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Name derivation:
Oscillation -- various movements of many strains can include trichome bending, rotation, and reversible translational "gliding" motion. Movements may be due to contractile proteins in the cell walls in combination with signalling between cells along the trichome. Taxonomic revisionists (Anagnostidis and Komarek 1998; Suda et al. 2003) argue for the name Planktothrix to replace Oscillatoria, at least for the bloom-forming plankton strains. Currently Planktothrix may be thought of as a synonym for Oscillatoria. As a non-molecular biologist my scant reading of molecular results suggests there is ambiguous or no reason to separate some Oscillatoria into what seems only a habitat-based (water-bloom-forming) new name.
Classification:
Oscillatoria Vaucher ex Gomont 1892; 60 of 1,052 species descriptions are currently accepted taxonomically (Guiry and Guiry 2013). Order Oscillatoriales, Family Oscillatoriaceae Tychonema Anagnostidis & Komárek, 1988 is not separated from Oscillatoria or other oscillatorialean genera in PhycoKey. See Guiry and Guiry 2013. Trichodesmium has been considered a synonym of Oscillatoria (Carpenter and Price 1976) but is treated separately in PhycoKey. Planktothrix Anagnostidis and Komárek 1988 is considered a synonym of Oscillatoria in PhycoKey. Planktothrix includes planktonic strains of Oscillatoria with gas vesicles and cells with lengths nearly the same as, or greater than, widths. Nevertheless Suda et al (2002) separate the genera using guidelines from Bergey’s Manual of Systematic Bacteriology (Castenholz and Waterbury 1989).
Molecular sequences:
A notable and personally vexing issue is the similarity and difference between a pair of planktonic strains O. agardhii and O. rubescens (or P. agardhii and P. rubescens). The two strains are indistinguishable microscopically except for color: O. agardhii is a dull green, and O. rubescens is a dull red. Both tend to occupy the metalimnetic region of lakes, often in dense but thin layers (Baker 1973), and usually do not co-occur in the same lake. A recent genetic study of microcystin genotypes suggests the importance of homologous recombination continuously occurring in bacteria, reinforced by the study of these two strains (Kurmayer and Gumpengerger 2006). What applies to one part of the genotype may well apply to others, including the ratio of light absorbing pigments that produce the difference in color, phycocyanin (blue) and phycoerithrin (red). My personal observation was a change from green to red in a metalimnetic sample from Deming Lake, MN USA that sat on an illuminated laboratory shelf for several months. Of course it’s possible that even a single trichome of P. rubescens could have been present in the sample, and overtook the population. Or – was there homogenous recombination during that time on the shelf? Work I’ve seen to date- confirm a nearly identical molecular sequence in at least part of the genome of O. agardhii (green) and O. rubescens (red). For example, part of the gas vesicle gene cluster is identical in three strains of O. rubescens and nearly identical (two base substitutions) to O. agardhii (Beard et al. 1999).
Morphology:
Trichomes (usually no sheath except under some stress), slight if at all 'eingeschnurt' ('incut' at cross walls between cells). Rigid and straight trichomes, or flexible and bending. Variable cell length and width (at least 2 - 20 µm) and length/width ratio (at least 0.1 - 10). A notable and personally vexing issue is the similarity and difference between a pair of planktonic strains O. agardhii and O. rubescens (or P. agardhii and P. rubescens). The two strains are indistinguishable microscopically except for color: O. agardhii is a dull green, and O. rubescens is a dull red. Both tend to occupy the metalimnetic region of lakes, often in dense but thin layers (Baker 1973), and usually do not co-occur in the same lake. A recent genetic study of microcystin genotypes suggests the importance of homologous recombination continuously occurring in bacteria, reinforced by the study of these two strains (Kurmayer and Gumpengerger 2006). What applies to one part of the genotype may well apply to others, including the ratio of light absorbing pigments that produce the difference in color, phycocyanin (blue) and phycoerithrin (red). My personal observation was a change from green to red in a metalimnetic sample from Deming Lake, MN USA that sat on an illuminated laboratory shelf for several months. Of course it’s possible that even a single trichome of P. rubescens could have been present in the sample, and overtook the population. Or – was there homogenous recombination during that time on the shelf?
Similar genera:
Lyngbya strains have a sheath visible at least at one end of the trichome. Microcoleus has a bundle of parallel Oscillatoria-like trichomes sharing a common sheath.
Diazotrophy – Nitrogen fixation – without heterocysts:
Similar to other filamentous cyanobacteria e.g. Trichodesmium, Microcoleus , and Lyngbya, Oscillatoria can fix nitrogen under aerobic conditions, perhaps only at night in the absence of photosynthesis. Still other genera can do so under micro-aerobic or anoxic conditions.
Anoxygenic Photosynthesis:
Oscillatoria limnetica in pure culture isolated from Solar Lake can shift back and forth between oxygenic and anoxygenic PS depending on absence or presence of H2S as an alternative electron source (Cohen et qal. 1975).
