Open AccessUDP‐sugar hydrolase isozymes in Salmonella enterica and Escherichia coli : Silent alleles of ushA in related strains of Group I Salmonella isolates, and of ushB in wild‐type and K12 strains of E. coli , indicate recent and early silencing events, respectively
Author(s) -
Edwards Catherine J.,
Innes David J.,
Burns Dennis M.,
Beacham Ifor R.
Publication year - 1993
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1993.tb06588.x
Subject(s) - escherichia coli , salmonella enterica , biology , salmonella , microbiology and biotechnology , gene , enterobacteriaceae , escherichia , serotype , hydrolase , genetics , bacteria , enzyme , biochemistry
Escherichia coli contains a single periplasmic UDP‐glucose hydrolase (5′‐nucleotidase) encoded by ushA. Salmonella enterica , serotype Typhimurium, also contains a single UDP‐glucose hydrolase but, in contrast to E. coli , it is membrane‐bound and is encoded by the non‐homologous ushB gene; Salmonella enterica (Typhimurium) also contains a silent allele of the ushA gene ( ushA 0 ). In this report, we show that nearly all natural isolates of Salmonella contain both UDP‐sugar hydrolases, i.e. they are UshA + UshB + . The only exceptions are all from sub‐group I ( S. gallinarum, S. pullorum , and most Typhimurium strains), are UshA − UshB + , and several have been shown to contain an ushA 0 allele. These data, together with the fact that these latter strains are closely related genetically, strongly suggests a recent silencing mutation(s). We also report the presence in E. coli K‐12, and in natural isolates of E. coli , of a DNA sequence which is homologous to the ushB gene of Salmonella ; since E. coli does not contain UshB activity, we tentatively refer to this sequence as ushB 0 . Since all E. coli strains investigated are UshB − , we conclude that the silencing mutation(s) occured relatively eary following the divergence of Escherichia coli and Salmonella from a common ancestor that was ushA + ushB + .