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C Guerrero

Publications and source records attributed to C Guerrero.

At least 55 records · Page 3Linked to original sources
PubMed1995

Up-regulation of a cysteine protease accompanies the ethylene-insensitive senescence of daylily (Hemerocallis) flowers.

The flowers of daylily (Hemerocallis x hybrida cv. Cradle Song) open at midnight, start to senesce 12 h later, and are completely senescent by the following midnight. Differential screening of a cDNA library constructed from tepals of flowers showing incipient senescence revealed 25 clones that were strongly up-regulated in senescent tepals. Re-screening and interactive Southern analysis of these clones revealed 3 families of up-regulated clones. Transcripts of one clone, SEN10, were not detectable at midnight, but increased dramatically as senescence proceeded. The derived amino acid sequence of the full-length cDNA (SEN102) has strong homology with cysteine proteases that have been reported from other plant tissues. The sequence contains a secretory signal peptide and a probable prosequence upstream of the mature protein. Amino acids critical to the active site and structure of cysteine proteases are conserved, and the C-terminus of the polypeptide has a unique putative endoplasmic reticulum retention signal -RDEL.

Amino Acid Sequence↗
PubMed1995

Molecular cloning of the hom-thrC-thrB cluster from Bacillus sp. ULM1: expression of the thrC gene in Escherichia coli and corynebacteria, and evolutionary relationships of the threonine genes.

A 6.5 kb DNA fragment containing the gene (thrC) encoding threonine synthase, the last enzyme of the threonine biosynthetic pathway, has been cloned from the DNA of Bacillus sp. ULM1 by complementation of Escherichia coli and Brevibacterium lactofermentum thrC auxotrophs. Complementation studies showed that the thrB gene (encoding homoserine kinase) is found downstream from the thrC gene, and analysis of nucleotide sequences indicated that the hom gene (encoding homoserine dehydrogenase) is located upstream of the thrC gene. The organization of this cluster of genes is similar to the Bacillus subtilis threonine operon (hom-thrC-thrB). An 1.9 kb BclI fragment from the Bacillus sp. ULM1 DNA insert 351 amino acids was found corresponding to a protein of 37462 Da. The thrC gene showed a low G + C content (39.4%) and the encoded threonine synthase is very similar to the B. subtilis enzyme. Expression of the 1.9 kb BcI DNA fragment in E. coli minicells resulted in the formation of a 37 kDa protein. The upstream region of this gene shows promoter activity in E. coli but not in corynebacteria. A peptide sequence, including a lysine that is known to bind the pyridoxal phosphate cofactor, is conserved in all threonine synthase sequences and also in the threonine and serine dehydratase genes. Amino acid comparison of nine threonine synthases revealed evolutionary relationships between different groups of bacteria.

Amino Acid Sequence↗
PubMed1995

A novel insertion element from Mycobacterium avium, IS1245, is a specific target for analysis of strain relatedness.

The insertion sequence IS1245 is a novel mycobacterial repetitive element identified in Mycobacterium avium. It encodes a transposase which exhibits a 64% amino acid similarity with IS1081, an insertion element present in the M. tuberculosis complex. The host range of IS1245 appears limited to M. avium as this element was not identified in M. intracellulare or in any other of 18 mycobacteria species tested. When IS1245 was used for restriction fragment length polymorphism (RFLP) analysis, human isolates characteristically presented a high number of copies (median, 16; range, 3 to 27) and a diversity of RFLP patterns comparable to that found by pulsed-field gel electrophoresis. Isolates from nonhuman sources differed both in number of copies and in RFLP pattern diversity: while swine isolates shared the characteristics of human strains, those from several avian sources exhibited a very low copy number of IS1245 and appeared clonal on the basis of RFLP.

Animals↗
PubMed1995

Use of restriction fragment length polymorphism as a genetic marker for typing Mycobacterium avium strains.

Restriction fragment length polymorphism (RFLP) was used to study 75 clinical isolates identified as Mycobacterium avium. Two repetitive insertion sequences, IS1311 and IS900, were used as DNA probes. Although less than 25% of isolates showed RFLP patterns with IS900, all strains gave banding patterns with IS1311. M. avium strains isolated from patients with AIDS exhibited marked polymorphism with both probes.

AIDS-Related Opportunistic Infections↗
PubMed1994

Directed mutagenesis of a regulatory palindromic sequence upstream from the Brevibacterium lactofermentum tryptophan operon.

