Morphological and physiological characteristics of a non-heterocystous strain of the cyanobacterium Mastigocladus laminosus Cohn from fumarolic soil on Mt Erebus, Antarctica

Summary

An unusual strain of the thermophilic cyanobacterium Mastigocladus laminosus occurs on warm soils on the volcano Mt Erebus (77°32′S, 167°8′E). It differs morphologically from the two genetically distinct forms described from thermal habitats elsewhere. Heterocysts are lacking and true-branching is rare. Its photosynthetic rate, and the contrasting rates of two less thermotolerant algae from Mt Erebus soils, Phormidium fragile (Cyanobacteria) and Pseudococcomyxa simplex (Chlorophyta), were measured over the range -2° to 62°C. The optimum temperature range of M. laminosus was 35° to 50°C. Photosynthetic response to temperature of all three algae in the laboratory correlated well with distribution patterns in the field, confirming that zonation patterns were temperature controlled. M. laminosus retained viability following exposure to deep-freezing, freeze-thaw cycles and desiccation. Viability of the alga in culture was lost following exposure to 50°C in darkness for 42 days and following 42 days in the light at 0°C. Discussion suggests the alga would survive long distance airborne dispersal in the desiccated condition but would not survive the duration of overwinter darkness on moist soils at the warmer end of its range of occurrence in the field.