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PubMed1989

Characterization of non-flocculent cells isolated from a culture of flocculent Saccharomyces cerevisiae NCYC 1001.

During cultivation of a flocculent yeast, Saccharomyces cerevisiae 1001, two cell fractions, flocs and free cells, appeared in the medium. Free cells contained cells with a normal ability to flocculate, less flocculent cells and not-flocculent cells. When the non-flocculent cells and not-flocculent cells. When the non-flocculent cell fraction from the postexponential phase of growth was collected and used as an inoculum, the culture showed synchronous growth. The floc forming ability of the yeast cells from this culture increased gradually with the number of divisions.

Chemical Precipitation↗
PubMed2006

Toxoid flocculation assay by laser light-scattering.

Internationally accepted designations of antigen content for toxoid vaccines are provided by the WHO in Lf (limes flocculationis) units, based on the formation of antigen-antibody complexes. The current assay method for Lf determination involves observation of the complexes by eye, making the development of a more objective system highly desirable. Here we report a novel detection system using a laser light-scattering platelet aggregometer. The system was highly reproducible and more objective than the current method. Only three sets of duplicate data were sufficient for statistically significant determination of toxoid Lf by parabolic regression.

Antigen-Antibody Complex↗
PubMed2002

Effect of sodium orthovanadate on glycosylation of the phosphopeptidomannans involved in the cell-cell aggregation of the yeast Kluyveromyces bulgaricus.

In studies of yeast flocculation it has been found that low concentrations of vanadium contained in sodium orthovanadate do not affect the growth and the cell-cell adhesion of the yeast Kluyveromyces bulgaricus, whereas high concentrations delay the growth of the yeasts and strongly inhibit flocculation. Moreover, higher sensitivity to Hygromycin B and calcofluor white was taken to imply altered cell wall integrity which is supported by compositional analysis of the extracted phosphopeptidomannans. Yeasts grown on sodium orthovanadate show a decrease in the percentage of phosphopeptidomannans and their compositions. It is proposed that the vanadium contained in sodium orthovanadate has a similar conformation to phosphorus and competes with phosphorus in phosphorylated compounds. The decrease of carbohydrate components and phosphorus linking to phosphopeptidomannans detected may alter their structure and modify ligand binding properties.

Cell Aggregation↗
PubMed1999

Development of a typing system for epidemiological studies of porcine toxin-producing Pasteurella multocida ssp. multocida in Denmark.

The aim of the present study was to evaluate capsular-typing, plasmid-profiling, phage-typing and ribotyping for epidemiological studies of toxin-producing Pasteurella multocida ssp. multocida in Denmark. The evaluation of methods was based on 68 strains from nasal swabs and 14 strains from pneumonic lungs. Strains from lungs were all of capsular Type A, whereas strains from nasal swabs were of both capsular Types A and D. Only 9% of the strains contained plasmids, which could not be associated with antibiotic resistance. Phage-typing divided 61% of strains into 10 groups, while 39% were non-typable. CfoI ribotyping divided strains into four groups of which one type contained 94% of isolates. HindIII ribotyping divided strains into 18 types. A total of 18 strains from The Netherlands, UK and USA were subjected to HindIII ribotyping, resulting in 13 types of which six were identical to ribotypes of Danish strains. Phage-typing of isolates from an outbreak of atrophic rhinitis involving six herds in 1985 showed the existence of an epidemic strain. This type was recognised in the herd suspected of being the source of the infections and in four of the five infected herds. These findings were supported by HindIII ribotyping, as 85% of isolates from all herds were assigned to one ribotype. In conclusion, HindIII ribotyping seems to represent a useful tool for epidemiological studies of toxigenic P. multocida ssp. multocida.

Animals↗
PubMed2001

Isolation and biochemical characterization of cell wall tight protein complex involved in self-flocculation of Kluyveromyces bulgaricus.

Flocculation of yeasts is a cell-cell aggregation phenomenon which is driven by interactions between cell wall lectins and cell wall heteropolysaccharides. In Sabouraud medium, Kluyveromyces bulgaricus was highly flocculent. Incubation of flocculent K. bulgaricus cells with EDTA or Hecameg led to extracts showing hemagglutinating and flocculating properties. Purification of the extracts by native PAGE gave two bands which allowed flocculation of deflocculated K. bulgaricus. Both bands with specific reflocculating activity were composed of five subunits, of which only three possessed weak reflocculating activity upon deflocculated yeast. The mixture of these three proteins allow the recovery of initial specific reflocculating activity of the complex. These three proteins, denoted p28, p36 and p48, presented, in their first 15 amino acids, homologies with glycolysis enzymes, i.e., 3-phosphoglycerate mutase, glyceraldehyde-3-phosphate dehydrogenase and enolase, respectively. However, no such enzymatic activity could be detected in the crude extract issued from treatment with EDTA and Hecameg of flocculent yeast cells. When yeasts had grown in glucose poor medium, flocculation was drastically affected. The EDTA and Hecameg crude extracts showed weak reflocculating activity. After PAGE, the protein complexes did not appear in the EDTA extract, but they did appear in the Hecameg crude extract. These results suggest that: (i) self-flocculation of K. bulgaricus depends on the expression of different floc-forming protein complex, (ii) these proteins are galactose specific lectins showing homologies in their primary structure with glycolysis enzymes.

