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

A number of mutants have been isolated which affect regulation of the nitrogen fixation (nif) gene cluster in Klebsiella pneumoniae and all of which are linked to glnA, the structural gene for glutamine synthetase (G.S.). These mutants were classified on the basis of their G.S. and nitrogenase activities in conditions of nitrogen limitation and excess. The plasmid R68.45 was then used to generate a number of R-primes carrying the glnA region of the K. pneumoniae chromosome. One of these R-primes (pGE10) was subsequently used in complementation analysis and by isolation of transposon-induced insertion mutations in pGE10 we have demonstrated the existence of a gene, glnG, closely linked to glnA. Mutations in glnG have a similar phenotype to glnG mutants described in Escherichia coli (Pahel and Tyler 1979) and Salmonella typhimurium (Kustu et al. 1979) in that substantially reduce G.S. activity but are not glutamine auxotrophs. GlnG mutants have very low nitrogenase activity indicating that the glnG product may be involved regulation of the nif gene cluster in K. pneumoniae.
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PMID:Complementation analysis of glnA-linked mutations which affect nitrogen fixation in Klebsiella pneumoniae. 612 Apr 41

We isolated pleiotropic mutants of Klebsiella aerogenes with the transposon Tn5 which were unable to utilize a variety of poor sources of nitrogen. The mutation responsible was shown to be in the asnB gene, one of two genes coding for an asparagine synthetase. Mutations in both asnA and asnB were necessary to produce an asparagine requirement. Assays which could distinguish the two asparagine synthetase activities were developed in strains missing a high-affinity asparaginase. The asnA and asnB genes coded for ammonia-dependent and glutamine-dependent asparagine synthetases, respectively. Asparagine repressed both enzymes. When growth was nitrogen limited, the level of the ammonia-dependent enzyme was low and that of the glutamine-dependent enzyme was high. The reverse was true in a nitrogen-rich (ammonia-containing) medium. Furthermore, mutations in the glnG protein, a regulatory component of the nitrogen assimilatory system, increased the level of the ammonia-dependent enzyme. The glutamine-dependent asparagine synthetase was purified to 95%. It was a tetramer with four equal 57,000-dalton subunits and catalyzed the stoichiometric generation of asparagine, AMP, and inorganic pyrophosphate from aspartate, ATP, and glutamine. High levels of ammonium chloride (50 mM) could replace glutamine. The purified enzyme exhibited a substrate-independent glutaminase activity which was probably an artifact of purification. The tetramer could be dissociated; the monomer possessed the high ammonia-dependent activity and the glutaminase activity, but not the glutamine-dependent activity. In contrast, the purified ammonia-dependent asparagine synthetase, about 40% pure, had a molecular weight of 80,000 and is probably a dimer of identical subunits. Asparagine inhibited both enzymes. Kinetic constants and the effect of pH, substrate, and product analogs were determined. The regulation and biochemistry of the asparagine synthetases prove the hypothesis strongly suggested by the genetic and physiological evidence that a glutamine-dependent enzyme is essential for asparagine synthesis when the nitrogen source is growth rate limiting.
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PMID:Asparagine synthetases of Klebsiella aerogenes: properties and regulation of synthesis. 612 99

Regulation of the synthesis of glutamine synthetase and of the arginine and glutamine transport systems (Ntr phenotype) in Salmonella have been shown to require two regulatory genes on the C-terminal side of the glnA gene (McFarland et al., 1981). We have cloned a HindIII-EcoRI DNA fragment from Escherichia coli coding for analogous properties with respect to the Ntr phenotype in E. coli. A plasmid containing this E. coli DNA fragment joined to another fragment carrying a cyanobacterial glnA gene (but no functional regulatory genes) was introduced into a Klebsiella pneumoniae mutant with a Gln-Ntr- phenotype, i.e., which could not derepress nitrogenase. The cyanobacterial gene made the Klebsiella strain Gln+ and the E. coli DNA fragment made the strain Ntr+, including the ability to derepress nitrogenase fully. Thus the products of the glnA-linked ntr genes of E. coli can regulate expression of the Ntr-dependent genes of Klebsiella.
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PMID:The ntr genes of Escherichia coli activate the hut and nif operons of Klebsiella pneumoniae. 612 88

Derepression of nitrogen fixation (nif) genes in Klebsiella pneumoniae following transfer from NH+4-sufficiency to N-free medium was preceded by rapid expansion of the guanosine 5'-diphosphate 3'-diphosphate (ppGpp) pool. When derepressed in N-free medium supplemented with glutamine (600 micrograms ml-1), expression from the nifH and nifL promoters, determined as beta-galactosidase activity in nif::lac merodiploid strains, was stimulated 7-fold and nitrogenase activity 26-fold; ppGpp did not accumulate, remaining at the levels found in NH+4-repressed populations. The relaxed mutant K. pneumoniae relA40, which accumulates only very low levels of ppGpp, showed partial derepression of nitrogenase activity in the presence of glutamine, thus ppGpp is unlikely to be an effector of nif expression. ATP and GTP levels were elevated under conditions where nif expression was enhanced, consistent with previous data suggesting that maintenance of ATP levels is a prerequisite for the expression of nif genes in K. pneumoniae.
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PMID:Nitrogenase synthesis in Klebsiella pneumoniae: enhanced nif expression without accumulation of guanosine 5'-diphosphate 3'-diphosphate. 639 16

