The effect of age on the structure and compostition of the cell walls of Choanephora cucurbitarum

The effect of age on the structure and composition of isolated and purified cell walls from cultures of Choanephora cucurbitarum was investigated by microchemical analyses, visible and infrared spectrophotometry, x-ray diffractometry and electron microscopy. Qualitative evaluation revealed the presence of lipids, proteins, neutral sugars, strong alkali soluble sugars, chitin, chitosan and uronic acids in the cell walls of both the 1 and 7 day old cultures. As the mycelium aged, there was a slight but statistically significant increase in the protein content, and a pronounced rise in the chitin and neutral sugar constituents of the cell walls. Conversely, the decrease in the chitosan content during this period had the net effect of altering the chitin: chitosan ratio from near unity in the younger cultures, to a 2:1 ratio in the 7 day old cell wall samples. Glutaraldehyde-osmium fixed thin sections of the 1 day old vegetative hyphae of £. curbitarum revealed the presence of a monolayered cell wall, which upon aging became bilayered. Replicas of acid hydrolysed cell walls demonstrated that both the 1 and 7 day old samples possessed an outer layer which was composed of finely granular amorphous material and randomly distributed microfibrils. The deposition of an inner secondary layer composed of parallel oriented microfibrils in the older hypha was correlated with an increase in the chitin content in the cell wall. The significance of these results with respect to the intimate relationship between composition and structure is discussed.

Hyperosmotic Stress and the Impact on Metabolite Formation and Redox Balance in Saccharomyces cerevisiae and Saccharomyces bayanus strains

Wine produced using an appassimento-type process represents a new and exciting innovation for the Ontario wine industry. This process involves drying grapes that have already been picked from the vine, which increases the sugar content due to dehydration and induces a variety of changes both within and on the surface of the grapes. Increasing sugar contents in musts subject wine yeast to conditions of high osmolarity during alcoholic fermentations. Under these conditions, yeast growth can be inhibited, target alcohol levels may not be attained and metabolic by-products of the hyperosmotic stress response, including glycerol and acetic acid, may impact wine composition. The further metabolism of acetic acid to acetylCoA by yeast facilitates the synthesis of ethyl acetate, a volatile compound that can also impact wine quality if present in sufficiently high concentrations. The first objective of this project was to understand the effect of yeast strain and sugar concentration on fermentation kinetics and metabolite formation, notably acetic acid and ethyl acetate, during fermentation in appassimento-type must. Our working hypotheses were that (1) the natural isolate Saccharomyces bayanus would produce less acetic acid and ethyl acetate compared to Saccharomyces cerevisiae strain EC-1118 fermenting the high and low sugar juices; (2) the wine produced using the appassimento process would contain higher levels of acetic acid and lower levels of ethyl acetate compared to table wine; (3) and the strains would be similar in the kinetic behavior of their fermentation performances in the high sugar must. This study determined that the S. bayanus strain produced significantly less acetic acid and ethyl acetate in the appassimento wine and table wine fermentations. Differences in acetic acid and ethyl acetate production were also observed within strains fermenting the two sugar conditions. Acetic acid production was higher in table wine fermented by S. bayanus as no acetic acid was produced in appassimento-style wine, and 1.4-times higher in appassimento wine fermented by EC-1118 over that found in table wine. Ethyl acetate production was 27.6-times higher in table wine fermented by S. bayanus, and 5.2-times higher by EC-1118, compared to that in appassimento wine. Sugar utilization and ethanol production were comparable between strains as no significant differences were determined. The second objective of this project was to bring a method in-house for measuring the concentration of pyridine nucleotides, NAD+, NADP+, NADH and NADPH, in yeast cytosolic extract. Development of this method is of applicative interest for our lab group as it will enable the redox balance of the NAD+/ NADH and NADP+/ NADPH systems to be assessed during high sugar fermentations to determine their respective roles as metabolic triggers for acetic acid production. Two methods were evaluated in this study including a UV-endpoint method using a set of enzymatic assay protocols outlined in Bergmeyer (1974) and a colorimetric enzyme cycling method developed by Sigma-Aldrich® using commercial kits. The former was determined to be limited by its low sensitivity following application to yeast extract and subsequent coenzyme analyses, while the latter was shown to exhibit greater sensitivity. The results obtained from the kits indicated high linearity, accuracy and precision of the analytical method for measuring NADH and NADPH, and that it was sensitive enough to measure the low coenzyme concentrations present in yeast extract samples. NADtotal and NADPtotal concentrations were determined to be above the lower limit of quantification and within the range of the respective calibration curves, making this method suitable for our research purposes.

