Bacterium

The genus Amphibacillus was established in 1990, and seven additional species were described in the past two decades. Amphibacillus jilinensis Y1^T is a facultatively anaerobic and alkaliphilic bacterium isolated from a soda lake in China. Here we describe the structural and genetic features of the draft genome about the type strain Y1^T (3,831,075 bp, with a G+C content of 37.27%). This is the first genome report of the Amphibacillus genus.     

Genomic Analysis of Melioribacter roseus,Facultatively Anaerobic Organotrophic Bacterium Representing a Novel Deep Lineage within Bacteriodetes/Chlorobi Group

Melioribacter roseus is a moderately thermophilic facultatively anaerobic organotrophic bacterium representing a novel deep branch within Bacteriodetes/Chlorobi group. To better understand the metabolic capabilities and possible ecological functions of M. roseus and get insights into the evolutionary history of this bacterial lineage, we sequenced the genome of the type strain P3M-2^T. A total of 2838 open reading frames was predicted from its 3.30 Mb genome. The whole proteome analysis supported phylum-level classification of M. roseus since most of the predicted proteins had closest matches in Bacteriodetes, Proteobacteria, Chlorobi, Firmicutes and deeply-branching bacterium Caldithrix abyssi, rather than in one particular phylum. Consistent with the ability of the bacterium to grow on complex carbohydrates, the genome analysis revealed more than one hundred glycoside hydrolases, glycoside transferases, polysaccharide lyases and carbohydrate esterases. The reconstructed central metabolism revealed pathways enabling the fermentation of complex organic substrates, as well as their complete oxidation through aerobic and anaerobic respiration. Genes encoding the photosynthetic and nitrogen-fixation machinery of green sulfur bacteria, as well as key enzymes of autotrophic carbon fixation pathways, were not identified. The M. roseus genome supports its affiliation to a novel phylum Ignavibateriae, representing the first step on the evolutionary pathway from heterotrophic ancestors of Bacteriodetes/Chlorobi group towards anaerobic photoautotrophic Chlorobi.     

Dissimilatory Reduction of Inorganic Sulfur by Facultatively Anaerobic Marine Bacteria

THREE STRAINS, SELECTED FROM A LARGE NUMBER OF NEWLY ISOLATED, FACULTATIVELY ANAEROBIC MARINE BACTERIA, REDUCED INORGANIC SULFUR COMPOUNDS OTHER THAN SULFATE ANAEROBICALLY IN DEFINED CULTURE MEDIA IN THE FOLLOWING DIFFERENT PATTERNS: (i) sulfite and thiosulfate were reduced to sulfide, and tetrathionate was reduced to thiosulfate; (ii) tetrathionate was reduced to thiosulfate only; or (iii) thiosulfate was reduced to sulfide only when pyruvate was the substrate. Comparison of anaerobic growth in the presence or absence of inorganic sulfur compounds indicated true dissimilatory reductions.     

Anaerobic Degradation of m-Cresol by a Sulfate-Reducing Bacterium

m-Cresol metabolism under sulfate-reducing conditions was studied with a pure culture of Desulfotomaculum sp. strain Groll. Previous studies with a sulfate-reducing consortium indicated that m-cresol was degraded via an initial para-carboxylation reaction. However, 4-hydroxy-2-methylbenzoic acid was not degraded by strain Groll, and no evidence for ring carboxylation of m-cresol was found. Strain Groll readily metabolized the putative metabolites of a methyl group oxidation pathway, including 3-hydroxybenzyl alcohol, 3-hydroxybenzaldehyde, 3-hydroxybenzoic acid, and benzoic acid. Degradation of these compounds preceded and inhibited m-cresol decay. 3-Hydroxybenzoic acid was detected in cultures that received either m-cresol or 3-hydroxybenzyl alcohol, and trace amounts of benzoic acid were detected in m-cresol-degrading cultures. Therefore, we propose that strain Groll metabolizes m-cresol by a methyl group oxidation pathway which is an alternate route for the catabolism of this compound under sulfate-reducing conditions.     

Thiobacillus cuprinus sp. nov., a Novel Facultatively Organotrophic Metal-Mobilizing Bacterium

Five strains of mesophilic, facultatively organotrophic, ore-leaching eubacteria were isolated from solfatara fields in Iceland and a uranium mine in the Federal Republic of Germany. The new organisms are aerobic gram-negative rods. They can use sulfidic ores or elemental sulfur as sole energy source, indicating that they belong to the genus Thiobacillus. Alternatively, they grow on organic substrates such as yeast extract, peptone, and pyruvate. In contrast to the other leaching bacteria known so far, the new isolates are unable to oxidize ferrous iron. They consist of extreme and moderate acidophiles growing optimally at pH 3 and 4, respectively. The extreme acidophiles showed leaching characteristics similar to those shown by Thiobacillus ferrooxidans, while the moderate acidophiles exhibited a pronounced preference for copper leaching on some chalcopyrite ores. The G+C content of the DNA is between 66 and 69 mol%, depending on the isolate. In DNA-DNA hybridization experiments, the new strains showed homologies among each other of >70%, indicating that they belong to the same species. No significant DNA homology to Thiobacillus reference strains was detectable. Therefore, the new isolates represent a new species of Thiobacillus, which we name Thiobacillus cuprinus. Isolate Hö5 is designated as the type strain (DSM 5495).     

