A long tail of CORFs display significant evidence of balancing selection
The majority of CORFs displayed negative Tajima’s D values (Figure 2). However, the distribution of CORFs was skewed right, and a long tail of CORFs displayed significantly positive Tajima’s D values. The CORF with the most positive Tajima’s D was the Multidrug efflux pump subunit AcrB from Bacteroides dorei (test for non-zero Tajima’s D, adjustedp -value = 4.46e-07). In addition, the Multidrug efflux pump subunit AcrA (membrane-fusion protein) from B. dorei was the fourth most positive CORF of all 566,958 CORFs (test for non-zero Tajima’s D, adjusted p -value = 9.84e-06). Similarly, several other multidrug transporters, including multiple homologs of AcrB and AcrA in other bacterial genera, displayed Tajima’s D values greater than 3, indicative of histories of balancing selection (Table S1, Figure 2).