Message from a human gut symbiont: sensitivity is a prerequisite for sharing

Trends Microbiol. 2004 Jan;12(1):21-8. doi: 10.1016/j.tim.2003.11.007.


Microbial genome sequencing projects are beginning to provide insights about the molecular foundations of human-bacterial symbioses. The intestine contains our largest collection of symbionts, where members of Bacteroides comprise approximately 25% of the microbiota in adults. The recently defined proteome of a prominent human intestinal symbiont, Bacteroides thetaiotaomicron, contains an elaborate environmental-sensing apparatus. This apparatus includes an unprecedented number of extracytoplasmic function (ECF) sigma-factors, and a large collection of novel hybrid two-component systems composed of membrane-spanning periplasmic proteins with histidine kinase, phosphoacceptor, response regulator receiver and DNA-binding domains. These sensors are linked to the organism's large repertoire of genes involved in acquiring and processing dietary polysaccharides ('the glycobiome'). This arrangement illustrates how a successful symbiont has evolved strategies for detecting and responding to conditions in its niche so that it can sustain beneficial relationships with its microbial and human partners.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Bacteroides / genetics
  • Bacteroides / physiology*
  • Gene Expression Regulation, Bacterial
  • Humans
  • Intestines / microbiology*
  • Models, Molecular
  • Molecular Sequence Data
  • Sigma Factor / metabolism
  • Signal Transduction
  • Symbiosis*


  • Bacterial Proteins
  • Sigma Factor