The inhibition of microorganisms by heavy metals

This paper examines the effects of heavy metals on microorganisms in the aqueous environment; the mechanisms by which metals may exert toxic effects on microbes and the factors affecting microbial response to metals; the ways in which microbial activity may alter the metal balance of an environment and the modifications produced in microbes by heavy metal ions; the effects of the toxic copper ion on the growth, respiration, magnesium content, cytochrome synthesis and osmotic sensitivity of some organisms studied in the laboratory; and the feasibility of the participation of microbes in geochemical processes considering the demonstrable resistance to toxic metals by some bacteria and the fact that natural environments may contain high levels of metals rendered less toxic by binding to natural chelating compounds.

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Zusammenfassung In dieser Arbeit werden verschiedene Wirkungen von Schwermetallen auf Mikroorganismen in wäßrigem Milieu untersucht. Es wird gezeigt, daß Schwermetalle toxische Wirkungen auf Mikroorganismen ausüben können und welche Faktoren die Reaktionen von Mikroben gegenüber Metallen bestimmen. Weiter wird beschrieben, wie die Mikrobenaktivität das Metallgleichgewicht in einem gegebenen Milieu verändern und beeinflussen kann und wie andererseits Änderungen in den Mikroben selbst durch Schwermetall-Ionen hervorgerufen werden. Dabei wird besonders die Wirkung des toxischen Kupfer-Ions auf das Wachstum, die Atmung, den Magnesiumgehalt, die Cytochromsynthese und die osmotische Empfindlichkeit einiger Mikroorganismen dargestellt. Die Anwesenheit von Mikroben bei geochemischen Prozessen wird unter Berücksichtigung der Resistenz einiger Bakterien gegenüber toxischen Metall-Ionen diskutiert. Dabei spielt die Tatsache eine große Rolle, daß durch Chelatbildung die Schwermetall-Ionen in der natürlichen Umwelt der Mikroorganismen ihre toxische Wirkung verlieren.

     

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.

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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.

     

Comparison of formalisms for attributing responsibility for climate change: Non-linearities in the Brazilian Proposal approach

The Brazilian Proposal for setting emission targets is based on attribution of responsibility for climate change due to historical emissions of greenhouse gases. Numerical models are used to calculate the temperature increase due to past emissions of greenhouse gases, and to partition the warming among nations or groups of nations. When non-linearities are included in the models, there are different approaches that can be used to partition global warming into regional or national contributions, and the methods give different results. Here we describe and compare seven different approaches for attributing indicators of climate change for regional emissions. We illustrate these methods with simple and realistic examples, and discuss their characteristics. Of the seven attribution methods discussed, two (the marginal and time-sliced methods) are seen as best-suited for attribution of climate change. Differences between attribution methods are typically up to a few percent for the examples considered, with differences greatest for regions with emission time histories that differ most from the average. The range due to choice of attribution method in the relative contributions of temperature change in 2000 is typically around one fifth of the range generated when other choices such as different models, forcing agents, feedbacks and other assumptions are included.     

A possible boundary condition in bacterial sulfur isotope fractionation

The sulfur isotopic effect (δ³⁴S) shown by batch cultures of six species of sulfate-reducing bacteria was ?14.6%. (S.D.4.1).Fractionation appeared to be independent of electron donor, temperature (between 35 and 55°) and the extent of sulfate reduction.     

Reversibility of bacterial sulfate redaction and its relevance to isotope fractionation

Using H₂³⁵S, anaerobic oxidation of sulfide to sulfate by D. desulfuricans was demonstrated. This was probably the result of a reversal of the sulfate reduction pathway.