摘要:

Microbial communities of stratified phototrophic bacteria in laminated intertidal sediments north of Estuary El Puente, near San Carlos, Baja California Sur, Mexico,‐were studied. This study describes the macroscopic and microscopic characteristics of the mats, including their annual growth. The mats were located in and along meandering mangrove‐lined tidal channels. Their thickness ranged from 0.5 to 25 cm. Square‐meter areas of polygonal mats were detected in several ponds infiltrated by sea water. The principal microbial community of the upper surface of various morphotypes of microbial mats was identified as cyanobacteria belonging to the generaMicrocoleus, Lyngbya, Phormidium,andOscillatoria.Other cyanobacte‐rial genera such asPseudanabaena, Spirulina, Synechococcus,andGloeocapsa,as well as many unidentified diatoms, were also present but at lower population densities. The second inward reddish layers of the microbial mats contained similar cyano‐bacterial genera plus anoxygenic phototrophic bacteria belonging to the generaChloroflexus, Thiocapsa, Chromatium, Prosthecochloris, Rhodopseudomonas,andChlorobium,as well as several unidentified bacteria. In situ measurements on the growth of the mats, from intermittent tide sites, showed an annual buildup of two layers: green and reddish. These layers corresponded to a vertical growth of 1.4±0.27 mm/year. Permanently submerged mats did not show vertical growth during the same period of time.

ISSN:0149-0451    

DOI:10.1080/01490459009377881

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Microscopic observations of calcrete soil samples in semiarid environments from Israel reveal a particular vesicular microfabric. The calcrete horizon is indurated but highly porous and all the pores are coated with a gray layer (quasi‐coating) of secondary calcium carbonate. Two kinds of needles are found inside the pores: thin and regular needles (calcite), and filaments with very sharp spikes that are of fungal origin. Analysis of the proportions of C, O, and Ca were made with an E.D.S. microprobe connected with a scanning electron microscope to distinguish calcite (CaCO3) from calcium oxalate (CaC2O4) and to differentiate inorganic from organic influences. Under biological control, calcium oxalate coexists with calcium carbonate; both contribute to rock diagenesis. In the pores, biological activity promotes a complex cycling of calcium leading to recementation of the matrix and further lithification. Thus, this kind of calcrete is due to geological evolution as much as to biochemical control.

ISSN:0149-0451    

DOI:10.1080/01490459009377882

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Mixed cultures derived from Boston Harbor sediments, which gave evidence of methylating tin compounds, yielded two isolates, each aBacillussp., which methylated CH3SnCl3to form (CH3)3SnX in coculture. Neither organism alone gave evidence of methylation. SnCl4and (CH3)2SnCl2were not methylated. Transfer of either organism to filtered medium containing CH3SnCl3in which the other had grown did not lead to methylation. Therefore methylation by the coculture is not simply a matter of cross‐feeding.

ISSN:0149-0451    

DOI:10.1080/01490459009377883

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Three hundred and thirty‐five strains of heterotrophic bacteria, isolated from various metal‐containing ores, were tested in submerged culture for their capacity to leach copper and antimony from tetrahedrite‐containing dolomitic ore (particle size <0.1 mm; Schwaz, Austria). Experiments showed that after 8 days of incubation, it was possible to differentiate between active and inactive strains. Maximum extraction values for copper (1.0%) and antimony (1.6%) were achieved withPseudomonasspp. after 8 days. Final pH values were 6.8 in sterile controls and slightly alkaline (up to pH 8.3) in inoculated flasks. Starch and glutamine (C/N ratio of 50:1) proved to be the best carbon and nitrogen sources for growth. Variation of the C/N source resulted in only a very slight increase in the rates of extraction for copper and antimony. Not even 24 h preliminary incubation of a culture before the ore was added improved metal extraction.

ISSN:0149-0451    

DOI:10.1080/01490459009377884

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490459009377885

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490459009377886

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490459009377887

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490459009377880

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor