Energy conservation in acidophilic bacteria

[This corrects the article on p. 580 in vol. 47.][This corrects the article on p. 584 in vol. 47.][This corrects the article on p. 594 in vol. 47.].     

Energy conservation in chemotrophic anaerobic bacteria

[This corrects the article on p. 100 in vol. 41.].     

PCR-mediated detection of acidophilic, bioleaching-associated bacteria.

The detection of acidophilic microorganisms from mining environments by culture methods is time consuming and unreliable. Several PCR approaches were developed to amplify small-subunit rRNA sequences from the DNA of six bacterial phylotypes associated with acidic mining environments, permitting the detection of the target DNA at concentrations as low as 10 fg.     

Extremely thermophilic acidophilic bacteria convergent with Sulfolobus acidocaldarius.

A series of extremely thermophilic acidophilic bacteria has been characterized as closely resembling the species Sulfolobus acidocaldarius except for a totally different guanosine-cytosine content in the DNA; some conceptual consequences of this situation are discussed. Both organisms also share special features, including a very characteristic type of ether lipid, with other extreme acidophilic thermophiles.     

Phylogenetic and biochemical characterization of acidophilic bacteria

Abstract: In the course of our studies to determine appropriate conditions to transform Thiobacillus ferrooxidans , we have adopted a tetrathionate-containing medium. A number of different, apparently stable colony morphologies have arisen from cultures presumed to be pure while grown on iron-containing medium. In an effort to assess whether these different morphologies are indicative of previously undetected contamination, or simply manifestations of physiological variability within a strain, we have applied a number of biochemical and genetic techniques, including cellular fatty acid analysis and 16S rRNA sequence determination. These data should allow us to unequivocally characterize and compare the organisms present in our cultures.     

Energy conservation in the decarboxylation of dicarboxylic acids by fermenting bacteria

Decarboxylation of dicarboxylic acids (oxalate, malonate, succinate, glutarate, and malate) can serve as the sole energy source for the growth of fermenting bacteria. Since the free energy change of a decarboxylation reaction is small (around –20 kJ per mol) and equivalent to only approximately one-third of the energy required for ATP synthesis from ADP and phosphate under physiological conditions, the decarboxylation energy cannot be conserved by substrate-level phosphorylation. It is either converted (in malonate, succinate, and glutarate fermentation) by membrane-bound primary decarboxylase sodium ion pumps into an electrochemical gradient of sodium ions across the membrane; or, alternatively, an electrochemical proton gradient can be established by the combined action of a soluble decarboxylase with a dicarboxylate/monocarboxylate antiporter (in oxalate and malate fermentation). The thus generated electrochemical Na⁺ or H⁺ gradients are then exploited for ATP synthesis by Na⁺- or H⁺-coupled F₁F₀ ATP synthases. This new type of energy conservation has been termed decarboxylation phosphorylation and is responsible entirely for ATP synthesis in several anaerobic bacteria. Received: 5 December 1997 / Accepted: 16 March 1998     

Conversion of hydrogen sulphide by acidophilic bacteria

Conversion of hydrogen sulphide (H₂S) by the bacterium Thiobacillus thiooxidans to sulphur or sulphate was demonstrated in a continuous column contacter using a countercurrent flow of gas and liquid medium. The initial conversion to sulphur was much faster than subsequent oxidation to sulphate, allowing for removal of elemental sulphur. The rate of H₂S removal increased with available surface area in the column bed and with time. The number of bacteria in the column increased very slowly with time, placing great importance on the initial concentration of bacteria in the column. Correspondence to: H. M. Lizama     

Respiratory components in acidophilic bacteria that respire on iron

Abstract

Microorganisms capable of aerobic respiration on ferrous ions are spread throughout eubacterial and archaebacterial phyla. Phylogenetically distinct organisms were shown to express spectrally distinct redox‐active biomolecules during autotrophic growth on soluble iron. A new iron‐oxidizing eubacterium, designated as strain Funis, was investigated. Strain Funis was judged to be different from other known iron‐oxidizing bacteria on the bases of comparative lipid analyses, 16S rRNA sequence analyses, and cytochrome composition studies. When grown autotrophically on ferrous ions, Funis produced conspicuous levels of a novel acid‐stable, acid‐soluble yellow cytochrome with a distinctive absorbance peak at 579 nm in the reduced state.

