Studies on the growth of Thiobacillus ferrooxidans

Effect of external pH perturbations on in vivo protein synthesis by the acidophilic bacterium Thiobacillus ferrooxidans

The response of the obligate acidophilic bacterium Thiobacillus ferrooxidans to external pH changes is reported. When T. ferrooxidans cells grown at pH 1.5 were shifted to pH 3.5, there were several changes in the general protein synthesis pattern, including a large stimulation of the synthesis of a 36-kDa protein (p36). The apparent low isoelectric point of p36, its location in the membrane fraction, and its cross-reaction with anti-OmpC from Salmonella typhi suggested that it may be a porin whose expression is regulated by extracellular pH.

Osmoregulatory expression of porin genes in Escherichia coli: a comparative study on strains B and K-12

Escherichia coli K-12 produces both the OmpF and OmpC porins, the relative amounts of which in the outer membrane are affected in a reciprocal manner by the osmolarity of the growth medium. In contrast, E. coli B produces only the OmpF porin, regardless of the medium osmolarity. In this study, it was revealed that there is an extensive deletion within the ompC locus of the E. coli B chromosome. Cloning and nucleotide sequencing of the regulatory gene, ompR, of E. coli B revealed that there are two amino acid alterations (Lys-6 to Asn and Ala-130 to Thr) in the amino acid sequence of the OmpR protein, as compared with that of E. coli K-12. It is suggested that these particular amino acid alterations are responsible for the constitutive expression of the ompF gene observed in E. coli B.

Thiosulfate oxidation by obligately heterotrophic bacteria

Thiosulfate was oxidized stoichiometrically to tetrathionate during growth on glucose byKlebsiella aerogenes, Bacillus globigii, B. megaterium, Pseudomonas putida, two strains each ofP. fluorescens andP. aeruginosa, and anAeromonas sp. A gram-negative, rod-shaped soil isolate, Pseudomonad Hw, converted thiosulfate to tetrathionate during growth on acetate. None of the organisms could use thiosulfate as sole energy source. The quantitative recovery of all the thiosulfate supplied to heterotrophic cultures either as tetrathionate alone or as tetrathionate and unused thiosulfate demonstrated that no oxidation to sulfate occurred with any of the strains tested. Two strains ofEscherichia coli did not oxidize thiosulfate. Thiosulfate oxidation in batch culture occurred at different stages of the growth cycle for different organisms:P. putida oxidized thiosulfate during lag and early exponential phase,K. aerogenes oxidized thiosulfate at all stages of growth, andB. megaterium andAeromonas oxidized thiosulfate during late exponential phase. The relative rates of oxidation byP. putida andK. aerogenes were apparently determined by different concentrations of thiosulfate oxidizing enzyme. Thiosulfate oxidation byP. aeruginosa grown in chemostat culture was inducible, since organisms pregrown on thiosulfate-containing media oxidized thiosulfate, but those pregrown on glucose only could not oxidize thiosulfate. Steady state growth yield ofP. aeruginosa in glucose-limited chemostat culture increased about 23% in the presence of 5-22 mM thiosulfate, with complete or partial concomitant oxidation to tetrathionate. The reasons for this stimulation are unclear. The results suggest that heterotrophic oxidation of thiosulfate to tetrathionate is widespread across several genera and may even stimulate bacterial growth in some organisms.

Degradation of substituted thiophenes by bacteria isolated from activated sludge

Actinomycetes were isolated from activated sludge acclimated to thiophene-2-carboxylic acid (T2C) or 5-methyl-thiophene-2-carboxylic acid (T5M2C). These isolates were apparently identical and were identified as strains ofRhodococcus. The strains could grow on T2C, T5M2C, or thiophene-2-acetic acid as sole sources of carbon and energy, but could not use thiophene, methyl thiophenes, several other substituted thiophenes, dibenzothiophene, dimethyl sulfide, or pyrrole-2-carboxylic acid. T2C was degraded quantitatively to sulfate, and its carbon was converted almost entirely to cell biomass and carbon dioxide. Growth yields indicated about 25% conversion of T2C-carbon to cell-carbon. Growth was not supported by thiosulfate or methionine, nor were these compounds oxidized.Rhodococcus strain TTD-1 grown on T2C oxidized both T2C and T5M2C with an apparent Km of 1.3×10(-5) M. Sulfide was also oxidized by T2C-grown organisms. This is the first demonstration of an actinomycete capable of the complete degradation of thiophene derivatives and of their use by it as sole substrates for growth.

