Markerless gene deletion system for sphingomonads

Here, we suggest that natural streptomycin resistance of many sphingomonads resides within rpsL. We constructed a dominant, streptomycin-sensitive rpsL allele and demonstrated its use as a counterselection marker in several sphingomonads. An rpsL-based markerless gene deletion system was developed and validated by deleting four genes in Sphingomonas sp. strain Fr1.