Cells of a normally rod-shaped bacterium (e. g., Bacillus subtilis) that have completely lost the ability to produce the MreB protein would mostly likely be

The bacterium will be a spherical shape

Explanation:

The responsible for the width of rod-shaped bacteria is the protein called MreB. This protein forms large microfilaments that are very similar to actin filaments found in eukaryotic cells. All the bacteria that are spherical by nature doesn't have the protein MreB. So, if a rod-shape bacterium that doesn't have a MreB protein or is altered this bacterium would be spherical-shape.