Isolation and characterization of the female sex pheromone of the sugar beet cyst nematode, heterodera schachtii, and an analysis of male precopulatory behaviour /

The sugar beet cyst nematode, Heterodera schachtii, is a major agricultural pest. The disruption of the mating behaviour of this plant parasite in the field may provide a means of biological control, and a subsequent increase in crop yield. The H. schachtii female sex pheromone, which attracts homospecific males, was collected in an aqueous medium and isolated using high performance liquid chromatography. Characterization of the male-attractive material revealed that it was heat stable and water soluble. The aqueous medium conditioned by female H. schachtii was found to be biologically active and stimulated male behaviour in a concentration dependent manner. The activity of the crude pheromone was specific to males of H. schachtii and did not attract second stage juveniles. Results indicated that vanillic acid, a putative nematode pheromone, is not an active component of the H. schachtii sex pheromone. Male H. schachtii exhibited stylet thrusting, a poorly understood behaviour of the male, upon exposure to the female sex pheromone. This behaviour appeared to be associated with mate-finding and was used as a novel indicator of biological activity in bioassays. Serotonin, thought to be involved in the neural control of copulatory behaviour in nematodes, stimulated stylet thrusting. However, the relationship between stylet thrusting induced by the sex pheromone and stylet thrusting induced by serotonin is not clear. Extracellular electrical activity was recorded fi-om the anterior region of H. schachtii males during stylet thrusting, and appeared to be associated with this behaviour. The isolation of the female sex pheromone of H. schachtii may, ultimately, lead to the structural identification and synthesis of the active substance for use in a novel biological control strategy.

An investigative study on the effects of black fly (diptera: simuliidae) sugar meals on reproductive success and parasite transmission /

Black flies are opportunistic sugar-feeders. They take sugar meals from Homopteran honeydew secretions or plant nectars, depending on availability. Homopteran honeydew secretions contain both simple and complex carbohydrates while plant nectars contain primarily simple carbohydrates. In order to determine whether honeydew secretions offer more energy than plant nectars to their insect visitors a study of wild-caught black flies was undertaken in Algonquin Provincial Park, Canada during the spring of 1 998 and 1 999. It was hypothesized that female black flies maintained on honeydew sugars will survive longer, produce more eggs and have a greater parasite vectoring potential than those maintained on artificial nectar or distilled water. Results demonstrated that: (1) host-seeking female Prosimulimfuscum/mixtum and Simulium venustum maintained on artificial honeydew did not survive longer than those maintained on artificial nectar when fed ad libitum; (2) fiiUy engorged S. venustum and Simulium rugglesi maintained on artificial honeydew did not produce more eggs than those maintained on artificial nectar when fed ad libitum; and (3) S. rugglesi did not have a greater vectoring potential of Leucocytozoon simondi when maintained on artificial honeydew as opposed to artificial nectar when fed ad libitum. However, all flies maintained on the two sugars (artificial honeydew and artificial nectar) survived longer, produce more eggs and had greater vectoring potential than those maintained on distilled water alone.

The application of gas liquid chromatography to the simultaneous analysis of sugars and sugar phosphates in biological samples /|nby David J. LeBlanc. -- 260 St. Catharines [Ont. : s. n.],

A study was undertaken' to determine the applicability of gas liquid chromatography to the simultaneous analysis of sugars and sugar phosphates from biological samples. A new method of silylation involving dimethylsulfoxide, hexamethyldisilazane, trimethylchlorosilane and cyclohexane (1:0.2:0.1:1) which rapidly silylated sugars and sugar phosphates was developed. Subsequent chromatography on a 5% SE-52 column gave good resolution of the sugar and sugar phosphate samples. Sugar phosphates decomposed during chromatography and were lost at the 7 x 10-3 ~mole level. Acidic ethanol extraction of yeast samples revealed background contamination from the yeast sample, the culture medium and the silylation reagents which would further limit the level of detection obtainable with the glc for sugars in biological samples to the 3 x 10-4 ~mole level.

