Madgwick, J. C.; Ralph, B. J.; School of Biological Technology, University of New South Wales, Kensington, N.S.W., Australia (1977)
      The filamentous green alga Hormidium fluitans (Gay) Heering grows extremely luxuriantly in turbulent outflows of mine drainage waters in Northern Territory, Australia, and on Bougainville Island, Papua-New Guinea. The drainage waters contain between 30 and 700 p.p.m. copper and have a pH range 3.2 - 5.3. The metal-concentrating ability of the naturally-occurring alga has been examined in respect of 25 elements; high concentration ratios have been noted for the elements, Ag, Al, Fe, Mo, Ti and V. In the case of copper, histochemical examination shows a possible binding of the metal in a cell-wall layer. An alkali-soluble fraction of the dried cells prepared from field samples of the alga, had a very high affinity for copper (11.8% of dry weight). This fraction made up about 1.5% of the cell polymers. The alga has been artificially cultivated in a number of modes, but grows best in vigorously sparged submerged culture on artificial mine water, in the presence of ore lumps. Under most laboratory conditions, motile and unicellular forms of the algae occur. It has been shown recently that culture filtrate from the algal growth stimulates the rate of iron oxidation and of growth of some Thiobacillus ferrooxidans strains, and enhances the rate of copper release from chalcopyrite ores.

      Coombes, A. J.; Lepp, N. W.; Phipps, D. A.; Department of Biology and Department of Chemistry, Liverpool Polytechnic, Byrom St., Liverpool, L3 3AF, U.K. (1977)
      When roots of bean plants (Phaseolus vulgaris L.) grown in solution culture, were supplied with increasing levels of copper, increases in the quantities of the positively charged forms of copper, calcium and magnesium which were leached from the foliage of such plants were observed. However, subsequent analysis of the results indicated the presence of a large interactive component in the observed variations, and incorporation of this factor showed that the observed increases in leaching were not significantly related to nutrient copper levels. Correlation between foliar copper levels and the quantity of all leached cations was obtained and the quantities of the individual elements leached were also highly correlated. This is good indication of the implication of a single factor as a causal agent for increased cation leaching. The leaching of anionic forms of the above elements was more variable. Anionic forms of all 3 elements were detected and the quantities leached showed similar trends, but due to large variability, only the effect of the treatments on anionic magnesium was significant. The number of samples containing anions was significantly reduced by an increased root copper supply.

      Wyckoff, Ralph W. G.; Davidson, Franklin D.; Department of Physics, University of Arizona Tucson, Arizona, USA (1977)
      Studies have been made of the composition, morphology and ability to metabolize sulfides of certain autotrophic microorganisms collected from the neighborhood of fumaroles. Some are thermophilic and resemble the Sulfolobus described in the United States by Brock and the Brierleys. Others, living at lower temperatures, resemble but are in certain respects different from thiobacteria. They have been more effective than sulfur bacteria in attacking chalcopyrite and their reaction with this mineral is described. Attention is given to their pleomorphism and to their possibly primitive nature. Differences noted between strains from different localities emphasize the desirability of obtaining and testing samples from many sources, Our

