ABSTRACT
The human body is host to trillions of microorganisms that are collectively referred to as the microbiota. This composite microbial ecosystem, built of bacteria, viruses, fungi, protists, and archaea, contains some of the most diverse and abundant life forms on the planet. Some of the key physiological services provided by gut bacteria include synthesis of vitamins, neurotransmitters, essential amino acids, and short-chain fatty acids, modulation of gut epithelial gene expression, transformation of bile acids, and metabolism of drugs. Characterizing the interactions that occur between humans and microbiota offers a window to understand those aspects that are most crucial for maintaining the health of the supraorganism. Proteobacteria comprise a rather heterogenous phylum of gram-negative bacteria that includes a wide variety of pathogenic genera, including Escherichia, Shigella, Salmonella, Vibrio, Helicobacter and Yersinia. Obesity, insulin-resistance, and metabolic syndrome are all characterized by chronic low-grade inflammatory states.
