Revista latinoamericana de microbiologia最新文献

The aim of this work was to search if the rat DNA polymerase beta can substitute the capability of DNA polymerase I to repair damage caused by the UV light in Escherichia coli. The oriC origin of replication from p beta 5 was replaced by the rep origin from pSC101 and named p beta 6. The presence of pol beta in the new construct was verified by PCR. E. coli polA-1 (WP6) was transformed with p beta 6. A protein with size similar to DNA Pol beta (40 kDa) was shown in the cell free extracts carrying pbeta5. In WP6/p beta 6 cell free extracts a slightly smaller protein was observed instead of the 40 kDa. DNA Pol beta was revealed by western analysis, with polyclonal antibodies, in strains with p beta 5. Yet, it was not detected in the western from WP6/p beta 6. A moderate change in UV resistance was observed in strains carrying p beta 5. However, in polAl carrying p beta 6 (WP6/p beta 6), irradiated with 60-90 J/m2 of UV light, the viability was increased by more than four orders of magnitude, when compared with the polA1 (WP6) strain, reaching approximately the same UV resistance as the strains with DNA polymerase I. The results suggests that probably Pol beta is rapidly degraded in the cell free extracts from WP6/p beta 6 and, it repairs the lethal effect of the UV light in E. coli.

Eighty Candida albicans strains, isolated from throat of patients at the Universitary Clinic of the Faculty of Superior Studies Iztacala of the National Autonomous University of Mexico, were analyzed. They were identified by microscopic and colony morphologies, germ tube test, and by auxanogram and zimogram. Minimal inhibitory concentrations (MIC) of 5-fluorocytosine, miconazole and amphotericin B were determined by microtiter broth dilution. MIC frequency distribution of 5-fluorocytosine showed a single peak (0.25-8.0 microg/ml), with 65% susceptible strains (MIC < or = 1.0 < or =g/ml) and 35% intermediate susceptible strains (MIC = 1.1-8 microg/ml). MIC frequency distribution of miconazole was threemodal with 6.25% susceptible (MIC = 1.562 microg/ml), 48.75% intermediate susceptible (MIC = 3.125-12.5 microg/ml), and 45% resistant (MIC = 25-50 microg/ml) strains. All strains were susceptible to amphotericin B (MIC= 0.0156-0.125 microg/m). These results shows that amphotericin B was the more active antimycotic, followed by 5-fluorocytosine, against the strains analyzed, and that miconazole was the less effective one.

Entamoeba histolytica is a parasite which causes health problems and there has been many approaches to know what is the factor causing its pathogenicity. In the present work, we assayed if the production of free radicals by the amoeba, has a relationship with the proteases activity. When we test the DMSO action (free radicals quenching activity) the specific activity of the proteases complex of the parasite were affected also. At 33.3% (V/V) concentration of DMSO it was present a maximal decrease of the initial activity (about 46% decrease), for to a higher concentrations existing a trend to recuperate the original activity, suggesting that the free radicals are an important factor for the hydrolysis grade of the protein substrate. All the differences except those between 46.7 and 66.6%, were significantly different compared with the control without any addition. The effects of Probucol and Probucol plus DMSO, compared to those caused by Metronidazol (MZ). We can observe that the quenchers caused a decrease on proteases activity similar to that of MZ (which is an antiparasite drug) and it was of c.a. 58% of activity decrease. These data suggest that the action of both, free radicals and proteases complex of Entamoeba histolytica, can account for the pathogenicity of the parasite.

Mycoplasmas are a bacterial group that is classified in the Mollicute class which includes Mycoplasmas, Spiroplasmas and Acholeplasmas. One hundred and seventy six species have been described in this group. Mycoplasmas are the smallest self living prokaryotes, they do not have a bacterial wall, their genomic size ranges from 577 to 2220 bpk, they are nutritional exigent so it is hard to culture them, but the development of molecular biology techniques has let us detect more mycoplasmas in different hosts. Mycoplasmas have been associated to acute and chronic diseases mainly in animals and humans while spiroplasmas have been found in arthropods, plants and flowers producing or not damage. Some recent studies have shown the role of some structural components of Mycoplasmas in pathogenesis, such as cytoskeleton proteins and adhesins, and the influence of some genetic characteristics on the development of an infectious disease.

The serological prevalence of Q fever in Mexico is unknown. A serological survey for Coxiella burnetii was undertaken on a randomly selected population of dairy cattle, beef cattle, goats and sheep flocks. Serological examination of animal sera for antibodies against Coxiella burnetii was carried out by the ELISA technique. The 28% of the dairy cattle and 10% of beef cattle examinated were antibody positive. Sera from goats and sheep also had antibodies against this rickettsia, 35% and 40% respectively.

