Biomedical subjects

C Hardisson

Publications and source records attributed to C Hardisson.

At least 37 records · Page 2Linked to original sources

PubMed1991

Protection against the lethal effect and arthritogenic capacity of Yersinia enterocolitica serovar O:3 for mice.

Protection against the intravenous lethal effect of Yersinia enterocolitica serovar O:3 for mice can be achieved by oral immunization with bacteria expressing the O:3 lipopolysaccharide (LPS). Under similar experimental conditions, Ca(2+)-dependent cells are more protective than their Ca(2+)-independent counterparts, live vaccines are more efficacious than killed ones, and parenteral immunization is more efficient than the oral route. Antibodies induced by enzyme-treated LPS from an O:3 strain are able to mediate protection against challenge with one homologous strain, but they do not prevent induction of arthritis.

Administration, Oral↗

PubMed1991

The effect of sinefungin and synthetic analogues on RNA and DNA methyltransferases from Streptomyces.

Sinefungin is an antibiotic structurally related to S-adenosylmethionine. It has been described as an inhibitor of RNA transmethylation reactions in viruses and eukaryotic organisms, but not in bacteria. We show here that sinefungin strongly inhibits RNA methyltransferase activity, but not the biosynthesis of these enzymes in Streptomyces. All the methylated bases found in Streptomyces RNA (1-methyladenine, N6-methyladenine, N6,N6-dimethyladenine and 7-methylguanine) are inhibited by this antibiotic. Experiments with sinefungin analogues show that specific changes in the ornithine radical of the molecule still preserve its inhibitory capability. The substitution of the adenine radical by uridine causes the loss of the inhibitory effect. These results and our former studies on Streptomyces DNA methylation, suggest that nucleic acid modification is the main target of sinefungin in Streptomyces.

Adenosine↗

PubMed1990

Effects of sinefungin and S-adenosylhomocysteine on DNA and protein methyltransferases from Streptomyces and other bacteria.

Sinefungin is a naturally occurring nucleoside isolated from cultures of Streptomyces griseolus and S. incarnatus. It is structurally related to S-adenosyl-methionine (SAM) and S-adenosyl-L-homocysteine (SAH). Its effect and level of action on prokaryotes has not been studied with the same detail as with eukaryotic cells. In this report we describe the effect of sinefungin and SAH on several Streptomyces methyltransferases (DNA and protein MTases) and on other bacterial DNA-MTases. Protein MTases are resistant to sinefungin, whereas DNA-MTases are inhibited. Adenine MTases however, seem more sensitive to this analogue than cytosine MTases.

Adenosine↗

PubMed1990

Purification and study of a bacterial glutathione S-transferase.

A glutathione S-transferase from Escherichia coli has been purified approximately 800-fold with an 11% activity yield by passage through DEAE Sephacel and glutathione-agarose affinity columns. Its functional form is a homodimer of two 24,000 Da polypeptides that catalyzes the binding of glutathione and 1-chloro-2,4-dinitrobenzene with Km values of 0.25 and 1.5 mM, respectively. Optima of pH and temperature were 7.5 and 35 degrees C. The activity was stimulated (30%) by ethylenediaminetetraacetic acid. The N-terminal amino acid sequence was: Met-Leu-Leu-Phe-Ile-Leu-Pro-Gly-Ala.

Amino Acid Sequence↗

PubMed1990

Proline uptake in Streptomyces clavuligerus.

Streptomyces clavuligerus was able to accumulate proline intracellularly throughout a wide range of external proline concentrations. Kinetic analysis of proline uptake indicated that this phenomenon is mediated by two saturable systems. One of them was a high-affinity system (Km = 11 microM), with low uptake capacity and specific for proline. The second system had lower affinity for proline (Km = 10.2 mM), higher uptake capacity, and was inhibited by several amino acids. Proline was not required as an inducer of the systems, which were neither repressed nor inhibited by ammonium.

Kinetics↗

PubMed1990

Yersinia enterocolitica serotype O:3 is arthritogenic for mice.

It is shown, for the first time, that Yersinia enterocolitica serotype O:3 is experimentally arthritogenic. Moreover, it is arthritogenic for the mouse, an optimal model for human yersiniosis. This arthritis can be induced by the oral route, the most common route in man. The pattern of joint disease closely parallels that of human reactive arthritis associated with this pathogen.

Animals↗

PubMed1990

Biosynthesis of oleandomycin by Streptomyces antibioticus: influence of nutritional conditions and development of resistance.