Amino Acid Sequence↗
PubMed2002

Production of an exopolysaccharide bioflocculant by Sorangium cellulosum.

AIMS: To isolate a new exopolysaccharide bioflocculant produced by the myxobacterium Sorangium cellulosum NUST06, and to characterize its chemical composition and expolysaccharide production relative to carbon source. METHODS AND RESULTS: Exopolysaccharide levels and biomass production by S. cellulosum NUST06 were analysed relative to carbon source. Glucose in the medium at a level of 3 g l(-1) completely inhibited cell growth and exopolysaccharide production, but low concentrations of glucose (1-2 g l(-1)) could stimulate cell utilization of starch. The chemical composition and flocculating activity of the NUST06 exopolysaccharide was investigated. The flocculant comprised 38.3% proteins and 58.5% carbohydrates, of which glucose, mannose and glucuronic acid were present at 51.3%, 39.2% and 10.5%, respectively. The flocculating activity of the NUST06 flocculant depended strongly on cations. CONCLUSIONS: It is feasible to produce an exopolysaccharide bioflocculant by the strain NUST06 in a mineral salts medium using starch as a carbon source. SIGNIFICANCE AND IMPACT OF THE STUDY: This strain may be advantageous for commercial bioflocculant production and may enrich existing knowledge of myxobacteria.

Carbon↗
PubMed2002

Evaluation of three flocculation methods for the purification of Cryptosporidium parvum oocysts from water samples.

AIMS: Evaluation of three flocculation methods for the purification of Cryptosporidium parvum oocysts from tap water. METHODS AND RESULTS: Ferric sulphate, aluminium sulphate and calcium carbonate were compared for their recovery efficiency of C. parvum oocysts from tap water. Lower mean recovery was achieved by calcium carbonate (38.8%) compared with ferric sulphate (61.5%) and aluminium sulphate (58.1%) for the recovery of 2.5 x 10(5) oocysts l(-1); 2.5 oocysts l(-1) and 1 oocyst l(-1) were adequately purified using ferric sulphate flocculation. In vitro excystation experiments showed that ferric sulphate flocculation does not markedly reduce the viability of oocysts. CONCLUSIONS: Ferric sulphate flocculation is a simple and effective tool for the purification of C. parvum oocysts from tap water. SIGNIFICANCE AND IMPACT OF THE STUDY: The high recovery rates and low impact on oocyst viability provided by ferric sulphate flocculation might be useful for the detection of Cryptosporidium oocysts in environmental water samples.

Alum Compounds↗
PubMed1979

Arctic trichinosis: two Alaskan outbreaks from walrus meat.

The arctic form of Trichinella spiralis that infects terrestrial and marine mammals is of importance in public health because persons living in arctic regions still depend on wild animals for economic subsistence. In 1975, an extended common-source epidemic of trichinosis attributed to consumption of walrus meat involved 29 persons in Barrow, Alaska. Of those persons eating this meat, 64% became ill, and the rate of infection of persons eating meat prepared with little or no cooking was four times as great as that of persons eating cooked meat. One year later a second outbreak occurred when a family ate partially cooked meat from an infected walrus. Clinical illness differed little from the disease acquired in temperature climates; however, only 70% had a positive bentonite flocculation titer, whereas 96% had eosinophilia. These epidemics of trichinosis are the first reported in Alaska to be associated with the consumption of walrus meat.

Alaska↗
PubMed1996

MIG1 overexpression causes flocculation in Saccharomyces cerevisiae.

MIG1, encoding a C2H2 zinc-finger repressor protein involved in carbon catabolite repression, was found to play a role in non-sexual flocculation of Saccharomyces cerevisiae. Disruption of MIG1 in a flocculent mutant strain of NCYC 227, resulted in a non-flocculent phenotype. Expression of MIG1 on a 2 mu pRS426 vector in a non-flocculent strain, YM 4134, caused flocculation; MIG1 on a high-copy-number LEU2-d plasmid caused intense flocculation in the same strain. Mutations in the SSN6 and TUP1 genes confer a flocculent phenotype in non-flocculent strains of S. cerevisiae, and it has been shown that Mig1 can tether the Ssn6p-Tup1p complex to the regulatory regions of glucose-repressible genes. Mutations in tup1 in a MIG1 background caused flocculation while double mutants of TUP1 and MIG1 did not flocculate. Based on these results, a model for the role of MIG1 in flocculation gene regulation is proposed.