Receipt from W.J. and J. McCalla, St. Catharines for sugar

Receipt from W.J. and J. McCalla, St. Catharines for sugar, March 3, 1888.

The effect of pH and ethanol on the astringent sub-qualities of red wine, and the implications for optimum grape maturity /

The first objective of this study was to identify appropriate sensory descriptors to assess the astringent sub-qualities of red wine. The influence of pH and ethanol on the sensation of astringency in red wine was evaluated, using a de-alcoholized red wine. A portion of the wine was adjusted to the pH values of 3.2, 3.4, 3.6 and 3.8, and another portion was adjusted to ethanol concentrations of 0%, 6%, 12%, and 15%. In addition, the pH 3.4 and 3.6 treatments were adjusted to an ethanol concentration of 12% and 15% all wines were then assessed sensorially and seventeen terms were identified, through panel discussion, to describe the mouth-feel and taste qualities: velvet, aggressive, silk/satin, dry, fleshy, unripe, pucker viscosity, abrasive, heat, chewy, acidity, grippy/adhesive, bitter, balance, overall astringency, and mouth-coat. Descriptive analysis profiling techniques were used to train the panel and measure the intensity of these attributes. It was found that decreasing pH values (averaged across all ethanol concentrations) showed an increase in the overall astringency of the wine. The combined treatments of ethanol and pH, real wine parameters (pH 3.4 and 3.6; 12% and 15% ethanol) did not have an effect on the perception of the astringent sub-qualities of the wine. A time intensity study was also included using the pH and ethanol adjusted wines, which showed that as the ethanol level of the wines increased so did the time to maximum intensity. The second objective was to identify appropriate sensory descriptors to evaluate the influence of grape maturity and maceration technique (grape skin contact) on the astringency sub-qualities of red vinifera wines from Niagara. The grapes were harvested across two dates, representing an early harvest and a late harvest. A portion of the Cabernet Sauvignon grapes wine was divided into three maceration treatments of oneweek maceration, standard two-week maceration, three-week maceration, and MCM. Another portion of both the early and late harvest Cabernet Sauvignon grapes were chaptalized to yield a final ethanol concentration of 14.5%. The wines were assessed sensorially and thirteen terms were identified, through panel discussion, to describe the mouth-feel and taste qualities: carbon dioxide, pucker, acidity, silk/chamois, dusty/chalky/powdery, sandpaper, numbing, grippy/adhesive, dry, mouthcoat, bitter, balance and, overall astringency. Descriptive analysis techniques were used to train the panel and measure the intensity of these attributes. The data revealed few significant differences in the mouth-feel of the wines with respect to maturity; which included differences in overall astringency and balance. There were varietal differences between Cabernet Sauvignon, Cabernet Franc, and Pinot Noir and differences for Cabernet Sauvignon wines due to the length and manner of maceration and as a result of chaptalization. Statistical analysis revealed a more complex mouth-feel for the Pinot Noir wines; and an increase in the intensity of the astringent sub-qualities as a result of the addition of sugar to the wines. These findings have implications for how processing decisions, such as optimum grape maturity and vinification methods may affect red wine quality.

Host-parasite relations in a mycoparasitic system : alterations in membrane permeability and lipid composition in Choanephora cucurbitarum infected by Piptocephalis virginiana /