The influence of different nutritional compounds on oleandomycin biosynthesis by Streptomyces antibioticus was studied, resulting in the design of a chemically defined medium for production of the antibiotic. Of the variety of carbon and nitrogen compounds tested, fructose and aspartic acid (carbon and nitrogen sources, respectively) supported the highest oleandomycin titres. Addition of propionate but not acetate, both precursors of the skeleton of the macrolide lactone ring, stimulated the biosynthesis of the antibiotic. Oleandomycin biosynthesis was repressed by glucose but not by phosphate. S. antibioticus develops oleandomycin resistance shortly before the antibiotic begins to be synthesized, showing a triphasic pattern of resistance: spores and producing mycelium are resistant, while non-producing mycelium is sensitive.

Amino Acids↗

PubMed1990

Purification of a glutathione S-transferase that mediates fosfomycin resistance in bacteria.

The enzyme that modifies fosfomycin by formation of an adduct with glutathione was purified 12-fold with a 56% activity yield by passage through DEAE Sephacel and high-performance liquid chromatography molecular exclusion columns. Its functional form was a homodimer of two 16,000-dalton polypeptides, which possibly showed an antiparallel alpha tertiary structure and which lacked marked hydrophobic regions. Visualization of the reaction was achieved by precolumn derivatization of glutathione and the adduct, separation by high-performance liquid chromatography, and fluorescence detection of both compounds. Temperature and pH optima were 20 to 30 degrees C and 8.25, respectively; Mn2+, Fe2+, and Co2+ enhanced the rate of modification; and Km values were 9.4 and 11 mM for fosfomycin and glutathione, respectively. Phosphoenolpyruvate did not interfere with fosfomycin modification. The enzyme was stable at 4 degrees C for at least 6 months but progressively lost its activity upon being heated for 60 min at temperatures over 30 degrees C.

Amino Acids↗

PubMed1990

Sensitivity to phages of Streptomyces coelicolor strains harbouring type II restriction endonucleases.

The role of type II restriction endonucleases in phage development in two different strains of Streptomyces coelicolor has been analyzed. Two of ten phages tested (phi A4 R4c 1) presented a low efficiency of plating (e.o.p.) in the studied strains. The isolation of host-range mutants of phi A4 and R4c 1, with improved e.o.p. and higher adsorption capability in these two bacterial strains, suggests that the presence of host endonucleases is not the main barrier for these phages, but rather adsorption inability.

Adsorption↗

PubMed1990

Structure of the DNA of five bacteriophages infecting Micromonospora.

The physical maps of the DNA of five bacteriophages (Mm1, OM2, OM3, Mm4 and Mm5) which infect Micromonospora are presented. The restriction analyses showed that all of them had linear, double-stranded DNA, but only four (Mm1, OM2, Mm4 and Mm5) presented cohesive ends. The phages showed no relationship in terms of their restriction maps or of DNA-DNA hybridization, with the exception of Mm4 and Mm5, which resulted to be very similar. Phage Mm5 presented a high level of resistance to chelating agents, although deletion mutants, all of them showing a single detection of 1.4 kb, were obtained by using extremely selective conditions.

Bacteriophages↗

PubMed1989

Calcium-dependent binding between calmodulin and lysozyme.

Calmodulin, an acidic protein that binds calcium with high affinity, has multiple roles in the activation of many enzymes involved in cellular regulation of eukaryotes. In this study we show that calmodulin binding to hen egg-white lysozyme, in a Ca2+-dependent way, was observed using electroblots incubated with biotinylated calmodulin and detected with avidin-alkaline phosphatase or for affinity chromatography on a gel calmodulin column. Antimicrobial activity of lysozyme was not modified in the presence of Ca2+-calmodulin.

Alkaline Phosphatase↗

PubMed1989

Streptogramins-inactivating activity in three producer streptomycetes.

The mechanism of self-resistance in three streptogramins-producing streptomycetes was analysed. The three organisms had ribosomes which were sensitive both to A- and B-components of the streptogramin complex. However, cell-free extracts of these producers showed streptogramins-inactivating activity which was independent on the addition of exogenous cofactors (S-adenosylmethionine, ATP or acetyl coenzyme A). The activity was retained by the extracts after dialysis and inactivated by boiling, indicating the presence of enzymatic activity. The inactivating activity was found throughout the growth cycle of the organisms indicating a constitutive nature.

Enzymes↗

PubMed1989

Regulation of nitrogen catabolic enzymes in Streptomyces clavuligerus.

