ANALYSIS OF GENES ENCODING THE CELL-DIVISION PROTEIN FTSZ AND A GLUTATHIONE SYNTHETASE HOMOLOG IN THE CYANOBACTERIUM ANABAENA SP PCC-7120

Heterocysts, cells specialized in nitrogen fixation in Anabaena sp. PC C 7120, lose the potential for cell division once fully differentiated . This suggests that cell division activity is differentially regulate d in heterocysts and vegetative cells. FtsZ has been shown to play a c rucial role in bacterial cell division. Two degenerate oligonucleotide primers were designed to detect, by polymerase chain reaction (PCR), an ftsZ homologue from the heterocystous cyanobacterium Anabaena sp. P CC 7120. A PGR-amplified DNA fragment was cloned and used as a probe t o isolate the entire ftsZ gene of Anabaena sp. PCC 7120. The deduced a mino acid sequence shares strong similarities with other FtsZ proteins , suggesting remarkable conservation of the FtsZ protein during evolut ion. An ORF downstream of ftsZ,which would be transcribed in the oppos ite direction compared to ftsZ,could encode a polypeptide with signifi cant sequence similarity to the glutathione synthetase from Escherichi a coil. Inactivation experiments in vivo for both ftsZ and the glutath ione synthetase gene did not yield any double recombinants either in t he presence or in the absence of combined nitrogen, suggesting that bo th genes are essential for cell growth under these conditions.