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J C Sousa

Publications and source records attributed to J C Sousa.

14 recordsLinked to original sources
PubMed1991

Characterization of beta-lactamases encoded by pathogenic strains of Escherichia coli from Portugal.

A survey of 2036 strains of Escherichia coli was conducted in Oporto, Portugal, to establish the prevalence of resistance to beta-lactam antibiotics. Isolates were from hospital and clinical practice patients, and were further divided into urinary and non-urinary pathogens. A high level of resistance to aminopenicillins (55.3%) was observed. Further examination of the resistant strains showed that the frequencies of occurrence of known beta-lactamases were as follows: TEM-1 (78.2% of resistant strains); SHV-1 (7.9%); TEM-2 (0.45%); OXA-1 (1.5%); HMS-1 (0.18%); TEM-1 + SHV-1 (4.2%). Other pairs of beta-lactamases were also identified in less than 2% of the resistant strains. In addition, 4.7% of the resistant strains produced elevated levels of a presumed chromosomal cephalosporinase, while 0.9% produced a ceftazimidase of pI 5.8-5.9 which was similar to TEM-6.

Anti-Bacterial Agents↗
PubMed1979

A Bacillus subtilis mutant requiring dipicolinic acid for the development of heat-resistant spores.

A Bacillus subtilis mutant is described which forms heat-resistant spores only in the presence of external dipicolinic acid (DPA). The mutation, dpa-1, is localized in a new sporulation locus, linked to pyrA. The dpa-1 strain is unable to synthesize DPA but can incorporate external DPA. The amount of DPA incorporated, the frequency of heat-resistant spores and their degree of resistance are all dependent on the concentration of external DPA. Spores of dpa- 1 strains exhibit normal resistance to most chemicals, including octanol and chloroform, but not to ethanol, pyridine, phenol and trichloroacetic acid. Complete resistance to the latter group depends on DPA. DPA incorporation is slow and apparently requires an energy supply but not protein synthesis. Direct involvement of DPA in the heat-resistance of the spores is suggested. Thin sections of DPA-less spores exhibit clearly visible cytoplasmic membranes and ribosomes. These structures are absent or less visible in the core of spores obtained with added DPA.

Bacillus subtilis↗
PubMed1979

Decadent sporulation mutants of Bacillus subtilis.

In decadent sporulation mutants, sporulating populations are heterogeneous: the cells reach successive chemical and physical resistances with progressively decreasing frequencies. Each decadent mutant can be characterized by the shape and slope of the curve describing the frequency of cells resistant to various agents ('the resistance spectrum'). In some mutants the resistance spectrum decreases progressively from xylene resistance to heat resistance; in other mutants it decreases rapidly between octanol resistance and chloroform resistance. Electron microscopy showed that in two mutants the majority of the cells are blocked at stages III and IV; the number of cells that develop further to reach successive morphological stages falls off progressively. In two other mutants most cells reach stage V. Cortexless spores are also frequent. One of the decadent mutations, SpoL1, was localized between aroD and acf. The phenotype of decadent mutants is discussed in terms of sequential gene activation.

Bacillus subtilis↗
PubMed1979

Genetic instability of sporulation-associated characters in a Bacillus subtilis mutant: relationship between sporulation, segregation and the synthesis of extracellular enzymes (kinetic studies).

In the genetically unstable, protease-overproducing 'medusa (M) strains of Bacillus subtilis, segregation of stable, wild-type-like B cells occurred mainly during sporulation. After the end of the exponential growth phase, a small fraction of M cells sporulated quickly and formed M spores, while the majority of the cells, after a 'critical period', gave rise to B segregants which sporulated after a delay. Segregation occurred without cell division. Delayed sporulation, segregation and protease overproduction are related. Similar but more complex results were obtained with the highly unstable TD strains. Sporulation and the kinetics of protease overproduction were also followed in several stable segregants. Depending on the strain, either the rate of protease production or both the rate and time course were affected. The results are interpreted in terms of sequential activation and de-activation of sporulation genes. The production of the alkaline and the neutral proteases was, in general, under common genetic control. In some strains alpha-amylase was also overproduced.