Stopped‐flow spectrophotometric kinetic studies were conducted on respiratory chain components isolated from cell‐free extracts of Thiobacillus ferrooxidans. Experimental results were consistent with a model where the primary oxidant of ferrous ions is a highly aggregated c‐type cytochrome that then reduces the periplasmic rusticyanin. The Fe(II)‐dependent, cytochrome c‐catalyzed reduction of the rusticyanin possessed three kinetic properties in common with corresponding intact cells that respire on iron: the same anion specificity, a similar dependence of the rate on the concentration of ferrous ions, and similar rates at saturating concentrations of ferrous ions     

The potential for diazotrophy in iron-and sulfur-oxidizing acidophilic bacteria

Acetylene reduction was observed with ferrousiron-oxidizingThiobacillus ferrooxidans, as expected from previous studies with this bacterium. Acetylene reduction was also found during the growth ofT. ferrooxidans on tetrathionate. OnlyLeptospirillum ferrooxidans, one of several other phylogenetically diverse, ferrous-iron-and/or sulfur-oxidizing acidophilic microorganisms, also reduced acetylene. A reduction of the oxygen concentration in the culture atmosphere was necessary to alleviate inhibition of nitrogenase activity. DNA sequences homologous tonif structural genes were found in both organisms. Diazotrophic growth ofL. ferrooxidans was inferred from an increase in iron oxidation in ammonium-free medium when the oxygen concentration was limited and from apparent inhibition by acetylene under these conditions.     

Transfer and expression of degradative and antibiotic resistance plasmids in acidophilic bacteria.

The genetic accessibility of selected acidophilic bacteria was investigated to evaluate their applicability to degrading pollutants in acidic environments. The IncP1 antibiotic resistance plasmids RP4 and pVK101 and the phenol degradation-encoding plasmid pPGH11 were transferred from neutrophilic bacteria into the extreme acidophilic eubacterium Acidiphilium cryptum at frequencies of 1.8 x 10(-2) to 9.8 x 10(-4) transconjugants per recipient cell. The IncQ antibiotic resistance plasmid pSUP106 was mobilizable to A. cryptum by triparental matings at a frequency of 10(-5) transconjugants per recipient cell. In the transconjugants, antibiotic resistances and the ability to degrade phenol were expressed. A. cryptum AC6 (pPGH11) grew with 2.5 mM phenol at a doubling time of 12 h and a yield of 0.52 g (dry cell weight) per g of phenol. A. cryptum harbored five native plasmids of 255 to 6.3 kb in size. Plasmids RP4 and pVK101 were transferred from Escherichia coli into Acidobacterium capsulatum at frequencies of 10(-3) and 2.3 x 10(-4) and to the facultative autotroph Thiobacillus acidophilus at frequencies of 1.1 x 10(-5) and 2.9 x 10(-6) transconjugants per recipient cell, respectively. Plasmid pPGH11 could not be transferred into the latter strains. T. acidophilus wild type contained six so far cryptic plasmids of 220 to 5 kb.     

Grazing of acidophilic bacteria by a flagellated protozoan

A biflagellated protozoan was isolated from an acidic drainage stream located inside a disused pyrite mine. The stream contained copious amounts of acid streamer bacterial growths, and the flagellate was observed in situ apparently grazing the streamer bacteria. The protozoan was obligately acidophilic, growing between pH 1.8 and 4.5, but not at pH 1.6 or 5.0, with optimum growth between pH 3 and 4. It was highly sensitive to copper, molybdenum, silver, and uranium, but tolerated ferrous and ferric iron up to 50 and 25 mM, respectively. In the laboratory, the protozoan was found to graze a range of acidophilic bacteria, including the chemolithotrophs Thiobacillus ferrooxidans, Leptospirillum ferrooxidans, and the heterotroph Acidiphilium cryptum. Thiobacillus thiooxidans and Thiobacillus acidophilus were not grazed. Filamentous growth of certain acidophiles afforded some protection against being grazed by the flagellate. In mixed cultures of T. ferrooxidans and L. ferrooxidans, the protozoan isolate displayed preferential grazing of the former. The possibility of using acidophilic protozoa as a means of controlling bacteria responsible for the production of acid mine drainage is discussed.Offprint requests to: Dr. D. B. Johnson.     

