Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0902000106 (2009)

For bacteria, which have notoriously twisted family trees, defining species boundaries requires close knowledge of both genetic and expressed characteristics.

A team led by Kostas Konstantinidis of the Georgia Institute of Technology in Atlanta and James Tiedje at Michigan State University in East Lansing investigated ten strains of bacteria from the genus Shewanella, a group with varied, often ecologically important, metabolic abilities. Genome and protein-expression data were already available for the strains.

By comparing these data sets, the team was able to link genetic factors to ecological role in more detail than before. Also, despite identical culture conditions, protein expression varied more than genome sequence in some cases, so gene regulation could be important for describing species.