Genetic and physical localization of the acetyl-coenzyme A synthetase gene ACS1 on chromosome I of Saccharomyces cerevisiae

The ACS1 gene, encoding acetyl-coenzyme A synthetase, was mapped genetically at the left arm of chromosome I between pURA3 and PYK1 at 19 and 28 cM respectively. Comparison with the physical map defined a recombinational ‘hot-spot’ in this region in addition to the one between CDC24 and PYK1.     

Comparative study of the consumption of virgin olive oil or seje on lipid profile and oxidation resistance of high density lipoprotein (HDL) of rat plasma

We compared the effect of the consumption of seje oil (Oenocarpus bataua), with that of olive oil, on plasma lipids and susceptibility in vitro to oxidation of high density lipoprotein (HDL) in the rat. Two groups often male Sprague Dawley rats were fed ad libitum, for a lapse of eight week, with a purified diets with 10g de seje oil or olive oil/100 g of diet (GS y GO respectively). The animals were exsanguinated at the end of the experimental after a 14 hour fast. Plasma was isolated by centrifugation, and the fractions of lipoproteins were separated from the plasma by sequential ultracentrifugation. Rats of GO had a statistically significant lower in concentration of TG (p < 0.05) compared with GS group. HDL fractions in both groups were oxidatively modified by incubation with copper ions. Differences in the fractions susceptibilities to peroxidation were studied by measuring the formation of thiobarbituric acid reactive substance (TBARS) for 3 hours. HDL in GS had a statistically significant decrease in TBARS formation (p < 0.05) relative to HDL of GO. This may be explained by the lower concentration of polyunsaturated fatty acids of HDL in GS compared with HDL in GO.     

Structural Investigations on the Anti‐HIV G‐Quadruplex‐Forming Oligonucleotide TGGGAG and Its Analogues: Evidence for the Presence of an A‐Tetrad

Several anti‐HIV aptamers adopt DNA quadruplex structures. Among these, “Hotoda's aptamer” (base sequence TGGGAG) was one of the first to be discovered. Although it has been the topic of some recent research, no detailed structural investigations have been reported. Here we report structural investigations on this aptamer and analogues with related sequences, by using UV, CD, and NMR spectroscopy as well as electrophoretic techniques. The addition of a 3′‐end thymine has allowed us to obtain a single, investigable quadruplex structure. Data clearly point to the presence of an A‐tetrad. Furthermore, the effects of the incorporation of an 8‐methyl‐2′‐deoxyguanosine at the 5′‐end of the G‐run were investigated.     

Coagulase-positive Staphylococci and Staphylococcus aureus in food products marketed in Italy

Staphylococcus aureus is a very common organism capable of producing several enterotoxins (SEs) that cause intoxication symptoms of varying intensity in humans when ingested through contaminated food. This paper reports the results of an investigation on the presence of Coagulase-Positive Staphylococci (CPS) and S. aureus in several food products marketed in Italy and on food contact surface swabs sampled from the food industry. A total of 11,384 samples were examined and 1971 of them (17.3%) were found to contain CPS. The assays performed on 541 CPS strains led to the identification of 537 S. aureus strains on which characterization of type A, B, C and D staphylococcal enterotoxins (SEA, SEB, SEC and SED) was performed. A total of 298 S. aureus strains (55.5%) produced one or more SEs: 33.9% of the strains produced SEC, 26.5% SEA, 20.5% SEA+SED, 13.4% SED, 2.7% SEB, 1.7% SEA+SEB, 0.7% SEC+SED and 0.3% produced SEA+SEC and SEB+SEC. The investigation highlighted that these organisms are very common and constitute a potential risk for consumers' health.     

Development of a multiplex PCR for rapid detection of verocytotoxin-producing Escherichia coli O26 in raw milk and ground beef

