摘要:

A carbon mass balance for photosynthesis, carbonate precipitation, out‐gassing, and respiration was calculated for a stream in Yorkshire, UK, from diurnal variations in total dissolved inorganic carbon (TDIC) and its isotopic composition. Complementary measurements of the photosynthetically available radiation, water temperature, pH, and dissolved calcium were taken at the springhead (site A) and downstream (site B). The difference in carbon isotope composition between the lower station and the springhead increases from a nighttime minimum of 3.4%oPDBto a daytime maximum of 7.1%o as a result of the biological and chemical processes affecting the dissolved inorganic carbon pool. The diurnal carbon balance input consisted of 194 mol carbon that entered via the spring (accounting for 94.6% of the budget) and 5.4% that was added by aquatic plant respiration. Of the output, 10.0% was fixed by photosynthesis, 12.2% was precipitated as CaCO3, and 9.4% was outgassed over 24 h. At midday 17.8% was fixed by photosynthesis, 15.2% was precipitated as CaCO3, and 8.5% was released by outgassing; 5.4% was still added by respiration. The δ13C value of TDIC showed a pronounced diurnal cycle and differed between sites A and B. The δ13C of cyanobacterial carbonate carbon was significantly higher than that of the travertine precipitated nearby and showed a downstream increase. These features relate the two types of calcareous deposits to the geochemical characteristics of the stream water and also to the biological community and its photosynthetic activity.

ISSN:0149-0451    

DOI:10.1080/01490459109385981

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Manganese‐reducing bacteria were isolated from a manganiferous silver ore mining site using enrichment procedures. The most rapid Mn(IV) reducer was identified asBacillus polymyxaand was designated as strain D1. Isolate D1 has no growth‐factor requirements and is mesophilic and neutrophilic. D1 respires glucose aerobically, under which conditions cyanide is bactericidal. Nonfermentable substrates such as lactate, acetate, citrate, and succinate cannot serve as sole carbon sources. D1 ferments glucose anaerobically, producing acetic acid, ethanol, and butanediol as major metabolic end products. Both anaerobic conditions and direct physical contact with pyrolusite (MnO2) particles were necessary for manganese reduction. Strain D1 is unique in that manganese serves as an ancillary electron acceptor during anaerobic fermentation. Kinetic experiments showed that D1 reduced manganese three to five times as rapidly as the widely studied Mn(IV)/Fe(III)‐reducing microorganismsShewanella putrefaciensMR‐1 andShewanella putrefa‐cienssp. 200. Strain D1 is capable of liberating silver via the reductive dissolution of refractory manganiferous ores.

ISSN:0149-0451    

DOI:10.1080/01490459109385982

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The dissolution of several normal and inverse ferrites byClostridiumsp. under anaerobic conditions occurs through enzymatic reductive dissolution of iron (direct action) and through organic acid metabolites (indirect action) produced by the bacteria. The iron in the octahedral coordination in normal spinel and in tetrahe‐dral coordination with the divalent metal in inverse spinel was solubilized by direct action of the bacteria. Although the extent of dissolution of the ferrites differed, there was no clear relationship between the type of ferrite (normal and inverse spinels) and the mechanism of dissolution. The inverse spinels containing cobalt and copper ferrites were solubilized by indirect and direct action, respectively. Among the normal spinels tested, manganese ferrite was solubilized by direct action, while zinc ferrite was solubilized by direct and indirect action. Nickel ferrite was not solubilized by direct or indirect action. Cobalt, copper, manganese, nickel, and zinc ferrites had no effect on the growth of the bacteria. Dissolution of toxic metals and iron from fossil and nuclear energy wastes containing ferrite compounds by anaerobic microbial activity could be significant.

ISSN:0149-0451    

DOI:10.1080/01490459109385983

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Samples of stromatolites, microbial mats, and sediments from four saline lakes (approximate seasonal salinity ranges 20–220%o) in Western Australia were used to establish enrichments for elective cultures of aerobic and anaerobic denitrifying chemolithoautotrophs that could grow with thiosulfate as sole energy source. Organisms of these types were obtained from all sources tested. Twenty‐four pure cultures were isolated, all of which were gram‐negative, rod‐shaped bacteria exhibiting a considerable diversity of metabolic capability. Isolation of these obligate and facultative sulfur‐oxidizing chemolithotrophs from the stromatolite and mat habitats indicates the possibility that these rod‐shaped bacteria contribute to the oxidative phase of the sulfur cycle in these habitats, in addition to oxidation by phototrophs orBeggiatoa. Only four of the pure cultures could grow without salt, but all 24 showed significant halophily, some tolerating 3 M NaCl. Three novel isolates of NaCl‐dependent, thiosulfate‐oxidizing, aerobic and denitrifying obligate chemolithotrophs are described. In addition, a facultatively heterotrophic halophilic strain growing either methylotrophically on methylamine or chemolithotrophically on thiosulfate aerobically or with anaerobic denitrification was found.

ISSN:0149-0451    

DOI:10.1080/01490459109385984

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The oldest sedimentary rocks on Earth, the 3.8‐Ga Isua Iron‐Formation in southwestern Greenland, are metamorphosed past the point where organic‐walled fossils would remain. Acid residues and thin sections of these rocks reveal ferric microstructures that have filamentous, hollow rod, and spherical shapes not characteristic of crystalline minerals. Instead, they resemble ferric‐coated remains of bacteria. Modern so‐called iron bacteria were therefore studied to enhance a search image for oxide minerals precipitated by early bacteria. Iron bacteria become coated with ferrihydrite, a metastable mineral that converts to hematite, which is stable under high temperatures. If these unusual morphotypes are mineral remains of microfossils, then life must have evolved somewhat earlier than 3.8 Ga, and may have involved the interaction of sediments and molecular oxygen in water, with iron as a catalyst. Timing is constrained by the early in fall of planetary materials that would have heated the planet's surface.

ISSN:0149-0451    

DOI:10.1080/01490459109385985

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Peter Westbroek. 1991.Life as a Geological Force. Dynamics of the Earth. W. W. Norton & Company, New York. 240 pp. U.S. $21.95 (cloth).

ISSN:0149-0451    

DOI:10.1080/01490459109385986

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490459109385987

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490459109385980

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor