Answer:
Bacteria is a member of a huge group of unicellular microbes that exhibit cell walls, however, are devoid of cell organelles and an organized nucleus, it even comprises some of the species that can result in disease. Bacteria are generally differentiated into three classes, categorized by shape, that is, cylindrical, spherical, and spiral.
A certain poison kills cells of humans by obstructing the pores in the nuclear membrane. However, the same poison would not kill the bacteria as bacteria are devoid of a nuclear membrane as it is a unicellular species, and is considered as a prokaryote.