Showing papers on "Growth medium published in 1997"
TL;DR: In this article, a set of Saccharomyces cerevisiae expression vectors has been developed in which transcription is driven by a hybrid tetO-CYC1 promoter through the action of a tetR-VP16 (tTA) activator.
Abstract: A set of Saccharomyces cerevisiae expression vectors has been developed in which transcription is driven by a hybrid tetO-CYC1 promoter through the action of a tetR-VP16 (tTA) activator. Expression from the promoter is regulated by tetracycline or derivatives. Various modalities of promoter and activator are used in order to achieve different levels of maximal expression. In the presence of antibiotic in the growth medium at concentrations that do not affect cell growth, expression from the tetO promoter is negligible, and upon antibiotic removal induction ratios of up to 1000-fold are observed with a lacZ reporter system. With the strongest system, overexpression levels comparable with those observed with GAL1-driven promoters are reached. For each particular promoter/tTA combination, expression can be modulated by changing the tetracycline concentration in the growth medium. These vectors may be useful for the study of the function of essential genes in yeast, as well as for phenotypic analysis of genes in overexpression conditions, without restrictions imposed by growth medium composition.
618 citations
TL;DR: Results indicate that PCx is an essential anaplerotic enzyme for growth on glucose in the absence of PEPCx, PCx has no anaplerosis significance for grow on acetate as the carbon source, and PCX is anessential anaplerotics enzyme forgrowth on lactate even in the presence ofPEPCx.
Abstract: The recent discovery that phosphoenolpyruvate carboxylase (PEPCx) is dispensable for growth and lysine production in Corynebacterium glutamicum implies that this organism possesses (an) alternative anaplerotic enzyme(s). In permeabilized cells of C. glutamicum, we detected pyruvate carboxylase (PCx) activity. This activity was effectively inhibited by low concentrations of ADP, AMP and acetyl-CoA. PCx activity was highest [45.5 nmol min-1 (mg dry wt)-1] in cells grown on lactate or pyruvate, and was about two- to threefold lower when the cells were grown on glucose or acetate, suggesting that formation of PCx is regulated by the carbon source in the growth medium. In cells grown at low concentrations of biotin (< 5 μg I-1), PCx activity was drastically reduced, indicating that the enzyme is a biotin protein. Growth experiments with the wild-type and a defined PEPCx-negative mutant of C. glutamicum on glucose showed that the mutant has a significantly higher demand for biotin than the wild-type, whereas both strains have the same high biotin requirement for growth on lactate and the same low biotin requirement for growth on acetate. These results indicate that (i) PCx is an essential anaplerotic enzyme for growth on glucose in the absence of PEPCx, (ii) PCx is an essential anaplerotic enzyme for growth on lactate even in the presence of PEPCx, and (iii) PCx has no anaplerotic significance for growth on acetate as the carbon source. In support of these conclusions, screening for clones unable to grow on a minimal medium containing lactate, but able to grow on a medium containing glucose or acetate, led to the isolation of PCx-defective mutants of C. glutamicum.
136 citations
TL;DR: It is demonstrated that SUR1/CSG1 is both genetically and biochemically related to CSG2, a gene encoding an intracellular Cu2+ transporter required for IPC mannosylation.
Abstract: Saccharomyces cerevisiae cells require two genes, CSG1/SUR1 and CSG2, for growth in 50 mM Ca2+, but not 50 mM Sr2+. CSG2 was previously shown to be required for the mannosylation of inositol-phosphorylceramide (IPC) to form mannosylinositolphosphorylceramide (MIPC). Here we demonstrate that SUR1/CSG1 is both genetically and biochemically related to CSG2. Like CSG2, SUR1/CSG1 is required for IPC mannosylation. A 93–amino acid stretch of Csg1p shows 29% identity with the α-1, 6-mannosyltransferase encoded by OCH1. The SUR1/CSG1 gene is a dose-dependent suppressor of the Ca2+-sensitive phenotype of the csg2 mutant, but overexpression of CSG2 does not suppress the Ca2+ sensitivity of the csg1 mutant. The csg1 and csg2 mutants display normal growth in YPD, indicating that mannosylation of sphingolipids is not essential. Increased osmolarity of the growth medium increases the Ca2+ tolerance of csg1 and csg2 mutant cells, suggesting that altered cell wall synthesis causes Ca2+-induced death. Hydroxylation of IPC-C to form IPC-D requires CCC2, a gene encoding an intracellular Cu2+ transporter. Increased expression of CCC2 or increased Cu2+ concentration in the growth medium enhances the Ca2+ tolerance of csg1 mutants, suggesting that accumulation of IPC-C renders csg1 cells Ca2+ sensitive.
