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

Escherichia coli C strains can grow at the expense of the two natural pentitols ribitol and D-arabitol, sugar alcohols previously thought not to be utilized by E. coli. E. coli strains K-12 and B cannot utilize either compound. The genetic loci responsible for pentitol catabolism in E. coli C, designated rtl and atl, are separate and closely linked. Each lies between metG and his and is highly co-transducible with metG and with a P2 prophage attachment site. rtl and atl readily can be transduced into E. coli K-12 or B strains, in which they integrate at, or very near, their E. coli C location. Transduction also can be used to insert rtl and atl into certain E. coli K-12 F' plasmids. No recombination between E. coli C strains and either K-12 or B strains occurs within the rtl-atl genetic region after interstrain conjugations or transductions. No cryptic rtl or atl genes in K-12 or B strains can be detected by complementation, recombination, or mutagenesis. These results are consistent with the view that the rtl-atl portion of the E. coli C chromosome has no counterpart in E. coli K-12 or B and may have been obtained from an extrageneric source. Detailed biochemical and genetic comparisons of penitol utilization in E. coli and Klebsiella aerogenes are in progress. The ability to catabolize xylitol is conferred upon E. coli C strains by a mutation at or adjacent to the rtl locus, whereas in E. coli K-12 or B strains harboring rtl an additional mutation at a separate locus is required for xylitol utilization.
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PMID:Genes for ribitol and D-arabitol catabolism in Escherichia coli: their loci in C strains and absence in K-12 and B strains. 109 16

A cryptic citrate transport gene (citA) from Salmonella typhimurium chromosome was cloned and its nucleotide sequence was determined. The cloned plasmid conferred citrate-utilizing ability on wild-type Escherichia coli, which cannot grow on citrate as the sole source of carbon. The resultant E. coli transformant was able to transport citrate. A 1,302-base-pair open reading frame with a preceding ribosomal binding site was found in the cloned DNA fragment. The 434-amino-acid protein that could be translated from this open reading frame is highly hydrophobic (69% nonpolar amino acid residues), consistent with the fact that the transport protein is an intrinsic membrane protein. The molecular weight of this protein was calculated to be 47,188. The gene sequence determined is highly homologous to those of Cit+ plasmid-mediated citrate transport gene, citA, from E. coli, the chromosomal citA gene from Citrobacter amalonaticus and the chromosomal cit+ gene from Klebsiella pneumoniae. The hydropathy profile of the deduced amino acid sequence suggests that this carrier has 12 hydrophobic segments, which may span the membrane lipid bilayer.
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PMID:Cloning and nucleotide sequence of the gene (citA) encoding a citrate carrier from Salmonella typhimurium. 171 53

The pathway construction for biosynthesis of aromatic amino acids in Escherichia coli is atypical of the phylogenetic subdivision of gram-negative bacteria to which it belongs (R. A. Jensen, Mol. Biol. Evol. 2:92-108, 1985). Related organisms possess second pathways to phenylalanine and tyrosine which depend upon the expression of a monofunctional chorismate mutase (CM-F) and cyclohexadienyl dehydratase (CDT). Some enteric bacteria, unlike E. coli, possess either CM-F or CDT. These essentially cryptic remnants of an ancestral pathway can be a latent source of biochemical potential under certain conditions. As one example of advantageous biochemical potential, the presence of CM-F in Salmonella typhimurium increases the capacity for prephenate accumulation in a tyrA auxotroph. We report the finding that a significant fraction of the latter prephenate is transaminated to L-arogenate. The tyrA19 mutant is now the organism of choice for isolation of L-arogenate, uncomplicated by the presence of other cyclohexadienyl products coaccumulated by a Neurospora crassa mutant that had previously served as the prime biological source of L-arogenate. Prephenate aminotransferase activity was not conferred by a discrete enzyme, but rather was found to be synonymous with the combined activities of aspartate aminotransferase (aspC), aromatic aminotransferase (tyrB), and branched-chain aminotransferase (ilvE). This conclusion was confirmed by results obtained with combinations of aspC-, tyrB-, and ilvE-deficient mutations in E. coli. An example of disadvantageous biochemical potential is the presence of a cryptic CDT in Klebsiella pneumoniae, where a mutant carrying multiple enzyme blocks is the standard organism used for accumulation and isolation of chorismate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Remnants of an ancient pathway to L-phenylalanine and L-tyrosine in enteric bacteria: evolutionary implications and biotechnological impact. 208 22

