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C Hardisson

Publications and source records attributed to C Hardisson.

At least 73 records · Page 4Linked to original sources
PubMed1985

Restriction-modification systems in Streptomyces antibioticus.

Several restriction systems were detected in different strains of Streptomyces antibioticus by using actinophages as biological indicators. Adsorption of phages to the bacteria, together with the study of the efficiency of plating gave an initial indication of restriction in three strains. The alternation of efficiency of plating values obtained from restricting and nonrestricting hosts, gave evidence for the presence of a restriction-modification system in another strain. No common modification systems were detected among the different strains tested. Two specific endonucleases with a possible role in restriction were detected in strains ATCC 11891 and ETH 7451, respectively.

Adsorption↗
PubMed1985

Evidence for the dispersion and evolution of R-plasmids from Serratia marcescens in a hospital.

Incompatibility tests were used to study the types, evolution and dispersion of R-plasmids from Serratia marcescens in a hospital over the period 1975-82. R-plasmids belonged to incompatibility groups IncM, IncC, IncP or were unclassified, or compatible with all the plasmids tested. In 1982, IncM plasmids, including varieties codifying different resistance patterns, predominated. The oldest members of the IncM group codified fewer R determinants and were of smaller size than the more recent ones. Plasmids of IncM and IncC are dispersed among other genera of Enterobacteriaceae.

Bacterial Infections↗
PubMed1985

Antibacterial activity of fosmidomycin on chromosomic and plasmid-determined fosfomycin-resistant strains.

The antibacterial activity of fosmidomycin (Fm) on chromosomic and plasmid-determined fosfomycin-resistant (For) strains of Gram-negative bacteria was studied. Presence of For-plasmids did not protect host bacteria from the antibiotic effect of Fm. In clinical isolates Fm was more active than Fo in 67% of the strains whereas Fo was more active for only 2%; 76% of the strains showed cross resistance to both antibiotics. The Fmr character was not transferred by conjugation. For mutants selected in the hospital environment as well as in the laboratory did not always show cross resistance with Fm, and the alterations in the transport systems of both antibiotics were not the only mechanism of cross resistance.

Anti-Bacterial Agents↗
PubMed1984

Resistance in inhibitors of RNA polymerase in actinomycetes which produce them.

Resistance to the endogenous antibiotic was studied in three actinomycetes that produce inhibitors of RNA polymerase. The three producers, Nocardia mediterranei (rifamycin producer), Streptomyces spectabilis (streptovaricin producer) and Streptomyces lydicus (streptolydigin producer), were each highly resistant to the antibiotic they produce (MIC greater than 200 micrograms ml-1) and in vivo RNA synthesis was also resistant. However, cross-resistance to the other RNA polymerase inhibitors was not found. Resistance to these antibiotics was due to target site modification, since the RNA polymerase enzymes of the three producing organisms were highly resistant in vitro to the corresponding antibiotic, and no antibiotic-inactivating enzymes were detected. A mutant was isolated from S. spectabilis which was sensitive to steptovaricin (its own product) and also showed an increased sensitivity to rifamycin and streptolydigin. This mutant had RNA polymerase which was extremely sensitive to the three antibiotics.

Actinomycetales↗
PubMed1984

[Development of resistance to aminoglycosides in hospital strains of Serratia].

A study on the evolution of resistance to six aminoglycosides in Serratia as well as the relationship with the annual consumption of each drug in a hospital over the period 1974-1981 was carried out. The incidence of modifying enzymes and their genetical location was determined in 38 isolates. It was found that: The variations in the percentage of Sm clinical isolates showed no relationship with the consumption of Sm. Two different types of enzymes are involved in this resistance: AAD(3''): adenylyltransferase and APH(3''): phosphotransferase. The resistance to Nm, Km and Gm seems to be directly related with the continuous consumption of these drugs. In all the strains under study (Nm-Km)r was due to an APH(3')(5)I: phosphotransferase, Gmr to two types of acetyltransferases: AAC(3)I, only found in strains isolated before 1977 and AAC(3)II which predominates in 1981. After introducing Tm (1975) and Ak (1979) in our environment, there was an increase in the number of resistant strains. Two acetyltransferases with Tm-affinity were found: AAC(3)II and AAC(6')IV, the latter showing affinity for AKr. It was determined that five of these enzymes are plasmid-mediated. The genetical location of a sixth enzyme (AAC(6')IV) has not been clarified.

Acetyltransferases↗
PubMed1984

[Prevalence and dispersion of plasmids conferring fosfomycin resistance in enterobacteria].

The mechanisms of resistance to fosfomycin which, at the present, predominate among clinical isolates of Serratia marcescens as well as the incidence and dispersion of For plasmids among other species of Enterobacteriaceae were studied. It was found that that 23 of the 29 strains under study phenotypically behaved as glp T- mutants, another as glp T- and uhp- and five of them showed no alterations in their transport system. Self-transferable plasmids involved in For were isolated from the latter. For plasmids were also found in strains of Klebsiella pneumoniae but not in other enterobacteria. Plasmids were studied in order to establish their resistance phenotype, molecular weight and incompatibility group. The data obtained along with the restriction pattern allow us to conclude that the trait For is linked to, at least, two different replicons.