131 citations
TL;DR: Low concentrations of butyrate in glucose depleted culture conditions were found to reduce apoptosis induced by glucose deprivation and increase cell yield in both cell lines, providing an explanation for the apparent opposite effects ofbutyrate on proliferation reported in vivo and in vitro.
Abstract: In vivo, butyrate is a major energy source for the colonic epithelium and is thought to stimulate proliferation. In contrast, butyrate in vitro has been shown to inhibit proliferation and induce differentiation and apoptosis in colonic epithelial cells. Most colon cell cultures are grown in medium containing high concentrations of glucose, whereas in vivo, the main energy source used by the colon cells is butyrate. The aim of this study was to determine whether the apparent contrasting roles of butyrate in vivo and in vitro could be as a consequence of differences in glucose availability. The sensitivity of two human colorectal tumour cell lines, one adenoma (S/RG/C2) and one carcinoma (HT29) to butyrate-induced growth inhibition and apoptosis was investigated to determine whether these cellular effects were altered under glucose depleted culture conditions. Glucose depletion resulted in increased apoptosis in both cell lines in the absence of butyrate. Butyrate in standard culture conditions (containing 25 mM glucose and 1 mM pyruvate) inhibited growth and induced apoptosis in both cell lines. However, low concentrations of butyrate in glucose depleted culture conditions (i.e. standard growth medium without glucose and pyruvate supplements) were found to reduce apoptosis induced by glucose deprivation and increase cell yield in both cell lines. The results show that in glucose depleted culture conditions, butyrate at low concentrations (0.5 mM for S/RG/C2, and 0.5 and 2 mM for HT29 cells) was found to be growth stimulatory whereas in the presence of glucose, these same concentrations of butyrate induced apoptosis. Thus, whether butyrate is growth stimulatory or growth inhibitory may depend on the availability of other energy sources. These observations may, in part, provide an explanation for the apparent opposite effects of butyrate on proliferation reported in vivo and in vitro.
114 citations
TL;DR: An Agrobacterium-mediated gene transfer method for production of transgenic melon plants has been optimized and succeeded in the transformation of leaf explants, and results are in accordance with the directional model of T-DNA transfer.
Abstract: An Agrobacterium-mediated gene transfer method for production of transgenic melon plants has been optimized The HAL1 gene, an halotolerance gene isolated from yeast, was inserted in a chimaeric construct and joined to two marker genes: a selectable-neomycin phosphotransferase-II (nptII)-, and a reporter-β-glucuronidase (gus)- The entire construct was introduced into commercial cultivars of melon Transformants were selected for their ability to grow on media containing kanamycin Transformation was confirmed by GUS assays, PCR analysis and Southern hybridization Transformation efficiency depended on the cultivar, selection scheme used and the induction of vir-genes by the addition of acetosyringone during the cocultivation period The highest transformation frequency, 3% of the total number of explants cocultivated, was obtained with cotyledonary explants of cv ‘Pharo’ Although at a lower frequency (13%), we have also succeeded in the transformation of leaf explants A loss of genetic material was detected in some plants, and results are in accordance with the directional model of T-DNA transfer In vitro cultured shoots from transgenic populations carrying the HAL1 gene were evaluated for salt tolerance on shoot growth medium containing 10 g l−1 NaCl Although root and vegetative growth were reduced, transgenic HAL1-positive plants consistently showed a higher level of tolerance than control HAL1-negative plants
99 citations
TL;DR: An optimization of growth medium composition led to an improvement in both growth and EPS production, and a temperature shift at the end of the exponential growth phase did not enhance the EPS production.