The levels of several enzymes involved in assimilation of different nitrogen compounds were investigated in Streptomyces clavuligerus in relation to the nitrogen source supplied to the cultures. Threonine dehydratase, serine dehydratase, proline dehydrogenase, histidase and urocanase were not decreased in the presence of ammonium. The latter two enzymes were induced by histidine in the culture medium, while proline dehydrogenase was induced by proline. Glutamine synthetase, urease and ornithine aminotransferase levels were higher with poor nitrogen sources and were repressed by ammonium. Arginase was induced by arginine and repressed by ammonium. Glutamine synthetase was rapidly inactivated upon addition of ammonium to the culture, and could be reactivated in vitro by treatment with snake venom phosphodiesterase, which suggested that adenylylation is involved in the inactivation. Three previously isolated mutants with abnormal glutamine synthetase activities showed pleiotropic effects on urease formation. All these data point to a mechanism controlling preferential utilization of some nitrogen sources in this species.

Ammonia↗

PubMed1989

Isolation and characterization of nitrogen-deregulated mutants of Streptomyces clavuligerus.

Two screening methods for isolation of mutants of Streptomyces clavuligerus with altered control of nitrogen metabolism enzymes are described. Thirty-eight prototrophic mutants with simultaneous deregulation of urease and glutamine synthetase were isolated. Nine mutants were examined in more detail and they also showed deregulated formation of arginase and ornithine aminotransferase. Different patterns of altered control of all four enzymes were observed. Inactivation of glutamine synthetase after ammonium shock took place to different extents in these nine strains, and seven of them had a thermosensitive glutamine synthetase activity. It is concluded that a system of nitrogen control, in which glutamine synthetase has a key role, is present in S. clavuligerus. Cephalosporin production was depressed by ammonium in all the mutants, irrespective of the alterations in nitrogen control of primary metabolism.

Arginase↗

PubMed1989

Selected characteristics of several strains of Lactobacillus plantarum.

Several relevant characteristics have been studied in nine Lactobacillus plantarum strains isolated from Cabrales cheese. They fermented lactose efficiently and possessed both beta-galactosidase and beta-phosphogalactosidase activities, but no significant proteolytic activity was detected. Antimicrobial susceptibility tests revealed no high level resistance to any of the fourteen compounds tested. All the strains had a high content of extrachromosomal DNA of unknown function. A recombinant plasmid comprising pUC19 from Escherichia coli and a small cryptic plasmid from L. plantarum has been constructed and may be used to develop a shuttle vector for these species.

Anti-Bacterial Agents↗

PubMed1989

[Ultrastructure of the intracellular development of bacteriophage phi C 31].

The intracellular development of the bacteriophage phi C31 in thermally induced cultures of the lysogen Streptomyces coelicolor 01 changes remarkably its cell structure. At 10 min post-induction, a big number of mesosomes are shown by the cells. At 30 min post-induction, the cytoplasm contains capsids which are still empty. At the end of the latent period mature virions are shown and immediately after, cell lysis occurs through the tip of germinative tubes. In old cultures (10 h or more) no viral progeny is detected. However, when the amino acid glycine is added to the culture medium, new virions are seen, but in smaller number than in germinating cultures. These results seem to indicate that the lysis happens at the tip of the germinative tubes probably because this is an area weakened by the preferential growth that takes place on it.

Bacteriophages↗

PubMed1988

Plasmid typing of Shigella sonnei epidemic strains and molecular relationship of their R-plasmids.

We conducted a surveillance program on epidemic and/or endemic Shigella strains in Asturias (Spain), their frequency and dispersion in our community, and their R-plasmids. We analyzed initial isolates of Shigella sonnei from two epidemic outbreaks using antibiotic resistance patterns and plasmid profile analysis as epidemiological markers. We found that the 2 outbreaks were caused by different S. sonnei strains, which respectively carried one and two R-plasmids together with other plasmids. The molecular relationship among these and three other R-plasmids from two S. sonnei strains isolated during a previous outbreak, were studied by restriction enzyme analysis and DNA-DNA hybridizations. We were able to establish different levels of relationship among the six R-plasmids.

DNA Restriction Enzymes↗

PubMed1988

Epidemiology of macrolide and lincosamide resistance in species of staphylococci in a general hospital.

During a 1-year period resistance to macrolides and lincosamides among staphylococci in a general hospital was studied. The macrolide-lincosamide resistance phenotype was found in 36.7% of coagulase-negative and in 3.7% of coagulase-positive species. Isolates showing this phenotype were more abundant from indwelling artificial devices, blood, respiratory tract and sterile fluids. The surgery and intensive care units of the hospital provided the highest proportion of such strains. Methicillin resistance was present in 13.9% of the staphylococci but no relationship between methicillin and macrolide-lincosamide resistance was observed.

Aminoglycosides↗