Growth of Facultatively Heterofermentative Lactobacilli on Starter Cell Suspensions

The growth of facultatively heterofermentative lactobacilli (FHL) on cell suspensions of the homofermentative Lactobacillus helveticus was investigated. Osmotic lysis of L. helveticus led to a significant increase of ribose. It decreased steadily in parallel with the growth of FHL, strongly suggesting that the bacteria used ribose as a growth substrate.     

Polysaccharide-degrading Enzymes are Unable to Attack Plant Cell Walls without Prior Action by a "Wall-modifying Enzyme"

A study of the degradation of plant cell walls by the mixture of enzymes present in Pectinol R-10 is described. A “wall-modifying enzyme” has been purified from this mixture by a combination of diethylaminoethyl cellulose, Bio Gel P-100, and carboxymethyl cellulose chromatography. Treatment of cell walls with the “wall-modifying enzyme” is shown to be a necessary prerequisite to wall degradation catalyzed by a mixture of polysaccharide-degrading enzymes prepared from Pectinol R-10 or by an α-galactosidase secreted by the pathogenic fungus Colletotrichum lindemuthianum. The action of the “wall-modifying enzyme” on cell walls is shown to result in both a release of water-soluble, 70% ethanol-insoluble polymers and an alteration of the residual cell wall. A purified preparation of the “wall-modifying enzyme” is unable to degrade a wide variety of polysaccharide, glycoside, and peptide substrates. However, the purified preparation of wall-modifying enzyme has a limited ability to degrade polygalacturonic acid. The fact that polygalacturonic acid inhibits the ability of the “wall-modifying enzyme” to affect cell walls suggests that the “wall-modifying enzyme” may be responsible for the limited polygalacturonic acid-degrading activity present in the purified preparation. The importance of a wall-modifying enzyme in developmental processes and in pathogenesis is discussed.     

Effects of Hydrostatic Pressure and Temperature on the Uptake and Respiration of Amino Acids by a Facultatively Psychrophilic Marine Bacterium

Studies of pressure and temperature effects on glutamic acid transport and utilization indicated that hydrostatic pressure and low temperature inhibit glutamate transport more than glutamate respiration. The effects of pressure on transport were reduced at temperatures near the optimum. Similar results were obtained for glycine, phenylalanine, and proline. Pressure effects on the transport systems of all four amino acids were reversible to some degree. Both proline and glutamic acid were able to protect their transport proteins against pressure damage. The data presented indicate that the uptake of amino acids by cells under pressure is inhibited, which is the cause of their inability to grow under pressure.     

Anaerobic Degradation of Cyanuric Acid, Cysteine, and Atrazine by a Facultative Anaerobic Bacterium

A facultative anaerobic bacterium that rapidly degrades cyanuric acid (CA) was isolated from the sediment of a stream that received industrial wastewater effluent. CA decomposition was measured throughout the growth cycle by using a high-performance liquid chromatography assay, and the concomitant production of ammonia was also measured. The bacterium used CA or cysteine as a major, if not the sole, carbon and energy source under anaerobic, but not aerobic, conditions in a defined medium. The cell yield was greatly enhanced by the simultaneous presence of cysteine and CA in the medium. Cysteine was preferentially used rather than CA early in the growth cycle, but all of the CA was used without an apparent lag after the cysteine was metabolized. Atrazine was also degraded by this bacterium under anaerobic conditions in a defined medium.     

Anaerobic Degradation of Ethylbenzene by a New Type of Marine Sulfate-Reducing Bacterium

