Question

1. SulA is a protein induced in Bacillus spp. In response to DNA damage, SulA blocks the formation of the FtsZ ring. Graph the average length of a wild-type cell and the average length of a mutant that constantly expresses SulA even if there is no DNA damage (a bar graph is fine). Explain your reasoning

Answer 1

For bacterial cell division; formation of Z ring is very important which dictate the cell the plane of division. Z ring is formed by the polymerisation of FtsZ protein, a actin homolog which starts polymerizing at the middle of the cell and form a ring like structure. The localization of the FtsZ protein will depend on the gradient of MinCD protein. At the two end of bacterial cell MinCD concentration is very high but at the middle of the cell MinCD concentration is very low. FtsZ polymerize and form Z ring where MinCD concentration is less that is at the middle of the cell. On the other hand, in response to DNA damage, SulA blocks the formation of the FtsZ ring by different regulatory pathway.

As the FtsZ ring formation is blocked due to the constitutive expression of SulA, cell will not divide, rather it will become elongated filamentous in shape.

Here I have taken cell length increase by 10 fold. It can even become 15 to 20 fold increase. (WT cell length = 2 m, mutant cell length = 20 m.)