scholarly journals Electron transfer to nitrogenase in Klebsiella pneumoniae. nifF gene cloned and the gene product, a flavodoxin, purified

1985 ◽  
Vol 231 (3) ◽  
pp. 743-753 ◽  
Author(s):  
J Deistung ◽  
F C Cannon ◽  
M C Cannon ◽  
S Hill ◽  
R N F Thorneley
Keyword(s):  
Electron Transfer ◽  
Klebsiella Pneumoniae ◽  
Gene Product ◽  
Type Strain ◽  
Wild Type Strain ◽  
Elevated Concentration ◽  
Multicopy Plasmid ◽  
Wild Type ◽  
Strain Characterization

The nifF gene of Klebsiella pneumoniae was cloned into a multicopy plasmid in order to construct a strain that synthesizes and retains an elevated concentration of the gene product relative to the wild-type strain. Characterization of the isolated flavodoxin, which serves as an electron donor to nitrogenase, shows unambiguously that it is the product of the nifF gene.

scholarly journals Role of Lung Epithelial Cells in Defense against Klebsiella pneumoniae Pneumonia

2002 ◽  
Vol 70 (3) ◽  
pp. 1075-1080 ◽  
Author(s):  
Guadalupe Cortés ◽  
Dolores Álvarez ◽  
Carles Saus ◽  
Sebastián Albertí
Keyword(s):  
Epithelial Cells ◽  
Klebsiella Pneumoniae ◽  
Type Strain ◽  
Pathogenic Bacteria ◽  
Wild Type Strain ◽  
Capsular Polysaccharide ◽  
Defense Mechanism ◽  
Lung Epithelial Cells ◽  
Wild Type ◽  
Lung Epithelial

ABSTRACT The airway epithelium represents a primary site for the entry of pathogenic bacteria into the lungs. It has been suggested for many respiratory pathogens, including Klebsiella pneumoniae, that adhesion and invasion of the lung epithelial cells is an early stage of the pneumonia process. We observed that poorly encapsulated K. pneumoniae clinical isolates and an isogenic unencapsulated mutant invaded lung epithelial cells more efficiently than highly encapsulated strains independent of the K type. By contrast, the unencapsulated mutant was completely avirulent in a mouse model of pneumonia, unlike the wild-type strain, which produced pneumonia and systemic infection. Furthermore, the unencapsulated mutant bound more epithelially produced complement component C3 than the wild-type strain. Our results show that lung epithelial cells play a key role as a host defense mechanism against K. pneumoniae pneumonia, using two different strategies: (i) ingestion and control of the microorganisms and (ii) opsonization of the microorganisms. Capsular polysaccharide avoids both mechanisms and enhances the virulence of K. pneumoniae.

scholarly journals Characterization of a Legionella pneumophila relA Insertion Mutant and Roles of RelA and RpoS in Virulence Gene Expression

2002 ◽  
Vol 184 (1) ◽  
pp. 67-75 ◽  
Author(s):  
Tal Zusman ◽  
Ohad Gal-Mor ◽  
Gil Segal
Keyword(s):  
Gene Expression ◽  
Stationary Phase ◽  
Gene Product ◽  
Legionella Pneumophila ◽  
Type Strain ◽  
Wild Type Strain ◽  
Insertion Mutant ◽  
Wild Type ◽  
Intracellular Growth ◽  
Virulence Gene Expression

ABSTRACT To investigate the involvement of RelA in the regulation of Legionella pneumophila virulence, a deletion substitution was constructed in the relA gene. The relA knockout resulted in an undetectable level of ppGpp in the cells during the stationary phase, but the original level was restored when the relA gene product was supplied on a plasmid. The effect of the relA mutation was examined with two systems that are known to be expressed during the stationary phase in L. pneumophila. Pigment production was found to be dependent on the relA gene product, and only one-half as much pigment was produced by the relA mutant as by the wild-type strain. Flagellum gene expression was also found to be dependent on the relA gene product, as determined with a flaA::lacZ fusion. However, the relA gene product was found to be dispensable for intracellular growth both in HL-60-derived human macrophages and in the protozoan host Acanthamoeba castellanii. To determine the involvement of the relA gene product in expression of L. pneumophila genes required for intracellular growth (icm/dot genes), nine icm::lacZ fusions were constructed, and expression of these fusions in the wild-type strain was compared with their expression in relA mutant strains. Expression of only one of the icm::lacZ fusions was moderately reduced in the relA mutant strain. Expression of the nine icm::lacZ fusions was also examined in a strain containing an insertion in the gene that codes for the stationary-phase sigma factor RpoS, and similar results were obtained. We concluded that RelA is dispensable for intracellular growth of L. pneumophila in the two hosts examined and that both RelA and RpoS play minor roles in L. pneumophila icm/dot gene expression.

scholarly journals Characterization of a Wild-Type Strain ofFrancisella TularensisIsolated from a Cat

