PubMed Health⌕ Search

Biomedical subjects

A A Viale

Publications and source records attributed to A A Viale.

15 recordsLinked to original sources
PubMed1992

Antimicrobial constituents of Gomphrena martiana and Gomphrena boliviana.

The antimicrobial activity of extracts and constituents of Gomphrena martiana and Gomphrena boliviana (Amaranthaceae) were determined in order to identify the compounds responsible for the folk-medicinal use of these plants. Each extract was evaluated against 20 microorganisms, including Gram-positive and Gram-negative bacteria, spore-forming Gram-positive bacteria, an acid-fast bacterium, a fungus and two yeasts. Fractionation of each petroleum ether (PE) extract yielded five 5,6,7-trisubstituted flavones that were separately tested showing high activity against M. phlei (minimum inhibitory concentration (MIC) 15, 20 and 75 micrograms/ml) approaching that of commercial bactericides. Other natural and synthetic flavonoids with diverse structures were also tested to define structure-activity relationships. Each EtOH extract was subsequently fractionated and monitored by bioassays leading to isorhamnetin 3-O-beta-robinobioside (MIC 50 micrograms/ml) in both instances. This glycoside is reported here for the first time in G. boliviana.

Flavonoids↗
PubMed1987

Porphyrin biosynthesis in Rhodopseudomonas palustris--XII. delta-Aminolevulinate synthetase switch-off/on regulation.

The high levels of delta-aminolevulinate synthetase (ALA-S) in Rhodopseudomonas palustris cells grown anaerobically in the light (Ph) decrease to those found in cells grown aerobically in the dark (A), when the former cultures were vigorously oxygenated; simultaneously bacteriochlorophyll (Bchl) synthesis abruptly halted leading to diminished steady-state specific Bchl content. When flushing oxygen was interrupted, enzymic activity increased, whether chloramphenicol was present or not in the medium; if the protein synthesis inhibitor was added when oxygenation started, ALA-S declined in the same fashion as in its absence, but thereafter reactivation of the enzyme was lower than before. Succinyl-CoA-synthetase and ALA-dehydratase activities were also measured under the conditions described, and no changes at all have been observed. The existence of different forms of ALA-S in R. palustris depending on growth conditions is postulated along with the formation of low molecular weight factors which can modulate ALA-S activity by binding to the enzyme; a widespread mechanism in the adaptation of micro-organisms to changes in environment. It is also proposed that this particular regulatory phenomenon, could be referred to as a switch off/on mechanism controlling ALA-S activity in R. palustris.

5-Aminolevulinate Synthetase↗
PubMed1985

[Adaptation of Rhodopseudomonas palustris to changes in atmospheric conditions].

The high level of delta-aminolaevulinate synthetase (ALA-S) in Rhodopseudomonas palustris cells grown under photosynthetic conditions decreased when they were vigorously aerated; moreover, the bacteriochlorophyll synthesis suddenly stopped. When aeration was interrupted, enzymatic level increased notably, but bacteriochlorophyll level did not. Chloramphenicol added to cultures when aeration was interrupted did not affect the increase of enzymic level. When it was added as the aeration started, the enzymic level decayed, but did not increase as notably when the aeration was interrupted. ALA-S in extracts of aerated cells underwent spontaneous activation when homogenates were stored at 4 degrees C. The effect of several activators on different forms of ALA-S is postulated in order to explain these findings.

5-Aminolevulinate Synthetase↗
PubMedDate not supplied

[Degradation of naphthalene-2-sulfonate by strains of Micromonospora].

It was possible to isolate several strains of Micromonospora sp. from waters of Rio Reconquista. They all were filamentous bacteria with lateral spores, highly resistant to Cr(III) and another heavy metal cations. All these strains were able to grow on naphthalene-2-sulphonate as sole carbon source in a mineral medium. The biodegradation of the xenobiotic proceeds via the formation of salicylate and gentisate. These compounds have been isolated and mass spectrometry identified.

Argentina↗
PubMedDate not supplied

Use of a CO2 electrode to monitor fermentations that use xenobiotic compounds as source of carbon.

Bacterial strains were isolated from contaminated waters, mud or soils. They are capable of growing in mineral medium with different chemicals as carbon source, such as aliphatic or aromatic hydrocarbons and polychlorinated biphenyls (PCBs). Most of these strains tolerate high concentrations (up to 30% v/v) of the xenobiotic substrates. This is particularly important for the development of fermenting processes to treat effluents or residues with a high content of contaminating compounds. An ion-specific potentiometric electrode (CO2) has been developed to measure CO2 production continuously. When the different strains were incubated in a mineral medium and in the presence of the corresponding substrate, a parallel between growth, substrate consumption and CO2 production was found. The developed system is suggested as an efficient and economical alternative to evaluate the potential of biodegradation by different microorganisms.

Alcaligenes↗
PubMedDate not supplied

Microbial dehalogenation of polychlorinated biphenyls in aerobic conditions.