Abstract: Extracellular polysaccharide production was studied by growing strain C83 of Lactobacillus rhamnosus in a chemically defined medium containing various carbon sources (glucose, fructose, mannose or maltose) at different concentrations. Mannose or a combination of glucose + fructose were by far the most efficient carbon sources. An optimization of growth medium composition led to an improvement in both growth and EPS production. When the strain was cultured at a lower temperature the EPS production increased. A temperature shift, at the end of the exponential growth phase, did not enhance the EPS production. The EPS synthesis by strain C83 was growth-related. The isolated slime had a sugar composition, as shown by three different methods, of glucose and galactose with a ratio of 1 : 1.
89 citations
TL;DR: Thin layer chromatographic analysis of the reaction mixture suggested 4-nitrocatechol was an intermediate of p-nitrophenol transformation by UG30.
Abstract: Pentachlorophenol-degrading Sphingomonas sp. UG30 and Sphingomonas chlorophenolica strains RA2 and ATCC 39723 can transform p-nitrophenol in either mineral salts-glutamate or mineral salts-glucose medium after an initial lag period. However, mineralization of p-nitrophenol by these bacterial strains was observed only in mineral salts-glucose medium. When p-nitrophenol was the sole nitrogen source in the growth medium, UG30 mineralized 32% of 140 mM [14C]p-nitrophenol which was 10% higher than the amount of [14C]p-nitrophenol mineralized in mineral salts-glucose medium. UG30 did not transform or mineralize p-nitrophenol (in a growth medium) in the absence of glucose or glutamate. All three strains released nitrite during p-nitrophenol degradation in mineral salts-glucose medium and mineral salts-glutamate medium. The transformation rate of p-nitrophenol by UG30 was dependent on the initial p-nitrophenol concentration, with the optimal rate being found at 310 μM of p-nitrophenol and inhibition observed at ≥1100 μM of p-nitrophenol. Pre-exposure of UG30 cells to p-nitrophenol eliminated the initial lag phase of p-nitrophenol transformation. However, pre-growth of UG30 cells on pentachlorophenol did not reduce the lag period for p-nitrophenol transformation. Both p-nitrophenol- and pentachlorophenol-induced UG30 cells degraded pentachlorophenol without any lag phase. Thin layer chromatographic analysis of the reaction mixture suggested 4-nitrocatechol was an intermediate of p-nitrophenol transformation by UG30.
58 citations
TL;DR: GTSF-2 is a versatile basal medium that will be useful for studying organ-specific differentiation in heterotypic coculture studies and when supplemented with simple additives, such as endothelial cell growth supplement (bFGF) or horse serum.
Abstract: The aim of this study was to test the versatility of a new basal cell culture medium, GTSF-2. In addition to traditional growth-factors, GTSF-2 contains a blend of three sugars (glucose, galactose, and fructose) at their physiological levels. For these studies, we isolated normal endothelial cells from human, bovine, and rat large blood vessels and microvessels. In addition, GTSF-2 was also tested as a replacement for high-glucose-containing medium for PC12 pheochromocytoma cells and for other, transformed cell lines. The cell growth characteristics were assessed with a novel cell viability and proliferation assay, which is based on the bioreduction of the fluorescent dye, Alamar Blue. After appropriate calibration, the Alamar Blue assay was found to be equivalent to established cell proliferation assays. Alamar Blue offers the advantage that cell proliferation can be measured in the same wells over an extended period of time. For some of the cell types (e.g., endothelial cells isolated from the bovine aorta, the rat adrenal medulla, or the transformed cells), proliferation in unmodified GTSF-2 was equivalent to that in the original culture media. For others cell types (e.g., human umbilical vein endothelial cells and PC12 cells), GTSF-2 proved to be a superior growth medium, when supplemented with simple additives, such as endothelial cell growth supplement (bFGF) or horse serum. Our results suggest that GTSF-2 is a versatile basal medium that will be useful for studying organ-specific differentiation in heterotypic coculture studies.
