What are the survival methods of micro organisms under unfavourable conditions

Okay, sorry but I have to correct the previous answer.

Yes, endospores are a method of bacterial survival under unfavorable conditions BUT they are not reproductive structures. They are purely survival structures.

Secondly, they are NOT metabolically active.

Lastly, they are able to survive for millions of years, not just a short amount of time.

I believe you are confusing endospores with fungal spores. They are not the same.

Through the use of spores! These are reproductive structures used by the microorganism to give it the ability to survive for a period of time under unfavorable conditions.

They also undergo a metabolic change where they go into a stationary phase...similar to hibernation, were the organism does not requires as much nutrients to survive!