scholarly journals Yersinia enterocolitica ClpB Affects Levels of Invasin and Motility

2000 ◽  
Vol 182 (19) ◽  
pp. 5563-5571 ◽  
Author(s):  
Julie L. Badger ◽  
Briana M. Young ◽  
Andrew J. Darwin ◽  
Virginia L. Miller
Keyword(s):  
Yersinia Enterocolitica ◽  
Insertion Mutant ◽  
Gene Transcript ◽  
Null Mutant ◽  
Early Stationary Phase ◽  
Flagellin Gene ◽  
Transposon Insertion ◽  
Isolation And Characterization ◽  
Mutant Phenotypes

ABSTRACT Expression of the Yersinia enterocolitica inv gene is dependent on growth phase and temperature. inv is maximally expressed at 23°C in late-exponential- to early-stationary-phase cultures. We previously reported the isolation of a Y. enterocolitica mutant (JB1A8v) that shows a decrease in invasin levels yet is hypermotile when grown at 23°C. JB1A8v has a transposon insertion within uvrC. Described here is the isolation and characterization of a clone that suppresses these mutant phenotypes of the uvrC mutant JB1A8v. This suppressing clone encodes ClpB (a Clp ATPase homologue). The Y. enterocolitica ClpB homologue is 30 to 40% identical to the ClpB proteins from various bacteria but is 80% identical to one of the two ClpB homologues ofYersinia pestis. AclpB::TnMax2 insertion mutant (JB69Qv) was constructed and determined to be deficient in invasin production and nonmotile when grown at 23°C. Analysis ofinv and fleB (flagellin gene) transcript levels in JB69Qv suggested that ClpB has both transcriptional and posttranscriptional effects. In contrast, a clpB null mutant, BY1v, had no effect on invasin levels or motility. A model accounting for these observations is presented.

scholarly journals Isolation and Characterization of a 1.7-kb Transposable Element from a Mutator Line of Maize

Genetics ◽  
1987 ◽  
Vol 117 (2) ◽  
pp. 297-307
Author(s):  
Loverine P Taylor ◽  
Virginia Walbot
Keyword(s):  
Direct Repeat ◽  
Repeat Sequence ◽  
Gene Probe ◽  
Gene Transcript ◽  
Chimeric Transcript ◽  
Purple Pigment ◽  
Isolation And Characterization ◽  
Internal Sequence ◽  
Normal Gene

ABSTRACT We have cloned and sequenced a 1.7-kb Mu element from a Mutator line of maize and compared its structure to Mu1, a 1.4-kb element. With the exception of a 385-bp block of DNA present in the 1.7-kb element, these transposable elements are structurally similar, sharing terminally inverted and internal direct repeated sequences. Derivation of 1.4-kb elements from the 1.7-kb class via deletion of internal sequence is suggested by the finding that a portion of the extra DNA in Mu1.7 is part of a truncated direct repeat sequence in the 1.4-kb element. An abundant poly(A)+ RNA homologous to a portion of this extra DNA is present in several tissues of both Mutator and non-Mutator lines. Analysis of transcripts from an unstable mutant bronze1 (bz) allele containing a Mu1.7 element inserted in an exon of the gene detects three species of poly(A)+ RNA that hybridize to a Bz1 (Bronze) gene probe: the largest contains the entire Mu1.7 element in the Bz1 gene transcript; another appears to be a spliced, chimeric transcript; the smallest is normal size Bz1 mRNA. The latter is most likely encoded by the normal-size alleles detected by Southern analysis of tissue expressing purple pigment, suggesting that normal gene function is restored by excision of the Mu1.7 element.

scholarly journals Isolation and Characterization of the Gene Coding for the Amidinotransferase Involved in the Biosynthesis of Phaseolotoxin in Pseudomonas syringae pv. phaseolicola

2001 ◽  
Vol 14 (4) ◽  
pp. 545-554 ◽  
Author(s):  
Gustavo Hernández-Guzmán ◽  
Ariel Alvarez-Morales
Keyword(s):  
Aspartic Acid ◽  
Pseudomonas Syringae ◽  
Sequence Similarity ◽  
Insertion Mutant ◽  
Halo Blight ◽  
Streptomyces Spp ◽  
Isolation And Characterization ◽  
Gene Coding ◽  
Blight Disease

