Competition for inorganic substrates among chemoorganotrophic and chemolithotrophic bacteria

In aerobic enrichment experiments with a chemostat, using phosphate-limited lactate medium, aSpirillum sp. predominated at the lower range of dilution rates. At the higher dilution rates an (chemoorganotrophic) unidentified rod-shaped bacterium came to the fore. The same result was obtained in competition experiments with pure cultures of the two bacteria. Growth parameters were: Rod, _max=0.48 hr^–1,k _s(PO₄ ^3–)=6.6×10^–N M;Spirillum, _max=0.24 hr^–1· k_s(PO₄ ^3–) =2.7×10^–8 M. TheSpirillum grew faster than the rod at low dilution rates, not only under phosphate-limitation but also in K⁺-,Mg²⁺-, NH₄ ⁺-, aspartate-, succinate-, and lactate-limited cultures. Both organisms showed little substrate specificity and could utilize a similar range of carbon and energy sources. The results support the view that part of the diversity among bacteria in the natural environment is based on selection toward substrate concentration. Another set of competition experiments was carried out with pure cultures of two marine obligately chemolithotrophic colorless sulfur bacteria,Thiobacillus thioparus andThiomicrospira pelophila. Tms. pelophila outgrewT. thioparus at low dilution rates under iron limitation, while the reverse was true at high dilution rates. It is concluded that the relatively fast growth ofTms. pelophila at low iron concentration may explain its higher sulfide tolerance. Organisms showing a selection advantage at very low concentrations of limiting substrates appear to have a relatively high surface to volume ratio.     

Dynamics of oxidation of inorganic sulphur compounds in upper soil horizons of spruce forests

Dynamics of oxidation of inorganic sulphur compounds to sulphate by the soil of spruce forests was investigated. Sulphide, sulphite and thiosulphate are oxidized to sulphate at a maximal rate at the beginning of the reaction, oxidation of elemental sulphur exhibits a lag phase. Linear relationships between the amounts of the produced sulphate and concentrations of substrates in the soil could be detected. On the basis of this finding a method for comparison of the oxidative activity of various soils was proposed.     

Competition between the facultatively chemolithotrophic Thiobacillus A2, an obligately chemolithotrophic Thiobacillus and a heterotrophic spirillum for inorganic and organic substrates

Competition in a chemostat between the versatile Thiobacillus A2 and the specialized T. neapolitanus for thiosulfate as the sole growth-limiting substrate, led to dominance of the specialized over the versatile organism, at dilution rates 0.025 h^-1. Increasing concentrations of acetate or glycollate in the thiosulfate medium caused increased relative numbers of T. A2 in steady states at D=0.07 h^-1. Eventually, with 10–12 mmol of organic substrate per litre, complete dominance of T. A2 over T. neapolitanus occurred.Mixed cultures of T. A2 and a specialized spirillumshaped heterotroph, competing for acetate as sole growth-limiting substrate resulted in complete dominance of the heterotroph at dilution rates of 0.07 and 0.15 h^-1. In this case increasing concentrations of thiosulfate in the acetate medium, up to 10 mM, eventually led to the elimination of the heterotroph.These results have been interpreted as evidence that T. A2 was growing mixotrophically. As the concentration of the second substrate was raised, the number of T. A2 cells increased and as a result T. A2 consumed an increasing portion of the common substrate.In mixed chemostat cultures containing all three organisms, T. A2 could maintain itself with all tested ratios of acetate and thiosulfate in the inflowing medium. The heterotroph was excluded from the culture below a relatively low acetate to thiosulfate ratio, whilst above a relatively high acetate to thiosulfate ratio T. neapolitanus was completely eliminated.These results were discussed in relation to the ecological niche of Thiobacillus A2-type organisms.     

Electron transfer during the oxidation of ammonia by the chemolithotrophic bacterium Nitrosomonas europaea

The combined action of ammonia monooxygenase, AMO, (NH(3)+2e(-)+O(2)-->NH(2)OH) and hydroxylamine oxidoreductase, HAO, (NH(2)OH+H(2)O-->HNO(2)+4e(-)+4H(+)) accounts for ammonia oxidation in Nitrosomonas europaea. Pathways for electrons from HAO to O(2), nitrite, NO, H(2)O(2) or AMO are reviewed and some recent advances described. The membrane cytochrome c(M)552 is proposed to participate in the path between HAO and ubiquinone. A bc(1) complex is shown to mediate between ubiquinol and the terminal oxidase and is shown to be downstream of HAO. A novel, red, low-potential, periplasmic copper protein, nitrosocyanin, is introduced. Possible mechanisms for the inhibition of ammonia oxidation in cells by protonophores are summarized. Genes for nitrite- and NO-reductase but not N(2)O or nitrate reductase are present in the genome of Nitrosomonas. Nitrite reductase is not repressed by growth on O(2); the flux of nitrite reduction is controlled at the substrate level.     

