R. centenum is a photosynthetic member of the Azospirillum clade, members of which exhibit three morphologically distinct cell types: swim cells, swarm cells and cyst cells [ 1, 4].
Three morphologically distinct cell types are observed during the R. centenum life cycle; swim cells, swarm cells and metabolically dormant cyst cells [ 1, 7].
Furthermore, as swarm cells begin to de-differentiate, the pmr operon expression is down-regulated, rapidly reaching the levels observed in swim cells.
In order to obtain further insight into the de-differentiation phase, we monitored the activity of the pmr operon during the transition from swarm to swim cells.
In addition to the development of cysts, R. centenum cells are also capable of differentiating into swim cells that have a single sheathed polar flagellum or swarm cells that have numerous unsheathed lateral flagella [ 34, 42, 43].
Certain swellings and para-axonemal structures, such as crystalline rods and noncrystalline rods and sheets, may be involved in photoreception, providing the swimming cell with a means for detecting light.
The newborn swimming cell would continue the ongoing round of differentiation, but without the lag.
The swimming cell elongated for several times during differentiation, and presented highly flagellated forms called swarming cell.
The raft would migrate on the surface for certain distance, and then divided back to the swimming cell.
This type of vegetable cells was short rod-shape with the length about 1.5 2 μm long, and fimbriated around the cell, also (e.g., swimming cell) (Mobley and Belas 1995).
