Microbes ubiquitously have symbiotic relationships with large organisms – macrobes – in every way: mutualistic, commensal, and parasitic. For multicellular eukaryotes, some microbial relations are vital.
Macrobes are cellular colonies, living symbiotically with microbes as a symbiorg. Every plant and every animal comprise a community: a macrobial host relying upon its microbiome for most every aspect of living, including metabolism, bodily defense (immune system), intelligence, reproduction, and many other functions. From a microbial perspective, multicellular organisms increase the number of venues in which they may thrive.
Beyond the microbiome, microbes are the foundation of a balanced ecosystem; the living framework of intricate, interdependent relationships among larger life and the environment.