Cell reproduction cycle of mycoplasma.

The cell reproduction cycle of parasitic wall-free bacteria, mycoplasma, is reviewed. DNA replication of Mycoplasma capricolum starts at a fixed site neighboring the dnaA gene and proceeds to both directions after a short arrest in one direction. The initiation frequency fits to the slow speed of replication fork and DNA content is set constant. The replicated chromosomes migrate to one and three quarters of cell length before cell division to ensure delivery of the replicated DNA to daughter cells. The cell reproduction is based on binary fission but a branch is formed when DNA replication is inhibited. Mycoplasma pneumoniae has a terminal structure, designated as an attachment organelle, responsible for both host cell adhesion and gliding motility. Behavior of the organelle in a cell implies coupling of organelle formation to the cell reproduction cycle. Several proteins coded in three operons are delivered sequentially to a position neighboring the previous organelle and a nascent one is formed. One of the duplicated attachment organelles migrates to the opposite pole of the cell before cell division. It is becoming clear that mycoplasmas have specialized cell reproduction cycles adapted to the limited genome information and parasitic life.