Q1. The common bacterium used in genetic engineering is:
A E. coli Correct
B Spirillum
C Rhizobium
D Diplococcus
Explanation
E. coli is the standard workhorse bacterium in genetic engineering because it grows quickly, is easy to culture, and has well-studied plasmids that can carry foreign DNA. It is widely used for cloning genes and producing recombinant proteins. Spirillum is a spiral-shaped bacterium, but it is not the usual laboratory host for this purpose. Rhizobium is important in nitrogen fixation in legume root nodules. Diplococcus describes paired spherical bacteria and is not the common genetic-engineering host asked here.