examined in Choanephora cucurbita rum during the early stages of infection by Piptocephalis virginiana » There was a small but consistent increase in the leakage of electrolytes, amino acids and sugars as a result of infection. These low levels of differential leakage in infected tissues are explained on the basis of the nature of this obligate, biotrophic, mycoparasitic system. Quantitative analysis of the twenty six amino acids and amino compounds detected in the leacheates — showed similar profiles in infected and control host and no new species of amino acids or amino compounds were detected in either infected or control host leacheates. Comparatively high amounts of aspartic acid, glutamic acid and alanine were found in the leacheates of host and infected host . Analyses of the sugars comprising the leacheates of infected and control host showed the presence of eight sugars, among which glucose was found in significant amounts (50-53%) ' The nutritional implication of this preferential leakage is discussed. No significant difference was observed in the leacheates of infected host sugar profiles compared with that of the control host. Profiles of the internal pool sugars of infected and control host did not reflect that obtained from the leacheate data, perhaps owing to leakage of sugars in a selective manner . Membrane lipid analyses yielded higher levels of lipid in infected host compared with the control, both at the 24 h and 36 h analyses. In addition, preliminary investigations of phosphorous-32 incorporation and turnover in phospholipids showed higher levels of 32p incorporation and turnover in infected host compared with the control. No apparent difference was noted in the profiles of the neutral lipid classes and the polar lipid classes of the membrane lipids as determined by one and two dimensional thin-layer chromatography respectively. However, a small but consistently higher degree of unsaturation was detected in the fatty acids of infected tissue compared with the control. Also, '^''-^^''^^'-'-^'^^c acid, a polyunsaturated fatty acid previously reported to show a direct correlation during the early stages of infection and the degree of parasitism of P. virginiana on C. cucurbitarum , was found in higher amounts in infected host membrane lipids compared with that of the control host. The implications of these membrane lipid alterations are discussed with particular reference to the small but consistently higher leakage of electrolytes, amino acids and sugars observed during infection in this study.

The effects of yeast inoculation rate and acclimatization to juice on icewine fermentation /

Icewine is an intensely sweet, unique dessert wine fennented from the juice of grapes that have frozen naturally on the vine. The juice pressed from the frozen grapes is highly concentrated, ranging from a minimum of 35° Brix to approximately 42° Brix. Often Icewine fennentations are sluggish, taking months to reach the desired ethanol level, and sometimes become stuck. In 6 addition, Icewines have high levels of volatile acidity. At present, there is no routine method of yeast inoculation for fennenting Icewine. This project investigated two yeast inoculum levels, 0.2 gIL and 0.5 gIL. The fennentation kinetics of inoculating these yeast levels directly into the sterile Icewine juice or conditioning the cells to the high sugar levels using a step wise acclimatization procedure were also compared. The effect of adding GO-FERM, a yeast nutrient, was also assessed. In the sterile fennentations, yeast inoculated at 0.2 gIL stopped fennenting before the required ethanol level was achieved, producing only 7.8% (v/v) and 8.1 % (v/v) ethanol for the direct and conditioned inoculations, respectively. At 0.5 gIL, the stepwise conditioned cells fennented the most sugar, producing 12.2% (v/v) ethanol, whereas the direct inoculum produced 10.5% (v/v) ethanol. The addition of the yeast nutrient GO-FERM increased the rate of biomass accumulation, but reduced the ethanol concentration in wines fennented at 0.5 gIL. There was no significant difference in acetic acid concentration in the final wines across all treatments. Fennentations using unfiltered Icewine juice at the 0.5 gIL inoculum level were also compared to see if the effects of yeast acclimatization and micronutrient addition had the same impact on fennentation kinetics and yeast metabolite production as observed in the sterile-filtered juice fennentations. In addition, a full descriptive analysis of the finished wines was carried out to further assess the impact of yeast inoculation method on Icewine sensory quality. At 0.5 gIL, the stepwise conditioned cells fennented the most sugar, producing 11.5% (v/v) ethanol, whereas the direct inoculum produced 10.0% (v/v) ethanol. The addition of the yeast nutrient GO-FERM increased the peak viable cell numbers, but reduced the ethanol concentration in wines fennented at 0.5 gIL. There was a significant difference 7 in acetic acid concentration in the final wines across all treatments and all treatments affected the sensory profiles of the final wines. Wines produced by direct inoculation were described by grape and raisin aromas and butter flavour. The addition of GO-FERM to the direct inoculation treatment shifted the aroma/flavour profiles to more orange flavour and aroma, and a sweet taste profile. StepWise acclimatizing the cells resulted in wines described more by peach and terpene aroma. The addition of GO-FERM shifted the profile to pineapple and alcohol aromas as well as alcohol flavour. Overall, these results indicate that the addition of GO-FERM and yeast acclimatization shortened the length of fermentation and impacted the sensory profiles of the resultant wines.