Pseudomonas syringae pv. phaseolicola is the causal agent of the “halo blight” disease of beans. A key component in the development of the disease is a nonhost-specific toxin, Nδ-(N'-sulphodiaminophosphinyl)-ornithyl-alanyl-homoarginine, known as phaseolotoxin. The homoarginine residue in this molecule has been suggested to be the product of Larginine:lysine amidinotransferase activity, previously detected in extracts of P. syringae pv. phaseolicola grown under conditions of phaseolotoxin production. We report the isolation and characterization of an amidinotransferase gene (amtA) from P. syringae pv. phaseolicola coding for a polypeptide of 362 residues (41.36 kDa) and showing approximately 40% sequence similarity to Larginine:inosamine-phosphate amidinotransferase from three species of Streptomyces spp. and 50.4% with an Larginine:glycine amidinotransferase from human mitochondria. The cysteine, histidine, and aspartic acid residues involved in substrate binding are conserved. Furthermore, expression of the amtA and argK genes and phaseolotoxin production occurs at 18°C but not at 28°C. An amidinotransferase insertion mutant was obtained that lost the capacity to synthesize homoarginine and phaseolotoxin. These results show that the amtA gene isolated is responsible for the amidinotransferase activity detected previously and that phaseolotoxin production depends upon the activity of this gene.

scholarly journals MFα1, the Gene Encoding the α Mating Pheromone of Candida albicans

2003 ◽  
Vol 2 (6) ◽  
pp. 1350-1360 ◽  
Author(s):  
Sneh L. Panwar ◽  
Melanie Legrand ◽  
Daniel Dignard ◽  
Malcolm Whiteway ◽  
Paul. T. Magee
Keyword(s):  
Candida Albicans ◽  
Fungal Pathogen ◽  
Null Mutant ◽  
Mating Pheromone ◽  
Gene Encoding ◽  
Human Fungal Pathogen ◽  
Isolation And Characterization ◽  
Α Pheromone

ABSTRACT Candida albicans, the single most frequently isolated human fungal pathogen, was thought to be asexual until the recent discovery of the mating-type-like locus (MTL). Homozygous MTL strains were constructed and shown to mate. Furthermore, it has been demonstrated that opaque-phase cells are more efficient in mating than white-phase cells. The similarity of the genes involved in the mating pathway in Saccharomyces cerevisiae and C. albicans includes at least one gene (KEX2) that is involved in the processing of the α mating pheromone in the two yeasts. Taking into account this similarity, we searched the C. albicans genome for sequences that would encode the α pheromone gene. Here we report the isolation and characterization of the gene MFα1, which codes for the precursor of the α mating pheromone in C. albicans. Two active α-peptides, 13 and 14 amino acids long, would be generated after the precursor molecule is processed in C. albicans. To examine the role of this gene in mating, we constructed an mfα1 null mutant of C. albicans. The mfα1 null mutant fails to mate as MTLα, while MTLa mfα1 cells are still mating competent. Experiments performed with the synthetic α-peptides show that they are capable of inducing growth arrest, as demonstrated by halo tests, and also induce shmooing in MTLa cells of C. albicans. These peptides are also able to complement the mating defect of an MTLα kex2 mutant strain when added exogenously, thereby confirming their roles as α mating pheromones.

scholarly journals Isolation and Characterization of Xenorhabdus nematophila Transposon Insertion Mutants Defective in Lipase Activity against Tween

2009 ◽  
Vol 191 (16) ◽  
pp. 5325-5331 ◽  
Author(s):  
Gregory R. Richards ◽  
Eugenio I. Vivas ◽  
Aaron W. Andersen ◽  
Delmarie Rivera-Santos ◽  
Sara Gilmore ◽  
...  
Keyword(s):  
Lipase Activity ◽  
Metabolic Pathways ◽  
Lipase Production ◽  
Xenorhabdus Nematophila ◽  
Transposon Insertion ◽  
Isolation And Characterization ◽  
Transposon Mutants ◽  
Conserved Gene ◽  
Insertion Mutants

ABSTRACT We identified Xenorhabdus nematophila transposon mutants with defects in lipase activity. One of the mutations, in yigL, a conserved gene of unknown function, resulted in attenuated virulence against Manduca sexta insects. We discuss possible connections between lipase production, YigL, and specific metabolic pathways.