Bacterial plasmids have become valuable markers for the comparison of strains of nosocomial gram-negative bacilli. The importance of plasmids in nosocomial infections is primarily due to their transferable antibiotic resistance genes (R plasmids), but other plasmid-mediated traits may eventually serve as potential markers. Stable cryptic plasmids have also served to relate outbreak strains, particularly nonfermenting strains of gram-negative bacteria. Klebsiella pneumoniae and Serratia marcescens have been the major plasmid-containing species in outbreaks involving single or multiple species. Outbreaks of single species with common plasmid patterns have included the Enterobacteriaceae, Pseudomonas aeruginosa, Pseudomonas cepacia, Ewingella americana, and Legionella pneumophila. Intrageneric spread of the same or similar R plasmids has nearly always occurred within the Enterobacteriaceae in large medical centers or Veterans Administration hospitals. High-risk nurseries and burn units have been conspicuous foci for R plasmid evolution. Hospital epidemiologists and clinical microbiologists will likely have an ever-increasing need to determine the plasmid content of gram-negative bacilli producing endemic and epidemic nosocomial infections.
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PMID:Plasmids as epidemiologic markers in nosocomial gram-negative bacilli: experience at a university and review of the literature. 353 13

In the Enterobacteriaceae, beta-glucosides are catabolized by a complex system formed of three permeases, with partly overlapping substrate specificities, and two hydrolytic enzymes, phospho-beta-glucosidase A and B, which hydrolyze only phosphorylated beta-glucosides. Some Enterobacteriaceae such as Klebsiella-Aerobacter (Enterobacter) possess the complete system; others possess only parts of it or may have a cryptic phospho-beta-glucosidase activity without permease activity. A screening test applied to strains belonging to several genera of Enterobacteriaceae showed that strains of Citrobacter, Hafnia, and Serratia exhibit a degree of similarity in phospho-beta-glucosidase activity and inducibility which could be useful in their taxonomic characterization; others, such as Aerobacter aerogenes, Erwinia, and Proteus vulgaris, are more heterologous. Owing to the presence of inducible phospho-beta-glucosidases A and B in Citrobacter, the fermentation of beta-methyl glucoside and the fermentation of arbutin in mixture with cellobiose could be of diagnostic value in the differentiation of Citrobacter from Salmonella. Wild-type strains of Escherichia coli, Shigella, and Salmonella are phenotypically similar in their inability to catabolize beta-glucosides, the presence of constitutive P-beta-glucosidase A, and the lack of beta-glucoside permeases I and II. Their beta-glucoside-fermenting mutants show, however, a phospho-beta-glucosidase and beta-glucoside permease activity which is characteristic for mutants from each genus. The differences in the phenotype of the mutants reflect probable differences in the presence of cryptic genes in the wild-type strains and could be of evolutionary significance.
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PMID:Taxonomic investigations on expressed and cryptic phospho-beta-glucosidases in Enterobacteriaceae. 489 9

Relationship between the resistance of Klebsiella spp. to beta-lactam antibiotics and the capacity of ampicillin and cephaloridin for penetration through the cell wall of this organism was studied. It was shown that Klebsiella sp. 182 and 600 were more sensitive to cephaloridin and more resistant to ampicillin than Klebsiella sp. D 535. Estimation of the cryptic index showed that the resistance of Klebsiella sp. 182 and 600 was mainly connected with permeability of their cell walls. In Klebsiella sp. D 535 ampicillin freely penetrated through the cell wall. In the strains tested, the levels of the resistance to oxacillin, benzylpenicillin and dicloxacillin correlated with the values of the cryptic index characterizing barrier function of the cell wall.
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PMID:[Effect of the cell wall permeability of Klebsiella spp. on beta-lactam antibiotic resistance]. 655 51

Bordetella bronchiseptica is a ureolytic mammalian respiratory pathogen. We have investigated the regulation of urease in B. bronchiseptica and the potential role of this enzyme in eukaryotic invasion and intracellular survival. Our results indicate urease is a bordetella virulence repressed gene. Urease activity in virulent B. bronchiseptica BB7865 is up-regulated from basal levels by 5 gl1 magnesium sulphate at 37 degrees C. At 30 degrees C, urease activity remained at basal levels, even in the presence on magnesium sulphate, suggesting a second temperature dependent mechanism of urease regulation was also operating. Urease was not inducible by 10 mM urea nor up-regulated in nitrogen limiting conditions. To evaluate the role of urease in intracellular invasion and survival urease-negative mutants of B. bronchiseptica BB7865 and B. bronchiseptica BB7866 were created by transposon mutagenesis, and compared to the urease-positive parental strains in a HeLa cell invasion assay. We demonstrate that increasing the concentration of urea in the assay increased survival of the urease-positive but not urease-negative strains after 24 h, suggesting that urease does have a role in intracellular survival. Partial DNA sequence analysis of an 11.0 kb EcoRI DNA fragment encoding urease activity revealed an open reading frame containing 50%, 45%, 45%, and 41% homology to the UreA urease subunit protein of Klebsiella aerogenes, Proteus vulgaris, Helicobacter pylori and Proteus mirabilis respectively. We also show Bordetella pertussis to contain sequences homologous with a DNA probe containing the gene encoding UreA of B. bronchiseptica indicating the possible presence of cryptic urease genes in this species.
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PMID:Molecular analysis of the bvg-repressed urease of Bordetella bronchiseptica. 893 44