Genetic improvement of acidophilic bacteria for biohydrometallurgical applications

Abstract

Recent success in introducing foreign genetic information into Acidiphilium and Thiobacillus ferrooxidans have opened the possibility of the improvement of the bioleaching properties of acidophilic bacteria through genetic means. The use of electroporation to transform acidophilic bacteria, while effective for diverse genera of bacteria, is potentially limited by observed strain dependence within a given species. Bacterial mating or conjugation may prove more widely applicable, but has not yet been demonstrated in T. ferrooxidans. An arsenic‐resistant, broad‐host‐range plasmid has been constructed and introduced by conjugation into Acidiphilium. This recombinant organism is being examined to assess whether it might lead to improved arsenopyrite leaching rates in mixed cultures with chemolithotrophs such as T. ferrooxidans and Leptospirillum ferrooxidans.     

Energy conservation and pyridine nucleotide reduction in chemoautotrophic bacteria: a thermodynamic analysis

Respiratory and reverse electron transport by chemoautotrophic bacteria have been formulated in chemiosmotic terms. A thermodynamic analysis of this model, assuming equilibrium conditions, indicates that respiration by most chemoautotrophs can generate a protonmotive force easily sufficient to drive both ATP synthesis and reverse electron transport.Dedicated to the memory of Roger Stanier, who first called to my attention the problem discussed here; and whose analysis of the relationship between it and the phenomenon of obligate autotrophy (Smith et al. 1967), although later shown to be inadequate, remains for me a model of creative biochemical insight     

嗜酸硫氧化细菌消解元素硫的研究进展

浸矿酸性环境下,金属硫化矿在Fe3+作用下,经过硫代硫酸盐途径或多聚硫化氢途径而分解的过程中导致大量元素硫的累积,进而可能在金属硫化矿表面形成疏水元素硫层,阻碍金属离子的进一步浸出。酸性环境下,惰性元素硫的消解必须借助嗜酸硫氧化细菌来实现。该消解过程包括嗜酸硫氧化细菌对元素硫的吸附、转运以及氧化转化等过程。本文对近年来嗜酸硫氧化细菌消解元素硫过程的相关研究进行了全面评述,认为有关嗜酸硫氧化细菌消解元素硫的分子机制的清晰阐述还有待人们通过对消解过程的各个环节的分子机制进行大量研究来实现。     

High performance fermentation process using methanol utilizing acidophilic bacteria

Using a methanol utilizing acidophilic MB 58 bacteria strain (IMET 10945^T), a stable fermentation process was performed in a pilot plant pressure fermenter of 250 l total volume for more than four months. Under the fermentation conditions (system pressure and retention time) used, productivities ranged between 2.3 and 9.4 BDM kg^?1. h^?1 and growth yields between 0.31 and 0.42. Models describe the correlations between yield and retention time. The mean value of growth yield amounts to 0.41 at a retention time of 6.5 h.     

Properties of membrane-bound ATPase of some acidophilic heterotrophic bacteria

Membrane-bound ATPase (EC 3.6.1.4) of acidophilic heterotrophic bacteria from mine environment was isolated and characterized. The enzyme preparations fromAcidiphilium symbioticum KM2 and the strains GS18h and GS19h have a pH optimum of 7.7, 8.2 and 7.7, respectively, in the presence of Mg²⁺ which is required for activity. In an assay system containing Mn²⁺ or Ca²⁺ only, some activity was also evident. These enzymes hydrolyzed inorganic diphosphate (PPi), guanosine triphosphate (GTP) and inosine triphosphate (ITP) as the better substrate than ATP and theK _m values of the enzymes with respect to ATP were determined to be 238, 157 and 228 μmol/L forA. symbioticum KM2 and the strains GS18h and GS19h, respectively. The activity was stimulated by sulfite while Zn²⁺, Hg²⁺, 4-chloromercuribenzoic acid (p-CMB) and the specific inhibitors of F₀F₁ type ATPase,viz. N,N′-dicyclohexylcarbodiimide (DCCD), oligomycin and azide reduced the activity of the enzyme preparations.