The lactose system in<i>Klebsiella aerogenes</i>V9A 2. Galactoside permeases which accumulate lactose or melibiose

Reeve, Eric; Braithwaite, J. A.

doi:10.1017/s001667230001346x

Cited by 12 publications

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“…However, the E. chrysanthemi mel permease resembles the K. aerogenes mel permease in its ability to transport lactose (23,35). In addition, the transport of lactose by the raffinose-induced permease in EC-C and its inhibition by melibiose and raffinose resembles the behavior of the raf permease in E. coli (29).…”

Section: Discussionmentioning

confidence: 99%

“…Klebsiella aerogenes possesses both a plasmidborne and a chromosomal lac operon (1, 21, 22, 24). Both K. aerogenes and Salmonella typhimurium possess mel operons similar to the E. coli operon (12,23).The substrate specificities of the lac and mel permeases differ among the various members of the Enterobacteriaceae. The lac permease of E. coli has wide specificity and transports a variety of a-and P-galactosides, including lactose, isopropyl-p-D-thiogalactopyranoside (IPTG), thiomethyl-,3-D-galactopyranoside (TMG), melibiose, and galactose (26).…”

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“…The mel permeases of E. coli and S. typhimurium are similar in specificity and can transport TMG, melibiose, and galactose, but not lactose or IPTG (12,19,26,30). The mel permease of K. aerogenes differs from those of E. coli and S. typhimurium in being able to transport lactose in addition to TMG, melibiose, and galactose (23,35).The rafoperon is plasmidborne in E. coli (18). It codes for the three genes involved in raffinose metabolism: agalactosidase, raffinose permease, and invertase (29,32).…”

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Lactose and melibiose metabolism in Erwinia chrysanthemi

Gray¹,

Lindner²,

Brand³

et al. 1986

J Bacteriol

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A Lac' mutant of Erwinia chrysanthemi was isolated from the Lac-wild type on lactose agar. (3-Galactosidase was expressed independently of lactose transport in both the mutant and the wild type, and neither strain expressed thiogalactoside transacetylase. Lactose transport and a-galactosidase, constitutive in the Lac' strain, were coordinately induced in the Lac-strain by melibiose and raffinose but not by isopropyl-,B-D-thiogalactopyranoside or thiomethyl-3-D-galactopyranoside. Melibiose was a strong inhibitor of both the melibiose-and the raffinose-induced lactose permeases, whereas raffinose was a strong inhibitor of only the raffinose-induced lactose permease.Many members of the family Enterobacteriaceae possess operons that code for enzymes involved in lactose and melibiose metabolism. In Escherichia coli, the lacZ gene codes for ,B-galactosidase, the lacY gene codes for lactose permease, and the lacA gene codes for thiogalactoside transacetylase (36). The mel operon of E. coli contains the A and B genes which code for a-galactosidase and melibiose permease, respectively (30). Klebsiella aerogenes possesses both a plasmidborne and a chromosomal lac operon (1, 21, 22, 24). Both K. aerogenes and Salmonella typhimurium possess mel operons similar to the E. coli operon (12,23).The substrate specificities of the lac and mel permeases differ among the various members of the Enterobacteriaceae. The lac permease of E. coli has wide specificity and transports a variety of a-and P-galactosides, including lactose, isopropyl-p-D-thiogalactopyranoside (IPTG), thiomethyl-,3-D-galactopyranoside (TMG), melibiose, and galactose (26). The mel permeases of E. coli and S. typhimurium are similar in specificity and can transport TMG, melibiose, and galactose, but not lactose or IPTG (12,19,26,30). The mel permease of K. aerogenes differs from those of E. coli and S. typhimurium in being able to transport lactose in addition to TMG, melibiose, and galactose (23,35).The rafoperon is plasmidborne in E. coli (18). It codes for the three genes involved in raffinose metabolism: agalactosidase, raffinose permease, and invertase (29,32). All three activities are coordinately induced by melibiose and raffinose (29, 32). Lactose transport by the raffinose permease is competitively inhibited by melibiose and raffinose (32).Erwinia chrysanthemi pv. zeae, the causal agent of soft rot in corn, is a member of the Enterobacteriaceae (34). Only two reports dealing with lactose metabolism in E. chrysanthemi have appeared (6,8) despite the use of lactose fermentation as a taxonomic marker in the classification of the Enterobacteriaceae. The 322 strains of E. chrysanthemi studied by Dickey (3) were all able to hydrolyze o-