Verocytotoxin-producing Escherichia coli (VTEC) O26 is an emergent pathotype that has caused an increasing number of sporadic cases and outbreaks of gastroenteritis, hemorrhagic colitis, and hemolytic uremic syndrome in the United States and Europe. Many cases are associated with the consumption of milk and undercooked or fermented meats. The stx(2) strains of VTEC O26 seem to be more likely to cause human infections than isolates expressing only stx(1). The isolation and identification of VTEC O26 from foods is labor intensive and time-consuming. We developed a multiplex PCR (M-PCR) assay for the identification and characterization of E. coli O26 VTEC and its detection in raw milk and ground beef. The method is based on the amplification of the wzx, stx(1), and stx(2) genes for the simultaneous detection of the O26 antigen and verocytotoxin types 1 and 2. This M-PCR assay had a sensitivity of 10(8) CFU/ml when applied to a bacterial suspension and of 10(6) CFU/ml or g when applied to both inoculated milk and minced beef samples. This M-PCR assay also was highly specific, and results were consistently negative for negative controls (nonpathogenic E. coli strains, uninoculated milk and beef samples, and samples inoculated with the nontarget microorganisms). This method could be used for the rapid detection of E. coli O26 VTEC from foods and for the rapid identification and characterization of clinical and environmental isolates.     

Ultraporous poly(l-lactide) scaffolds prepared with quaternary immiscible polymer blends modified by copolymer brushes at the interface

The activity of polystyrene-block-poly(l-lactide) (PS-b-PLLA) and polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer brushes located at a PS/PLLA interface were employed as a route to control the final microstructure of 95% void volume, ultraporous PLLA scaffolds. The latter were initially prepared from melt-processed quaternary blends of ethylene propylene diene rubber/poly(?-caprolactone)/polystyrene/poly(l-lactide) (EPDM/PCL/PS/PLLA) 45/45/5/5%vol. modified with the diblock copolymers. The blends display a layer comprised of the PS and PLLA phases located at the interface of the co-continuous EPDM and PCL phases. When the PS-b-PLLA copolymer is added, sub-micrometric PLLA droplets are encapsulated within the PS continuous layer phase. In comparison, both the PS and PLLA phases compete for the encapsulation process when the PS-b-PMMA is used, indicating that the microstructure of the PLLA phase can be fine-tuned with an adequate choice of interfacial modifier. These effects were investigated by analyzing the microstructure of ternary high-density polyethylene (HDPE)/PS/PMMA 80/10/10%vol. blends displaying PS/PMMA shell/core composite droplets in a HDPE matrix. An inversion of the shell/core structure is observed when the PS-b-PLLA copolymer is used to compatibilize the PS/PMMA interface, whereas no such restructuring occurs with the PS-b-PMMA. These effects are explained by the activity and swelling powers of the copolymer brushes. For the EPDM/PCL/PS/PLLA quaternary systems modified with the PS-b-PMMA, the PLLA homopolymer phase significantly penetrates and swells the PMMA blocks due to their mutual high affinity, as compared to the classical like-prefers-like compatibilization approach. The swelling of the blocks will tend to bend the interface toward the PS phase in order to minimize the lateral compression of the PMMA blocks. A similar effect explains the reversal of the PS/PMMA shell/core structure in the HDPE/PS/PMMA ternary system. This level of control ultimately leads to quite significant differences in microstructures and surface textures for the PLLA scaffolds.     

Cloning and disruption of a gene required for growth on acetate but not on ethanol: the acetyl-coenzyme A synthetase gene of Saccharomyces cerevisiae.

A DNA fragment of Saccharomyces cerevisiae with high homology to the acetyl-coenzyme A (acetyl-CoA) synthetase genes of Aspergillus nidulans and Neurospora crassa has been cloned, sequenced and mapped to chromosome I. It contains an open reading frame of 2139 nucleotides, encoding a predicted gene product of 79.2 kDa. In contrast to its ascomycete homologs, there are no introns in the coding sequence. The first ATG codon of the open reading frame is in an unusual context for a translational start site, while the next ATG, 24 codons downstream, is in a more conventional context. Possible implications of two alternative translational start sites for the cellular localization of the enzyme are discussed. A stable mutant of this gene, obtained by the gene disruption technique, had the same low basal activity of acetyl-CoA synthetase as wild-type cells when grown on glucose but completely lacked the strong increase in activity upon entering the stationary phase, providing direct proof that the gene encodes an inducible acetyl-CoA synthetase (ACS1) of yeast. As expected, the mutant was unable to grow on acetate as sole carbon source. Nevertheless, it showed normal induction of isocitrate lyase on acetate media, indicating that activity of acetyl-CoA synthetase is dispensable for induction of the glyoxylate cycle in S. cerevisiae. Surprisingly, disruption of the ACS1 gene did not affect growth on media containing ethanol as the sole carbon source, demonstrating that there are alternative pathways leading to acetyl-CoA under these conditions.