Anaerobic dark energy generation in the mat-building cyanobacterium Microcoleus chthonoplastes
Microbial mats are characterized by strong diel fluctuations in oxygen concentration which to a large extent can be attributed to the physiology of the cyanobacteria (Revsbech et al. 1983). In the light these organisms carry out oxygenic photosynthesis resulting in oxygen supersaturation of the mat. In the dark the primary mode of energy generation is respiration of endogenous glycogen (Smith 1982). However, in well-established microbial mats diffusion of oxygen in the mat will normally be insufficient to cover the demands and, as a result, the mat will turn anoxic. Evidently, the cyanobacteria have to switch to another way of energy generation in order to survive. Organisms isolated from such habitats were investigated for their mechanisms of anaerobic dark energy generation and turned out to be capable of fermentation. Forinstance, Oscillatoria limnetica, which thrives in the sulfide-rich hypolimnion of Solar Lake (Sinai) displays a homolactic fermentation using endogenous storage glucan as the substrate (Oren and Shilo 1979). Alternatively, this organism is capable of anaerobic respiration using elemental sulfur as the electron acceptor. Another mat-building cyanobacterium, Oscillatoria limosa, carries out a heterolactic and homoacetic fermentation simultaneously (Heyer et al. 1989). In the presence of elemental sulfur this organism stops producing hydrogen and sulfide is produced instead. Oscillatoria terebriformis was isolated from a hot-spring microbial mat and produces lactate form exogenous glucose or fructose (Richardson and Castenholz 1987).
KeywordsFermentation Sulfide Lactate Respiration Pyruvate
Unable to display preview. Download preview PDF.
- Ehrlich HE (1990) Geomicrobiology (2nd ed) Marcel Dekker Inc, New York and Basel, pp 283–346Google Scholar
- Moezelaar R, Bijvank SM, Kuiper F, Stal U (1992) Anaerobic dark energy generation in cyanobactena. Abstract 6th International Symposium onMicrobial Ecology, Barcelona SpainGoogle Scholar
- Revsbech NP, Jøgensen BB, Blackburn TH, Cohen Y (1983) Microelectrode studies of the photosynthesis and O2, H2S and pH profiles of a microbial mat. Limn OceanogrGoogle Scholar
- Richardson LL, Castenholz RW (1987) Enhanced survival of the cyanobacterium Oscillatoria terebriformis in darkness under anaerobic conditions. Appl Environm Microbiol 53: 2151–2158Google Scholar
- Smith AJ (1982) Modes of cyanobacterial carbon metabolism. In: Carr NG, Whitton BA (eds) The biology of cyanobacteria. Blackwell Scientific Publications, Oxford, pp 47–85Google Scholar
- Stal LJ, Krumbein WE (1986) Metabolism of cyanobacteria in anaerobic sediments. Actes de Colloques 3 (2ième Colloque International de Bacteriologie marine, Brest, 1–5 Octobre 1984), pp 301–309Google Scholar