Anti-Bacterial Agents↗
PubMed1983

High calcium content in Streptomyces spores and its release as an early event during spore germination.

The metal ion content of spores of five Streptomyces species was studied. A general feature of this study was the finding of a very high calcium content (1.1 to 2.1% of the dry weight). Accumulation of calcium occurred preferentially during the sporulation process. Spore calcium was located in the integument fraction, and more than 95% of the calcium was removed from intact spores by ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid. Several divalent cations (Mg2+, Mn2+, Zn2+, and Fe2+) which induced darkening of spores and loss of heat resistance also caused the release of calcium from spores. In addition, darkening of spores was blocked by metabolic inhibitors, whereas calcium excretion was not affected. Two different categories of events in the initiation of germination may be differentiated; first, calcium release from spores which is not energy dependent and is a consequence of triggering of germination by some divalent cations, and second, some other events including loss of heat resistance, loss of spore refractility, and a decrease in absorbance, with at least one energy-dependent step.

Calcium↗
PubMed1983

Pattern of protein degradation during germination of Streptomyces antibioticus spores.

The pattern of protein degradation during germination of Streptomyces antibioticus spores was studied by the pulse and chase technique. Two different protein fractions were found. First, a fraction of the proteins synthesized during the darkening process (20-30%) was quickly degraded in the 30 min following the labelling period. This rapid protein degradation was partially inhibited by protease inhibitors: p-chloromercuribenzoic acid, phenylmethylsulphonylfluoride, and o-phenanthroline. Second, the remaining 70-80% and the entire protein population formed during spore swelling and germ tube emergence were degraded with a lower and constant rate (3.3-6.0% /h). A stable mRNA fraction of the dormant spores was translated upon incubation of the spores in a minimal synthetic medium (MSM) or in distilled water. However, the degradation of these proteins did not occur unless the spores were then incubated in the MSM. A strong correlation between the degradation pattern of these proteins and that of those quickly degraded at the beginning of germination was observed. Protease activity in cell-free extracts of dormant spores was detected. Inhibition studies suggest the presence of serine, thiol, and metalloproteases. The protease activity, using casein as substrate, remained constant during the darkening process and started to increase progressively from the beginning of spore swelling.

Bacterial Proteins↗
PubMed1982

Transfer of drug-resistance plasmids by conjugation from nosocomial strains of Serratia marcescens to Escherichia coli in biological fluids of human origin.

Six independent isolates of multi-resistant Serratia marcescens associated with nosocomial infections were examined for their ability to transfer drug-resistance plasmids by conjugation to Escherichia coli in biological fluids of human origin, such as normal and pathological urine, faeces, blood plasma and ascitic fluid. Luria broth was used as a control. Positive transfer was found in all media assayed. The different patterns of linked transferable resistance found in the transconjugants corresponded to the phenotypic expression of five plasmids. The frequencies of transfer varied with plasmid types and media employed. The culture media did not affect the phenotypic expression of the plasmids.

Bacteriological Techniques↗
PubMed1980

Glucose inhibibion of galactose-induced synthesis of beta-galactosidase in Streptomyces violaceus.

Various carbon compounds inhibited galactose induced synthesis of a beta-galactosidase activity in Streptomyces violaceus. Glucose and 2-deoxyglucose, but not methyl-alpha-D-glucose, caused inhibition of galactose uptake activity. In addition, glucose, or one of its metabolites, inhibited the synthesis of the glactose uptake system. Therefore it is concluded that the main inhibitory activity of glucose on galactose induced enzyme synthesis is exerted through inducer exclusion. Other carbon sources, such as D-ribose, D-gluconate, cellobiose or DL-alpha-glycerophosphate, did not inhibit uptake of the inducer galactose and may exert their effect through catabolite repression, inactivation or direct enzyme inhibition.

Carbohydrates↗
PubMed1980

Germination of spores of Micromonospora chalcea: physiological and biochemical changes.

Germinating spores of Micromonospora chalcea pass through three morphological stages: darkening, swelling and germ tube emergence. The process of germination has pH and temperature optima of 8.0 and 40 degrees C, respectively, and is not affected by activation treatments. Darkening, accompanied by a loss of heat resistance and refractility and a decrease in absorbance of the dormant spores, needs only energy, which can be obtained from endogenous sources, and exogenous cations. Agents that inhibit ATP formation block darkening, but inhibitors of macromolecular synthesis do not affect it. Swelling requires exogenous carbon but not nitrogen sources and is characterized by a 30 to 40% increase in spore diameter. RNA synthesis is necessary for swelling and inhibitors of protein synthesis delay this process. During this stage, maximum respiratory, cytochrome oxidase and catalase activities are reached. DNA synthesis starts at the beginning of germ tube emergence. This final stage requires both exogenous carbon and nitrogen sources and the sequence of macromolecular synthesis is RNA, protein and, finally, DNA. Rifampicin, streptomycin and mitomycin C prevent protein and DNA synthesis regardless of when added during germination. Rifampicin inhibits [3H]uridine incorporation immediately but there is a delay of about 160 min in the case of streptomycin or mitomycin C.

