Marine environment microbial mats

Barbara, G. M. and Mitchell, J. G., Formation of 30- to 40-micrometer-thick laminations by highspeed marine bacteria in microbial mats, Appl. Environ. Microbiol., 62, 3985, 1996. 

Bebout, B.M., Fitzpatrick, M.W., and Paerl, H.W. (1993) Identification of the sources of energy for nitrogen fixation and physiological characterization of nitrogen-fixing members of a marine microbial mat community. Appl. Environ. Microbiol. 59, 1495-1503. 

Bebout, B. M., Paerl, H. W., Crocker, K. M., and Prufert, L. E. (1987). Diel interactions of oxygenic photosynthesis and nitrogen fixation (C2H2 reduction) in a marine microbial mat community. Appl. Environ. Microbiol. 53, 2353—2362. 

Nitrogen fixation in the marine environment occurs in benthic (sediments and microbial mats) and pelagic environments, and in salt marsh soils (see Carpenter and Capone, Chapter 4, this volume). Since very diverse microorganisms that span the Bacteria and Archaea domains of life can fix nitrogen, it is often difficult to ascertain which organisms are responsible for observed nitrogen fixation rates. Our discussion of the application of molecular approaches to the study of marine nitrogen fixation is brief because it has been reviewed extensively elsewhere (Carpenter and Capone, Chapter 4, this volume Foster and O MuUan Chapter 27, this volume Scanlan and Post, Chapter 24, this volume Paerl and Zehr, 2000 Zehr and Ward, 2002 Zehr et al., 2003). 

It is also possible to use antibody based approaches to assay the accumulation of enzymes involved in denitrification pathways in environmental samples. Ward and Cockroft (1993) developed antisera to nitrite reductase from a marine Pseudomonas stutzeri isolate, and assayed sediment, water column and microbial mat samples. The antibody identified nitrite reductase in mat samples and was more specific than a DNA probe designed against the same species (Ward and Cockroft, 1993). JVIore recently, other strains of denitrifiers have been isolated from both sediment and water column samples. Sequence information regarding the denitrifying genes should prove invaluable for future refinement of both sequence based approaches and the development of additional antibodies to denitrifiers important in the marine environment. 

Moisander, P. H., Shiue, L., Steward, G. F., Jenkins, B. D., Bebout, B. M., and Zehr, J. P. (2006). Apphcation of a niJH ohgonucleotide microarray for profiling diversity of N-2-fixing microorganisms in marine microbial mats. Environ. Microbiol. 8, 1721—1735. 

Visscher P. T., Gritzer R. E., and Leadbetter E. R. (1999) Low-molecular-weight sulfonates, a major substrate for sulfate reducers in marine microbial mats. Appl. Environ. Microbiol. 65, 3272-3278. 

Stromatolites and microbialites Stromatolites are "laminated lithified sedimentary growth structures that form by accretion, through the addition of new laminae away from the point or surface of accretion." They normally are made up of carbonate minerals and thought to have formed in a shallow water environment. Modern freshwater stromatolites are made up of algal and cyanobacte-rial filaments. In the marine environment they form microbial mats and columns. These comparisons led many scientists to believe that stromatolites found in the ancient record are biogenic in origin and that they are in fact microbialites. That is, they are sedimentary structures in which minerals are precipitated as either a by-product of microbial metabolisms or as a by-product of microbial decay. 

Noffke, N., Hazen, R., and Nhleko, N., 2003. Earth s earliest microbial mats in a siliclastic marine environment (2.9 Ga Mozzan Group, South Africa). Geology, 31, 673-6. 

In hot arid areas where the continental shelf meets the land, marine sabkha-type environments exist. For example, on theTrucial coast ofAbu Dhabi shallow marine carbonate sediments are reworked and bound by microbial mats. In the upper intertidal zone these mats... 

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