Soil heterotrophic bacteria in transformations of inorganic sulphur

The occurrence of biochemical activities of the sulphur cycle was followed in isolates of heterotrophic bacteria from the fermentative horizon of a spruce stand, a grass-covered withered spruce stand and of mountain ash and birch stand in the area strongly influenced by sulphur immissions. The occurrence of bacteria capable of reducing S⁰ to S²⁻, oxidizing S⁰ and S₂O₃ ²⁻ to SO₄ ²⁻ and solubilizing S⁰ increased in the above order. The occurrence of producers of thiosulphate sulphurtransferase (rhodanese), thiosulphate oxidase and sulphite oxidase increased and the level of the production of these enzymes increased as well. Heterotrophic bacteria (mostly pseudomonads) from the grass-covered stands exhibit more activities of the sulphur cycle than bacteria from the spruce stand without ground vegetation.     

Effects of organic matter on sulphur oxidation in soil and influence of sulphur oxidation on soil nitrification

Summary The effects of wheat straw and pressed sugar beet pulp on sulphur oxidation were determined in a loam soil amended with 1% (w/w) elemental sulphur. Wheat straw stimulated the oxidation of elemental sulphur over the first 2 to 3 weeks of the incubation period, resulting in an increase in LiCl-extractable sulphate. After 4 to 7 weeks incubation however, the only significant increase in soil sulphate followed the 1% straw addition, while at week 7 sulphate concentrations in the 0.25% and 5.0% straw amended soils were lower than the control. Pressed sugar beet pulp (1% w/w) initially stimulated the oxidation of elemental sulphur in the soil, but by weeks 3 to 7 of the incubation period rates of oxidation in pulp-amended soils were lower than the control. Towards the end of the incubation period however, sulphate concentrations in the amended soils exceeded the control values, significantly so by week 11. The concentration of thiosulphate and tetrathionate also increased in soils receiving sugar beet pulp. Nitrification was inhibited in soils in which sulphur oxidation was actively occurring. Although possible alternatives are mentioned, such inhibition appears to result from a decrease in soil pH brought about by the oxidation of elemental sulphur to sulphuric acid.     

Bioremoval of organic and inorganic sulphur from coal samples

The microbial ecology of different Spanish coal samples has been studied. Several bacteria have been isolated from enrichment cultures and characterised and their biodesulphurization abilities evaluated. Using morphological and physiological properties, different isolates have been related to species of the Xanthomonas, Pseudomonas, Chryseomonas and Moraxella genera. Some of the isolates, B(30)15 and T(30)10, gave important levels of organic desulphurization, close to 70%. Other isolates, B(30)7 and B(30)8, were able to remove inorganic sulphur with high efficiencies, over 67%. One of the isolates, B(30)10, metabolically related to Xanthomonas maltophila, was able to remove both organic and inorganic sulphur at neutral pH, with efficiencies of 69% and 68% respectively. The results obtained underline the potential use of some of these strains for industrial coal desulphurization processes. Received: 26 June 1998 / Received revised: 1 October 1998 / Accepted: 2 October 1998     

Biochemistry of the oxidation of lignin by Phanerochaete chrysosporium

The objective of this research was to identify the biochemical agents responsible for the oxidative degradation of lignin by the white-rot fungus Phanerochaete chrysosporium. We examined the hypothesis that activated oxygen species are involved, and we also sought the agent in ligninolytic cultures responsible for a specific oxidative degradative reaction in substructure model compounds. Results of studies of the production of activated oxygen species by cultures, of the effect of their removal on ligninolytic activity, and of their action on substructure model compounds support a role for hydrogen peroxide (H(2)O(2)) and possibly superoxide (O(2)(*)(-)) in lignin degradation. Involvement of hydroxyl radical (*OH) or singlet oxygen (1O(2)) is not supported by our data. The actual biochemical agent responsible for one important oxidative C-C bond cleavage reaction in non-phenolic lignin substructure model compounds, and in lignin itself, was found to be an enzyme. The enzyme is extracellular, has a molecular weight of 42,000 daltons, is azide-sensitive, and requires H(2)O(2) for activity.     

Arsenite oxidation by a facultative chemolithotrophic bacterium SDB1 isolated from mine tailing

An arsenite (As[III])-oxidizing bacterium, SDB1, was isolated from mine tailing collected from the Sangdong mine area in Korea and showed chemolithotrophic growth on As[III] and CO₂ as the respective electron and carbon sources. SDB1 is Gram-negative, rod-shaped, and belongs to the Sinorhizobium-Ensifer branch of α-Proteobacteria. Growth and As[III] oxidation was enhanced significantly by the presence of yeast extract (0.005%) in minimal salt medium containing 5 mM As[III]; decreasing the doubling time from 9.8 to 2.1 h and increasing the As [III] oxidation rate from 0.014 to 0.349 pmol As [III] oxidized cell⁻¹ h⁻¹. As[III] oxidation nearly stopped at pH around 4 and should be performed at pH 7∼8 to be most effective. SDB1 was immobilized in calcium-alginate beads and the oxidation capacity was investigated. Specific As[III] oxidation rates obtained with SDB1 (10.1−33.7 mM As[III] oxidized g⁻¹ dry cell h⁻¹) were 10∼16-times higher than those reported previously with a heterotrophic bacterial strain (Simeonova et al., 2005). The stability and reusability of immobilized SDB1 strongly suggested that the immobilized SDB1 cell System can make the As[III] oxidation process technically and economically feasible in practical applications.     

Patterns of growth and oxidation of natural pyrites by the representatives of acidophilic chemolithotrophic microorganisms

The patterns of the growth and oxidation of different types of natural pyrites were studied for the three microbial species adapted to these substrates and belonging to phylogenetically remote groups: gram-negative bacterium Acidithiobacillus ferrooxidans, gram-positive bacterium Sulfobacillus thermotolerans, and the archaeon Ferroplasma acidiphilum. For both A. ferrooxidans strains, TFV-1 and TFBk, pyrite 4 appeared to be the most difficult to oxidize and grow; pyrite 5 was oxidized by both strains at an average rate, and pyrite 3 was the most readily oxidized. On each of the three pyrites, growth and oxidation by TFBk were more active than by TFV-1. The effectiveness of the adaptation of S. thermotolerans Kr1^T was low compared to the A. ferrooxidans strains; however, the adapted strain Kr1^T showed the highest growth rate on pyrite 3 among all the cultures studied. No adaptation of strain Kr1^T to pyrite 5 was observed; the rates of growth and pyrite oxidation in the third transfer were lower than in the first transfer. The strain F. acidiphilum Y^T was not adapted to pyrites 3 and 5; the rates of growth and pyrite oxidation were the same in the first five transfers. The strains of three species of the microorganisms studied, A. ferrooxidans, S. thermotolerans, and F. acidiphilum, grew on pyrite 3 (holetype (p) conductivity) and oxidized it better than pyrite 5 (mixed-type (n-p) conductivity). The most readily oxidized were the pyrites with a density of 5.6–5.7 g/cm³ and high resistance values (ln R = 8.8). The pyrite oxidation rate did not depend on the type of conductivity. Changes in the chromosomal DNA structure were revealed in strain TFBk on adaptation to pyrites 3 and 4 and in the TFV-1 plasmid profile on adaptation to pyrite 3. Correlation between genetic variability and adaptive capabilities was shown for A. ferrooxidans. No changes in the chromosomal DNA structure were found in S. thermotolerans Kr1^T and F. acidiphilum Y^T on adaptation to pyrites 3 and 5. Plasmids were absent in the cells of these cultures.     

Thiosulphate oxidation in the phototrophic sulphur bacterium Allochromatium vinosum

Two different pathways for thiosulphate oxidation are present in the purple sulphur bacterium Allochromatium vinosum: oxidation to tetrathionate and complete oxidation to sulphate with obligatory formation of sulphur globules as intermediates. The tetrathionate:sulphate ratio is strongly pH-dependent with tetrathionate formation being preferred under acidic conditions. Thiosulphate dehydrogenase, a constitutively expressed monomeric 30 kDa c-type cytochrome with a pH optimum at pH 4.2 catalyses tetrathionate formation. A periplasmic thiosulphate-oxidizing multienzyme complex (Sox) has been described to be responsible for formation of sulphate from thiosulphate in chemotrophic and phototrophic sulphur oxidizers that do not form sulphur deposits. In the sulphur-storing A. vinosum we identified five sox genes in two independent loci (soxBXA and soxYZ). For SoxA a thiosulphate-dependent induction of expression, above a low constitutive level, was observed. Three sox-encoded proteins were purified: the heterodimeric c-type cytochrome SoxXA, the monomeric SoxB and the heterodimeric SoxYZ. Gene inactivation and complementation experiments proved these proteins to be indispensable for thiosulphate oxidation to sulphate. The intermediary formation of sulphur globules in A. vinosum appears to be related to the lack of soxCD genes, the products of which are proposed to oxidize SoxY-bound sulphane sulphur. In their absence the latter is instead transferred to growing sulphur globules.     

Microbial oxidation of elemental sulphur in brown soil

Plant and Soil - Brown soil formed from loamy clay was examined for its ability to produce sulphate from added elemental suphur. At higher rates of sulphur applications the pH of a slightly acid...     

Rates of sulfide mineral oxidation by acidophilic chemolithotrophic microbial communities from various sources

A correlation was observed between the rate of oxidation of pure sulfide minerals (pyrite, pyrrhotite, and arsenopyrite) by communities of acidophilic chemolithotrophic microorganisms (ACM) and the mineral substrate where these communities were formed. The ACM community formed during continuous oxidation of the pyrite-arsenopyrite ore concentrate (Kyuchus deposit) exhibited the highest rate of pyrite oxidation. The highest rate of pyrrhotite oxidation was observed for the ACM community developed during semicontinuous oxidation of the pyrrhotite-containing pyrite-arsenopyrite ore concentrate (Olympiadinskoe deposit), by the communities isolated from the pyrrhotite concentrate, and ore of the Shanuch deposit. In the case of arsenopyrite oxidation, the ACM community isolated during oxidation of the Olympiadinskoe ore concentrate grew without a lag phase. Other communities commenced arsenopyrite oxidation at various rates only after a two-day lag phase. The similarity of the mineralogical characteristics of pure sulfide minerals with those of the minerals in the substrates where the ACM communities developed may affect the rates of oxidation.     

Species composition of the association of acidophilic chemolithotrophic microorganisms participating in the oxidation of gold-arsenic ore concentrate

The species composition of the microbial association involved in industrial tank biooxidation of the concentrate of refractory pyrrhotite-containing pyrite-arsenopyrite gold-arsenic ore of the Olympiadinskoe deposit at 39°C was studied by cultural and molecular biological techniques. Pure microbial cultures were isolated, their physiological characteristics were investigated, and their taxonomic position was determined by 16S rRNA gene sequencing. The library of 16S rRNA gene clones obtained from the total DNA isolated from the biomass of the pulp of industrial reactors was analyzed. The diversity of microorganisms revealed by cultural techniques in the association of acidophilic chemolithotrophs (Acidithiobacillus ferrooxidans, Leptospirillum ferriphilum, Sulfobacillus thermosulfidooxidans, Ferroplasma acidiphilum, Alicyclobacillus tolerans, and Acidiphilium cryptum) was higher than the diversity of the 16S rDNA clone library (At. ferrooxidans, L. ferriphilum, and F. acidiphilum). The combination of microbiological and molecular biological techniques for the investigation of the biodiversity in natural and anthropogenic microbial communities promotes detection of new phylogenetic microbial groups in these communities.     

Biochemistry of the oxidation of lignin by Phangerochate chrysosporium

The objective of this research was to identify the biochemical agents responsible for the oxidative degradation of lignin by the white-rot fungus . We examined the hypothesis that activated oxygen species are involved, and we also sought the agent in ligninolytic cultures responsible for a specific oxidative degradative reaction in substructure model compounds. Results of studies of the production of activated oxygen species by cultures, of the effect of their removal on ligninolytic activity, and of their action on substructure model compounds support a role for hydrogen peroxide (H₂O₂) and possibly superoxide (O₂ ·^-) in lignin degradation. Involvement of hydroxyl radical (·OH) or singlet oxygen (¹O₂) is not supported by our data. The actual biochemical agent responsible for one important oxidative C-C bond cleavage reaction in non-phenolic lignin substructure model compounds, and in lignin itself, was found to be an enzyme. The enzyme is extracellular, has a molecular weight of 42,000 daltons, is azide-sensitive, and requires H₂O₂ for activity.     

Microbial transformations of inorganic sulphur compounds in soil under conditions of heterocontinuous cultivation

Development and activity of the association of the sulphur cycle bacteria, represented byThiobacillus thioparus andDesulfovibrio sp., were followed in chernozem soil continuously supplemented with sodium thiosulphate. The technique of heterocontinuous cultivation made it possible (i) to determine changes in the individual components of microflora involved in successive metabolic steps, their time and space sequence, (ii) to follow changes in the transformations of substrate and formation of metabolic products, and (iii) to reach a steady state in the system. A possible use of this approach for the evaluation of the effect of ecological factors, for modelling microbiological processes of the sulphur cycle, for the investigation of trophic relationships among microorganisms in natural and artificial association and for the evaluation of the geochemical activity of sulphur bacteria is discussed.