The N2 fixing bacteria Klebsiella pneumoniae, Azospirillum brasilense, Rhodopseudomonas sphaeroides and Rhodospirillum rubrum, but not Azotobacter vinelandii accumulate the glutamine analogue methionine sulfoximine in the cell. In the accumulating cells methionine sulfoximine inhibits ammonium transport. Accumulation and inhibition are prevented by glutamine.
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PMID:Uptake of methionine sulfoximine by some N2 fixing bacteria, and its effect on ammonium transport. 641 71

The nitrogen fixation (nif) genes of Rhodopseudomonas capsulata appear to be much more widely dispersed than those of the well-studied Klebsiella pneumoniae. In both organisms the genes coding for the structural components of the nitrogenase complex, nifHDK, comprise a single unit of transcription. Only in the photosynthetic bacterium, however, are there multiple copies of these genes. The extra copies are normally silent but they can be activated by mutation, detected as nif+ pseudorevertants of nif- deletions of the expressed nifHDK genes. Glutamine is required for the repression of nif gene transcription in R. capsulata.
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PMID:Organization and regulation of nitrogen fixation genes of Rhodopseudomonas capsulata. 644 24

A mutant of the enterobacterium Klebsiella pneumoniae with a defect in the hisF gene (in the histidine biosynthesis pathway) was isolated, which can only grow with high but not low ammonia concentrations. The mutated hisF product can use ammonia for the formation of the imidazole ring of histidine but not glutamine provided by the hisH product. Site-directed insertional mutagenesis of hisH led to the same dependence of prototrophic growth on high ammonia levels. The nucleotide sequence of K. pneumoniae hisF is almost identical to that of hisF from other enterobacteria. Similarities of the hisF product with the hisA product and of HisH sequences with the glutamine binding domains of TrpG-type amidotransferases provide additional evidence for the functions of the hisF and hisH products in histidine biosynthesis, namely that HisF catalyzes the ammonolytic cleavage of N'-(5'-phosphoribulosyl)-formimino-5- aminoimidazole-4-carboxamide ribonucleotide either utilizing free ammonia or deriving the ammonia moiety from glutamine bound to HisH.
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PMID:Function of hisF and hisH gene products in histidine biosynthesis. 818 43

The signal sequence of the Klebsiella oxytoca puIG gene product, which is required for extracellular secretion of the enzyme pullulanase, is similar in many respects to the corresponding segment of the precursors of type IV (me-Phe) pilins. The significance of this similarity is confirmed by the observation that the puIO gene product processes prePuIG at the consensus type IV prepilin peptidase cleavage site at the amino-terminal end of the PuIG signal sequence. Like most type IV pilins, processed PuIG was found to have a methylated amino-terminal phenylalanine residue. Site-directed mutagenesis was used to replace amino acids in prePuIG that correspond to residues shown by others to be essential for processing, methylation and assembly of type IV pilins. The glycine residue on the amino-terminal side of the prePuIG cleavage site is absolutely required for processing and for pullulanase secretion. The glutamate residue at position 11(+5) is also required for pullulanase secretion but not for processing or methylation. This result contrasts with that reported for corresponding variants of Pseudomonas aeruginosa type IV prepilin, which were processed but only inefficiently N-methylated. Cleavage of prePuIG and pullulanase secretion were both unaffected by replacement of the phenylalanine residue on the carboxy-terminal side of the cleavage site by leucine, isoleucine or valine, by a conservative substitution within the hydrophobic core of the prePuIG signal sequence, or by a glutamine to proline substitution within the processed segment. However, replacement of the same glutamine residue by arginine abolished secretion without affecting either processing or methylation.
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PMID:Processing and methylation of PuIG, a pilin-like component of the general secretory pathway of Klebsiella oxytoca. 841 82

Enterobacterial mutants defective in the nitrogen control regulatory system (Ntr) generally display a pleiotropic phenotype with regard to expression and regulation of several enzymes and transport systems involved in the assimilation of N sources. This report describes the isolation and characterization of similar pleiotropic mutants of Klebsiella pneumoniae that cannot be complemented by ntr genes. The strains excreted ammonia, were unable to grow on a number of N sources, and contained low glutamine:2-oxoglutarate amino transferase and normal, but unmodifiable glutamine synthetase activities and a nitrogenase level largely unaffected by ammonium, but still repressible by an amino acid mixture. Genetic studies suggested that this phenotype is due to overexpression of an unknown regulatory protein.
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PMID:Ammonia-excreting mutants of Klebsiella pneumoniae with a pleiotropic defect in nitrogen metabolism. 908 15

Internal pool sizes of glutamine and glutamate in Klebsiella pneumoniae grown under nitrogen limitation or nitrogen sufficiency were measured to study the signal transduction of external nitrogen limitation. K. pneumoniae cells were grown in an anaerobic, ammonium-limited chemostat culture. At a growth rate of 0.217 h(-1), the steady state ammonium concentration in the culture was 55 microm, correlating with repression of the nitrogen fixation (nif) genes. At growth rates below 0.138 h(-1), the ammonium concentration in the culture dropped below 0.5 microm and the nif genes became derepressed. During the transition from nitrogen sufficiency to nitrogen limitation, the internal glutamine pool in K. pneumoniae decreased by a factor of approximately 6. The glutamate pool, however, remained stable. Similarly, in anaerobic batch cultures with different limiting nitrogen sources, the glutamine pool generally decreased by a factor of 7 to 9 when nif gene derepression was achieved. All the limiting nitrogen sources used resulted in decreased growth rates compared with growth under nitrogen excess, suggesting an inverse relationship between glutamine pool size and doubling time. These studies indicate that K. pneumoniae perceives external nitrogen limitation as internal glutamine limitation.
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PMID:Internal glutamine and glutamate pools in Klebsiella pneumoniae grown under different conditions of nitrogen availability. 1101 74


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