A cloned 9.6-kb fragment of Brevibacterium lactofermentum DNA, carrying the entire trp operon and upstream regulatory sequences, produces a polycistronic 7.0-kb transcript as detected by hybridization with an internal probe. The transcription start point (tsp) was identified by S1 mapping. The operator-promoter (OP) region subcloned in Escherichia coli and B. lactofermentum promoter-probe vectors exhibited about tenfold higher activity in B. lactofermentum. A 14-bp wild-type (wt) palindrome located at bp -15 to -28 was mutated to change the conserved adenine adjacent to the axis of symmetry. The wt and mutated OP regions were coupled to the amy reporter gene (encoding alpha-amylase [Amy]) or to the 5' region (trpE and trpG genes) of the trp operon, for expression studies. Constructions with the regulatory signals coupled to the wt trpE-trpG genes were introduced in a B. lactofermentum trpE mutant (obtained by gene disruption). The mutation in the palindrome did not affect the promoter activity in B. lactofermentum or E. coli when grown in minimal medium. Tryptophan repressed the OP as assayed by the anthranilate synthase (AS) activity in B. lactofermentum in constructions with the wt OP region, but surprisingly, caused a large stimulation of either AS or the Amy reporter activity, in constructions with the mutated OP. The palindromic sequence is, therefore, involved in a dual repression-stimulation control of expression of the trp operon.

Anthranilate Synthase↗
PubMed1994

Cloning and nucleotide sequence of Mycobacterium tuberculosis gyrA and gyrB genes and detection of quinolone resistance mutations.

The emergence of multidrug-resistant strains of Mycobacterium tuberculosis has resulted in increased interest in the fluoroquinolones (FQs) as antituberculosis agents. To investigate the frequency and mechanisms of FQ resistance in M. tuberculosis, we cloned and sequenced the wild-type gyrA and gyrB genes, which encode the A and B subunits of the DNA gyrase, respectively; DNA gyrase is the main target of the FQs. On the basis of the sequence information, we performed DNA amplification for sequencing and single-strand conformation polymorphism analysis to examine the presumed quinolone resistance regions of gyrA and gyrB from reference strains (n = 4) and clinical isolates (n = 55). Mutations in codons of gyrA analogous to those described in other FQ-resistant bacteria were identified in all isolates (n = 14) for which the ciprofloxacin MIC was > 2 micrograms/ml. In addition, we selected ciprofloxacin-resistant mutants of Mycobacterium bovis BCG and M. tuberculosis Erdman and H37ra. Spontaneously resistant mutants developed at a frequency of 1 in 10(7) to 10(8) at ciprofloxacin concentrations of 2 micrograms/ml, but no primary resistant colonies were selected at higher ciprofloxacin concentrations. Replating of those first-step mutants selected for mutants with high levels of resistance which harbored gyrA mutations similar to those found among clinical FQ-resistant isolates. The gyrA and gyrB sequence information will facilitate analysis of the mechanisms of resistance to drugs which target the gyrase and the implementation of rapid strategies for the estimation of FQ susceptibility in clinical M. tuberculosis isolates.

Anti-Infective Agents↗
PubMed1994

Analysis and expression of the thrC gene of Brevibacterium lactofermentum and characterization of the encoded threonine synthase.

The thrC gene of Brevibacterium lactofermentum was cloned by complementation of Escherichia coli thrC auxotrophs. The gene was located by deletion mapping and complementation analysis in a 2.9-kb Sau3AI-HindIII fragment of the genome. This fragment also complemented a B. lactofermentum UL1035 threonine auxotroph that was deficient in threonine synthase. A 1,892-bp DNA fragment of this region was sequenced; this fragment contained a 1,446-bp open reading frame that encoded a 481-amino-acid protein having a deduced M(r) of 52,807. The gene was expressed in E. coli, by using the phage T7 system, as a 53-kDa protein. The promoter region subcloned in promoter-probe plasmids was functional in E. coli. A Northern analysis revealed that the gene was expressed as a monocistronic 1,400-nucleotide transcript. The transcription start point of the thrC gene was located by S1 mapping 6 bp upstream from the translation initiation codon, which indicated that this promoter was one of the leaderless transcription-initiating sequences. The threonine synthase overexpressed in B. lactofermentum UL1035 was purified almost to homogeneity. The active form corresponded to a monomeric 52.8-kDa protein, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme required pyridoxal phosphate as its only cofactor to convert homoserine phosphate into threonine.

Amino Acid Sequence↗
PubMed1994

Transcriptional analysis and regulatory signals of the hom-thrB cluster of Brevibacterium lactofermentum.