45 citations
TL;DR: Cultivation conditions for the extracellular production of a hybrid β-glucanase from Bacillus were established by using Escherichiacoli JM109 carrying the plasmid pLF3, which contained a novel secretion system consisting of the kil gene (killing protein) ofplasmid ColE1 under the stationary-phase promoter of either the fic or the bolA gene.
Abstract: Cultivation conditions for the extracellular production of a hybrid β-glucanase from Bacillus were established by using Escherichiacoli JM109 carrying the plasmid pLF3. This plasmid contained a novel secretion system consisting of the kil gene (killing protein) of plasmid ColE1 under the stationary-phase promoter of either the fic or the bolA gene, an omega interposon (Prentki and Krisch 1984) located upstream of the promoters and a hybrid β-glucanase gene of Bacillus. When controlled by the fic promoter, the kil gene led to a higher total production of β-glucanase and a higher protein secretion than when it was under control of the bolA promoter. When the effect of different distances between the stationary-phase promoters and the kil gene was investigated, a shorter distance was generally found to result in a higher secretion. With a complex growth medium, the kinetics of extracellular production of the enzyme depended on several operating variables, such as the salt concentration (NaCl) and the oxygen supply, which were varied by changing the culture volume and the shaking speed. In defined media the secretion of β-glucanase into the medium was increased significantly by the addition of glycerol as a carbon source and by prolonged cultivation. The strain with the highest production and secretion yield of β-glucanase [E. coli JM109(pLF3)] was tested on the fermenter scale.
45 citations
TL;DR: When cells of Saccharomyces cerevisiae were grown aerobically under glucose-repressed conditions, ethanol production displayed a hyperbolic relationship over a limited range of magnesium concentrations up to around 0.5 mM.
Abstract: When cells of Saccharomyces cerevisiae were grown aerobically under glucose-repressed conditions, ethanol production displayed a hyperbolic relationship over a limited range of magnesium concentrations up to around 0.5 mM. A similar relationship existed between available Mg2+ and ethanol yield, but over a narrower range of Mg2+ concentrations. Cellular demand for Mg2+ during fermentation was reflected in the accumulation patterns of Mg2+ by yeast cells from the growth medium. Entry of cells into the stationary growth phase and the time of maximum ethanol and minimum sugar concentration correlated with a period of maximum Mg2+ transport by yeast cells. The timing of Mg2+ transport fluxes by S. cerevisiae is potentially useful when conditioning yeast seed inocula prior to alcohol fermentations.
45 citations
TL;DR: Luminescence microscopy data, emission, and circular dichroism spectral data are reported as copper is incorporated into metallothionein by the yeast Saccharomyces cerevisiae, showing that the cellular incorporation of copper proceeds via several species, eventually leading to storage of the copper in the form of Cu-metallothionin.
TL;DR: It is concluded that supplementation of E. coli cultures with moderate amounts of glycine substantially stimulates the synthesis of exportable proteins and further enhances their yield by discharge into the growth medium.
Abstract: The effect of each of 20 different amino acid supplements to the growth medium of Escherichia coli on the extracellular release of a periplasmic recombinant cytochrome b5 was investigated. Only glycine, and to a lesser extent histidine, stimulated the synthesis of secretory cytochrome b5, as well as its discharge into the medium. Extracellular amounts of cytochrome b5 accrued with increasing concentrations of exogenous glycine and duration of the culture period, in spite of the fact that increasing glycine in the medium progressively inhibited cell growth. For example, 1% medium glycine caused a 50% reduction in bacterial growth, but doubled the periplasmic pool of cytochrome b5 to over 25 micrograms of cytochrome b5/ml of culture at 24 h, a period during which almost all of cellular haemoprotein pool was turned over into the medium. A comparative study of the exportable form of cytochrome b5 with a (non-secretory) cytoplasmic-resident counterpart indicated that the periplasmic cytochrome b5 content was selectively discharged into the medium when less than 1% glycine was present, but, at higher doses, a significant proportion of the additional extracellular haemoprotein was derived from cell lysis. Optimal level of periplasmic discharge of the cytochrome required both active protein synthesis and the presence of a glycine supplement in the medium from the onset of bacterial growth. Phase-contrast and scanning electron microsocopy of glycine-grown Escherichia coli showed that the cells had a 3-7-fold enlarged "eyeball' spheroidal morphology, with a condensed pericircular cytoplasm. The bulk of the volume in such hypertrophied cells consisted of the periplasm; this was reflected by the progressively lowered buoyancy of E. coli cultured with increasing amounts of glycine. The fragility of such cells was apparent by their marked sensitivity to lysis at glycine concentrations above 1%. We conclude that supplementation of E. coli cultures with moderate amounts of glycine substantially stimulates the synthesis of exportable proteins and further enhances their yield by discharge into the growth medium.
