title: Polymorphism in Escherichia coli: rtl atl and gat regions behave as chromosomal alternatives.
abstract: Amongst forty wild strains of Escherichia coli, sixteen utilized galactitol (as did K12) and seven utilized ribitol (as did C) of which six utilized D-arabitol; none utilized all three polyols. Transduction of genes for ribitol utilization (rtl+) to strains able to utilize galactitol (gat+), whether K12 or wild strains, using wild strains and E. coli C as donors always resulted in loss of the galactitol phenotype. The genes for D-arabitol use (atl+) were always cotransduced with rtl+ in interstrain crosses. We confirm and extend the mapping of gat+ (Lengeler, 1977) and rtl+ atl+ (Reiner, 1975) in their respective hosts, K12 and C, by showing both regions to be 50% cotransducible with metG and 3% cotransducible with fpk. In reciprocal transductions, gat+ replaced rtl+ atl+. In partial diploids, rtl+ atl+ and gat+ regions did not interfere with each other's expression. Transfer of rtl+ from an Rtl+ Atl- donor by R plasmid (pE10)-mediated conjugation, gave Gat- transconjugants of K12 in which rtl+ and a kanamycin resistance gene were 100% cotransducible in the metG region of the chromosome. It is suggested that the rtl+ atl+ and gat+ genes (or parts of them) act as alternative, or mutually exclusive, regions in the chromosome. Possible reasons for the existence of alternative characters are discussed.
mesh_terms: D002874:Chromosome Mapping; D003227:Conjugation, Genetic; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D004376:Galactitol / Q000378:metabolism; D005798:Genes, Bacterial; D005838:Genotype; D011110:Polymorphism, Genetic; D012255:Ribitol / Q000378:metabolism; D013402:Sugar Alcohols / Q000378:metabolism; D014161:Transduction, Genetic
chemical_list: D013402:Sugar Alcohols; D004376:Galactitol; D012255:Ribitol; C014999:arabitol