2004 ◽  
Vol 16 (5) ◽  
pp. 374-381 ◽  
Author(s):  
Thomas J. Inzana ◽  
Gretchen E. Glindemann ◽  
Gerald Snider ◽  
Susan Gardner ◽  
Lisa Crofton ◽  
...  
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type

scholarly journals Roles of Capsule and Lipopolysaccharide O Antigen in Interactions of Human Monocyte-Derived Dendritic Cells and Klebsiella pneumoniae

2009 ◽  
Vol 78 (1) ◽  
pp. 210-219 ◽  
Author(s):  
B. Evrard ◽  
D. Balestrino ◽  
A. Dosgilbert ◽  
J.-L. J. Bouya-Gachancard ◽  
N. Charbonnel ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Klebsiella Pneumoniae ◽  
Type Strain ◽  
Wild Type Strain ◽  
Cytokine Production ◽  
Human Monocyte ◽  
Confocal Laser ◽  
Wild Type ◽  
O Antigen ◽  
Th1 Cytokine

ABSTRACT In humans, Klebsiella pneumoniae is a saprophytic bacterium of the nasopharyngeal and intestinal mucosae that is also frequently responsible for severe nosocomial infections. Two major factors of virulence, capsular polysaccharide (CPS) and lipopolysaccharide (LPS) O antigen, are involved in mucosal colonization and the development of infections. These bacterial surface structures are likely to play major roles in interactions with the mucosal immune system, which are orchestrated by a network of surveillance based on dendritic cells (DCs). To determine the roles of K. pneumoniae CPS and LPS in the DC response, we investigated the response of immature human monocyte-derived DCs to bacterial challenge with a wild-type strain and its isogenic mutants deficient in CPS or LPS O-antigen production. As observed by flow cytometry and confocal laser microscopy, the rate of phagocytosis was inversely proportional to the amount of CPS on the bacterial cell surface, with LPS playing little or no role. The K. pneumoniae wild-type strain induced DC maturation with upregulation of CD83, CD86, and TLR4 and downregulation of CD14 and DC-SIGN. With CPS mutants, we observed a greater decrease in DC-SIGN, suggesting a superior maturation of DCs. In addition, incubation of DCs with CPS mutants, and to a lesser extent with LPS mutants, resulted in significantly higher Th1 cytokine production. Combined, our findings suggest that K. pneumoniae CPS, by hampering bacterial binding and internalization, induces a defective immunological host response, including maturation of DCs and pro-Th1 cytokine production, whereas the LPS O antigen seems to be involved essentially in DC activation.

scholarly journals Role of β-Lactamases and Porins in Resistance to Ertapenem and Other β-Lactams in Klebsiella pneumoniae

2004 ◽  
Vol 48 (8) ◽  
pp. 3203-3206 ◽  
Author(s):  
George A. Jacoby ◽  
Debra M. Mills ◽  
Nancy Chow
Keyword(s):  
Klebsiella Pneumoniae ◽  
Outer Membrane ◽  
Type Strain ◽  
Wild Type Strain ◽  
Outer Membrane Proteins ◽  
Wild Type ◽  
Resistant Mutants ◽  
High Level ◽  
Level Resistance

ABSTRACT High-level resistance to ertapenem was produced by β-lactamases of groups 1, 2f, and 3 in a strain of Klebsiella pneumoniae deficient in Omp35 and Omp36. From a wild-type strain producing ACT-1 β-lactamase, ertapenem-resistant mutants for which the ertapenem MICs were up to 128 μg/ml and expression of outer membrane proteins was diminished could be selected.

scholarly journals Regulation and Characterization of a Newly Deduced Cell Wall Hydrolase Gene (cwlJ) Which Affects Germination of Bacillus subtilis Spores

1998 ◽  
Vol 180 (6) ◽  
pp. 1375-1380 ◽  
Author(s):  
Shu Ishikawa ◽  
Kunio Yamane ◽  
Junichi Sekiguchi
Keyword(s):  
Bacillus Subtilis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Catalytic Domain ◽  
Slow Release ◽  
Dipicolinic Acid ◽  
Northern Hybridization ◽  
Predicted Amino Acid Sequence ◽  
Wild Type

ABSTRACT The predicted amino acid sequence of Bacillus subtilis ycbQ (renamed cwlJ) exhibits high similarity to those of the deduced C-terminal catalytic domain of SleBs, the specific cortex-hydrolyzing enzyme of B. cereus and the deduced one of B. subtilis. We constructed acwlJ::lacZ fusion in the B. subtilischromosome. The β-galactosidase activity and results of Northern hybridization and primer extension analyses of the cwlJgene indicated that it is transcribed by EςE RNA polymerase. cwlJ-deficient spores responded to bothl-alanine and AGFK, the A 580 values of spore suspensions decreased more slowly than in the case of the wild-type strain, and the mutant spores released less dipicolinic acid than did those of the wild-type strain during germination. However, the mutant spores released only slightly less hexosamine than did the wild-type spores. In contrast, B. subtilis sleB spores did not release hexosamine at a significant level. While cwlJand sleB spores were able to germinate, CJSB (cwlJ sleB) spores could not germinate but exhibited initial germination reactions, e.g., partial decrease inA 580 and slow release of dipicolinic acid. CJSB spores became slightly gray after 6 h in the germinant, but their refractility was much greater than that of sleB mutant spores. The roles of the sleB and cwlJmutations in germination and spore maturation are also discussed.