TL;DR: Group D1 egg-contaminating Salmonella grown under inducing conditions deviated from their expected H-antigen immunoreactivity, suggesting possible consequences for the interpretation of the Kauffman-White identification scheme.
Abstract: Salmonella enterica grown on solid medium containing iron, thiosulfate and 100 mM hexoses and amino acids underwent cell surface differentiation involving increased flagellation (electrophoretic isotypes 60, 54 and 50 kDa), conversion from rough to smooth lipopolysaccharide, and assembly of a matrix that penetrated 1.4% agar. Flagellation was also induced in the avian pathogen S. enterica var Pullorum, which is diagnostically defined as aflagellate. Induction correlated closely with a simple colonial color change when Hektoen Enteric agar was used as the basal growth medium. Group D1 egg-contaminating Salmonella grown under inducing conditions deviated from their expected H-antigen immunoreactivity, suggesting possible consequences for the interpretation of the Kauffman-White identification scheme.
TL;DR: It was concluded that all strains of S. cerevisiae display the osmotic hypersensitivity phenomenon in qualitative terms while the quantitative values differ, and it was proposed that growth rate does not dictate the level of osmoticsensitivity.
Abstract: Osmotic hypersensitivity is manifested as cellular death at magnitudes of osmotic stress that can support growth. Cellular capacity for survival when plated onto high NaCl media was examined for a number of laboratory and industrial strains of Saccharomyces cerevisiae. During respiro-fermentative growth in rich medium with glucose as energy and carbon source, the hypersensitivity phenomenon was fairly strain invariant with a threshold value of about 1 M-NaCl; most strains fell within a 300 mM range in LD10 values (lethal dose yielding 10% survival). Furthermore, all but one of the strains displayed similar differential death responses above the threshold value, i.e. ten-fold decreased viability for every 250 mM increase in salinity. Addition of small amounts of salt to the growth medium drastically improved tolerance and shifted the hypersensitivity threshold to higher NaCl concentrations. This salt-instigated tolerance could partly be reversed by washing in water. The washing procedure depleted cells of the glycerol that they had accumulated under saline growth, and the contribution from glycerol to the improved tolerance was about 50% in the two strains examined. Growth on derepressing carbon sources like galactose, ethanol or glycerol gave strain-dependent responses. The laboratory strain X2180-1A drastically improved tolerance while the bakers' yeast strain Y41 did so only marginally. It was concluded that all strains of S. cerevisiae display the osmotic hypersensitivity phenomenon in qualitative terms while the quantitative values differ. It was also proposed that growth rate does not dictate the level of osmotic hypersensitivity of S. cerevisiae.
TL;DR: Reducing the rate of protein synthesis by lowering either growth temperature or isopropyl-beta-D-thiogalactopyranoside (IPTG) concentration alleviated two problems of Expression of chicken and rat liver bifunctional enzyme in Escherichia coli.
TL;DR: This work investigates the fatty acid composition of Xenorhabdus species when grown at 15, 20, 25 or 30°C on media containing one of two primary carbon sources: glucose or lipids from the insect host, Galleria mellonella and recommends addition of complex fatty acid sources that resemble natural host lipids to growth medium for mass producing entomopathogenic nematodes.