The analysis of behavior of man in the field of biology is carried out through bioethics, considered the science of the survival. In the microbiology, there are numerous discoveries related with pathogenic microorganisms, including those that can be used as weapons in a biological war or in an attack considered bioterrorism. The scientist involved in microbiology can participate with his knowledge in the development and improvement of bioweapons, however from the point of view of bioethics it is not acceptable that he works in an investigation related with these topics, because the defense research can evolve in offensive one. The war is an antisurvival activity, therefore it is not acceptable. In the same way, the biological weapons composed with virus, fungi or alive bacteria, or with toxins from them, neither they are morally accepted. After the terrorist attacks with anthrax in the United States in 2001, the world scientific community in the field of microbiology should show against the use of the microorganisms like bioweapons, at the time of promoting the idea that the responsible use for the microorganisms is a moral imperative for all microbiologists around the world, since the biological weapons are a threat for the human life.

Arbuscular mycorrhizal fungi (AMF) are able to increase root enzymatic activity of acid and alkaline phosphatases. However, the role of AMF on phosphatase activity has not been reported in papaya (Carica papaya L.), which is frequently established at places with soil phosphorus (P) deficiencies. The goals of this research were to determine the effect of Glomus claroideum (Gc), and plant growth promoting rhizobacterium Azospirillum brasilense strain VS7 [Ab]) on root phosphatase activity and seedling growth of Carica papaya L. cv. Red Maradol under low P conditions. There were four treatments-colonization with: 1) Gc, 2) Ab, 3) Gc+Ab, and 4) non-inoculated seedlings. Plants were established in a coarse sand:sandy loam substrate under P-limitation (11 microg P ml(-1)), supplied with a modified Long Ashton Nutrient Solution. Seedling growth was severely reduced by low P. Gc+Ab inoculated plants had greater total dry matter and leaf area than non-colonized plants. Gc-inoculated plants had greater leaf area than non-colonized plants. Treatments did not differ in leaf area ratio, specific leaf area and, total chlorophyll content. There was a non-significant effect on stem relative growth rate with Gc and Gc+Ab plants. Mycorrhizal colonization enhanced the bacterial population 3.4-fold in the Gc+Ab treatment compared with the population quantified in Ab treatment. Soluble and extractable root acid phosphatase activity (RAPA) was higher in Gc inoculated plants. We discussed on the possible relation among both inoculated microorganisms and also with the P-limitation which plants were established.

The Thermus aquaticus DNA Polymerase I (Taq Pol I) gene was cloned into the pOSEX4 plasmid under the osmo-inducible promoter proU and subsequently expressed into the Escherichia coli MKH13 strain. The suitability of the enzyme in polymerase assays was determined in standard 35S dATP incorporation tests and by PCR. The Taq Pol I expression in this system, which is under the control of the osmotic pressure in the growth medium, was analyzed in different media and in different sodium chloride concentrations. A study of the osmolarity effects in the growth of the strain and in Taq Pol I expression shows that an increase in sodium chloride concentration limits the growth. At 0.25 M of NaCl maximum activity was observed; at higher values of osmolarity, we found an unexpected decline of activity. This is the first report of using the pOSEX vector for the expression of an heterologous protein and it is very advantageous to make a regulated, non toxic, simple and cost-effective manner of induction in a biotechnology process using just NaCl or other non-permeable osmolyte.

Fifty Aeromonas caviae strains from intestinal infection in different Cuban provinces were identified by the Aerokey II method and virulence factors were investigated. The strains did not produce haemolysins but other exoenzymes such as proteases, lipases, and DNases; additionally, all isolates adhered to the HEp-2 cell line by the Carrello method and this did not correlate with other virulence factors presence which demonstrates that the haemolysin phenotypic expression is not necessary for these strains to be pathogenic and that pathogenicity is multifactorial, each strain expressing at least one virulence factor.

The bacteriocin PsVP-10 is a 2.6 Kda peptide which was isolated and purified from Pseudomonas sp. This bacteriocin possesses lethal activity over Enterococcus faecalis, Salmonella typhimurium and Shigella flexneri. The experimental assays showed that the bacteriocin is able to be adsorbed by all cells of these bacterial species and also by their isolated cell walls. It was observed that the resistant mutants and their respective cell walls are unable to adsorb the bacteriocin. Assays performed with spheroplasts obtained from sensitive bacterial species and their resistant mutants show a rapid lethal effect of the bacteriocin PsVP-10. This results indicated furthermore, it is also shown that the optimal pH and temperature for the adsorption were 7.2 and 37 degrees C, respectively. The study carried out with organic solvents like methanol, ethanol, isopropanol and the detergents sodium dodecyl sulfate and triton X-100 showed a moderate inhibition of the bacteriocin lethal action for the Gram negative cells. The enzymes lysozime, protease XIV and trypsine type III-S did not present any effect over the adsorption capacity of the bacteriocin with any of the bacterial species studied.