An investigation of sugar feeding by black flies (Diptera: Simuliidae)

Although much research has been conducted on blood-meal acquisition in adult female black flies (Diptera: Simuliidae), the same cannot be said for sugarmeals. Both sexes feed on sugar which provides energy for flight and it has been commonly held that nectar is the major carbohydrate source. This thesis addresses the question of whether a non-floral carbohydrate source, specifically homopteran honeydew, is ingested by male and female black flies. Black flies reared in the laboratory have been observed to readily ingest freshly excreted and older (dry) honeydew when presented with honeydew coated tamarack branches. Field work was conducted in Algonquin Park, Ontario in the spring and summer of 1993. Three separate studies were designed to test whether homopteran honeydew is an important carbohydrate source for black flies and whether flies from different habitats utilize different sugar sources. The sugars melezitose and / or stachyose are known to occur in a variety of homopteran honeydews and therefore were used as indicators of honeydew feeding by black flies. In the first study, black flies were collected with insect nets from a stand of Larix larcina heavily infested with honeydew - producing homopterans (Adelges lariciatus). Six black fly species were captured: Simulium venustum, S. rostra tum, S. vittatum, Stegopterna mutata, S. aureum and S. quebecense. Samples of honeydew and individual black flies were tested using thin layer chromatography (T. L. C.) with fructose, glucose, sucrose, turanose, melezitose, raffinose and stachyose as standards. All sugars except turanose and melezitose were found in the adelgid honeydew samples. Since the sugar melezitose was absent from ~ honeydew samples, stachyose was used to indicate that black flies were feeding from this particular honeydew source. Of the 201 black flies tested, 194 contained sugars which occurred in 16 combinations. Stachyose combinations excluding melezitose, present in 45.9 % of flies, were used to indicate that black flies had been feeding on the adelgid honeydew. In the second study, black flies were collected in the morning and evening on 8 collection dates, using a vehicle mounted insect net. The crops and midguts of 10 male and 10 female Simulium venustum were dissected on each sample date. In total the gut contents of 320 individual flies were analysed by T. L. C. The sugars identified from these flies were present in the following proportions: fructose (100.0%), glucose (100.0%), sucrose/turanose (50.4%), melezitose (30.3%), raffinose (18.8%) and stachyose (8.7%). These sugars occurred in fourteen different combinations. It is argued that the presence of melezitose and / or stachyose indicates that black flies had fed on homopteran honeydew. Significantly more female flies (40.0%) than male flies (27.5%) had fed on honeydew. In the third study, adult black flies were sampled by sweep netting vegetation in four habitats in the morning and evening on 8 collection dates. The habitats are as follows: (1) Davies Bog, (2) Abandoned Air Field (dominated by blueberries, Vaccinium spp.), (3) Deciduous Habitat and (4) Coniferous Habitat. Sugars in the crops and midguts of female flies were tested by T. L. C. and, for S. venustum, it was found that significantly fewer flies (18.8%) from the Air Field contained honeydew than from the other three sites (Davies Bog, 34.4%; Deciduous Habitat, 36.2%; Coniferous Habitat, 25.0%). Of the 1287 black flies tested individually by T. L. C. 441 (34.3%) contained melezitose and / or stachyose sugars indicating that this proportion of the population were feeding from Homopteran honeydew. It is therefore clear that floral (nectar) sugars are not the only source of carbohydrates available to black flies.

Isolation and partial characterization of host cell wall surface glycoproteins: their involvement in agglutination, attachment and appressorium formation by piptocephalis virginiana