Biochemistry of the chemolithotrophic oxidation of inorganic sulphur

A historical review is presented of the elucidation of the mechanisms of oxidation of inorganic sulphur compounds and of electron transport in the thiobacilli. A unitary mechanism, consistent with current knowledge, is proposed. The significance of polythionates is discussed. The relations between oxidation mechanisms, substrate-level and electron transport-dependent phosphorylation, energy-dependent NAD+ reduction and efficiency of growth are assessed in order to evaluate the efficiency of energy conservation in different species. The unresolved problems are identified for the benefit of those planning further assaults on the last redoubts of the thiobacilli.

Dimethyl sulfoxide as an electron acceptor for anaerobic growth

The isolation from lake mud of a bacterium which can use dimethyl sulfoxide (DMSO) as an electron acceptor for growth is described. The isolate, called strain DL-1, was a small, gram negative, non-motile spiral. The sole product of DMSO reduction was dimethyl sulfide (DMS). Other electron acceptors used by the isolate included sulfite, thiosulfate, elemental sulfur, methionine sulfoxide, tetramethylene sulfoxide, nitrate, and oxygen (microaerophilically). Sulfate was not reduced and could not even be assimilated. Lactate or succinate could serve as electron donors, with acetate as the main product. Hydrogen could be used as an electron donor if acetate was present in the medium as a carbon source. The organism has a c-type cytochrome, and most likely uses electron transport phosphorylation during DMSO reduction. Cultures of Desulfovibrio sp., Escherichia coli, Pseudomonas aeruginosa, and Proteus vulgaris were tested for growth using DMSO as an electron acceptor, and only the Proteus strain grew. Both Proteus and strain DL-1 are versatile at coupling reductions with energy generation. There is a marked resemblance between strain DL-1 and the recently described sulfur-reducing spirillum of Wolfe and Pfennig.

Use of membrane filters for the enumeration of autotrophic thiobacilli

A new membrane filter technique for field use was developed for the enumeration of either aerobic or anaerobic, autotrophic, sulfur-oxidizing bacteria in waters and soils. Immediately after collection, samples were filtered through sulfur-coated filters and incubated in selective media. Acidification or gas evolution was used as a growth indicator of aerobic and anaerobic thiobacilli, respectively, and related to the initial number of cells deposited on the filter.

Heterotrophic growth of Thiobacillus A2 on sugars and organic acids

Thiobacillus A2 grew on a number of organic acids, pentoses, hexoses and alpha-linked disaccharides, but not on beta-linked disaccharides or galactosides. Growth was slow on glucose, although fast-growing strains were selectively isolated. Additive growth rates occured on glucose and galactose; growth on glucose with fructose, pyruvate or gluconate was biphasic rather than diauxic; fructose was used preferentially over glucose; slow growth on glucose was accelerated by some disaccharides; growth on acetate, fumarate or succinate with glucose gave diauxic growth with preferential use of the acid and repression of glucose incorporation. Acetate and succinate tended to be used preferentially even with cultures grown on them in mixture with fructose or sucrose.

The uptake and assimilation of sulphate by Thiobacillus ferrooxidans

Sulphate was rapidly bound by cell suspensions of Thiobacillus ferrooxidans. The binding was depressed by tetrathionate but was unaffected by Group VI anions, cysteine or methionine. Increasing uptake of sulphate was observed in cell suspensions incubated in the presence of ferrous iron. The bulk of 35S-sulphate was removed from the organisms by washing with dilute sulphuric acid and the remaining label was incorporated into cold trichloroacetic acid-soluble compounds. 35S-labelled adenosine 5'-sulphatophosphate was produced from ATP and 35S-sulphate by cell suspensions and in cell-free extracts. There was no evidence for the production of adenosine 3'-phosphate 5'-sulphatophosphate assayed by a very sensitive bioluminescence method.