Abstract
Summary Induction of akinete formation in Anabaena torulosa ensued with high frequency in nitrogen/carbon sources or their combinations in 10 d old cultures while nitrogen free medium supported low frequency of akinetes by 20th d. The akinetes in nitrogen/carbon sources have undergone germination too readily and the hormogones accumulated granular contents resulting in a second generation of small circular akinetes. This has been designated as microcycle akinete formation. The increase of light intensity and volume of medium with nitrate or nitrite induced the formation of akinetes and microcycle akinetes without any change in the period of akinete formation. The addition of 2,4-dinitrophenol DNP), streptomycin and chloroamphenicol in the two nitrogen sources reduced the frequency of akinetes, germination and microcycle akinetes. Inhibition of nitrate utilization by 3-(3,4-dichlorophenyl)-N-N′dimethyl urea (DCMU) completely suppressed growth, akinete and microcycle akinete formation. In control cultures, nitrate uptake reached a steady state level with akinete and microcycle akinete differentiation. The contents of glycogen and cyanophycin granule polypeptide (CGP) decreased from akinete stage to microcycle akinete formation as well as a decline in the activity of glutamine synthetase (GS). The significance of these features has been discussed.
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