From soils contaminated with polychlorinated biphenyls (PCBs) a strain of Alcaligenes sp. able to grow in a mineral medium with a commercial mixture of PCBs as carbon source was isolated. This strain consumed up to 200 ppm in seven days in laboratory conditions. After 24 h of incubation, some new congeners of PCBs could be recognized by mass spectrometry. Through the identification of these compounds it was possible to postulate examples of possible transformations by dechlorinations of penta- and tetra-chlorinated congeners into tri-chlorinated ones. The properties of the isolated strain are appropriate for bioremediation of contaminated areas and also for using in bioreactors in order to remove the xenobiotic chemical.

Alcaligenes↗
PubMedDate not supplied

[Bacteriochlorophyll a synthesis in Rhodopseudomonas palustris].

By means of electron microscope it was demonstrated that photosynthetically-grown Rhodopseudomonas palustris exhibits an intracytoplasmic membrane system (Figure 1a), which is not observed in aerobically-dark grown bacteria (Figure 1b). The content of bacteriochlorophyll alpha and the enzyme activity of succinil-CoA-synthetase, ALA-sinthetase and ALA-dehydratase in several media grown Rhodopseudomonas palustris could be measured. Aerobically-dark grown cells do not synthetize bacteriochlorophyll alpha and the activity of ALA-synthetase is lower than in photosynthetically-grown cells (Table 1), suggesting a possible regulatory role for this enzyme in the pigment biosynthesis. Some inhibitors of electron transport and uncouplers of photophosphorylation inhibit both the bacterial growth and bacteriochlorophyll alpha biosynthesis (Table 2), while the levels of ALA-synthetase are not affected. If the incubation in the presence of these kinds of compounds is prolongated, the effects disappear. Although the regulatory role of ALA-synthetase should be very important, apparently it would not be the unique regulatory factor for bacteriochlorophyll alpha biosynthesis in Rhodopseudomonas palustris.

5-Aminolevulinate Synthetase↗
PubMedDate not supplied

[Effect of light intensity on the biosynthesis of bacteriochlorophylls in Rhodomicrobium vannielii and Rhodopseudomonas palustris].

The activity of aminolevulinate-synthetase in crude extracts of R. vannielii was determined. Its properties are very similar to those of the enzyme from R. palustris. With increasing light intensity on cultures of both microorganisms, their specific growth rates increases and the concentration of bacteriochlorophyll decreases. ALA-synthetase exhibits a dual-pattern; its activity remains at a high constant level up to 4 x 10(4) erg cm-2 seg-1, decreasing at higher light intensities (Figures 1 and 2). The activity of succinil-CoA-synthetase of both microorganisms and ALA-dehydrase of R. palustris remain constant over the entire range of light intensities used, but the ALA-dehydrase of R. vannielii shows the same dual-pattern as ALA-synthetase (Table 1), namely a constant high level at the lower light intensities, decreasing at the higher ones. With dialysis the activity of ALA-synthetase of both microorganisms decreases only in extracts from low light intensity grown bacteria, while it did not decrease in extracts from bacteria grown at high light intensities.

5-Aminolevulinate Synthetase↗
PubMedDate not supplied

A decalin-consuming bacterial community.

A bacterial community able to degrade cis- and trans-decalin (decahydronaphthalene) in the presence of n-decane could be isolated. It was composed by a couple of Pseudomonas strains (D1 and D2, respectively). Neither the community nor the isolated strains were able to grow on decalin alone. D1 grew on decalin plus n-decane. Both could grow on n-decyl alcohol, acetate and adipate. From hydrocarbonated substrates it would be generated a metabolic chain which allows the growth of the community members, and then it resulted to be stable. Characteristics of both strains are described.

Acetates↗
PubMedDate not supplied

[2-Naphthalene-sulphonic acid degrading microorganisms].

Derivatives of anionic surfactants, specially naphthalene sulphonates, when discharged into natural waters are accumulated in waters and sediments because of their poor biodegradability. A four-membered bacterial community, able to degrade the sodium salt of 2-naphthalene-sulphonic acid (2NS), was isolated from Río Reconquista. All the isolated strains consisted of gram-negative, strictly aerobic rods, with a strong proteolytic activity and resistance to high levels of cations like Cr (III), Hg (II), Cd (II) and Pb (II). Some of them were resistant to gentamicin, amikacin and chloramphenicol. These strains appeared to be related to the genera Pseudomonas and Alcaligenes. When isolated, if growing on 2NS, a brown-dark pigment is formed by three of them, resulting in an inhibition of growth. The presence of a Pseudomonas aeruginosa strain avoided the production of pigment and resulting in a complete consume of 2NS.

Alcaligenes↗
PubMedDate not supplied

[Biodegradation of a commercial mixture of polychlorinated biphenyls].

A bacterial strain capable of growing on a commercial mixture of polychlorinated biphenyls (PCBs) was isolated from PCBs-contaminated soil. The isolate was identified as a Klebsiella oxytoca strain, able to grow on 6-chloroquinoline and chlorobenzene. The above mentioned PCBs mixture contains several congeners of bi-, tri- and tetra-chloro biphenyls. Xenobiotic consumption could be measured by an assay in glass-stoppered flask. After three days PCBs were almost completely degraded with the production of phenolic and/or acidic products, that were consumed after seven days.

Biodegradation, Environmental↗