Toxicity:
At least some strains of Oscillatoria produce hepatoxic microcystins (especially O. agardhii and O. rubescens)(Meriluoto et al. 1989), and neurotoxic anatoxin (Skulberg et al. 1992, Viaggiu et al. 2004). Optimal conditions for production of hepatotoxins in four strains of O. agardhii included high N concentration (in the range 0.42 – 84 mg N L^-1), low light (in the range 12 – 95 mmol photons m^-2 s^-1), at 25 C. The red form (O. rubescens) produced similar amounts at 15 – 25 C (Sivonen 1990).
Inhibition of Daphnia:
Edmondson and Litt (1982) suggested that Oscillatoria trichomes interfered with the filter-feeding mechanism of Daphnia thus delaying their appearance in Lake Washington, WA USA until reduction of the trichomes. A direct test of the hypothesis was supported with tests of the growth of Daphnia pulicaria in the presence of Oscillatoria agardhii and an optimal food source, Cryptomonas erosa (Infante and Abella 1985).
Habitat:
Oscillatoria (Planktothrix) inhabits a wide range of environments from freshwater to marine, plankton to benthos. In highly organic habitats such as salt marshes colorless strains can often be found. Some strains (botanical 'species') including O. agardhii and O. rubescens form distinctive dense layers in the metalimnion of mesotrophic freshwater lakes, or blooms at the surface of more eutrophic lakes. An example from Minnesota USA is a study in the meromictic mesotrophic Deming Lake (Baker et al. 1969)
References:
Anagnostidis, K., and J. Komarek 1988. Modern approach to the classification system of cyanophytes. 3 – Oscillatoriales. Arch. Hydrobiol. Suppl. 80 (Algol Stud. 50-53):327-472. Baker, A.L., A.J. Brook and A. Klemer 1969. Some photosynthetic characteristics of a naturally occurring population of Oscillatoria agardhii var. isothrix Gomont. Limnology and Oceanography 14(3):.327-333. Beard, S.J., B.A. Handley, P.K. Hayes and A.E. Walsby 1999. The diversity of gas vesicle genes in Planktothrix rubescens from Lake Zurich. Microbiology 145:2757-2768). Carpenter, E.J. and C.C. Price 1975. Marine Oscillatoria (Trichodesmium): explanation for aerobic nitrogen fixation without heterocysts. Science 191(4233):1278-1280. Castenholz, R.W. and J.B. Waterbury 1989. Group I. Cyanobacteria. Preface. In: Bergey’s Manual of Systematic Bacteriology, vol. 3:1710-1727. Staley, J.T., M.P. Bryant, N. Pfennig and J.G. Holt (Eds.). Williams and Wilkins, Baltimore. Cohen, Y., E. Padan and M. Shilo 1975. Facultative anoxygenic photosynthesis in the cyanobacterium Oscillatoria limnetica. Journal of Bacteriology 123(3):855-861. Edmondson, W.T. and A.H. Litt. 1982. Daphnia in Lake Washington. Limnology and Oceanography 27:272-293. Guiry, M.D. and G.M. Guiry 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 05 August 2013. Infante, Aida, and S.E.B. Abella 1986. Inhibition of Daphnia by Oscillatoria in Lake Washington. Limnology and Oceanography 30(5):1046-1052. Kurmayer, R., and M. Gumpenber 2006. Diversity of microcystin genotypes among populations of the filamentous cyanobacteria Planktothrix rubescens and Planktothrix agardhii. Molecular Ecology 15: 3849-3861. Meriluoto, J.A.O., A. Sandström, J.E. Eriksson, G. Remaud, A. G. Craig and J. Chattopadhyaya 1989. Structure and toxicity of a peptide hepatotoxins from the cyanobacterium Oscillatoria agardhii. Toxicon 27(9):1021-1034. Sivonen, K. 1990. Effects of light, temperature, nitrate, orthophosphate, and bacteria on growth of and hepatotoxins production by Oscillatoria agardhii strains. Applied and Environmental Microbiology 56(9):2658-2666. Skulbert, O.M., W.W. Carmichael, R.A. Andersen, S. Matsunaga, R.E. Moore and R. Skulberg 1992. Investigations of a neurotoxic oscillatoriacean strain (Cyanophyceae) and its toxin. Isolation and characterization of homoanatoxin-a. Environmental Toxicological Chemistry 11:321-329. Suda, S., M.M. Watanabe, S. Otsuka, A. Mahakahant, W. Yongmanitchai, N. Nopartnaraporn, Y. Liu, and J.G. Day 2003. Taxonomic revision of water-bloom-forming species of oscillatorioid cyanobacteria. Viaggiu, E., S. Melchiorre, F. Volpi, A. Di Corcia, R. Mancini, L. Garibaldi, G. Crichigno and M. Bruno 2004. Anatoxin-a toxin in the cyanobacterium Planktothrix rubescens from a fishing pond in northern Italy. Environmental Toxicology 19:191-197. Zimmerman, U. 1969. Ökologische und physiologische Untersuchungen an der planktischen Blaualge Oscillatoria rubescens D.C. unter besonderer Berücksichtung von Licht und Temperatur. Schweizerische Zeitschrift fur. Hydrologie. 31:1-58.
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