Two genes, hom (encoding homoserine dehydrogenase) and thrB (encoding homoserine kinase), of the threonine biosynthetic pathway are clustered in the chromosome of Brevibacterium lactofermentum in the order 5' hom-thrB 3', separated by only 10 bp. The Brevibacterium thrB gene is expressed in Escherichia coli, in Brevibacterium lactofermentum, and in Corynebacterium glutamicum and complements auxotrophs of all three organisms deficient in homoserine kinase, whereas the Brevibacterium hom gene did not complement two different E. coli auxotrophs lacking homoserine dehydrogenase. However, complementation was obtained when the homoserine dehydrogenase was expressed as a fusion protein in E. coli. Northern (RNA) analysis showed that the hom-thrB cluster is transcribed, giving two different transcripts of 2.5 and 1.1 kb. The 2.5-kb transcript corresponds to the entire cluster hom-thrB (i.e., they form a bicistronic operon), and the short transcript (1.1 kb) originates from the thrB gene. The promoter in front of hom and the hom-internal promoter in front of thrB were subcloned in promoter-probe vectors of E. coli and corynebacteria. The thrB promoter is efficiently recognized both in E. coli and corynebacteria, whereas the hom promoter is functional in corynebacteria but not in E. coli. The transcription start points of both promoters have been identified by primer extension and S1 mapping analysis. The thrB promoter was located in an 87-bp fragment that overlaps with the end of the hom gene. A functional transcriptional terminator located downstream from the cluster was subcloned in terminator-probe vectors.

Amino Acid Sequence↗
PubMed1993

Meningitis due to Aeromonas species: case report and review.

In recent years, Aeromonas species has been reported to cause extraintestinal infections with a growing frequency. Meningitis due to Aeromonas species is, however, a rare entity. We report a case of aeromonas meningitis in a 54-year-old man with a history of chronic alcoholic liver disease who, after an episode of gastroenteritis, developed an acute clinical picture characteristic of meningitis with septic shock and ecthyma gangrenosum. Aeromonas veronii (biogroup sobria) was isolated from cultures of blood as well as from cultures of stool, peritoneal fluid, skin lesion, and CSF specimens (obtained by lumbar puncture). Our review of seven additional cases of aeromonas meningitis in the world literature revealed that this condition is generally secondary to metastatic dissemination from primary bacteremia. Aeromonas meningitis, which may or may not be preceded by gastroenteritis, presents clinically as bacterial meningitis, although the presence of skin lesions may increase suspicion of the diagnosis. Third-generation cephalosporins are probably the therapy of choice for patients with aeromonas meningitis.

Aeromonas↗
PubMed1992

Chemical and structural similarities in wall polysaccharides of some Penicillium, Eupenicillium and Aspergillus species.

Various fractions were extracted from cell-wall material of Eupenicillium crustaceum, Penicillium brevi-compactum, P. decumbens, Aspergillus flavipes and A. ochraceus. The most characteristic fractions, which may have chemotaxonomic relevance, were F1I, an alpha-(1-3) glucan (alkalisoluble, water-insoluble), which amounted to 16.2-32.5% of the cell-wall material, and F1S (alkali and water-soluble) which represented 2.5-6.2% of the cell-wall material and was identified as a beta-(1-5) galactan. 13C-NMR spectra of the F1S fractions showed the same pattern for all the fungal species, characteristic of beta-(1-5) linked galactofuranose.

Aspergillus↗
PubMed1992

The bleomycin resistance gene of transposon Tn5 is an excellent marker for transformation of corynebacteria.

Corynebacteria are highly sensitive to the glycopeptide antibiotic bleomycin. The bleomycin resistance gene of transposon Tn5 is expressed very efficiently in Brevibacterium lactofermentum. This gene constitutes an excellent marker for selection of transformants of corynebacteria. The bleomycin resistance gene is expressed from the same promoter as the neomycin resistance gene, which is already used as marker in many vectors of corynebacteria. The promoter of the neo-ble cluster is expressed in a variety of Gram-negative and Gram-positive microorganisms and eucaryotic organisms.

Biotechnology↗
PubMed1991

[Epidemic outbreak of methicillin-resistant Staphylococcus aureus in a general hospital. Preliminary report].

The incidence of MRSA infections in Spain had remained in a low level through the years, being MRSA usually less than 1.5% of all S. aureus isolates. Since October 1988, we have detected in our hospital a MRSA outbreak. The epidemic started in the surgical wards, and spread through the rest of the institution. The incidence of cases was higher in the ICU's, areas that act as "multipliers" of the outbreak. In spite of standard control measures, the total number of patients with MRSA was 245 in April 1990. We studied prospectively a sample of 100 MRSA patients: thirty-six percent were colonized and 46% infected. The more common source of infection was the lower respiratory tract and primary bacteremia. The infection-related mortality was 30%. Our MRSA strain belong to phage type III, and shows a characteristic multiple antibiotic resistant pattern, the MRSA strain is sensitive to vancomycin, fusidic acid, phosphomycin and cotrimoxazole. Over the entire outbreak period, the MRSA strain developed resistance to rifampin, imipenem-cilastatin and ciprofloxacin. In spite of all control measures implemented, the outbreak can not have been totally controlled, and MRSA is now an endemic pathogen in our institution. Therefore, major changes in therapeutic approach to nosocomial infections have been since then introduced.

Adult↗