Cell surface proteins obtained by alkaline extraction from isolated cell walls of Mortierella pusilla and M. candelabrum, host and nonhost, respectively, to the mycoparasite, Piptocephalis virginiana, were tested for their ability to agglutinate mycoparasite spores. The host cell wall protein extract had a high agglutinating activity (788 a.u. mg- t ) as compared with the nonhost extract (21 a.li. mg- t ). SDS-polyacrylamide gel electrophoresis of the cell wall proteins revealed four protein bands, a, b, c, and d (Mr 117, 100, 85 and 64 kd, respectively) at the host surface, but not at the nonhost surface, except for the faint band c. Deletion of proteins b or c from the host cell wall protein extract significantly reduced its agglutinating activity. Proteins band c, obtained as purified preparations by a series of procedures, were shown to be two glycoproteins. Carbohydrate analysis by gas chromatography demonstrated that glucose and Nacetylglucosamine were the major carbohydrate components of the glycoproteins. It was further shown that the agglutinating activity of the pure preparation containing both band c was 500-850 times that of the single glycoproteins, suggesting the involvement of both glycoproteins in agglutination. The results suggest that the glycoproteins band c are the two subunits of agglutinin present at the host cell surface. The two glycoproteins band c purified from the host cell wall protein extract were further examined after various treatments for their possible role in agglutination, attachment and appressorium formation by the mycoparasite. Results obtained by agglutination and attachment tests showed: (1) the two glycoprotein-s are not only an agglutinin responsible for the mycoparasite spore agglutination, but may also serve as a receptor for the specific recognition, attachment and appressorium formation by the mycoparasite; (2) treatment of the rnycoparasite spores with various sugars revealed that arabinose, glucose and N-acetylglucosamine inhibited the agglutination and attachment activity of the glycoproteins, however, the relative percentage of appressorium formation was not affected by the above sugars; (3) the two glycoproteins are relatively stable with respect to their agglutinin and receptor functions. The present results suggest that the agglutination and attachment may be mediated directly by certain sugars present at the host and mycoparasite cell surfaces while the appressorlum formation may be the response of complementary combinations of both sugar and protein, the two parts of the glycoproteins at the interacting surfaces of two fungi.

Isolation and partial characterization of a complementary protein from the mycoparasite, Piptocephalis virginiana, which specifically binds to two glycoproteins b and c of the host cell surface

Presence of surface glycoprotein in Piptocephalis virginiana that recognizes the host glycoproteins band c, reported earlier from our laboratory, was detected by immunofluorescence microscopy. Germinated spores of P. virginiana treated with Mortierella pusilla cell wall protein extract, primary antibodies prepared against glycoproteins band c and FITC-goat anti-rabbit IgG conjugate showed fluorescence. This indicated that on the surfaces of the biotrophic mycoparasite P. virginiana , there might be a complementary molecule which recognizes the glycoproteins band c from M. pusilla. Immunobinding analysis identified a glycoprotein of Mr 100 kDa from the mycoparasite which binds with the host glycoproteins band c, separately as well as collectively. Purification of this glycoprotein was achieved by (i) 60% ammonium sulfate precipitation, (ii) followed by heat treatment, and (iii) Sephadex G-IOO gel filtration. The glycoprotein was isolated by preparative polyacrylamide gel electrophoresis by cutting and elution. The purity of the protein ·was ascertained by SDS-PAGE and Western blot analysis. Positive reaction to periodic acid-Schiff reagent revealed the glycoprotein nature of this 100 kDa protein. Mannose was identified as a major sugar component of this glycoprotein by using a BoehringerMannheim Glycan Differentiation Kit. Electrophoretically purified glycoprotein was used to raIse polyclonal antibody in rabbit. The specificity of the antibody was determined by dot-immunobinding test and western-blot analysis. Immunofluorescence mIcroscopy revealed surface localization of the protein on the germ tube of Piptocephalis virginiana. Fluorescence was also observed at the surfaceJ of the germinated spores and hyphae of the host, M. pusilla after treatment with complementary protein from P. virginiana, primary antibody prepared against the complementary protein and FITC-goat anti-rabbit IgG conjugate.

Probing cell surfaces of host and nonhost species of a mycoparasite, using FITC-labeled lectins

