Attachment of lactic acid bacteria to beef-muscle surfaces

The effect of immersion time and cell concentration in the attachment of several lactic acid bacteria with antibacterial activity to beef-muscle surface was studied. The number of firmly attached bacteria increased with immersion time in the case ofPediococcus acidilacti, Lactobacillus sake, Lactococcus cremoris (two strains) andPediococcus acidilacti. Pediococcus pentosaceus, Lactococcus lactis andLactobacillus curvatus reached maximum adhesion after 15–30 min. The highest strength of attachment (Sr values) were observed after 15–30 min of contact, time except forP. pentosaceus. For all strains, the number of bacteria adhering to meat increased with increasing cell concentration in the adhesion medium. The highest strength of attachment was observed at a cell concentration of 10⁵/mL mainly forL. sake, L. lactis andL. cremoris. Due to their attachment characteristics,L. sake, L. lactis andL. cremoris are proposed as potential biocontrol agents because they could grow on meat surface and limit the potential attachment of pathogenic microorganisms.     

Headspace gas composition in fourPrunus avium cultivars with differing photosynthetic capabilities

Summary Endogenous and exogenous volatile substances were analyzed during 30 days' incubation of four cultivars of thePrunus avium species grown in vitro on a proliferation medium. Cultivars Bigarreau Moreau and Bigarreau Burlat show photosynthetic capability at 35 μmol·m⁻²·s⁻¹; oxygen concentration slightly increased (22 to 24%), carbon dioxide was lowered to less than 300 μ·liter⁻¹, and low ethylene (0.8 to 1.2·liter⁻¹) accumulation was recorded. Quite different headspace evolution was observed during growth of cultivars Victoria and Casavecchia: a large oxygen concentration decrease was accompanied by a sharp carbon dioxide increase (19%) and ethylene boost (4 to 5 μl·liter⁻¹). The evolution of these gaseous metabolites has been correlated to photosynthetic incapability and respiratory stress responsible for leaf yellowing and tissue softening observed when acetaldehyde and ethanol started to form in cultivars Victoria and Casavecchia. Dry and fresh weight were measured, and no substantial difference was recorded among cultures with low and high photosynthetic capability. Evidence is reported that different genotypes within the same species may follow different metabolic pathways.     

Growth stimulation of rat fetal hepatocytes in response to hepatocyte growth factor: modulation of c-myc and c-fos expression.

Hepatocyte growth factor, which is a potent growth factor for primary cultured adult hepatocytes, strongly stimulated DNA synthesis of rat fetal (20-day of gestation) hepatocytes. Its mitogenic capacity, measured as (3H)-thymidine incorporation into acid precipitable material was dose dependent, being detectable at 1 ng/ml and maximal at 5 ng/ml. Over 15% of the cells entered into S-phase and mitosis as judged by flow cytometric analysis of the cell cycle. HGF had additive effects with transforming growth factor-alpha, whereas transforming growth factor-beta strongly inhibited DNA synthesis of fetal hepatocytes stimulated by HGF. HGF induced c-fos and c-myc expression in a time-dependent manner, with a maximum at 30 min for c-fos and 8 h for c-myc. These results suggest that HGF may act as a proliferative factor during fetal liver growth.     

trans-Complementation of a Staphylococcus aureus agr Mutant by Staphylococcus lugdunensis agr RNAIII

RNAIII from Staphylococcus lugdunensis (RNAIII-sl) in a Staphylococcus aureus agr mutant partially restored the Agr phenotype. A chimeric construct consisting of the 5′ end of RNAIII-sl and the 3′ end of RNAIII from S. aureus restored the Agr phenotype to a greater extent, suggesting the presence of independent regulatory domains.     

H-ras Induces Glucose Uptake in Brown Adipocytes in an Insulin- and Phosphatidylinositol 3-Kinase-Independent Manner

Fetal brown adipocytes (parental cells) expressed mainly Glut4 mRNA glucose transporter, the expression of Glut1 mRNA being much lower. At physiological doses, insulin stimulation for 15 min increased 3-fold glucose uptake and doubled the amount of Glut4 protein located at the plasma membrane. Moreover, phosphatidylinositol (PI) 3-kinase activity was induced by the presence of insulin in those cells, glucose uptake being precluded by PI 3-kinase inhibitors such as wortmannin or LY294002. H-ras^lys12-transformed brown adipocytes showed a 10-fold higher expression of Glut1 mRNA and protein than parental cells, Glut4 gene expression being completely down-regulated. Glucose uptake increased by 10-fold in transformed cells compared to parental cells; this uptake was unaltered in the presence of insulin and/or wortmannin. Transient transfection of parental cells with a dominant form of active Ras increased basal glucose uptake by 5-fold, no further effects being observed in the presence of insulin. However, PI 3-kinase activity (immunoprecipitated with anti-αp85 subunit of PI 3-kinase) remained unaltered in H-ras permanent and transient transfectants. Our results indicate that activated Ras induces brown adipocyte glucose transport in an insulin-independent manner, this induction not involving PI 3-kinase activation.     

Purification and Characterization of an Extracellular Protease from Penicillium chrysogenum Pg222 Active against Meat Proteins

An extracellular protease from Penicillium chrysogenum (Pg222) isolated from dry-cured ham has been purified. The purification procedure involved several steps: ammonium sulfate precipitation, ion-exchange chromatography, filtration, and separation by high-performance liquid chromatography. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis and gel filtration, the purified fraction showed a molecular mass of about 35 kDa. The hydrolytic properties of the purified enzyme (EPg222) on extracted pork myofibrillar proteins under several conditions were evaluated by SDS-PAGE. EPg222 showed activity in the range of 10 to 60°C in temperature, 0 to 3 M NaCl, and pH 5 to 7, with maximum activity at pH 6, 45°C, and 0.25 M NaCl. Under these conditions the enzyme was most active against tropomyosin, actin, and myosin. EPg222 showed collagenolytic activity but did not hydrolyze myoglobin. EPg222 showed higher activity than other proteolytic enzymes like papain, trypsin, and Aspergillus oryzae protease. The N-terminal amino acid sequence was determined and was found to be Glu-Asn-Pro-Leu-Gln-Pro-Asn-Ala-Pro-Ser-Trp. This partial amino acid sequence revealed a 55% homology with serine proteases from Penicillium citrinum. The activity of this novel protease may be of interest in ripening and generating the flavor of dry-cured meat products.     

Molecular markers linked to the aluminium tolerance gene Alt1 in rye (Secale cereale L.)

 Rye has one of the most efficient group of genes for aluminium (Al) tolerance among cultivated species of Triticeae. This tolerance is controlled by at least two independent and dominant loci (Alt1 and Alt3) located on chromosomes 6RS and 4R. We used two pooled DNA samples, one of Al-tolerant individuals and another of Al-sensitive plants from one F₂ that segregated for the Alt1 locus. We also used two pooled DNA samples, one with genotypes 11 and another with genotypes 22 for the Lap1 locus (leucin aminopeptidase) from another F₂ progeny that segregated for this locus, located on the 6RS chromosome arm. We identified several RAPD markers associated with the pooled Al-tolerant plants and also with one of the bulks for the Lap1 locus. The RAPD fragments linked to Alt1 and Lap1 genes were transformed into SCAR markers to confirm their chromosomal location and linkage data. Two SCARs (ScR01 ₆₀₀ and ScB15 ₇₉₀₀ ) were closely linked to the Alt1 locus, ScR01 ₆₀₀ located 2.1 cM from Alt1 and ScB15 ₇₉₀ located 5.5 cM from Alt1, on the 6RS chromosome arm. These SCAR markers can aid in the transfer of Al tolerance genes into Al-sensitive germplasms. Received: 9 December 1997 / Accepted: 12 May 1998     

New insights on the specificity of heparin and heparan sulfate lyases from Flavobacterium heparinum revealed by the use of synthetic derivatives of K5 polysaccharide from E. coli. and 2-O-desulfated heparin

The capsular polysaccharide from E. Coli, strain K5 composed of ...-->4)beta-D-GlcA(1-->4)alpha-D-GlcNAc(1-->4)beta-D-GlcA (1-->..., chemically modified K5 polysaccharides, bearing sulfates at C-2 and C-6 of the hexosamine moiety and at the C-2 of the glucuronic acid residues as well as 2-O desulfated heparin were used as substrates to study the specificity of heparitinases I and II and heparinase from Flavobacterium heparinum. The natural K5 polysaccharide was susceptible only to heparitinase I forming deltaU-GlcNAc. N-deacetylated, N-sulfated K5 became susceptible to both heparitinases I and II producing deltaU-GlcNS. The K5 polysaccharides containing sulfate at the C-2 and C-6 positions of the hexosamine moiety and C-2 position of the glucuronic acid residues were susceptible only to heparitinase II producing deltaU-GlcNS,6S and deltaU,2S-GlcNS,6S respectively. These combined results led to the conclusion that the sulfate at C-6 position of the glucosamine is impeditive for the action of heparitinase I and that heparitinase II requires at least a C-2 or a C-6 sulfate in the glucosamine residues of the substrate for its activity. Iduronic acid-2-O-desulfated heparin was susceptible only to heparitinase II producing deltaU-GlcNS,6S. All the modified K5 polysaccharides as well as the desulfated heparin were not substrates for heparinase. This led to the conclusion that heparitinase II acts upon linkages containing non-sulfated iduronic acid residues and that heparinase requires C-2 sulfated iduronic acid residues for its activity.     

Molecular systematics of the parasitic protozoan Giardia intestinalis.

The long-standing controversy regarding whether Giardia intestinalis is a single species prevalent in both human and animal hosts or a species complex consisting of morphologically similar organisms that differ in host range and other biotypic characteristics is an issue with important medical, veterinary, and environmental management implications. In the past decade, highly distinct genotypes (some apparently confined to particular host groups) have been identified by genetic analysis of samples isolated from different host species. The aim of this study was to undertake a phylogenetic analysis of G. intestinalis that were representative of all known major genetic groups and compare them with other Giardia species, viz. G. ardeae, G. muris, and G. microti. Segments from four "housekeeping" genes (specifying glutamate dehydrogenase, triose phosphate isomerase, elongation factor 1 alpha, and 18S ribosomal RNA) were examined by analysis of 0.48-0.69-kb nucleotide sequences determined from DNA amplified in polymerase chain reactions from each locus. In addition, isolates were compared by allozymic analysis of electrophoretic data obtained for 21 enzymes representing 23 gene loci. The results obtained from these independent techniques and different loci were essentially congruous. Analyses using G. ardeae and/or G. muris as outgroups supported the monophyly of G. intestinalis and also showed that this species includes genotypes that represent at least seven deeply rooted lineages, herein designated assemblages A-G. Inclusion of G. microti in the analysis of 18S rRNA sequence data demonstrated the monophyly of Giardia with the same median body morphology but did not support the monophyly of G. intestinalis, instead placing G. microti within G. intestinalis. The findings support the hypothesis that G. intestinalis is a species complex and suggest that G. microti is a member of this complex.