Characterization of transmissible genetic elements from sucrose-fermenting Salmonella strains

Abstract

Two of seven sucrose-fermenting Salmonella strains obtained from clinical sources were found capable of conjugal transfer of the sucrose fermentation (Scr+) property to the Escherichia coli K-12 strain WR3026. The genetic elements conferring this Scr+ property, designated scr-53 and scr-94, were then conjugally transmissible from E. coli WR3026 Scr+ exconjugants to other strains of E. coli at frequencies of 5 x 10-I to 5 x 10-I for the scr-53 element and 10 6 to 10-s for the scr-94 element. In E. coli hosts, both of these elements were compatible with F-lac and with each of six previously characterized transmissible lac elements. No antibiotic resistance characteristics or colicin production were discovered to be associated with either scr-53 or scr-94. Neither scr element generated a male host response to the female-specific phage XII, but the scr-53 element rendered its E. coli host sensitive to the male-specific phage R-17. E. coli hosts containing scr-53 were susceptible to lysis by Plvir, and transduction of the scr-53 element was accomplished with this phage. The scr-53 element was isolated from E. coli WR3026, Scr+ transductants, and E. coli WR2036 Scr+ exconjugants as a covalently closed circular deoxyribonucleic acid molecule with a molecular weight (determined by electron microscopy) of approximately 52 x 106. Receipt of the scr-94 element rendered E. coli hosts of this element unsusceptible to lysis by Plvir, although adsorption of the phage by an E. coli WR3026 exconjugant containing scr-94 occurred as efficiently as it did on WR3026 itself. Repeated examination of E. coli strains harboring scr-94, as well as of the Salmonella strain which initially contained it, did not reveal the presence of circular deoxyribonucleic acid. The synthesis of the sucrose cleaving enzyme was inducible in E. coli exconjugants containing either scr-53 or scr-94.

Molecular analysis of two ScrR repressors and of a ScrR–FruR hybrid repressor for sucrose and D‐fructose specific regulons from enteric bacteria

“…Tel. (541) 929 2290; Fax (541) 969 2870. piasmids (Wohlhieter et al, 1975;Schmid ef a/., 1982;Cowan et ai. 1991) or the chromosome (Alaeddinoglu and Charles, 1979;Bockmann etal, 1992;Wehmeier et ai, 1989).…”

The porin RafY encoded by the raffinose plasmid pRSD2 of Escherichia coli forms a general diffusion pore and not a carbohydrate‐specific porin

“…Another example for such a system presence of RafY define it as a channel-forming component. is the single-copy plasmid pUR400 [16], which allows the up-From these experiments the single-channel conductance and the take and fermentation of sucrose in enteric bacteria [17,18]. It selectivity of RafY could be derived.…”

Co-transfer of two plasmids determining bacteriocin production and sucrose utilization in Streptococcus faecium

“…S. faecium M16/25 was identified as a transconjugant of S. faecium M16 because of Up to now genetic determinants of sucrose utilization have been found to exist only on plasraids of Gram-negative bacteria such as E. coli (25-MDa plasmid) [15] and two strains of Salmonella sp. [16,17] (5-MDa and 51-MDa plasmids). Comparatively little is known about the involvement of plasmids in degradation of sucrose in Gram-positive bacteria, although lactose plasmids have been identified in various lactic streptococci [18,19] and Lactobacillus casei [20].…”