Data for further development of the flagellar antigen genetics of the species Escherichia coli are reported. Two new flagellin genes named fllA and flmA were found in E. coli 781-55, E2987-73, and E223-69, the test strains for E. coli flagellar antigens H44, H55, and H54, respectively (collection of the International Escherichia and Klebsiella Centre of the World Health Organization, Copenhagen, Denmark). Two alleles of fllA were identified that encode flagellar antigens H44 (fllA44) and H55 (fllA55), and the only flmA allele found (flmA54) encodes antigen H54. The sites of their integration in the E. coli K-12 chromosome after P1-mediated transduction were approximately determined and found to be separate from each other and from the known regions of flagellar genes of E. coli and salmonellae. The region of flm54 was found to repress the expression of some alleles of the flagellin gene fliC. In addition, cryptic genes encoding antigens H4 and H38 were found in phenotypically monophasic test strains 781-55 and E2987-73, respectively.
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PMID:New flagellin-specifying genes in some Escherichia coli strains. 947 55

Plasmid pTKH11, originally obtained by electroporation of a Klebsiella oxytoca plasmid preparation into Escherichia coli XAC, expressed a high level of an AmpC-like beta-lactamase. The enzyme, designated CMY-5, conferred resistance to extended-spectrum beta-lactams in E. coli; nevertheless, the phenotype was cryptic in the K. oxytoca donor. Determination of the complete nucleotide sequence of pTKH11 revealed that the 8,193-bp plasmid encoded seven open reading frames, including that for the CMY-5 beta-lactamase (blaCMY-5). The blaCMY-5 product was similar to the plasmidic CMY-2 beta-lactamase of K. pneumoniae and the chromosomal AmpC of Citrobacter freundii, with 99.7 and 97.0% identities, respectively; there was a substitution of phenylalanine in CMY-5 for isoleucine 105 in CMY-2. blaCMY-5 was followed by the Blc and SugE genes of C. freundii, and this cluster exhibited a genetic organization identical to that of the ampC region on the chromosome of C. freundii; these results confirmed that C. freundii AmpC was the evolutionary origin of the plasmidic cephamycinases. In the K. oxytoca host, the copy number of pTKH11 was very low and the plasmid coexisted with plasmid pNBL63. Analysis of the replication regions of the two plasmids revealed 97% sequence similarity in the RNA I transcripts; this result implied that the two plasmids might be incompatible. Incompatibility of the two plasmids might explain the cryptic phenotype of blaCMY-5 in K. oxytoca through an exclusion effect on pTKH11 by resident plasmid pNBL63.
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PMID:Characterization and nucleotide sequence of a Klebsiella oxytoca cryptic plasmid encoding a CMY-type beta-lactamase: confirmation that the plasmid-mediated cephamycinase originated from the Citrobacter freundii AmpC beta-lactamase. 1034 51

The Escherichia coli K-12 genome (ECO) was compared with the sampled genomes of the sibling species Salmonella enterica serovars Typhimurium, Typhi and Paratyphi A (collectively referred to as SAL) and the genome of the close outgroup Klebsiella pneumoniae (KPN). There are at least 160 locations where sequences of >400 bp are absent from ECO but present in the genomes of all three SAL and 394 locations where sequences are present in ECO but close homologs are absent in all SAL genomes. The 394 sequences in ECO that do not occur in SAL contain 1350 (30.6%) of the 4405 ECO genes. Of these, 1165 are missing from both SAL and KPN. Most of the 1165 genes are concentrated within 28 regions of 10-40 kb, which consist almost exclusively of such genes. Among these regions were six that included previously identified cryptic phage. A hypothetical ancestral state of genomic regions that differ between ECO and SAL can be inferred in some cases by reference to the genome structure in KPN and the more distant relative Yersinia pestis. However, many changes between ECO and SAL are concentrated in regions where all four genera have a different structure. The rate of gene insertion and deletion is sufficiently high in these regions that the ancestral state of the ECO/SAL lineage cannot be inferred from the present data. The sequencing of other closely related genomes, such as S.bongori or Citrobacter, may help in this regard.
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PMID:Comparison of the Escherichia coli K-12 genome with sampled genomes of a Klebsiella pneumoniae and three salmonella enterica serovars, Typhimurium, Typhi and Paratyphi. 1112 89


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