Base competition of DNA isolated from Thiobacillus ferrooxidans grown on different substrates

The present study indicates some anomalies with respect to the DNA base composition of Thiobacillus ferrooxidans when it is cultured on different substrates. The % GC of the DNA of this bacterium has been calculated by three different methods (melting temperature, CsCl density gradient centrifugation and ultra-violet absorbancy ratios) using Escherichia coli and Rhodospirillum rubrum as references. The main values for T. ferrooxidans grown on ferrous iron, chalcopyrite and lead sulfide concentrates were calculated to be 56.0, 60.1 and 54.4% GC respectively. Although these large differences are not completely understood, an attempt has been made to explain this phenomenon.

Inhibition of growth, iron, and sulfur oxidation in Thiobacillus ferrooxidans by simple organic compounds

Iron and sulfur oxidation by Thiobacillus ferrooxidans as well as growth on ferrous iron were inhibited by a variety of low molecular weight organic compounds. The influences of chemical structure of the organic inhibitors, pH, temperature, physical treatment of cells, and added inhibitory or stimulatory inorganic ions and iron oxidation suggest that a major factor contributing to the inhibitory effects on iron oxidation is the relative electronegativity of the organic molecule. The data also suggest that inhibitory organic compounds may (i) directly affect the iron-oxidizing enzyme system, (ii) react abiologically with ferrous iron outside the cell, (iii) interfere with the roles of phosphate and sulfate in iron oxidation, and (iv) nonselectively disrupt the cell envelope or membrane.

Energetic aspects of the metabolism of reduced sulphur compounds in Thiobacillus dentrificans

Yields of Thiobacillus dentrificans on different substrates were compared. The organism was grown in a chemostat at a dilution rate of 0.03 h-1. From the difference in the cell yields with (1) oxygen (6.40 g carbon per mole thiosulphate) and (2) nitrate (4.51 g carbon per mole thiosulphate) as an electron acceptor the experimental value for Y ATP was estimated to be 1.75. The efficiency of the biosynthetic system would be 42% if 1 ATP should be needed in reversed electron transport, and 57% if this was 2 ATP per electron pair. It could be calculated that during anaerobic oxidation of thiosulphate with nitrate 1.41 or 1.16 ATP per 2 electrons are generated if 1 or 2 ATP respectively per thiosulphate is formed in substrate-level phosphorylation. For aerobic oxidation these figures are 2.40 and 2.16, respectively.

New medium for isolating iron-oxidizing and heterotrophic acidophilic bacteria from acid mine drainage

A new solid medium is described for growing iron and heterotrophic bacteria from acid mine drainage (AMD). Examination of AMD from five states revealed several kinds of colonies of iron-oxidizing bacteria: (i) smooth, (ii) smooth with secondary growth sectors or branching, (iii) star-shaped, (iv) radiating lobe, and (v) flat-rough. All AMD samples yielded whitish colonies that could not use ferrous iron, sulfur, or hydrogen, nor could they grow on nutrient agar, brain heart infusion agar, or Trypticase soy agar. Glucose and sucrose supported growth if the sugar-salts medium was at pH 3.0. The new iron medium has several advantages over others: (i) easy preparation, (ii) rapid growth, (iii) larger colonies, (iv) differentiation of colony morphology, and (v) detection of a new group of heterotrophic acidophilic bacteria.

Nonautotrophic Thiobacillus in acid mine water

Nonautotrophic thiobacilli were isolated from the acidic water of a coal mine. Based on their mixotrophic physiology, the isolates are regarded as strains of Thiobacillus perometabolis.

Effect of water potential on growth and iron oxidation by Thiobacillus ferrooxidans

The effect of water potential on the growth of two strains of Thiobacillus ferrooxidans was determined by adding defined amounts of sodium chloride or glycerol to the culture medium. The two strains differed slightly, and the most tolerant strain had a minimum water potential for growth of minus 15 to minus 32 bars when chloride was used and minus 6 bars when glycerol was used. In another approach, the limiting water potential was determined by equilibrating small amounts of culture medium with atmospheres of relative humidities equivalent to specific water potentials, and the ability of the organism to grow and oxidize ferrous iron was determined. Under these conditions, which are analogous to those which might control water potential in a coal refuse pile or copper leaching dump, the lower limit at which iron oxidation occurred was minus 23 bars. The water potential of some coal refuse materials in which T. ferooxidans was present were determined, and it was found that the water potentials at which the organism was active in these habitats were similar to those at which it was able to grow in culture. However, marked variation in water potential of coal refuse materials was found, presumably due to differences in clays and organic materials, and some coal refuse materials would probably never have water potentials at which the organism could grow. Some literature on the water potentials in copper leach dumps is reviewed, and it is concluded that control of water potential is essential to maximize the success of leaching operations. Because adequate drainage is necessary in a leach dump to ensure sufficient aeration, in many cases water availability in leach dumps may restrict the development of the bacterium necessary for the process.