Bacterial Proteins↗
PubMed1980

Plasmid-determined resistance to fosfomycin in Serratia marcescens.

Multiple-antibiotic-resistant strains of Serratia marcescens isolated from hospitalized patients were examined for their ability to transfer antibiotic resistance to Escherichia coli by conjugation. Two different patterns of linked transferable resistance were found among the transconjugants. The first comprised resistance to carbenicillin, streptomycin, and fosfomycin; the second, and more common, pattern included resistance to carbenicillin, streptomycin, kanamycin, gentamicin, tetracycline, chloramphenicol, sulfonamide, and fosfomycin. The two types of transconjugant strains carried a single plasmid of either 57 or 97 megadaltons in size. Both of these plasmids are present in parental S. marcescens strains resistant to fosfomycin. The 57-megadalton plasmid was transformed into E. coli.

Anti-Bacterial Agents↗
PubMed1980

Occurrence of polysaccharide granules in sporulating hyphae of Streptomyces viridochromogenes.

Evidence of the presence of polysaccharide polymers is shown in Streptomyces sp. for the first time. Cytochemical methods revealed the occurrence of polysaccharide granules in sporulating hyphae of Streptomyces viridochromogenes. Onset of the sporogenesis coincided with the appearance of the granules, which reached a maximum number during the early stages of maturation. The later stages of maturation showed a decrease of these granules, and in mature spores no granules were observed.

Cytoplasmic Granules↗
PubMed1979

Induction of beta-galactosidase in Streptomyces violaceus.

Synthesis of beta-galactosidase by Streptomyces violaceus was induced by D-galactose and L-arabinose, and to a lesser extent by lactose, D-arabinose, and methyl-beta-D-galactopyranoside. The synthesis of the enzyme was linear and started to increase 2--3 h after induction by galactose, reaching a maximum after 5--7 h. The highest level of specific activity was observed in 2% galactose, with an increase of 45 times over the basal level in glycerol. Isopropyl-beta-D-thiogalactopyranoside (IPTG) and methyl-beta-D-thiogalactopyranoside (TMG) inhibited induction by D-galactose, but did not influence enzymatic activity. Cellular extracts hydrolyzed O-nitrophenyl-beta-D-galactopyranoside, but did not significantly hydrolyze lactose, melibiose, p-nitrophenyl-alpha-D-galactopyranoside, p-nitrophenyl-beta-D-fucoside, or p-nitrophenyl-beta-D-glucopyranoside. Rifampicin and chloramphenicol inhibited beta-galactosidase synthesis in non-preinduced and in preinduced cells. The inhibition by chloramphenicol was reversible.

Arabinose↗
PubMed1978

Protoplast-like structures formation from two species of Enterobacteriaceae by fosfomycin treatment.

A procedure for protoplasts formation from Escherichia coli and Serratia marcescens by treatment with fosfomycin alone is described. This method gives high and low yields of stable protoplasts from E. coli and S. marcescens respectively. In the last case numerous spheroplasts were obtained. Electron micrographs of intact cells, protoplasts and spheroplasts are shown.

Anti-Bacterial Agents↗
PubMed1978

Fine structure, physiology and biochemistry of arthrospore germination in Streptomyces antibioticus.

During germination, Streptomyces antibioticus arthrospores passed through stages: darkening, swelling and germ tube emergence. The first stage, darkening, whose main features were a decrease in absorbance and a loss of refractility, only required exogenous divalent cations (Ca2+, Mg2+ or Fe2+) and energy that can be obtained from the spore reserves. This stage was blocked by agents that inhibit ATP formation but not by antibiotics that inhibit macromolecular synthesis. The second stage, swelling, needed an exogenous carbon source and was not blocked by mitomycin C. In this stage, the spores exhibited the highest cytochrome oxidase and catalase activities and respiratory quotient. The last stage, germ tube emergence, required additional carbon and nitrogen sources. Ammonium compounds were superior to nitrate. Dry weight remained constant during the stages of darkening and swelling, with a rapid increase from the moment of germ tube emergence. Optimum pH and temperature for germination were 8.0 and 45 degrees C, respectively. Heat treatment (55 degrees C for 10 min) had no effect on germination. The fine structure of the spore underwent important changes during germination. The wall of the swollen spore became stratified and the inner layer was continuous with the germ tube wall. Macromolecular synthesis occurred in the sequence RNA, protein and then DNA. Rifampicin, streptomycin and mitomycin C prevented synthesis when added at the start of incubation. The same effect was obtained if the addition was made during germination, except with mitomycin C which inhibited DNA, but not RNA and protein synthesis.

Anti-Bacterial Agents↗