Blotting, Northern↗
PubMed2005

Flocculation onset in Saccharomyces cerevisiae: the role of nutrients.

AIMS: To examine the role of the nutrients on the onset of flocculation in an ale-brewing strain, Saccharomyces cerevisiae NCYC 1195. METHODS AND RESULTS: Flocculation was evaluated using the method of Soares, E.V. and Vroman, A. [Journal of Applied Microbiology (2003) 95, 325]. For cells grown in chemically defined medium (yeast nitrogen base with glucose) or in rich medium (containing yeast extract, peptone and fermentable sugars: fructose or maltose), the onset of flocculation occurred after the end of exponential respiro-fermentative phase of growth being coincident with the attainment of the lower level of carbon source in the culture medium. Cells, in exponential respiro-fermentative phase of growth, transferred to a glucose-containing medium without nitrogen source, developed a flocculent phenotype, while these carbon source starved cells, in the presence of all other nutrients that support growth, did not flocculate. In addition, cells in exponential phase of growth, under catabolite repression, when transferred to a medium containing 0.2% (w/v) of fermentable sugar (fructose or maltose) or 2% (v/v) ethanol, showed a rapid triggering of flocculation, while when incubated in 2% (v/v) glycerol did not develop a flocculent phenotype. CONCLUSIONS: The onset of flocculation occurs when a low sugar and/or nitrogen concentration is reached in culture media. The triggering of flocculation is an energetic dependent process influenced by the carbon source metabolism. The presence of external nitrogen source is not necessary for developing a flocculent phenotype. SIGNIFICANCE AND IMPACT OF THE STUDY: This work contributes to the elucidation of the role of nutrients on the onset of flocculation in NewFlo phenotype yeast strains. This information might be useful to the brewing industry, in the control of yeast flocculation, as the time when the onset of flocculation occurs can determine the fermentation performance and the beer quality.

Beer↗
PubMed2003

Development and application of different methods for the detection of Toxoplasma gondii in water.

Two methods, centrifugation and flocculation, were evaluated to determine their efficiencies of recovery of Toxoplasma gondii oocysts from contaminated water samples. Demineralized and tap water replicates were inoculated with high numbers of sporulated or unsporulated T. gondii oocysts (1 x 10(5) and 1 x 10(4) oocysts). The strain, age, and concentration of the seeded oocysts were recorded. Oocysts were recovered either by centrifugation of the contaminated samples at various g values or by flocculation with two coagulants, Fe(2)(SO(4))(3) and Al(2)(SO(4))(3). The recovery rates were determined with the final pellets by phase-contrast microscopy. Sporulated oocysts were recovered more effectively by flocculation with Al(2)(SO(4))(3) (96.5% +/- 21.7%) than by flocculation with Fe(2)(SO(4))(3) (93.1% +/- 8.1%) or by centrifugation at 2,073 x g (82.5% +/- 6.8%). For the unsporulated oocysts, flocculation with Fe(2)(SO(4))(3) was more successful (100.3% +/- 26.9%) than flocculation with Al(2)(SO(4))(3) (90.4% +/- 19.1%) or centrifugation at 2,565 x g (97.2% +/- 12.5%). The infectivity of the sporulated oocysts recovered by centrifugation was confirmed by seroconversion of all inoculated mice 77 days postinfection. These data suggest that sporulated Toxoplasma oocysts purified by methods commonly used for waterborne pathogens retain their infectivity after mechanical treatment and are able to induce infections in mammals. This is the first step in developing a systematic approach for the detection of Toxoplasma oocysts in water.

Alum Compounds↗
PubMed1975

Relationship between cell-bound dextransucrase and the agglutination of Streptococcus mutans.

Dextran-induced agglutination of Streptococcus mutans cells is independent of cell-bound dextransucrase activity. Toluene extraction or the presence of Hg2+ or Cu2+ markedly decreased or completely abolished cell-bound dextransucrase activity without adversely affecting dextran-induced cell agglutination. Cells treated by heating at 100 C until cell-bound dextransucrase was completely inactivated continued to agglutinate when induced by dextran-induced cell agglutination resulted from cell treatment with trypsin and several other enzymes, as well as from ethylenediaminetetraacetic acid treatment, without a corresponding loss of cell-bound dextransucrase activity. Cells possessed a greater avidity for branched dextrans of low molecular weight than for linear dextrans of the same weight, indicating that size alone does not determine the efficiency of dextran as an inducer of agglutination. Divalent metal ions were required for both sucrose- and dextran-induced agglutination of S. mutans K1-R cells. Although normal cells of strain 6715-49 did not appear to require divalent cations for agglutination, heat- and ethlyenediaminetetraacetic acid-treated cells specifically required Ca2+. The role of Ca2+ in cell agglutination may be either to activate the cell-surface dextran receptor or to form specific intercellular Ca2+ bridges.

Agglutination↗