Temporal separation of cell division and diazotrophy in the marine diazotrophic cyanobacterium Trichodesmium erythraeum IMS101


  • Present address: Beatriz Díez, Departament de Biologia Marina i Oceanograa, Institut de Ciències del Mar (CMIMA, CSIC), E-08003 Barcelona, Spain.

  • Editor: Hermann Bothe

Correspondence: Gustaf Sandh, Department of Botany, Stockholm University, S-106 91 Stockholm, Sweden. Tel.: +46 8 163 918; fax: +46 8 165 525; e-mail: sandh@botan.su.se


Examination of the diurnal patterns of basic cellular processes in the marine nonheterocystous diazotrophic cyanobacterium Trichodesmium revealed that the division of cells occurred throughout the diurnal cycle, but that it oscillated and peaked at an early stage in the dark period. Transcription of the early cell division gene ftsZ and the occurrence of the FtsZ protein showed a similar diurnal rhythmicity that preceded the division of cells. DNA replication (dnaA gene transcription) occurred before the transcription of ftsZ and hetR, the latter encoding the key heterocyst differentiation protein. Transcription of ftsZ and hetR in turn preceded the development of the nitrogen-fixing diazocytes and nifH transcription, and were at the minimum when diazotrophy was at the maximum. The nifH gene transcription showed a negative correlation to the circadian clock gene kaiC. Together, the data show a temporal separation between cell division and diazotrophy on a diurnal basis.