Isolation and characterization of mutants of Rhizobium meliloti unable to synthesize poly-β-hydroxybutyrate

1994 ◽  
Vol 40 (10) ◽  
pp. 823-829 ◽  
Author(s):  
Silvana Povolo ◽  
Riccardo Tombolini ◽  
Antonella Morea ◽  
Alistair J. Anderson ◽  
Sergio Casella ◽  
...  
Keyword(s):  
Rhizobium Meliloti ◽  
Tn5 Transposon ◽  
Transposon Insertion ◽  
Isolation And Characterization ◽  
Transmission Electron ◽  
Genome Level ◽  
Acetylene Reducing Activity ◽  
Phb Synthase ◽  
Dna Profiles

The isolation and characterization of four mutants of Rhizobium meliloti unable to synthesize poly-β-hydroxybutyrate (PHB) are reported. The mutants were independently obtained via Tn5 transposon mutagenesis and exhibited physiological and cytomorphological characteristics similar to those of the parental strain, as well as overlapping DNA profiles. These were assessed at both the plasmid and total genome level, using for the latter the sensitive technique of pulsed-field gel electrophoresis in a contour-clamped homogeneous electric field. With respect to the parental PHB+ strain, the loss of PHB-synthesizing ability in the four mutants was demonstrated by gas chromatography, transmission electron microscopy, and enzymatic tests. Localization studies of Tn5 insertion showed that the PHB− phenotype had, in all mutants, a transposon insertion in the same region, although not in the same position. The symbiotic traits (nodule-inducing ability on Medicago sativa and acetylene-reducing activity of nodules) of the mutants did not differ significantly from those of the parental R. meliloti.Key words: Rhizobium meliloti, poly-β-hydroxybutyrate (PHB), PHB synthase.

Isolation and Characterization of Magbane, a Magnesium-Lethal Mutant of Paramecium

Genetics ◽  
2001 ◽  
Vol 158 (3) ◽  
pp. 1061-1069
Author(s):  
Jocelyn A Hammond ◽  
Robin R Preston
Keyword(s):  
Culture Medium ◽  
Single Gene ◽  
Wild Type ◽  
Lethal Mutant ◽  
Isolation And Characterization ◽  
Highly Sensitive ◽  
K Current ◽  
Mutant Phenotypes ◽  
Genetic Mutants

Abstract Discerning the mechanisms responsible for membrane excitation and ionic control in Paramecium has been facilitated by the availability of genetic mutants that are defective in these pathways. Such mutants typically are selected on the basis of behavioral anomalies or resistance to ions. There have been few attempts to isolate ion-sensitive strains, despite the insights that might be gained from studies of their phenotypes. Here, we report isolation of “magbane,” an ion-sensitive strain that is susceptible to Mg2+. Whereas the wild type tolerated the addition of ≥20 mm MgCl2 to the culture medium before growth was slowed and ultimately suppressed (at >40 mm), mgx mutation slowed growth at 10 mm. Genetic analysis indicated that the phenotype resulted from a recessive single-gene mutation that had not been described previously. We additionally noted that a mutant that was well described previously (restless) is also highly sensitive to Mg2+. This mutant is characterized by an inability to control membrane potential when extracellular K+ concentrations are lowered, due to inappropriate regulation of a Ca2+-dependent K+ current. However, comparing the mgx and rst mutant phenotypes suggested that two independent mechanisms might be responsible for their Mg2+ lethality. The possibility that mgx mutation may adversely affect a transporter that is required for maintaining low intracellular Mg2+ is considered.

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