Cell surfaces of susceptible host species (Mortierella pusllla and Cboanepilora cucurbitarum ), resistant host (Pilascolomyces articulosus ), nonhost (Mortierella candelabrum ) and the mycoparasite (Piptocepilalis virginiana) were examined for sugar distribution patterns using light and fluorescent microscopy techniques. The susceptible host, resistant host and the mycoparasite species exhibited a similar sugar distribution profile; they all showed N-acetyl glucosamine and D-glucose on their cell wall surfaces. The nonhost cell wall surface showed a positive binding reaction to FITClectins specific for N-acetyl glucosamine and also for OI.-fucose, N-acetyl galactosamine and galactose. Treatment of these fungi with mild concentrations of proteinases (both commercial as well as the mycoparasiteproteinase) resulted in the revelation of additional sugars on the fungal cell walls. The susceptible host treated with proteinase expressed higher levels of N-acetyl glucosamine and D-glucose. The susceptible host also showed the presence of OI.-fucose, N-acetyl galactosamine and galactose. The proteinasetreated susceptible host cell walls also showed an increase in the levels of attachment with the mycoparasite. Treatment of the resistant host with proteinases revealed OI.-fucose in addition to N-acetyl glucosamine and D-glucose. Treatment of the nonhost cell wall with proteinase resulted in the exposure of low levels of D-glucose, in addition to sugars found on the untreated nonhost cell wall surface. The mycoparasite treated with proteinase revealed OI.-fucose, N-acetyl galactosamine and galactose on its cell surface in addition to the sugars N-acetyl glucosamine and D-glucose. Protoplasts were isolated from hosts and nonhost fungi and their surfaces were examined for sugar distribution patterns. The susceptible host and nonhost protoplast membranes showed all the sugars (N-acetyl glucosamine, D-glucose, (It.-fucose, N-acetyl galactosamine and galactose) tested for. The resistant host protoplast membrane however, had only N-acetyl glucosamine and D-glucose exposed. This sugar distribution profile resembles that exhibited by the untreated resistant host cell wall, as well as that shown by the untreated mycoparasite cell surface. Only susceptible host protoplasts were successful in attaching to the mycoparasite surface. Resistant host protoplasts did not show any interaction with the i mycoparasite cell surface. Both susceptible as well as resistant host protoplasts were incapable of attaching to agarose beads surface-coated with specific carbohydrates. The mycoparasite however, did attach to agarose beads surface-coated with either N-acetyl glucosamine, D-glucose/Dmannose or o:,- methyl-D-mannose. The relevance of the cell wall and the protoplast membrane in the light of the present results, in reacting appropriately to bring about either a susceptible, a resistant or a nonhost response has been discussed.

An investigation into the effects of homopteran honeydew sugars versus floral nectar sugars on black fly longevity, flight performance and digestion /

Floral nectar is thought to be the primary carbohydrate source for most dipteran species. However, it has been shown that black flies (Burgin & Hunter 1997 a,b,c), mosquitoes (Foster 1995; Burkett et al. 1999; Russell & Hunter 2002), deer flies (Magnarelli & Burger 1984; Janzen & Hunter 1998; Ossowski & Hunter 2000), horse flies (Schutz & Gaugler 1989; Hunter & Ossowski 1999) and sand flies (MacVicker et al. 1990; Wallbanks et al. 1990; Cameron et al. 1992, 1995; Schlein & Jacobson 1994, 1999; Hamilton & EI Naiem 2000) feed on homopteran honeydew as well as floral nectar. Prior to 1997 floral nectar was thought to be the main source of carbohydrates for black flies. However, Burgin & Hunter (1 997a) demonstrated that up to 35% of black flies had recently consumed meals of homo pte ran honeydew. This information has necessitated a re-assessment of many life history aspects of black flies. Attempts are being made to examine the effects of nectar versus honeydew on black fly fecundity and parasite transmission (Hazzard 2003). Recently, Stanfield and Hunter (unpublished data) have shown that in female black flies, honeydew sugars produce flights of longer distance and duration than do nectar sugars. This thesis examines two aspects of black fly biology as it relates to sugar meal consumption. First, the effects of honeydew and nectar on black fly longevity are examined. Second, the proximate causation behind longer flight performances in honeydew-fed flies will be examined. The comparison between these two sources is important because nectar is composed of mainly simple sugars (monosaccharides and disaccharides) whereas honeydew is composed of both simple and complex sugars (including trisaccharides and tetrasaccharides ).

Icewine fermentation by Saccharomyces cervisiae : fundamental stress responses and comparative fermentation dynamics

Please consult the paper edition of this thesis to read. It is available on the 5th Floor of the Library at Call Number: Z 9999.5 B63 P54 2007