Organisms that may be part of the normal bacterial flora, but can--under certain conditions--cause disease are known as pathogens. g

Bacteria pathogens.

Explanation:

This is because bacteria pathogens are single celled organisms that can cause diseases. Though many bacteria do not cause disease but the pathogenic bacteria have the ability to cause infections and become harmful to their host. Bacteria tend to adapt to their environment and they can turn pathogenic if the immune response of the host eventually become environment , it becomes pathogens. Examples of bacteria pathogens are salmonella, E.coli, listella e.t.c.

a physical change is being made.