Abstract: The bacterium Xenorhabdus sp. is symbiotically associated with the entomopathogenic nematode Steinernema riobravis. This nematode is produced in monoxenic culture with Xenorhabdus sp. and is sold as a biological insecticide. Acceptable yields in fermentors can only be achieved in the presence of vigorous growth of the bacterium. We investigated the fatty acid composition of Xenorhabdus species when grown at 15, 20, 25 or 30 degrees C on media containing one of two primary carbon sources: glucose or lipids from the insect host, Galleria mellonella. Both temperature and primary carbon source significantly affected lipid quantity and quality in Xenorhabdus sp. Bacteria grown with insect lipids as a primary carbon source accumulated more lipids with greater proportion of longer chain fatty acids than bacteria grown with glucose as a primary carbon source. Cells grown with insect lipids at 15 degrees C had a lower lipid content than cells grown on the same media at 20, 25 or 30 degrees C. Increasing growth temperature increased saturated fatty acids and decreased unsaturated fatty acids, irrespective of carbon source. We recommend addition of complex fatty acid sources that resemble natural host lipids to growth medium for mass producing entomopathogenic nematodes. This could provide nematode quality similar to in vivo-produced nematodes.
TL;DR: Through the development of the model, and the application of predictions derived from it to the laboratory situation, continuous culture of E. neoaphidis was achieved for the first time.
TL;DR: The composition of the growth media was optimized for the enzyme production and the continuous production of the enzymes was investigated, finding the higher the glycine concentration the greater the number of enzymes produced.
TL;DR: When a standardized FAME protocol needs to be designed for taxonomic purposes, a thorough evaluation of the influence of the growth medium on bacterial fatty acid composition is recommended.
TL;DR: PCBs transformation was also observed in resting cells grown on other substrates such as glucose and glycerol, and the presence of PCB congeners in the growth medium increased the lag phase for the growth of cells on a biphenyl substrate but not on a Glycerol substrate.
Abstract: Resting cells of Pseudomonas strain LB400 are known to transform polychlorinated biphenyls (PCBs) when the cells are previously grown on biphenyl. In this study, PCB transformation was also observed in resting cells grown on other substrates such as glucose and glycerol. The presence of PCB congeners in the growth medium increased the lag phase for the growth of cells on a biphenyl substrate but not on a glycerol substrate. Supplementation of the degradation medium with biphenyl dramatically decreased the rate of PCB congener transformation, while the presence of glycerol or glucose had little or no effect on PCB transformation rates. Removal rates with biphenyl-grown cells in the standard degradation medium for 2,4,2′,4′-tetrachlorobiphenyl, 2,4,5,2′,5′-pentachlorobiphenyl, and 2,3-dichlorobiphenyl were 1.06, 1.66, and 224 μmol/(L∙h), respectively. Relative rates of transformation of 2,3-dichlorobiphenyl by biphenyl-, glucose-, and glycerol-grown cells were 100:36:36 and were similar to the relative rate...
TL;DR: It is observed that the lipopolysaccharide type was a stable feature of the strain and persisted in cells at all phases of the growth cycle, during differentiation of bacteria into bacteroids and when the cells were grown under environmental stress.
Abstract: We recently showed that Rhizobium galegae strains had two different lipopolysaccharide types, short and long O-chain. In the present study we observed that the lipopolysaccharide type was a stable feature of the strain. Both types persisted in cells at all phases of the growth cycle, during differentiation of bacteria into bacteroids and when the cells were grown under environmental stress. When R. galegae strains were grown at low pH or in medium containing aluminum or salt, simulating conditions in acid soils of temperate regions and osmotic stress, respectively, the tolerance of low pH was associated with the long O-chain lipopolysaccharide and abundant acidic polysaccharide production.
TL;DR: The obligate methylotroph Methylobacillus flagellatum was grown in the presence of different ammonium concentrations and the regulation of the enzymes associated with ammonium assimilation was investigated in steady-state and transient growth regimes.
