摘要:

Cocci of phosphate‐sequestering bacteria were found in the water column off Namibia where Recent phosphorites are forming. Furthermore, recent work on bacterial populations in the Benguela upwelling system shows that the population that occurs during non‐upwelling periods is dominated by phosphate‐sequestering bacteria(Pseudomonas, Acinetobacter,). These are the bacteria that effect phosphorus removal from biological activated sludge systems in wastewater treatment plants. Our conclusion is that these bacteria act in a similar manner in natural systems as they are known to do in wastewater treatment plants and that they play an active role in phosphate concentration and phosphorite genesis.

ISSN:0149-0451    

DOI:10.1080/01490459309377935

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Pluricentimetric colonies ofNostoc parmelioidesexhibit two types of calcifications: (1) rhombs, either isolated, chains, or grouped in elongate masses around sheathless trichomes in the interior of the colony; or (2) discs with fibroradiating and concentric fabric, in which radial elements are elongate, stacked, upside‐down, bell‐shaped monocrystals, with concentric laminations in cross section. The discs could be the result of a very peculiar calcification of an epiphytic organism, probably a bacterium. These structures can be referred to as bacterial microstromatolites.

ISSN:0149-0451    

DOI:10.1080/01490459309377936

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

High concentrations of aliphatic organic acids (∼1 mM acetate) in groundwater from a petroleum hydrocarbon‐contaminated aquifer are associated with elevated concentrations (∼30 μg/L) of lead. This pattern suggests that toxic effects of lead have contributed to the observed accumulation of organic acids. This hypothesis was tested by examining the effects of lead on carbon mineralization and organic acid accumulation in petroleum‐contaminated aquifer material incubated under different terminal electron‐accepting conditions. Lead was found to inhibit fermentation (organic acid accumulation) as well as microbial carbon mineralization (CO2or CH4production) under aerobic, nitrate‐reducing, sulfate‐reducing, and methanogenic conditions. Thus Pb does not appear to be the primary cause of organic acid accumulation at the field site. Rather, substantial accumulation of aliphatic organic acids occurred only in methanogenic microcosms, and only trace amounts of acetic acid were detected in sulfate‐reducing microcosms. This pattern parallels field observations in which high organic acid concentrations were detected in methanogenic zones, but only low concentrations of acetic acid were detected in sulfate‐reducing zones.

ISSN:0149-0451    

DOI:10.1080/01490459309377937

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The unsaturated (vadose) zone in arid and semiarid regions can be >100 m thick and may receive little or no moisture recharge from the surface. The microbiological properties of the vadose zone are of interest because of the potential for microorganisms to impact the fate and transport of contaminants in these environments. At numerous sites in the western United States, large volumes of wastewater or process water have been disposed of directly to the surface or shallow subsurface and have subsequently migrated through the vadose zone to the groundwater. The purpose of this study was to determine and compare the microbial properties of pristine and impacted vadose zone sediments. Vadose zone sediments from depths ranging from 24 to 90 m were obtained from 3 boreholes drilled on the Hanford site in south‐central Washington State. One borehole was located in a pristine area and the other two were located in areas where wastewater had been disposed of directly to the surface and near subsurface. An open‐flow centrifugation method was used to determine unsaturated hydraulic conductivity for the sediments, allowing construction of characteristic curves relating the hydraulic conductivity (K) to the volumetric water content (8). By comparing the volumetric water content of sediments obtained prior to centrifugation to their water content over a range of K(θ), it could be determined which vadose zone samples had been subjected to artificial recharge. Elevated concentrations of nitrate and the presence of carbon tetrachloride in vadose sediments were also used as indicators that sediments had been impacted by past waste disposal practices. Those vadose zone paleosol samples receiving artificial recharge had higher populations of culturable bacteria (log 1.0–6.6 CFU g−1) and were able to mineralize organic substrates more rapidly than a pristine paleosol. Thus, the in situ microbial population was stimulated by increased moisture from artificial recharge and/or from contaminants. In contrast, culturable bacteria were near or below detection in unimpacted fluvial and flood sands. The few culturable microorganisms that were present in unimpacted vadose sediments were either associated with the sediments at the time of deposition or transported from the surface during the last major proglacial flood, approximately 13,000 years ago.

ISSN:0149-0451    

DOI:10.1080/01490459309377938

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Samples of water and sediment from a marine, shallow hydrothermal vent in Vulcano (Eolian Islands, Italy) were collected during an annual cycle of observations in order to study the occurrence and distribution of aerobic, chemolithotrophic, sulfur‐oxidizing bacteria that can grow with thiosulfate as sole energy source. Twenty‐five pure cultures were isolated, all of which were gram‐negative, rod‐shaped bacteria. They were tested for morphological, cultural, biochemical characteristics and for antibiotic sensitivity. The results were arranged in a data matrix and analyzed by Sokal and Michener's similarity coefficient and clusterized according to variance. Three distinct clusters, represented, respectively, byThiobacilius‐like bacteria isolated directly from the vent‐water,Pseudomonas‐like heterotrophs from sediment in the immediate vicinity of the vent, andThiobacterium‐like forms from both water and sediment samples, were distinguished according to their ecophysiological properties. The presence of obligate and facultative sulfur‐oxidizing bacteria in the sulfide‐containing hydrothermal water suggests that the rod‐shaped bacteria isolated from the site contribute to the oxidative phase of the sulfur‐cycle in this habitat. No filamentous forms were encountered. The chemosynthetic activity of sulfur‐oxidizing bacteria adds to the primary productivity of the photosynthetic microorganisms living in the water column and at the sediment surface.

ISSN:0149-0451    

DOI:10.1080/01490459309377939

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490459309377940

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490459309377934

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor