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Query: UMLS:C0519030 (Klebsiella)
 21,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In Escherichia coli K-12 the naturally occurring hexitols D-mannitol, D-glucitol, and galactitol are taken up and phosphorylated via three distinct transport systems by a mechanism called either group translocation or vectorial phosphorylation. For every system, a membrane-bound enzyme II-complex of the phosphoenolpyruvate-dependent phosphotransferase system has been found, each requiring phosphoenolpyruvate, enzyme I, and HPr or alternatively P-HPr as the phosphate donor. Cells with a constitutive synthesis of all hexitol transport systems but with low P-HPr levels have very low transport and phosphorylating activities in vivo, although 40 to 90% of the enzyme II-complex activities are detected in cell extracts of such mutants. No indications for additional hexitol transport systems, especially for systems able to transport and accumulate free hexitols as in Klebsiella aerogenes, have been found. Substrate Km, and Vmax of the three transport systems for several hexitols and hexitol analogues have been determined by growth rates, transport activities, and in vitro phosphorylating activities. Each system was found to take up several hexitols, but only one hexitol serves as the inducer. This inducer invariably is the substrate with the highest affinity. Since bacterial transport systems, as a general rule, seem to have a relatively broad substrate specificity, in contrast to a more restricted inducer specificity, we propose to name the system inducible by D-mannitol and coded by the gene mtlA the D-mannitol transport system, the system inducible by D-glucitol and coded by gutA the D-glucitol transport system, and the system inducible by galactitol and coded by gatA the galactitol transport system.
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PMID:Nature and properties of hexitol transport systems in Escherichia coli. 110 Jun 8

A model for the domain structure of sigma 54-dependent transcriptional activators, based on sequence data, has been tested by examining the function of truncated and chimaeric proteins. Removal of the N-terminal domain of NtrC abolishes transcriptional activation, indicating that this domain is positively required for activator function. Over-expression of this domain as a separate peptide appears to titrate out the phosphorylating activity of NtrB. Removal of the N-terminal domain of NifA reduces activation 3-4-fold. The residual activity is particularly sensitive to inhibition by NifL, suggesting that the role of the N-terminal domain is to block the action of NifL in derepressing conditions. The C-terminal domain of NtrC showed repressor activity when expressed as a separate peptide. This domain is necessary for activator function even when NtrC binding sites are deleted from promoters. A point mutation in the ATP-binding motif of the NtrC central domain, Ser169 to Ala, also abolished activator function. Exchanging the N-terminal domains of Klebsiella pneumoniae NtrC, NifA and Escherichia coli OmpR, did not produce any hybrid activity, suggesting that N-terminal domains in the native proteins specifically recognize the rest of the molecule.
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PMID:The function of isolated domains and chimaeric proteins constructed from the transcriptional activators NifA and NtrC of Klebsiella pneumoniae. 218 Dec 38

Two multiresistant Klebsiella pneumoniae strains isolated from cerebrospinal fluid of human neonates were analyzed for their plasmid content. Two of the plasmids harbored by these strains, pJHCMW1 (11 kilobase pairs) and pJHCMW4 (75 kilobase pairs), carried genetic determinants for amikacin resistance. These plasmids also encoded resistance to kanamycin, tobramycin, and ampicillin which could be transferred to Escherichia coli by conjugation. Extracts from transconjugant derivatives carrying pJHCMW4 produced an acetyltransferase activity that acetylated all three aminoglycosides. Transconjugant derivatives carrying pJHCMW1 encoded both acetylating and phosphorylating activities. Southern blot hybridization analysis indicated considerable DNA homology between these two plasmids.
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PMID:Plasmid-encoded amikacin resistance in multiresistant strains of Klebsiella pneumoniae isolated from neonates with meningitis. 352 78

Sisomicin is a naturally occurring aminoglycoside antibiotic produced by Micromonospora inyoensis, while dibekacin and netilmicin are both semisynthetic aminoglycosides. Dibekacin is 3',4'-dideoxykanamycin B and netilmicin is 1-N-ethyl sisomicin. In both cases, these modifications render the agents insusceptible to some of the enzymes found in resistant strains of bacteria which inactivate the parent compounds. Antibacterial activity: All 3 drugs show bactericidal activity against a wide range of Gram-negative bacteria (including E. coli, Enterobacter, Klebsiella and Proteus spp. and Ps. aeruginosa) and also against staphylococci; however, in common with other amino-glycosides, streptococci are usually resistant (except when beta-lactam antibiotics are used in combination) and anaerobic organisms are not sensitive. Sisomicin is closely related structurally to gentamicin Cla, but in vitro studies have shown it to have superior activity to gentamicin against Ps. aeruginosa, closely paralleling the activity of tobramycin, while still possessing the high activity of gentamicin against Serratia and other Gram-negative rods. However, sisomicin is inactivated by virtually all bacterial enzymes which inactivate gentamicin and tobramycin. Nevertheless, it retains useful activity against a number of gentamicin-resistant strains of Ps. aeruginosa which are resistant by non-enzymatic (possibly permeability barrier) mechanisms; in this respect it closely resembles tobramycin. Dibekacin closely resembles tobramycin structurally and in vitro it seems to have a very similar antibacterial spectrum, including activity against some strains of Ps. aeruginosa resistant to gentamicin. Netilmicin has a generally broader antibacterial spectrum than gentamicin, tobramycin, sisomicin or debekacin and is resistant to inactivation by phosphorylating and adenylylating enzymes; however, it is inactivated by all acetylases, apart from acetylase 3-I. Its spectrum is therefore not as wide as that of amikacin against 'gentamicin-resistant' strains. Nonetheless, it is intrinsically more active than amikacin, weight-for-weight, against sensitive strains, apart possibly from Ps. aeruginosa. In fact, its activity against species of the Enterobacteriaceae and staphylococci sensitive to gentamicin is of the same order as the latter and possibly better for Klebsiella-Enterobacter species. All 3 agents show marked antibacterial synergy with a variety of beta-lactam antibiotics against a range of bacteria. Pharmacokinetically, sisomicin, netilmicin and dibekacin all behave like gentamicin. All 3 drugs are excreted in the urine unchanged and have beta-phase elimination half-lives of around 2 to
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PMID:Sisomicin, netilmicin and dibekacin. A review of their antibacterial activity and therapeutic use. 637 62

A mutant strain of Klebsiella aerogenes was constructed and, when incubated anaerobically with L-fucose and glycerol, synthesized and excreted a novel methyl pentitol, 6-deoxy L-talitol. The mutant was constitutive for the synthesis of L-fucose isomerase but unable to synthesize L-fuculokinase activity. Thus, it could convert the L-fucose to L-fuculose but was incapable of phosphorylating L-fuculose to L-fuculose 1-phosphate. The mutant was also constitutive for the synthesis of ribitol dehydrogenase, and in the presence of sufficient reducing power this latter enzyme catalyzed the reduction of the L-fuculose to 6-deoxy L-talitol. The reducing equivalents required for this reaction were generated by the oxidation of glycerol to dihydroxyacetone with an anaerobic glycerol dehydrogenase. The parent strain of K. aerogenes was unable to utilize the purified 6-deoxy L-talitol as a sole source of carbon and energy for growth; however, mutant could be isolated which had gained this ability. Such mutants were found to be constitutive for the synthesis of ribitol dehydrogenase and were thus capable of oxidizing 6-deoxy L-talitol to L-fuculose. Further metabolism of L-fuculose was shown by mutant analysis to be mediated by the enzymes of the L-fucose catabolic pathway.
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PMID:Biosynthesis and catabolism of 6-deoxy L-talitol by Klebsiella aerogenes mutants. 698 6