Why do bacteria thrive even in hostile environments

Due to their high adaptability

Explanation:

Bacteria have high mutations rates hence they increase their chances of having a sub-population that can adapts to an extreme environment they have been introduced to. Forthwith their genes can passed on to bacteria generations both vertically and horizontally. Bacteria also share their genes through horizontal transfer (conjugation) hence advantageous genes can be passed rapidly to the rest of the population in one generation.