Abstract: The obligate methylotroph Methylobacillus flagellatum was grown in the presence of different ammonium concentrations and the regulation of the enzymes associated with ammonium assimilation was investigated in steady-state and transient growth regimes. As the medium changed from C-limitation to dual C/N- and finally to N-limitation, the culture passed through three definite growth phases. The NADP+-dependent glutamate dehydrogenase (GDH) was present under ammonium limitation of the culture growth (at 2 mmol l-1 of ammonium in the growth medium) and increased in response to an increase in nitrogen availability. Glutamine synthetase (GS) and glutamate synthase (GOGAT) activities were negligible during C- and C/N-limitation. In N-limited cells the GOGAT activity increased as the dilution rate increased up to 0.35 h-1, and then sharply dropped. In the N-sufficient cultures both NAD+- and NADP+-dependent isocitrate dehydrogenase (NAD-ICDH and NADP-ICDH) activities were up-regulated as dilution rate increased, but in the N-limited culture the NAD-ICDH activity was up-regulated whereas NADP-ICDH one was down-regulated. Pulse additions of ammonium and methanol demonstrated the coordinate regulation of the GDH and ICDHs activities. When pulses were added to the C/N-limited cultures, there was an immediate utilization of the nutrients, resulting in an increase in biomass; at the same time the GDH and ICDH activities increased and the GS and GOGAT activities decreased. When the same ammonium/methanol pulse was added into the N-limited culture, there was a 3-hours delay in the culture response, after which the substrates were utilized at rates close to the ones shown by the C/N-limited culture after the analogous pulse.
TL;DR: The predictive model for growth of S. rosei in cucumber juice should prove useful in modeling the mixed culture (yeast and lactic acid bacteria) fermentation of brined, whole cucumbers.
TL;DR: Six extracellular yeast glycoproteins were prepared from three yeast species in osmoticequilibrium and unequilibrium environments and used as non‐penetrating cryoadditives and glycoprotein secreted by the strain Dipodascus australiensis was found to be the most effective cryoadditive.
Abstract: Six extracellular yeast glycoproteins were prepared from three yeast species in osmotic equilibrium and unequilibrium environments and used as non-penetrating cryoadditives. The glycoprotein secreted by the strain Dipodascus australiensis into the growth medium containing NaCl (8% w/v) was found to be the most effective cryoadditive. It was possible to use this glycoprotein alone (without penetrating agent DMSO) for the cryoprotection of the yeasts studied.
TL;DR: It is demonstrated that culturing prior to irradiation in 40% growth medium alone increases cell survival and that incubation in 40%.
Abstract: Previous observations have shown that cells cultured in standard growth medium (100%) demonstrated similarly enhanced survival when incubated postirradiation either in non-growth-promoting conditioned medium or in growth-promoting 40% growth medium (Reddy and Lange, Radiat, Res. 119, 338-347, 1989). From these results, it was suggested that nutrient dilution altered radiosensitivity by a mechanism independent of progression of cells through the cell cycle. In this study, we have examined the effects on radiosensitivity of incubation in 40% growth medium prior to irradiation on both log- and plateau-phase Chinese hamster V79 cells and the effects on the distribution of cells in the cell cycle of incubation in 40% or 100% growth medium before and after irradiation. Radioresistance increased by a factor of 1.5-1.6 compared to 100% growth medium for both log-phase and plateau-phase cells cultured in 40% growth medium prior to X irradiation and incubated in either 40% growth medium or conditioned medium after X irradiation. The cell cycle distributions of log-phase cells in 100% and 40% growth medium before irradiation were identical. The change in cell cycle distribution induced by 10 Gy did not differ among log-phase cells incubated for 3 h postirradiation in 100% growth medium, 40% growth medium or conditioned medium. These results, in addition to supporting our previous conclusions, demonstrate that culturing prior to irradiation in 40% growth medium alone increases cell survival and that incubation in 40% growth medium before and after irradiation maximizes the survival of V79 cells.
TL;DR: A simple relationship was observed in growth medium, between the dissociation constant of the acid used to control pH and the minimum pH at which Salmonellae and Escherichia coli initiate growth, and a simple method was proposed to predict the minimum growth pH for a given strain and different acid types.
TL;DR: The induction of metabolic changes in suspension cultured cells of Catharanthus roseus upon elicitation has been investigated and Cytoplasmic levels of Pi, phosphomonoesters, and Uridine Diphasphate glucose (UDP-Glc) were unaffected by eliciation.
