Final answer:
The dormant stage where bacteria survive harsh conditions is known as the viable-but-non-culturable (VBNC) state, and they can also form endospores that germinate when conditions improve.
Step-by-step explanation:
The dormant stage that bacteria enter when the environment makes the bacteria's survival difficult is called the viable-but-non-culturable (VBNC) state. This survival mechanism allows bacteria to endure environmental stress by going into a dormant state. In this state, they are not actively growing and cannot be cultured in a laboratory. However, these bacteria are not dead and can become culturable again through a process known as resuscitation when conditions improve. Some bacteria can also form endospores, which occur during the stationary phase of bacterial growth. Endospores are highly resistant and can stay dormant for extended periods, sometimes thousands of years, before they germinate and reenter an active vegetative state when conditions are favorable.