scholarly journals Characterization of melanin produced by a wild-type strain of Bacillus thuringiensis

2004 ◽  
Vol 50 (4) ◽  
pp. 183-188 ◽  
Author(s):  
Yuehua Chen ◽  
Yinyue Deng ◽  
Jinhong Wang ◽  
Jun Cai ◽  
Gaixin Ren
Keyword(s):  
Bacillus Thuringiensis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type

Purification and characterization of a β-glucosidase from Streptomyces lividans 66

1990 ◽  
Vol 36 (1) ◽  
pp. 53-56 ◽  
Author(s):  
Anca Mihoc ◽  
Dieter Kluepfel
Keyword(s):  
High Performance Liquid Chromatography ◽  
Molecular Sieve ◽  
Type Strain ◽  
High Performance ◽  
Wild Type Strain ◽  
Streptomyces Lividans ◽  
Wild Type ◽  
Purification And Characterization ◽  
Anion Exchange Column

An intracellular β-1, 4-D-glucosidase (EC 3.2.1.21) was isolated from the mutant strain HP-3 of Streptomyces lividans 66 which produced about 12 times more enzyme than the wild-type strain. The purification was carried out by anion exchange column chromatography followed by high-performance liquid chromatography on DEAE and on molecular sieve columns. The enzyme is glycosylated and has an apparent Mr of 51 000 and a pI of 4.3. Its activity was optimal at pH 6.5 and at a temperature of 40 °C. The Km and the Vmax on cellobiose were 3.1 mM and 65.6 μmol min−1 mg−1 of enzyme. Key words: β-glucosidase, Streptomyces lividans, purification, characterization.

scholarly journals Homologous, homeologous, and illegitimate repair of double-strand breaks during transformation of a wild-type strain and a rad52 mutant strain of Saccharomyces cerevisiae.

1994 ◽  
Vol 14 (2) ◽  
pp. 1278-1292 ◽  
Author(s):  
C Mezard ◽  
A Nicolas
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gene Product ◽  
Type Strain ◽  
Wild Type Strain ◽  
Double Strand Breaks ◽  
Linear Plasmid ◽  
Wild Type ◽  
Dsb Repair ◽  
Strand Breaks ◽  
In The Wild

Different modes of in vivo repair of double-strand breaks (DSBs) have been described for various organisms: the recombinational DSB repair (DSBR) mode, the single-strand annealing (SSA) mode, and end-to-end joining. To investigate these modes of DSB repair in Saccharomyces cerevisiae, we have examined the fate of in vitro linearized replicative plasmids during transformation with respect to several parameters. We found that (i) the efficiencies of both intramolecular and intermolecular linear plasmid DSB repair are homology dependent (according to the amount of DNA used during transformation [100 ng or less], recombination between similar but not identical [homeologous] P450s sequences sharing 73% identity is 2- to 18-fold lower than recombination between identical sequences); (ii) the RAD52 gene product is not essential for intramolecular recombination between homologous and homeologous direct repeats (as in the wild-type strain, recombination occurs with respect to the overall alignment of the parental sequences); (iii) in contrast, the RAD52 gene product is required for intermolecular interactions (the rare transformants which are obtained contain plasmids resulting from deletion-forming intramolecular events involving little or no sequence homology); (iv) similarly, sequencing data revealed examples of intramolecular joining within the few terminal nucleotides of the transforming DNA upon transformation with a linear plasmid with no repeat in the wild-type strain. The recombinant junctions of the rare illegitimate events obtained with S. cerevisiae are very similar to those observed in the repair of DSB in mammalian cells. Together, these and previous results suggest the existence of alternative modes for DSB repair during transformation which differ in their efficiencies and in the structure of their products. We discuss the implications of these results with respect to the existence of alternative pathways and the role of the RAD52 gene product.

scholarly journals Comparison of the Host Responses to Wild-Type and cpsB Mutant Klebsiella pneumoniae Infections

2006 ◽  
Vol 74 (9) ◽  
pp. 5402-5407 ◽  
Author(s):  
Matthew S. Lawlor ◽  
Scott A. Handley ◽  
Virginia L. Miller
Keyword(s):  
Klebsiella Pneumoniae ◽  
Mouse Model ◽  
Type Strain ◽  
Wild Type Strain ◽  
Capsular Polysaccharide ◽  
Cytokine Production ◽  
Host Responses ◽  
Cellular Infiltration ◽  
Wild Type ◽  
Highly Virulent

ABSTRACT Previously, we established an intranasal mouse model of Klebsiella pneumoniae infection and validated its utility using a highly virulent wild-type strain and an avirulent capsular polysaccharide mutant. In the present study we compare the host responses to both infections by examining cytokine production, cellular infiltration, pulmonary histology, and intranasal immunization.

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