ISSN:0149-0451    

DOI:10.1080/01490450050023782

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Although many studies on fungi and geological processes have been published in recent years, books and congress proceedings on geomicrobiology focus mainly on prokaryotes and algae. Therefore, it is the aim of this review to summarize data on the fungal impact on geological processes. These processes include the alteration and weathering of rock and minerals, the accumulation of metals, and the conversion of fossil organic carbon. Fossil records and fungi in subsurface environments are also discussed. This article especially emphasizes the role of epi- and endolithic black meristematic fungi, discussing their deteriorative potential on rock as well as their taxonomy and phylogeny. Moreover, the impact of fungi on weathering of monuments and building materials is described and new methods to study fungi-material interactions are presented. The data summarized here show that "geomycology" is a highly interesting discipline in view of basic geological research, as well as biotechnological application.

ISSN:0149-0451    

DOI:10.1080/01490450050023791

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Acidic biofilms present on cave walls in the sulfidic region of the Frasassi Gorge, Italy, were investigated to determine their microbial composition and their potential role in cave formation and ecosystem functioning. All biofilm samples examined had pH values < 1.0. Scanning electron microscopy of the biofilms revealed the presence of various filaments and rods associated in large clusters with mineral crystals. Qualitative energy-dispersive x-ray analysis was used to determine that the crystals present on the cave walls, associated with the microbial biofilm, were composed of calcium and barium sulfate. Ribosomal RNA-based methods to determine the microbial composition of these biofilms revealed the presence of at least two strains of potential acidophilic, sulfur-oxidizing bacteria, belonging to the generaThiobacillusandSulfobacillus. An acid-producing strain ofThiobacillussp. also was obtained in pure culture. Stable isotope ratio analysis of carbon and nitrogen showed that the wall biofilms are isotopically light, suggesting that in situ chemoautotrophic activity plays an important role in this subsurface ecosystem.

ISSN:0149-0451    

DOI:10.1080/01490450050023809

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

The shell of the bivalve Montacuta ferruginosa is covered with a rust-colored biofilm. This biofilm includes filamentous bacteria and protozoa encrusted with a mineral, rich in ferric ion and phosphate. The aim of this research was to study two possible microbial iron precipitation pathways in the biofilm, namely, microbial iron oxidation and microbial degradation of organic Fe(III) complexes. The iron-oxidizing activity was assayed spectrophotometrically by monitoring the formation of the dye Wurster blue in biofilm extracts. Iron-oxidizing activity was effectively detected in extracts obtained by oxalic acid treatment of biofilm fragments. Extracts obtained without oxalic acid treatment, heated extracts, or extracts supplemented with HgCl 2 did not show any activity. This suggests that an iron-oxidizing factor (IOF), possibly an enzyme, coprecipitated with the mineral. Additional information gathered by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, gel-filtration chromatography, and UV spectrophotometry indicate that the IOF would be a small peptide or glycopeptide (1,350 Da). Microbial degradation of organic Fe(III) complexes was assayed with biofilm fragments incubated in a medium containing ferric citrate. Analysis of the supernatants after various intervals revealed that the complex was degraded by living microorganisms much faster than in the heat-killed negative controls. We conclude that ferric iron precipitation in the biofilm may proceed by way of microbial Fe(II) oxidation as well as microbial degradation of organic Fe(III) complexes.

ISSN:0149-0451    

DOI:10.1080/01490450050023818

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

The oxidation of pyrite in a mine tailings heap in Romania was studied to clarify the contribution of acid drainage to the death of vegetation on the eastern slope of the tailings. Where vegetation died, pyrite oxidation was detected as deep as 1 m, as indicated by the brownish color of the samples. At these sitesThiobacillus ferrooxidans-like bacteria were present with cell counts of 10 3g andThiobacillus thiooxidans-like bacteria occurred with cell counts of 10 g. At the western slope, where vegetation thrived, cell counts of < 10 g were measured. Correspondingly, leaching activity and concentrations of pyrite oxidation products such as sulfate and elemental sulfur were markedly higher on the eastern slope than on the western slope. These differences were mainly a result of the high acid neutralization potential in the material from the western slope, which kept the pH in a neutral range allowing for plant growth. In contrast, on the eastern slope with its low acid neutralization potential, the pH dropped to 3 to 4, increasing the solubility of phytotoxic elements. The death of the vegetation could result from the lowered pH and the increased amount of toxic elements, or, most likely, a combination of these factors.

ISSN:0149-0451    

DOI:10.1080/01490450050023827

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Population densities of anaerobic Fe(III)-reducing bacteria (FeRB) and aerobic heterotrophs were inversely correlated in the surficial (0-2 cm) layers of Sapelo Island, Georgia, salt marsh sediments. In surficial sediments where densities of aerobic heterotrophs were low, the density of culturable FeRB correlated positively with the concentration of amorphous Fe(III) oxyhydroxides extractable by ascorbate. High FeRB densities and a decrease with depth of ascorbate-extractable Fe(III) were observed in the upper 6 cm of a tidal creek core. Culturable sulfate-reducing bacteria (SRB) and SRB-targeted rRNA signals were also detected in the upper 6-cm depth. The disappearance of FeRB below 6 cm, however, coincided with a large increase in the abundance of SRB. Thus, when FeRB are not limited by the availability of readily reducible amorphous Fe(III) oxyhydroxides, FeRB may outcompete SRB for growth substrates.Shewanella putrefaciens- andGeobacteraceae-targeted rRNA signals were at or below detection limits in all sediment samples, indicating that these FeRB are not predominant members of the active FeRB populations. The ubiquitous presence of FeRB at the sites studied challenges the traditional view that dissimilatory Fe(III) reduction is not an important pathway of organic carbon oxidation in salt marsh sediments.

ISSN:0149-0451    

DOI:10.1080/01490450050023836

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490450050023845

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor