Microbial mats: A joint venture

doi:10.1016/0025-3227(93)90146-M

Marine Geology

Volume 113, Issues 1–2, July 1993, Pages 3-25

https://doi.org/10.1016/0025-3227(93)90146-M Get rights and content

Abstract

Microbial mats characteristically are dominated by a few functional groups of microbes: cyanobacteria, colorless sulfur bacteria, purple sulfur bacteria, and sulfate-reducing bacteria. Their combined metabolic activities result in steep environmental microgradients, particularly of oxygen and sulfide.

The driving force of most microbial mats is photosynthesis by cyanobacteria and algae. Subsequently, sulfate-reducing bacteria, using excretion-, lysis-, and decomposition products of cyanobacteria, produce sulfide by the dissimilatory reduction of sulfate. The sulfide can be reoxidized to sulfate by colorless and purple sulfur bacteria.

Colorless sulfur bacteria are chemotrophic organisms primarily oxidizing sulfide and other reduced forms of sulfur with oxygen to obtain energy. The oxidation of reduced sulfur species also provides reducing equivalents for the reduction of carbon dioxide to cellular carbon. The final product of sulfide oxidation is sulfate, with elemental sulfur, deposited extracellularly, as the principal intermediate.

Purple sulfur bacteria primarily are anaerobic phototrophic organisms using sulfide and other reduced forms of sulfur exclusively as the electron donor for the reduction of CO₂ to cellular carbon. Usually, sulfur is temporarily stored intracellularly. The final product of the oxidation of reduced forms of sulfur is sulfate.

The niches for these metabolically different groups of microbes in ecosystems with steep, often non-overlapping, gradients of oxygen and sulfide appear to be spatially separated. However, maximum viable counts of colorless sulfur bacteria and purple sulfur bacteria were both found in the top 5–10 mm of mats. Unexpectedly, viable counts of sulfate-reducing bacteria also peaked at the same depth horizon.

Sulfide is inhibitory for most oxygenic phototrophs. Sulfide production immediately underneath the layer of cyanobacteria might inhibit their growth, and, consequently, that of the entire ecosystem. In microbial mats this effect is minimized by the combined action of colorless and purple sulfur bacteria. Colorless sulfur bacteria generally have a much higher affinity for sulfide than purple sulfur bacteria, however, in microbial mats, their activity is hampered by low oxygen supply rates. As shown by pure culture studies with colorless sulfur bacteria, sulfide is incompletely oxidized when oxygen is short in supply, resulting in the production of potential electron donors for purple sulfur bacteria, such as sulfur, thiosulfate and polysulfides. In the absence of purple sulfur bacteria, colorless sulfur bacteria would not be able to maintain a low sulfide concentration due to shortage of oxygen, which in turn would result in increased inhibition of oxygenic photosynthesis.

It thus appears that the combined action of all four groups of functional microbes mentioned effectively results in optimal growth of these recent “stromatolites”.

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Microbial mats: A joint venture

Abstract

FEMS Microbiol. Ecol.

FEMS Microbiol. Ecol.

FEMS Microbiol. Ecol.

Neth. J. Sea Res.

FEMS Microbiol. Ecol.

FEMS Microbiol. Ecol.

FEMS Microbiol. Ecol.

Geochim. Cosmochim. Acta

Mar. Chem.

Precambrian Res.

FEMS Microbiol. Ecol.

FEMS Microbiol. Ecol.

Geochim. Cosmochim. Acta

FEMS Microbiol. Ecol.

The geochemical sulphur enrichment of recent organic matter by polysulfides in the Solar-Lake

Ancient stromatolites and microbial mats

Studies on the sulphur bacteria

Anal. Bot.

A novel type of energy metabolism involving fermentation of inorganic sulphur compounds

Nature

Chemolithotrophic growth of Desulfovibrio sulfodismutans sp. nov. by disproportionation of inorganic sulfur compounds

Arch. Microbiol.

Photoexcretion and fate of glycolate in a hot spring cyanobacterial mat

Appl. Environ. Microbiol.

Microbial mats in marginal marine environments: Shark Bay, Western Australia and Spencer Gulf, South Australia

Aerobic sulfate reduction in microbial mats

Science

Photosynthetic and behavorial versatility of the cyanobacterium Oscillatoria boryana in a sulfide-rich microbial mat

FEMS Microbiol. Ecol.

Oxygenic photosynthesis, anoxygenic photo-synthesis and sulfate reduction in cyanobacterial mats

Photosynthesis in cyanobacterial mats and its relation to the sulfur cycle: a model for microbial sulfur interactions

Sulfide dependent anoxygenic photosynthesis in the cyanobacterium Oscillatoria limnetica

Nature

Facultative anoxygenic photosynthesis in the cyanobacterium Oscillatoria limnetica

J. Bacteriol.

Hydroxide decomposition of DMSP to DMS

J. Geophys. Res. Lett.

Comparative functional ultrastructure of two hypersaline submerged cyanobacterial mats: Guerrero Negro, Baja California Sur, Mexico and Solar Lake, Sinai, Egypt

Interactions between phototrophic bacteria in sediment ecosystems

Hydrobiol. Bull.

Growth of the phototrophic purple sulfur bacterium Thiocapsa roseopersicina under oxic/anoxic regimens in the light

FEMS Microbiol. Ecol.

Growth and metabolism of the purple sulfur bacterium Thiocapsa roseopersicina under combined light/dark and oxic/anoxic regimens

Arch. Microbiol.

Aerobic respiration in sulfate-reducing bacteria

FEMS Microbiol. Lett.

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Nature

Photooxidation of cyanobacteria in natural conditions

Appl. Environm. Microbiol.

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J. Gen. Microbiol.

Anaerobic free-living protozoa: growth efficiencies and the structure of anaerobic communities

FEMS Microbiol. Ecol.

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Biostabilisierung von Sandwatten durch Mikroorganismen

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J. Bacteriol.

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Prediction of coastal sediment stability from photopigment content of mats of purple sulphur bacteria

Nature

Sulfate reduction in the presence of low levels of oxygen in water column of the Cariaco Trench

Limnol. Oceanogr.

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Science

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Geomicrobiol. J.

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Mar. Biol.

The sulfur cycle of a coastal marine sediment (Limfjorden, Denmark)

Limnol. Oceanogr.

A comparison of methods for the quantification of bacterial sulfate reduction in coastal marine sediments. I. Measurement with radiotracer techniques

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