Microorganisms and the natural environment

Microorganisms are potentially capable of carrying out chemical transformations of organic and inorganic materials on a large scale. Their activity involves many reactions which may participate in geobiological formations. The microorganisms are affected by the environment and the environment has an influence on the microbial population. The presence or absence of certain compounds is critical for microbiological growth. As no pure strain of organisms exists in nature in complete isolation, it is necessary to consider the effect of individual biological systems on each other. Microorganisms are known for their ability to adjust themself to changes in the environment. This adjustment can demonstrate in reversible non-heriditary adaptive processes or more permanent heriditary forms, mutation.

---

Zusammenfassung Mikroorganismen sind in der Lage, organische und anorganische Verbindungen in großem Maßstab umzuformen. Ihre Teilnahme an geologischen Prozessen spielt möglicherweise eine große Rolle. Mikroorganismen werden durch ihre Umwelt beeinflußt und wirken ihrerseits wieder zurück auf diese. Die An- oder Abwesenheit bestimmter Verbindungen wirkt entscheidend auf das mikrobiologische Wachstum. Da einzelne Organismen in der Natur nicht isoliert existieren können, müssen die Wechselwirkungen biologischer Systeme betrachtet werden. Die Fähigkeit sich an Veränderungen der Umwelt anzupassen, ist eine bekannte Fähigkeit der Mikroorganismen. Diese Anpassungsfähigkeit kann in reversiblen oder in nichtreversiblen erblichen Veränderungen (Mutationen) zum Ausdruck kommen.

     

Biological and abiological processes in a simulated sedimentary system

A simulated sedimentary system, capable of being controlled and monitored for a considerable length of time without undue disturbance, has been assembled and applied to specific problems of the genesis of stratiform Pb‐Zn ore deposits. Results have been obtained relevant to: (i) the concentration of Pb and Zn from brines to underlying sediments; (ii) the behaviour of microorganisms in metal‐rich, highly saline environments; (iii) the precipitation diagenesis of calcium and magnesium carbonates; and (iv) the diagenesis of organic matter.

The experiment has demonstrated the feasibility of simulating a complex sedimentary environment in the laboratory and has indicated the potential of such systems for the investigation of geobiological problems.     

The transformation of nesquehonite into hydromagnesite

Nesquehonite, synthesized in the laboratory, can be readily altered to hydromagnesite via an intermediate phase which is morphologically similar to hydromagnesite. This intermediate phase exhibits an X-ray pattern similar to that of the newly discovered mineral dypingite. The transformation is accompanied by a large loss of water, with resulting increase in magnesium. Chemical analysis indicates that dypingite occurs in a range of phases from slightly altered nesquehonite to hydromagnesite. The alteration of nesquehonite at 52°C is exceedingly rapid, explaining why hydromagnesite is the more common hydrate in nature. This formation of a new mineral via the aqueous phase also occurs in the solid state at temperatures in excess of 100°C, as indicated by differential thermal analysis and thermal gravimetric analysis.     

Banded sulphide ores: The experimental production of monomineralic sulphide bands in sediments

Summary Banded sulphide ores of the McArthur River type are characterized by large numbers of conformable, monomineralic sulphide bands. These appear to have formed prior to consolidation of the host sediments. This paper describes a series of laboratory experiments designed to test the possibility that the bands could have been generated by the migration of metal, sulphide, and possibly carbonate ions through unconsolidated sedimentary materials or slowly settling suspensions. It is concluded that ionic migration processes probably occur during the formation of these banded sulphide ores, in conjunction with the deposition of metalliferous mud layers.

---

Zusammenfassung Die Schichten der Schwefelerze des Typs vom McArthur Fluß sind charakterisiert durch eine Vielzahl von Parallelen, die ausschließlich aus Schwefelschichten bestehen. Diese scheinen sich vor der Verfestigung der Sedimentenmasse gebildet zu haben. Dieser Aufsatz beschreibt eine Reihe von Laboratoriums-Experimenten, die die Möglichkeit untersuchen sollten, ob diese Schichten entstehen konnten durch die Wanderung von Metall-, Schwefeloder möglicherweise Kohlensäure-Ionen durch noch nicht verfestigtes oder sich langsam setzendes Sedimentmaterial. Es wird daraus gefolgert, daß wahrscheinlich während der Formation dieser Schwefelerz-Schichten in Verbindung mit der Ablagerung metallhaltiger Schlammlagen Ionenwanderungen stattfinden.

     

Simulation of sedimentary Ore-Forming processes: Concentration of Pb and Zn from brines into organic and Fe-bearing carbonate sediments

An experimental sedimentary system comprising a tank of 4 m³ capacity equipped for monitoring chemical, mineralogical, and biological changes has been used to investigate the mechanisms by which Pb and Zn may be removed from solution in sulphide-deficient brines and concentrated in sediments. In the experimental system, Pb and Zn together with ferric hydroxides (probably lepidocrosite), organic matter, and a variety of calcium and magnesium carbonate phases, were deposited from an aerobic, highly saline, Pb and Zn-rich brine supporting a vigorous growth of the green alga Chlorococcus sp. The resultant organic and Febearing carbonate sediments contained Pb up to 0.5% and Zn up to 1.0%. Overall concentration factors compared with the overlying brine were in the range 200 to 300. Pb was removed from solution mainly by coprecipitation with carbonate phases; the Pb content of the two major carbonate phases decreasing in the order aragonite to monohydrocalcite. Zn was deposited in association with the Fe-bearing minerals. Complexing of Pb and Zn by organic matter, and the direct precipitation of Pb and Zn carbonates and/or hydroxides made, at most, a secondary contribution to the overall concentration process.     

The concentration of Cu(II), Pb(II) and Zn(II) from aqueous solutions by particulate algal matter

Experimental studies of the reactions of Cu(II), Pb(II), and Zn(II) in aqueous solutions with organic matter derived from fresh samples of the green filamentous algae Ulothrix spp. and the green unicellular algae Chlamydomonas spp. and Chlorella vulgaris show that, under suitable conditions, a significant proportion of the metals is removed from solution by sorption onto the particulate organic matter of the algal suspension.The metal sorption is strongly suppressed by H⁺ but is only marginally influenced by the proportion of whole cells in the suspension and by complexing of metals in solution by the soluble organic matter. The presence of relatively small amounts of the cations Na⁺ and Mg²⁺ in solution reduces the sorption of Zn(II) to near zero, but Pb(II) and Cu(II) sorption occurs to an appreciable extent even in strong brines. This may be a means for the selective precipitation of Pb(II) from brines rich in Pb(II) and Zn(II).Metal “saturation” values indicate that particulate algal matter of the type used in these experiments could sorb sufficient quantities of metal to form an ore deposit if a weight of organic matter of similar order of magnitude to that of the inorganic sediments in the deposits was available. However, the metal sorption is an equilibrium reaction, and the experimentally determined “enrichment factors” suggest that the “saturation” values could be approached only in solutions whose metal contents were initially at least two orders of magnitude above those of normal seawater.