Alleles↗
PubMed1979

Effects of local anesthetics on bacterial cells.

The membrane effects of chlorpromazine, nupercain, tetracain, and procain were studied using Bacillus cereus, B. megaterium, B. subtilis, and Streptococcus faecalis, protoplasts from S. faecalis, and isolated membranes from B. subtilis. Chlorpromazin, nupercain, and tetracain produced characteristic micromorphological alterations after treatment for 5 to 30 min at pH 7.0 and 20 degrees C; the membrane staining pattern changed from asymmetric to symmetric, complex mesosome-like structures appeared, and membrane fractures and solubilization occurred. Procain at concentrations up to 100 mM did not induce detectable alterations. Protoplasts were quickly lysed by 10 mM tetracain. A rapid and extensive leakage of K+ was induced by chlorpromazin, nupercain, and tetracain. Procain (100 mM) induced a slight K+ leakage. The membrane respiratory activity of intact B. cereus cells (as measured by the triphenyl tetrazolium reduction) and the succinic dehydrogenase activity of B. subtilis isolated membranes were found to be inhibited by the four local anesthetics. The concentrations that produced 50% inhibition of those activities are correlated with the hydrophobicities of the anesthetic molecules.

Anesthetics, Local↗
PubMed1978

Ultrastructure and development of an exosporium-like outer spore envelope in Bacillus subtilis.

An exosporium-like outermost envelope is occasionally observed in thin sections of Bacillus subtilis spores. Treatment of the mature spores with urea and mercaptoethanol (sometimes completed by sodium dodecyl sulfate) or with NaOH, disorganizes and partially solubilizes the outer spore coat. This treatment permits a clear visualization of the exosporium in all spores of several B. subtilis strains. Exosporium appears either as a single sheet, 8-9 nm thick, or with a triple-layered unit membrane-like profile. Frequently it exhibits a crystal-like periodic pattern. The exosporium primordium appears first at stage IV, and its development is apparently independent of the formation of the cortex and of the spore coats. No morphological relationship was found between the outer forespore membrane and the exosporium.

Bacillus subtilis↗
PubMed1978

Ultrastructural effects of chemical agents and moist heat on Bacillus subtilis. I--Effects on vegetative cells.

The ultrastructural alterations induced by treatment of vegetative Bacillus subtilis cells with organic solvents, trichloroacetic acid (TCA) and moist heat were examined by electron microscopy. Organic solvents disorganize the membrane and change the asymmetric unit membrane profile to a symmetric profile. They also lead to partial solubilization of the membrane and produce small or extensive gaps. Membrane damaging activity increases in the following order: xylene = toluene less than octanol less than choroform. TCA coagulates the cytoplasm which shows large, electron-dense, pronase-sensitive blocks. Moist heat alters both the membrane and the cytoplasm.

Bacillus subtilis↗
PubMed1978

Ultrastructural effects of the chemical agents and moist heat on bacillus subtilis. II.--Effects on sporulating cells.

When sporulating cells are treated with the organic solvents (xylene, toluene, octanol and chloroform), with TCA or with moist heat (10 min at 80 degree C), the sporangial cells exhibit the same ultrastructural changes as do the vegetative cells. The forespores undergo similar changes after early but not after late treatment. Resistance toward the killing effect and toward ultrastructural alterations appear in the same order. One could correlate the appearance of resistances with precise ultrastructural events as follows:--xylene resistance: cortex formation (stage IV);--resistance to toluene, octanol and chloroform: coat development and cortex maturation (respectively early, middle and late stage V);--TCA and heat resistance: spore maturation (stage VI). The possible mechanisms of the chemical resistances are discussed.

Bacillus subtilis↗
PubMed1976

Bacterial mesosomes. Real structures or artifacts?

