microbiome

The human microbiota consists of the 10-100 trillion symbiotic microbial cells harbored by each person, primarily bacteria in the gut; the human microbiome consists of the genes these cells harbor.

Mostly, the microbiome is beneficial. It helps with digestion and enables people to extract a lot more calories from their food than would otherwise be possible. Research over the past few years, however, has implicated it in diseases from atherosclerosis to asthma to autism.