Based on Eubacterium rectale gene EUBREC_1343. As seen in gene expression experiments (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE14737), it appears to be upregulated in the presence of Bacteroides thetaiotaomicron vs when isolated in culture [1].

1: Characterizing a model human gut microbiota composed of members of its two dominant bacterial phyla. Mahowald MA, Rey FE, Seedorf H, Turnbaugh PJ et al. Proc Natl Acad Sci U S A 2009 Apr 7;106(14):5859-64. PMID:19321416