The ultrastructural study of membrane organization in gram-positive bacteria related to the OSO4 fixation conditions revealed that large, complex mesosomes are observed only when the bacteria are subjected to an initial fixation with 0.1%OSO4 in the culture broth, as in the prefixation step of the Ryter-Kellenberger procedure. Evidence was obtained suggesting that the large mesosomes are produced by this prefization. The kinetic study of the membrane morphological alterations occurring during the prefixation of Bacillus cereus with 0.1%OSO4 in the culture broth showed that the amount of mesosome material increases linearly from zero to a maximum observed at 1.7 min of prefixation and that at about this time a maximum is reached for the number of mesosomes per unity of cell area and for the average individual mesosome area. The large mesosomes observed in gram-positives fixed by the complete Ryter-Kellenberger procedure would be the result of the membrane-damaging action of 0.1%OSO4. Such damaging action was deduced from the observation thay 0.1%OSO4 quickly lyses protoplasts and induces a quick and extensive leakage of intracellular K+ from B. cereus and Streptococcus faecalis. In support of that interpretation is the observation that in bacteria subjected to several membrane-damaging treatments, mesosome-like structures are seen after three different fixation procedures. In bacteria initially fixed with 1% OSO4, 4% OSO4 or 2.5% glutaraldehyde, no large complex mesosomes are observed, small and simple invaginations of the cytoplasmic membrane being present. The size of these minute mesosomes is inversely proportional that causes of fixation. Uranyl acetate was found among the studied fixatives the one to the rate the least damage to bacterial membranes. This fixative satisfactorily preserves protoplasts. In bacteria initially fixed with uranyl acetate no mesosomes were found. The results of the present work throw serious doubts on the existence of mesosomes, both large and small, as real structures of bacterial cells. It is proposed that a continuous cytoplasmic membrane without infoldings (mesosomes) would be the real pattern of membrane organization in gram-positives.

Bacillus cereus↗
PubMed1976

Assessing the development of daily living skills in patients with spina bifida.

The development of independence in daily living skills of 256 patients with spina bifida was assessed by means of a new Functional Activities scoring system. The score was derived from nine categories of activity; five are to do with self-care, three with locomotion and one with social interaction. The reasons for the variation in achievement between individuals with the same degree of paralysis are discussed, as are the differences in learning curves for single activities. The scoring system enables a quantitative assessment to be made of the current status of an individual patient, and enables more realistic therapeutic goals to be set.

Activities of Daily Living↗
PubMed1976

Effects of phenethyl alcohol on Bacillus and Streptococcus.

The activity of phenethyl alcohol (PEA) on Bacillus cereus, B. megaterium, and Streptococcus faecalis was studied by electron microscopy of thin sections and by the assay of intracellular K+ leakage. S. faecalis was unaffected by PEA at concentrations up to 0.5%, B. cereus was severely damaged by 0.5% PEA, and B. megaterium behaved intermediately. Important membrane ultrastructural alterations were observed in B. cereus cells treated with 0.5% PEA, namely the change in the geometry of the membrane profile from asymmetric to symmetric, the occurrence of prominent, complex mesosome-like structures, and membrane fracturing and solubilization. Protoplasts from B. megaterium were found to be quickly lysed by 0.5% PEA due to the disruption of the cytoplasmic membrane. The electron microscopic observations, together with the results of the study of the K+ efflux from B. cereus and B. megaterium, indicate that PEA primarily and directly damages the cytoplasmic membrane of sensitive bacteria. The breakdown of the permeability barrier probably is responsible for the observed bactericidal action of 0.5% PEA on B. cereus.

Bacillus cereus↗
PubMedDate not supplied

Pleiotropic control mutations affecting the sporulation of Bacillus subtilis.

Mutations affecting quantitatively the production of the sporulation-associated extracellular alkaline protease were isolated and characterized. They fall into at least five genes, three of which, ScoA, B and C, were mapped in the argC-metC region. The pleiotropic effects of these mutations concern several or all of the following: rate and timing of protease production, synthesis of alkaline phosphatase, time-course of spore formation. Electron microscopic evidence indicates delayed switch from one morphological stage to another. The nature of the Sco mutations and the genetic regulation of sporulation are discussed.

Alkaline Phosphatase↗