Influence of phosphate on Nostochopsis-like morphology (Cyanobacteria)

ABSTRACT

Two cyanobacterial strains developed morphology characteristic of Nostochopsis, i.e. with many heterocysts in side branches when grown in low phosphate medium. When grown in high phosphate medium both strains developed morphology characteristic of Fischerella muscicola. The converse did not occur with two culture strains classified as Fischerella in that neither developed Nostochopsis morphology when grown in low phosphate. However, there was a slight increase in the percentage of heterocysts that were closely attached to main trichome axes rather than to a cell-forming part of the axis. However, all analysed strains had similar increases in surface phosphomonoesterase activities under low phosphate. Because some literature on Nostochopsis in the field indicates that it can be found only at one time of year, the possibility is discussed that it is recognised only when phosphate is limited. It seems likely that contradictory results in past molecular literature resulted from the same strain being compared in different studies, one using low and the other using high phosphate medium. Our molecular analysis supports morphological differences between the studied strains, and taxonomic assignments are discussed on the basis of previous phylogenetic analyses.

Abbreviations: PMEase; phosphomonoesterase activity; pNPP, para-nitrophenyl phosphate

KEYWORDS:

• Fischerella
• Heterocyst location
• Molecular comparison
• Nostochopsis
• Organic phosphate
• Phosphate limitation
• Thailand

ACKNOWLEDGEMENTS

We are grateful to those who helped with the study in various ways. Prof. Yuwadee Peerapornpisal (Chiang Mai University, Thailand) provided the Nostochopsis strain which stimulated our interest, and subsequent discussions including her then students M. Motham and Sorachat Thiamdao (both now Dr). Prof. J.D. Wehr (Fordham University, N.Y.) collected a sample from a river site where he had previously found the species. BAW was taken to a stream with abundant Nostochopsis in Mizoram Province, India, by Prof. D.N. Tiwari (Banaras Hindu University) and Dr R. Lalfakzuala (Mizoram University).

Additional information

Funding

This research was supported by a grant from the Ministerio de Economía, Industria y Competitividad, Spain, CGL2017-86258-R.