Final answer:
Bacteria form protective structures called endospores during their inactive stage, which are highly resistant and enable survival through extreme conditions. Endospores are different from capsules which aid in protection and attachment.
Step-by-step explanation:
Certain bacteria, during their inactive stage, form outer coverings known as endospores. These specialized structures are highly resistant and can protect the bacterium's genetic material in extreme conditions such as lack of nutrients, extreme temperatures, chemicals, and radiation. Endospores are not reproductive spores like those of fungi but are rather a means for the bacterial cell to remain dormant until favorable conditions return.
Structurally, endospores are distinct from the other extracellular structures such as capsules, which are commonly polysaccharide layers outside the bacterial cell wall providing protection and aiding in attachment to surfaces. While capsules play a role in biofilm formation and in protecting against dehydration, endospores are specifically for the purpose of survival during stress. Other structures like flagella, pili, and fimbriae serve for locomotion, genetic exchange, and attachment respectively, but none match the resilience of endospores.
It's also worth noting that capsules can contribute to a bacterium's virulence by preventing phagocytosis and facilitating attachment to host tissues, further illustrating the specialized roles of bacterial coatings and structures in response to environmental challenges.