I came across a link to this article by Lynn Margulis, The Germs of Life, published in Orion magazine, about microbial ancestors, how the roles they have played in our evolution and still play in our ecosystems are becoming better understood.
1. "Bacterial nitrogen fixation enriches the soil at no cost to us."
2. "..the photosynthesis that excretes oxygen and makes food for all life is carried out by the blue-green bacteria called cyanobacteria—both the free-living kind and those that became chloroplasts in the cells of algae and plants."
3. Even disease-causing bacteria play a role in overall systems health - e.g., anthrax bacteria prevent overgrazing/kill grazers, saving the soil so it can grow new crops.
4. Bacteria in our gut tubes provide essential vitamins, assist digestion.
5. Bacteria in our orifices enhance metabolism, block opportunistic infection (like yeast), help our immune system sustain itself.
6. Mitochondria along with other cell "parts", perhaps,(such as cilia) evolved from various "communities" of different species of bacteria-like life which cooperated for survival, learned to live in "community."
7. Cilia are a feature of many of the sensory cells of the nervous system.
8. Everything social we do as humans, bacteria already invented long before. Humans will go extinct long before bacteria and other microbes do.