Anaerobic degradation of the aromatic hydrocarbon ethylbenzene was studied with sulfate as the electron acceptor. Enrichment cultures prepared with marine sediment samples from different locations showed ethylbenzene-dependent reduction of sulfate to sulfide and always contained a characteristic cell type that formed gas vesicles towards the end of growth. A pure culture of this cell type, strain EbS7, was isolated from sediment from Guaymas Basin (Gulf of California). Complete mineralization of ethylbenzene coupled to sulfate reduction was demonstrated in growth experiments with strain EbS7. Sequence analysis of the 16S rRNA gene revealed a close relationship between strain EbS7 and the previously described marine sulfate-reducing strains NaphS2 and mXyS1 (similarity values, 97.6 and 96.2%, respectively), which grow anaerobically with naphthalene and m-xylene, respectively. However, strain EbS7 did not oxidize naphthalene, m-xylene, or toluene. Other compounds utilized by strain EbS7 were phenylacetate, 3-phenylpropionate, formate, n-hexanoate, lactate, and pyruvate. 1-Phenylethanol and acetophenone, the characteristic intermediates in anaerobic ethylbenzene degradation by denitrifying bacteria, neither served as growth substrates nor were detectable as metabolites by gas chromatography-mass spectrometry in ethylbenzene-grown cultures of strain EbS7. Rather, (1-phenylethyl)succinate and 4-phenylpentanoate were detected as specific metabolites in such cultures. Formation of these intermediates can be explained by a reaction sequence involving addition of the benzyl carbon atom of ethylbenzene to fumarate, carbon skeleton rearrangement of the succinate moiety (as a thioester), and loss of one carboxyl group. Such reactions are analogous to those suggested for anaerobic n-alkane degradation and thus differ from the initial reactions in anaerobic ethylbenzene degradation by denitrifying bacteria which employ dehydrogenations.     

Isolation and Characterization of a Facultatively Aerobic Bacterium That Reductively Dehalogenates Tetrachloroethene to cis-1,2-Dichloroethene

A rapidly-growing facultatively aerobic bacterium that transforms tetrachloroethene (PCE) via trichloroethene (TCE) to cis-1,2-dichloroethene (cis-1,2-DCE) at high rates in a defined medium was isolated from a contaminated site. Metabolic characterization, cellular fatty acid analysis, and partial sequence analysis of 16S rRNA showed that the new isolate, strain MS-1, has characteristics matching those of the members of the family Enterobacteriaceae. Strain MS-1 can oxidize about 58 substrates including many carbohydrates, short-chain fatty acids, amino acids, purines, and pyrimidines. It can transform up to 1 mM PCE (aqueous) at a rate of about 0.5 (mu)mol of PCE(middot) h(sup-1)(middot)mg (dry weight) of cell(sup-1). PCE transformation occurs following growth on or with the addition of single carbon sources such as glucose, pyruvate, formate, lactate, or acetate or with complex nutrient sources such as yeast extract or a mixture of amino acids. PCE dehalogenation requires the absence of oxygen, nitrate, and high concentrations of fermentable compounds such as glucose. Enterobacter agglomerans biogroup 5 (ATCC 27993), a known facultative bacterium that is closely related to strain MS-1, also reductively dehalogenated PCE to cis-1,2-DCE. To our knowledge, this is the first report on isolation of a facultative bacterium that can reductively transform PCE to cis-1,2-DCE under defined physiological conditions. Also, this is the first report of the ability of E. agglomerans to dehalogenate PCE.     

Xylooligosaccharide Utilization by the Ruminal Anaerobic Bacterium Selenomonas ruminantium

Fermentation of xylooligosaccharides by 11 strains of Selenomonas ruminantium was examined. Xylooligosaccharides were prepared by the partial hydrolysis of oat spelt xylan in dilute phosphoric acid (50 mM, 121°C, 15 min) and were added to a complex, yeast extract-Trypticase-containing medium. Strains of S. ruminantium varied considerably in their capacity to ferment xylooligosaccharides. Strains GA192, GA31, H18, and D used arabinose, xylose, and the oligosaccharides xylobiose through xylopentaose, as well as considerable quantities of larger, unidentified oligosaccharides. Other strains of S. ruminantium (HD4, HD1, 20-21a, H6a, W-21, S23, 5-1) were able to use only the simple sugars present in the substrate mixture. The ability of S. ruminantium strains to utilize xylooligosaccharides was correlated with the presence of xylosidase and arabinosidase activities. Both enzyme activities were induced by growth on xylooligosaccharides, but no activity was detected in glucose- or arabinose-grown cultures. Xylooligosaccharide-fermenting strains of S. ruminantium exhibited considerable variation in substrate utilization patterns, and the assimilation of individual carbohydrate species also appeared to be regulated. Lactic, acetic, and propionic acids were the major fermentation end products detected. Received: 2 August 1997 / Accepted: 18 September 1997     

Ultrastructure and Cell Division of a Facultatively Parasitic Strain of Bdellovibrio bacteriovorus

Some aspects of cell development and division of Bdellovibrio bacteriovorus strain UKi2 were examined by use of electron microscopic techniques. Under saprophytic and parasitic conditions of growth, the comma-shaped cells enlarge, elongate, and form helical filaments. The mechanism of division appears to consist of an asymmetrical constriction of the filamentous cell by the cytoplasmic membrane, accompanied by a breakdown of the outer layers of the cell wall in the division region. During regeneration of the cell wall, the flagellum and flagellar sheath are formed. The development of the flagellum of the daughter cell is initiated prior to separation of the newly formed cells from the filament. Observations of B. bacteriovorus UKi2 grown under saprophytic and parasitic conditions indicate that development and ultrastructure are similar in both modes of growth.