Both of these microbes are important in all kinds of ways. One of these, as I bet you know, is that they can cause diseases in plants and animals. For example, one type of bacteria causes tuberculosis (TB). And a type of virus called HIV causes AIDS. Both these diseases are killing millions of people, mostly in poor countries.
Bits of virus called 'promoter sequences' are used in genetic
are like a switch which turns a gene on. The commonest one is
from a virus which infects cauliflowers: cauliflower mosaic
virus. Bits of bacteria called plasmids are also used because
these tiny loops of genetic material can readily move from one
bacterium to another. This is called horizonatal gene transfer
and enables bacteria to swap useful genes. Plasmids carry genes
which make bacteria resistant to antibiotics or make them manufacture
toxins (poisons). They can also carry genes which scientists
have inserted -- spliced -- into them. Plasmids allow bacteria
to quickly become resistant to antibiotics like penicillin.