Cell division without FtsZ--a variety of redundant mechanisms.

Until 1998 it looked like all bacteria and archaea used a universal cytokinetic machine based on FtsZ. A dozen completely sequenced bacterial genomes all had an ftsZ gene, as did the several sequenced archaeal genomes. Then in 1998-1999 two species of Chlamydia were sequenced and found to have no ftsZ (Stephens et al., 1998; Kalman et al., 1999). Enthusiasts of FtsZ could hold out some hope for its primacy by thinking that these obligate parasites might use some host machinery for division. But the next year the genome of Aeropyrum pernix, a free living thermophilic archeon, was found to be without ftsZ (Kawarabayasi et al., 1999). Additional sequences suggested that the entire kingdom of Crenarchaea managed life and cell division without FtsZ. Among the bacteria the following are now known to have no ftsZ: the phylum Planctomycetes (Pilhofer et al., 2008), which is related to Chlamydiae but is free-living; Calyptogena okutanii (Kuwahara et al., 2007) and Carsonella ruddi (Nakabachi et al., 2006), both intracellular symbionts; Ureaplasma urealiticum (Glass et al., 2000) and Mycoplasma mobile (Jaffe et al., 2004). Since all of these prokaryotes divide, there must be mechanisms for cell division that are not based on FtsZ. © 2010 Blackwell Publishing Ltd.