(A) In LB broth, the wild type (strain E264) was mixed with the BtaR1- mutant CM157, the BtaR2- mutant CM159 or the BtaR3- mutant CM161 at a starting mutant relative abundance of 1%. All mutants were KmR. As a control we mixed the wild type with CM218, a KmR strain derived from the wild type. Results are percent of total colonies that are KmR (% mutants). The control shows there is little cost associated with the KmR marker. (B) LB broth pure culture growth curves of CM224, a TpR wild-type strain and the KmR BtaR1- mutant. Data for Figure 1B for the statistical analysis described in the text are in the Figure 1—source data 1). (C) 24-hour LB broth coculture. The TpR marked wild type) mixed with the KmR marked wild type), or the BtaR1 mutant. KmR bacteria were started at 1% of the population and each coculture was grown in a flask for 24 hr. Bacteria were enumerated by colony counts for total coculture yield (CFU/mL) and percent KmR mutants in the population (open symbols are CFU/mL, closed symbols are percent of mutants). Bars show the mean and range of at least three biological replicates. (D) Agar surface competitions. Wild type with the BtaR1- mutant, the BtaR2- mutant or the BtaR3- mutant at a starting mutant abundance of 1%. As a control we mixed the wild type with the KmR strain derived from the wild type. Data are means of at least three biological replicates. Some ranges are not visible, as they were small and within the size of the symbols.