were added to 0 8 ml of the culture broth after 30 min incubation at 37 u00b0 c under shaking 9 ml lb medium were added this was followed by another 30 min incubation step at 37 u00b0 c then 4 u03bcg ml chloramphenicol were added and the incubation was continued for another 2 hours finally the tubes were transferred into a 37 u00b0 c dry incubator where they were left overnight on the next morning the culture was filtered through a 0 45 u03bcm filter and stored at 4 u00b0 c or directly used for transduction for the transduction of the riboflavin overproducing strain rb50 prf69 the strain was grown on a tbab plate at 37 u00b0 c overnight cells of this plate were used to inoculate 25 ml lb medium klett 20 30 when the culture reached klett 175 0 8 ml of the cells were mixed with 0 2 ml of a pbs 1 phage lysate from strain bs3402 prepared as described above after 30 min incubation at 37 u00b0 c under shaking cells were spun down and suspended in 1 ml vy medium this was followed by 1 h incubation under the identical conditions 200 to 1000 u03bcl of the transduced cells were plated on a selection plate containing 2 u03bcg ml neomycin grown colonies were tested for neomycin resistance after gdna isolation example 1 a standard pcr using primer tkt 1s and rec 2as was done to confirm the replacement of the tkt wild type gene.