Abstract: The induction of metabolic changes in suspension cultured cells of Catharanthus roseus upon elicitation has been investigated. Addition of a yeast glucan preparation to the growth medium resulted in induction of phenylalanine ammonia lyase. Phosphate uptake and metabolism of elicited cells was followed by 31P nuclear magnetic resonance. The uptake rate of Pi from the medium by oxygenated cells of C. roseus was reduced immediately after elicitation. Despite this reduced Pi uptake elicited cells had significantly increased amounts of ATP (twofold increase within 6 h). Cytoplasmic levels of Pi, phosphomonoesters, and Uridine Diphasphate glucose (UDP-Glc) were unaffected by eliciation. Furthermore, the cytoplasmic and vacuolar pH remained constant after addition of elicitor.
Journal Article•
TL;DR: A method was developed for the determination of microorganism concentrations on air filters of HVAC systems, and the influence of different test parameters on the microbiological results was examined by considering various used air filters from several such systems.
Abstract: A method was developed for the determination of microorganism concentrations on air filters of HVAC systems, and the influence of different test parameters on the microbiological results was examined by considering various used air filters from several such systems. Microorganisms are detected by shaking air filter samples in fluid, where their concentration is then determined as surface cultures. Since varying the shaking time (30, 60, 90 min) had no influence on the quantitative microorganism determination, a shaking time of 60 minutes was chosen for detection of bacteria, yeasts and moulds. Incubation of blood agar plates either for 4 days at 20 degrees C +/- 2 degrees C or for 2 days at 36 degrees C +/- 1 degree C yielded identical concentrations of bacteria and yeasts. Since results obtained with malt extract agar and Czapek-Dox agar are comparable, one of the two culture media is sufficient for the quantitative determination of moulds on air filters. For statistical evaluation, the inoculation of three parallel agar plates per growth medium was found to be adequate, and the arithmetic mean and the median proved to be equivalent. Investigation on the detection rate showed that, on the average, the method developed demonstrated 80% of the microorganisms detectable on an air filter sample. Thus a simple method is available for quantitative determination of microorganisms on air filters.
Journal Article•
TL;DR: Results indicate that the iron-stressed conditions influence the staphylococcal adhesion to collagen, which is weaker when cells come from iron-rich medium.
Abstract: The aim of this study was to investigate the influence of iron present in the growth medium of Staphylococcus aureus on the bacterial adhesion to collagen. The experiments were extended to determinate the siderophore production and to examine the S. aureus isolates surface hydrophobicity. The addition of iron to metal deficient defined medium causes the change in hydrophobicity of the examined S. aureus strains surfaces from hydrophilic to hydrophobic. The presence of iron in staphylococcal growth medium alters also the adhesion to the surface covered with collagen. Four out of six S. aureus strains adhere to collagen weaker when cells come from iron-rich medium. Majority of tested strains produce markedly less of siderophores in media containing the excess of iron (1 and 10 microM Fe) and there is no staphylococcal siderophore activity in the growth medium with a very high concentration of this compound (120 microM Fe). The obtained results indicate that the iron-stressed conditions influence the staphylococcal adhesion to collagen.
01 Jan 1997
TL;DR: In this article, the growth conditions for the regeneration of encapsulated somatic carrot embryos into plantlets were tested and the germination rate and frequency of morphologically normal and abnormal plantlet were recorded.
Abstract: Growth conditions (growth substratum, maturation and sucrose supply) for the regeneration of encapsulated somatic carrot embryos into plantlets were tested. The germination rate and frequency of morphologically normal and abnormal plantlets were recorded. Germination rates were high (80–95%) and identical in all growth substrata. There was no conversion into plantlets on the liquid medium. The total conversion rates into plantlets on agar and sand were the same (35–40%), but there were significant differences in the rate of conversion into morphologically normal plantlets (20% on agar and 40% on sand), due to secondary embryogenesis on the agar. Rates of conversion into normal plantlets were still lower when a maturation step was included prior to sowing. The time required for seedling development was much longer than for seedlings from natural seeds. Plantlet production from these embryos also requires a carbohydrate supply in the growth medium. Thus, regeneration should not be evaluated by the germination rates alone, but by the rate of conversion into normal plantlets. A sterilized sand growth substratum supplied with carbon and other nutrients appears to be most appropriate for plant regeneration.