Co-transduction mapping in Serratia marcescens

The linkage of 34 auxotrophic markers in strain HY of Serratia marcescens was studied by means of transductions with phages x and y. The markers could be ordered into 18 loci of different auxotrophies by transduction crosses with phage x (markers in trans-position) 17 of which showed to be linked to at least one of the other loci. A linear map of this section of the genome was constructed. It corresponds well to the map of 8 loci derived from transductive crosses (markers in cis-position) with phage y. Since a virion can transduce about 5 loci at the same time the map represents only a small section of the Serratia genome. No similarity to any part of the maps of Escherichia or Salmonella can be detected. It is discussed why most auxotrophic mutations which were induced by nitrosoguanidine map in this small genomic region.