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Lactose and melibiose metabolism in Erwinia chrysanthemi

Gray¹,

Lindner²,

Brand³

et al. 1986

J Bacteriol

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“…(1) recombination between the Lac plasmid and the host chromosome could lead to inactivation of the lac Y gene to give ML~, or of both the Y and Z genes to give ML~/ + , and further recombination could recreate the original plasmid or the third form of the plasmid; or (2) transposition of an IS fragment could produce the same effects without involving the chromosome; or (3) illegitimate recombination within the Lac plasmid could be responsible for the changes H-> -j + and -I-> =•-/ + , while the apparent reversions to the + state were the result of mutations to constitutivity of one of the two host galactoside permeases (other than that of the lac operon) able to accumulate lactose (Reeve & Braithwaite, 1973a). The results described below suggest that both mechanisms (1) or (2) and mechanism (3) are at work in different cases.…”

Section: Introductionmentioning

confidence: 99%

The lactose system ofKlebsiella aerogenesV9A: 5. Lac-permease defective mutants of twoKlebsiellaLac plasmids and their apparent reversion to wild type

Reeve¹

1976

Genet. Res.

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The Lac plasmids in two Klebsiella strains, V9A and RE 1544, give characteristic Lac-permease defective mutations which produce a lactose-negative (ML~) phenotype in the host strain, in spite of the presence of a lac operon on the chromosome. These ML~ clones can revert to the wild-type (ML + ) phenotype, and the mechanism of this reversion is examined. In V9A carrying its own Lac plasmid (F K lac), it is shown that reversion of ML~ to ML+ is usually the result of mutation to constitutivity of one of two galactoside permeases which are not induced by lactose but accumulate lactose when otherwise induced or made constitutive. However, in one out of the 51 ML+ revertants tested the mechanism of reversion appeared to be a change back to wild type of the Lac plasmid's own permease gene. In V9A carrying the Lac plasmid (pRE6) from RE1544, successive changes of phenotype were obtained of ML+ to ML-to ML+ to ML~ to ML+; these were all found to be the result of changes in the plasmid permease gene, and could be simply explained if an IS sequence could insert and excise from this gene. INTRODUCTIONMany Klebsiella strains exhibit a strong lactose-positive phenotype after incubation for 16-20 h on MacConkey Lactose Agar (ML agar). A number of such strains have been shown to contain a (Lac) plasmid which carries a lac operon, and also a chromosomal lac operon giving about 10 % as much /#-galactosidase activity as the plasmid operon. In consequence, loss of the plasmid gives a host strain showing a weak lactose-positive phenotype on ML agar (Reeve & Braithwaite, 19736).A curious feature shown by V9A, one of the Klebsiella strains examined which carries a Lac plasmid, is that it gives colonies of three distinct phenotypes on ML agar. These are strong lactose-positive (ML+), weak positive (MLH+) and negative (ML~), and the three phenotypes are consistently obtained and easily distinguished from each other on ML agar. ML~ and ML-'+ colonies are found occasionally when cells of the ML+ type are plated out, and each breeds true except that ML~ clones

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Die Virulenz‐Plasmide der Enterobacteriaceae

Tschäpe

Rische

1974

J of Basic Microbiology

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The lactose system inKlebsiella aerogenesV9A 2. Galactoside permeases which accumulate lactose or melibiose

Cited by 12 publications

References 15 publications

Lactose and melibiose metabolism in Erwinia chrysanthemi

Lactose and melibiose metabolism in Erwinia chrysanthemi

The lactose system ofKlebsiella aerogenesV9A: 5. Lac-permease defective mutants of twoKlebsiellaLac plasmids and their apparent reversion to wild type

Die Virulenz‐Plasmide der Enterobacteriaceae

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