One would expect to find this protein involved in the elonga

One would expect to find this protein involved in the elongation of Bacillus anthracis to form its typical shape. Autolysin MreB Ftsz Tubulin

Solution

MreB is an actin homolog that polymerizes to create filaments at the cytoplasmic side of the plasma membrane in order to promote elongation.

Therefore, the correct answer is MreB.