You would be dead without the bacteria you have to help you along. But I'm not sure how this relates to a planet where said bacteria, if they exist, are sitting at the top of the biological pyramid.
Yeah, funny thing "defending" bacteria.
I guess my point is that very simple organisms can have large a impact (on us, given the anthropocentric view I'm replying to here). Viruses for instance.
In a vibrant ecosystem, sure. But Mars is a dessicated husk of what might once have been a green thriving world. These remaining bacteria/fungi/whatever are like bugs on a corpse. Not an ecosystem; a fragment of a perhaps once-complex ecosystem and worth study. But not anything that should prevent or delay exploration of a planet.
