Heterocystous cyanobacterium

Figure 10.5 Scheme of electron transfer in a filamentous heterocystous cyanobacterium. 

El-Shehawy, R., Lugomela, C., Ernst, A., and Bergman, B. (2003). Diurnal expression of hetR and diazocyte development in the filamentous non-heterocystous cyanobacterium Trichodesmium erythraeum. Microbiology-SGM. 149, 1139—1146. 

Ohki, K., Zehr, J. P., Falkowski, P. G., and Fujita, Y. (1991). Regulation of nitrogen-fixation by different nitrogen sources in the marine non-heterocystous cyanobacterium Trichodesmium sp. NIBB 1067. Arch. Microbiol 156, 335-337. 

Fredriksson, C., and Bergman, B. (1997). Ultrastructural characterization of cells speciahzed for nitrogen fixation in a non-heterocystous cyanobacterium, Trichodesmium. Protoplasma 197, 76—85. 

Wyman, M., Zehr, J. P., and Capone, D. G. (1996). Temporal variability in nitrogenase gene expression in the diazotrophic filamentous non-heterocystous cyanobacterium Trichodesmium thie-bautii. Appl. Environ. Microbiol. 62, 1073—1075. 

Some of the earliest reports of planktonic symbiosis describe the association of a heterocystous cyanobacterium, Richelia intracellularis, with various diatoms, including Rhizosolenia (Ostenfeld and Schmidt, 1901), Hemiaulus spp. and Guinardia cylindms (Siindstrom, 1984 Taylor, 1982 ViUareal, 1992). Up to 13 different species of Rhizosolenia have been reported with Richelia symbionts however some authors (Soumia, 1970 Siindstrom, 1984) questioned the host identity, argued that many were misidentified, and proposed that most of the Rhizosolenia species were just varieties of R. clevei. 

Lemmerman (1905) was one of the first to depict the unique association of another heterocystous cyanobacterium, Calothrix rhizosoleniae, attached to the spines of a Chaetocoeros compressus diatom. Norris (1961) noted that the cyanobionts only attach transversely to the intercellular spaces of the diatom with the heterocyst closest to the host diatom. Others report the same symbiont as R. intracellularis (G6mez et al., 2005 Janson et ai, 1999 Karsten, 1907 Norris, 1961), thus there is... 

A few other symbioses have been described between a heterocystous cyanobacterium of similar morphology to Ambaena and Nostoc cells residing with Coscinodiscus sp. and Roperia tessellata diatoms, respectively (Taylor, 1982 Villareal, 1992). Interestingly, Carpenter (2002 Plate Ilb) found the cyanobionts of a Coscinodiscus sp. diatom collected near Zanzibar similar in cell morphology and diameter to a unicellular Synechocystis sp. 

Rai, A. N., Borthakur, M., and Bergman, B. (1992). Nitrogenase derepression, its regulation and metabolic changes associates with diazotrophy in the non-heterocystous cyanobacterium Plectonema boryanum PCC 73110. J. Gen. Microbiol. 138, 481-491. 

Saino, T., and Hattori, A. (1982). Aerobic nitrogen fixation by the marine non-heterocystous cyanobacterium Trichodesmium (OsciUatoria) spp. Its protective mechanism against oxygen. Mar. Biol. 70, 251-254. 

Houchins, J.P. and Burris, R.H. (1981a). Occurrence and localization of two distinct hydrogenases in the heterocystous cyanobacterium Anabaena sp. strain 7120. J. Bacteriol 146,209-214. 

Llama, M.J., Serra, J.L., Rao, K.K. and Hall, D.O. (1979). Isolation and characterization of the hydrogenase activity from the non-heterocystous cyanobacterium Spirulina maxima. FEBS Lett. 98, 342-346. 

Pkormidium laminosum is a filamentous thermophilic cyanobacterium, non-heterocystous, that can fix nitrogen under microaerophilic conditions. Anabaena azollae is a species of nitrogen Hxing, heterocystous cyanobacterium which is usually found as a symbiont of aquatic ferns Azolla. 

---