Thiobacillus acidophilus sp. nov.; isolation and some physiological characteristics

After a brief exposition to glucose, Thiobacillus acidophilus was isolated from a culture of iron-grown T. ferrooxidans. Physicochemical analysis of its DNA showed a G+C content of 62.9-63.2%. The new isolate grows best at 25-30 degrees C and at pH 3.0. Growth is possible between pH 1.5 and 6.0. Thiobacillus acidophilus is apparently strictly aerobic. Ammonium salts are the only suitable source of nitrogen. The bacterium is a facultative autotroph. In addition to elemental sulfur, it obtains energy from organic compounds such as D-glucose, D-galactose, D-fructose, D-mannitol, D-xylose, D-ribose, D-arabinose, L-arabinose, sucrose, sodium citrate, malic acid,dl-aspartic acid, and dl-glutamic acid. Thiobacillus acidophilus possesses the key enzymes of the tricarboxylic acid (TCA) cycle including NAD-and NADP-linked isocitric dehydrogenase and alpha-ketoglutarate dehydrogenase, and the key enzymes of the hexose monophosphate pathway (glucose-6-phosphate and 6-phosphogluconate dehydrogenase, and fructose 1,6-diphosphate aldolase). NADH oxidase has been found in particulate fraction of extracts. Rhodanese and thiosulfate oxidase have also been detected.

Relationship between growth and metabolic activity in the strict chemolithotroph, Thiobacillus thiooxidans

The metabolic activity of Thiobacillus thiooxidans was found to decrease rapidly as stationary phase was approached. Keeping the culture at constant pH (4.0) and supplementation with CO2 did not effect the decrease in metabolic activity although growth was increased. The respiration rate of cells obtained from stationary phase was negligible. No growth was obtained when the pH was adjusted to pH 6.0. Measurement of pyruvic acid, an inhibitor of metabolic activity, showed that it reached only about 1.0 × 10−5 M during the early stages of growth and then decreased during exponential growth.

Degradation of oil shale by sulfur-oxidizing bacteria

Approximately 40% of oil shale can be solubilized by the action of sulfur-oxidizing bacteria. Thiobacillus thiooxidans and Thiobacillus concretivorous are equally effective in solubilization. Continuous leaching experiments show that this process can be completed within 14 days. The growth of Thiobacillus and the production of acid were measured under several conditions. Almost all of the CaMg(CO(3))(2) was removed by this process, leaving a complex of silica and kerogen that could be burned as low-energy fuel. The silica-kerogen complex had not yet been biologically degraded.

Oxidation of metal sulfides by Thiobacillus ferrooxidans grown on different substrates

Thiobacillus ferrooxidans, grown on either ferrous sulfate, lead sulfide concentrate, or chalcopyrite concentrate demonstrated oxygen uptake and CO2 fixation in the presence of ferrous sulfate, chalcopyrite ore, pyrite ore, and red antimony trisulfide. Lead suifide-grown cells could oxidize lead sulfide ore and galena, using the energy obtained for CO2 fixation. All three cell types could oxidize nickel sulfide, but could not fix CO2 in the presence of this substrate. The solubilization of metals from the substrates and the crystallographic changes in the insoluble residues are reported.

Toxic and immunological differences among lipopolysaccharides from Thiobacillus ferrooxidans grown autotrophically and heterotrophically

Lipopolysaccharides (LPS) extracted from Thiobacillus ferrooxidans grown on ferrous iron, elemental sulfur, or glucose as energy source were studied for general chemical composition, toxicity, and antigenic or immunogenic properties. LPS from iron-grown cells (Fe-LPS) and from glucose-grown cells (Glu-LPS) had similar chemical composition, but that from sulfur-grown cells (S-LPS) differed significantly, especially in content of hexosamine, 2-keto-3-deoxyoctonate, and heptose. All had weak to moderate endotoxic properties, but Fe-LPS was considerably more active than the others in the several assays performed. S-LPS was very weakly immunogenic; the other two stimulated strong antibody responses in rabbits. Immunodiffusion tests in agar gel revealed marked differences among the LPS antigens of cells grown with different energy sources.

Thiosulfate- and sulfide-dependent pyridine nucleotide reduction and gluconeogenesis in intact Thiobacillus neapolitanus

Nicotinamide adenine dinucleotide phosphate (reduced form) is formed more rapidly after the addition of thiosulfate to suspensions of intact Thiobacillus neapolitanus in the absence of CO(2) than nicotinamide adenine dinucleotide (reduced form). Measurement of acid-stable metabolites shows this phenomenon to be the result of rapid reoxidation of nicotinamide adenine dinucleotide (reduced form) by 3-phosphoglyceric acid and other oxidized intermediates, which are converted to triose and hexose phosphates, and that, in reality, the rate of nicotinamide adenine dinucleotide (oxidized form) reduction exceeds that of nicotinamide adenine dinucleotide phosphate (oxidized form) by approximately 4.5-fold. The overall rate of pyridine nucleotide reduction by thiosulfate (264 nmol per min per mg of protein) is in excess of that rate needed to sustain growth. Pyridine nucleotide reduction, adenosine triphosphate synthesis, and carbohydrate synthesis are prevented by the uncoupler m-Cl-Carbonylcyanide phenylhydrazone. Sodium amytal inhibits pyridine nucleotide reduction and carbohydrate synthesis are prevented by the uncoupler m-Cl-carbonylcyanide observations are reproduced when sulfide serves as the substrate. The rate of pyridine nucleotide anaerobic reduction with endogenous substrates or thiosulfate is less than 1% of the aerobic rate with thiosulfate. We conclude that the principal, if not the only, pathway of pyridine nucleotide reduction proceeds through an energy-dependent and amytal-sensitive step when either thiosulfate or sulfide is used as the substrate.