      Brierley, J. A.; Le Roux, N. W.; Department of Biology, New Mexico Institute of Mining and Technology Socorro, NM 87801, USA; Department of Industry, Warren Spring Laboratory Stevenage, Hertfordshire SG] 2BX, England (1977-07)
      A rod-shaped microbe, isolated from an Icelandic thermal spring grows well at 50° C and oxidises metal sulphides e.g., pyrite (FeS,), pentlandite ((NiFe) SQ) and chalcopyrite (CuFeS,). Initial isolation on a modified ferrous iron medium at pH 3.6 and 60° C indicated that the bacteria were capable of oxidising ferrous iron but that growth was poor. For good growth on sulphide minerals, yeast extract is a requirement. This paper reports on the oxidation of soluble ferrous iron and pyrite by this microbe. The microbe grows slowly at 30° C using ferrous iron but does not grow on pyrite; growth on the latter substrate begins at 40° C. Growth on iron occurs at 50° C, but not at 55° C; growth on pyrite is present at 55° C but not at 60° C. The microbe grows using sulphur as an energy source. The thermophile also grows when yeast extract provides the only apparent energy source. Pyrite-grown cells were used for manometric experiments. Using ferrous iron, the oxygen uptake was non-linear, decreasing with time; the rate increased with increasing pH from 1.3 to 3.2 and also increasing ferrous iron concentration to 8] mM Fe(II). The rate then remained the same at 111mM Fe(II). Using pyrite, the oxygen uptake was linear, the rate being a maximum at pH 2.6. Oxidation of pyrite was slight at pH 1.1 and 3.5. The greatest rate of pyrite oxidation occurred with 100 g c pyrite, the largest concentration tested. Oxygen uptake during the manometric tests with ferrous iron was not greatly affected by the absence of yeast extract; pyrite oxidation was slightly greater without yeast extract. The relevance of the activity of this microbe to biohydrometallurgy is discussed.

      Barbic, F.; Lucic, J.; Babic, M.; Institut fur die Technologie von Nuklearrohstoffen und anderen mineralischen Rohstoffen, Belgrad (1977-07)
      Various sulphur compounds were investigated as energy sources for the growth of Th. ferrooxidans. At the same time the tolerance of Th. ferrooxidans for various compounds was examined. Th. ferrooxidans responds in different ways to sulphur compounds, depending on their kind and concentration. Some of the sulphur compounds examined can replace iron as an energy source. The compounds examined can be lethal to Th. ferrooxidans depending on their concentration.

      Brock, Thomas D.; Department of Bacteriology, University of Wisconsin, Madison, WI 53706 U.S.A. (1977-07)
      Acidophilic bacteria of the genera Thiobacillus and Sulfolobus reduce ferric iron when growing on elemental sulfur as an energy source. This process can be demonstrated aerobically in T. thiooxidans and S, acidocaldarius, but only anaerobically in T. ferrooxidans, since under aerobic conditions this latter organism reoxidizes the ferrous iron it produces as a result of ferric reduction. Since oxidation of sulfide minerals probably proceeds through the intermediary accumulation of elemental sulfur, the bacterial coupling of elemental’sulfur and ferric iron may be important in the overall process of sulfide mineral oxidation, especially when 0, is limiting. Considerations of the environment and ecology of leach dumps suggest that 0, is often limiting, and anaerobic conditions may develop. Thus, the bacterial catalysis of the elemental sulfur-ferric iron reaction may play a major role in the effective operation of a leaching process.

      Karavaiko, G. I.; Pirovarova, T. A.; Institute of Microbiology, USSR Academy of Sciences, Moscow (1977-07)
      The mechanism of transport sulphur both outside and inside the cells was studied. Macroroentgen structural analysis and electronicmicroscopic researches showed that the membrane structures of thiobacilli carry out not only the oxidation function, but the transport function as well, which consists in the extraction of the formed sulphur from cell. This mechanism of sulphur deposition develops ac-— cording to the exocytosis type. The transport of elemental sulphur inside the cell involves the surface membrane structures (vesicles), while oxidation of the sulphur to sulphuric acid takes place on the outer surface of the cytoplasmic membrane. The vesicles are supposed also to participate in the primary dissolution of elemental sulphur at the site of contact of the cells with the mineral. The study of bacterial oxidation of sulphide minerals has shown the electrochemical nature of microbiological oxidation of sulphide minerals, which takes place at the level of its electronic structure. Pyrite with hole conductivity (with the cation deficit in composition) is oxidized by means of Thiobacillus ferrooxidans not only much more intensively, but also continuously as compared to pyrite with electron conductivity. Thiobacilli play a leading role in the oxidation of reduced sulphur compounds under natural conditions. The mechanism of this process however have not been studied sufficiently well so far. The main purpose of this work was to study the mechanism of sulphur transport, when sulphur was deposited or oxidized by thiobacilli, by means of cytological and cytochemical techniques. We believed that the mechanism,of sulphur transport either from, or into, the cell must be closely related to the submicroscopic organization of thiobacilli

      Le Roux, N. W.; Marshall, Vivian M.; Warren Spring Laboratory, Stevenage, Herts., England (1977-07)
      The aim was to study the effect of visible and ultra-violet light on some members of the genus Thiobacillus. This genus is one more example of an aerobic organism which undergoes what appears to be the widespread phenomenon of light inhibition. Light inhibition of thiobacilli has been observed before and these other observations are presented. In the present study the effect of both visible and U-V light on three species was considered viz. T.thiooxidans, T.thioparus and T.ferrooxidans, the latter species being studied more thoroughly with respect to different intensities and wavelengths of light and the shielding effect of bacterial numbers and ferric iron. The photoreactivation of T.ferrooxidans cells after irradiation by U-V light was also examined, Using unfiltered, visible light, there was an inhibitory effect on all three of the thiobacilli irrespective of the energy source being used. When selected wavelengths were studied it was seen that the blue end of the visible spectrum was most inhibitory. A relationship between ferric iron concentration and protection from visible light» was shown and the beneficial protective effect of particulate suspensions was demonstrated. afforded by ferric iron and cell numbers was assessed. Photoreactivation of U-V irradiated cells by exposure to visible light showed that this phenomenon occurred using wavelengths of visible light which, by themselves, were inhibitory. Some practical implication of these findings are offered.

      Tuovinen, Olli H.; Department of General Microbiology, University of Helsinki, Malminkatu 20, SF-00100 Helsinki 10, Finland (1977-07)
      During growth on ferrous-iron Thiobactllus ferrooxidans assimilated sulphate into cellular material. Sulphate was rapidly bound by the cells and activated into adenosine 5'-sulphatophosphate prior to its reduction to sulphite and sulphide. The sulphate activation was mediated by the ATP-sulphurylase enzyme. The heterotrophic strain of 7. ferrooxidans assimilated sulphate via the same route. Sulphate was not assimilated by the bacteria during growth on thiosulphate. Adenosine 3'- phosphate 5'-sulphatophosphate was not formed and APS-kinase activity not detected in T. ferrooxtdans grown on ferrous-iron, thiosulphate or glucose. Thiosulphate oxidation was preceded by its cleavage to sulphide and sulphite and the outer S-atom of thiosulphate was also incorporated into cellular material. Tetrathionate was formed from thiosulphate by the thiosulphate-oxidizing enzyme but this pathway was not studied any further. The thiosulphate-oxidizing enzyme activity was not detected in iron-grown 7m. ferrooxtdans. Enzymes mediating the oxidation of thiosulphate linked to oxidative and substrate-level phosphorylation were present in 7. ferrooxtdans grown autotrophically on ferrous-iron or thiosulphate or heterotrophically on glucose.

      Kelly, D. P.; Eccleston, M.; Jones, Carol A.; Department of Environmental Sciences, University of Warwick, Coventry CV4 7AL, England; Glaxo Research Ltd., Sefton Park, Stoke Poges, Buckinghamshire, England (1977-07)
      Thiobacillus ferrooxidans was cultured in continuous flow chemostats on FeSO, at pHl.6 and K was subject to one or other of non-competitive product inhibition (NCP1) or 254% at pH2.5. On iron as the limiting substrate, growth predominatly competitive product inhibition (PCP1). This resulted in premature washout at dilution rates dependent on the concentration of FeSO, in the medium feed. Growth yield, apparent maintenance energy requirement and maximum specific growth rate ae were determined over a wide range of dilution rates for cultures subject to either NCPl or PCP1l. With tetrathionate as the limiting substrate no inhibition effects were observed in the chemostat pH2.5, although tetrathionate is an inhibitory substrate at some pH values. Yield, apparent maintenance and ee page eater For both substrates, true growth yield, Yo (g dry wt per g atom Fe or g mole KS 96 oxidized) was determined from the experimental data and enabled calculation 24 of the Yarp (g dry wt per mole ATP available from each substrate) and the probable ° + ° : . . . ATP requirement for NAD reduction during iron oxidation.