Growth medium

About: Growth medium is a research topic. Over the lifetime, 1889 publications have been published within this topic receiving 59171 citations. The topic is also known as: culture medium & culture media.

Growth studies of Wolinella recta, a gram‐negative periodontopathogen

Abstract: The effects of varying concentrations of ammonium formate, fumarate, nitrate, pyruvate and hemin, on growth and end-product formation in Wolinella recta ATCC 33238 were examined. Mycoplasma broth base supplemented with 30 mM formate and 20 mM fumarate supported growth of W. recta to an optical density of 0.471 with a generation time of 2.15 h. Increasing formate and fumarate concentrations to 150 mM and 75 mM, respectively, resulted in a maximum optical density of 0.600. Neither stirring nor the addition of pyruvate, enhanced growth. Hemin was not required for growth. Growth of W. recta in a defined medium required the addition of at least 0.4% yeast extract. In both complex and defined media, fumarate supported significantly higher maximum optical densities than nitrate. The omission of formate from the growth medium or the adjustment of the pH of the medium to 6.6 resulted in essentially no growth of W. recta. The metabolic products of growth on nitrate and fumarate were nitrite and succinate, with ammonia and hydrogen sulfide also being observed. Growth in all media was accompanied by increases in pH to a maximum of 8.0.

Proline biosynthesis in Saccharomyces cerevisiae: molecular analysis of the PRO1 gene, which encodes gamma-glutamyl kinase.

Abstract: The PRO1 gene of Saccharomyces cerevisiae encodes the 428-amino-acid protein gamma-glutamyl kinase (ATP:L-glutamate 5-phosphotransferase, EC 2.7.2.11), which catalyzes the first step in proline biosynthesis. Amino acid sequence comparison revealed significant homology between the yeast and Escherichia coli gamma-glutamyl kinases throughout their lengths. Four close matches to the consensus sequence for GCN4 protein binding and one close match to the RAP1 protein-binding site were found in the PRO1 upstream region. The response of the PRO1 gene to changes in the growth medium was analyzed by measurement of steady-state mRNA levels and of beta-galactosidase activity encoded by a PRO1-lacZ gene fusion. PRO1 expression was not repressed by exogenous proline and was not induced by the presence of glutamate in the growth medium. Although expression of the PRO1 gene did not change in response to histidine starvation, both steady-state PRO1 mRNA levels and beta-galactosidase activities were elevated in a gcd1 strain and reduced in a gcn4 strain. In addition, a pro1 bradytrophic strain became completely auxotrophic for proline in a gcn4 strain background. These results indicate that PRO1 is regulated by the general amino acid control system.

Effects of cadmium and of YAP1 and CAD1/YAP2 genes on iron metabolism in the yeast Saccharomyces cerevisiae.

Abstract: Summary: Saccharomyces cerevisiae was more resistant to cadmium when the growth medium contained excess iron. Cadmium reduced the amount of iron taken up by cells during growth, and the cell ferrireductase activity was also strongly inhibited. These effects depended on the YAP1 and CAD1/YAP2 gene dosage. The growth rate of cells in iron-deficient conditions and their ferrireductase activity in the absence of added cadmium were also strongly affected by the dosage of YAP1 and CAD1/YAP2 genes. Our results suggest an indirect influence of these genes on iron metabolism, possibly via modification of the cell redox status.

Isolation of Amidase-negative Mutants of Pseudomonas aeruginosa by a Positive Selection Method Using an Acetamide Analogue

Abstract: Pseudonionas aeruginosa is resistant to many amino acid and purine and pyrimidine analogueswhich causegrowth inhibition of Escherichiacoliand this has precluded the use of such analogues for the isolation of mutants either resistant to feedback repression or derepressed for the synthesis of biosynthetic enzymes (Holloway, 1969). Calhoun & Jensen (1972) were able to increase the sensitivity of P. aeruginosa to certain metabolic analogues by changing the carbon source in the growth medium. p-Amino-phenylalanine and /j-a-thienylalanine did not inhibit the growth of P. aeruginosa on minimal agar plates with glucose as the carbon source but with fructose there was pronounced growth inhibition and resistant colonies were isolated from the inhibition zones after a few days of incubation. Calhoun & Jensen (I 972) suggest that the metabolic pool of cells growing on fructose is relatively low in the precursors for the synthesis of aromatic amino acids so that analogues of these acids are able to compete successfully for certain enzymes and exert a growth inhibitory effect. These results suggest that if growth media can be devised which decrease the metabolic pools of precursors of other amino acids it might be possible to increase the sensitivity of P. aerriginosa to metabolic analogues and thereby isolate regulatory mutants. Leisinger, Haas & Hegarty (1972) found that P. aeruginosa was more sensitive to growth inhibition by indospicine (an analogue of arginine) when the cultures were grown on an ornithine medium, than in a glucose + arginine medium. With 2 mM-indospicine the doubling time in ornithine medium was increased eightfold from the control culture while in the glucose + arginine medium the increase was only twofold. With 2 mwcanavanine the mean generation time was increased twofold in both media. For catabolic enzymes it could be predicted that if a substrate analogue could give rise to a toxic product it should be possible to increase the sensitivity of the culture to the analogue by arranging growth conditions so that the bacteria contained a high level of the enzyme concerned. Hynes & Pateman (1970) found that mutants of Aspergillus rzidulatis which produced acetamidase constitutively were more sensitive to growth inhibition by fluoracetamide than was the wild-type strain. They were able to isolate acetamide-negative mutants from a semiconstitutive mutant plated on an acetate medium containing 2 mg fluorace, tamide/ml after treatment of a conidial suspension with N-methyl-N’-nitro-N-nitrosoguanidine. We have adapted this method to enable us to isolate amidase-negative mutants of Pseudomonas aeruginosa by using growth media which allow the maximum rate of amidase synthesis by the parental strains. Pseudomonas aeruginosa PAC I produces an aliphatic amidase which is induced by acetamide and propionaniide and allows these two amides to be used as the carbon and nitrogen sources for growth. Constitutive mutants have been isolated on S/F plates containing sodium succinate (I (;;) and formamide (0.1 (:/o). Formamide is a poor substrate and very

Production of 3-hydroxydecanoic acid by recombinant Escherichia coli HB101 harboring phaG gene.

Abstract: Heterogenous expression of (R)-3-hydroxydecanoyl-ACP:CoA transacylase gene (phaG) isolated from Pseudomonas putida in Escherichia coli HB101 led to the extracellular production of 3-hydroxydecanoic acid (3HD) in a growth medium consisting of carbon source non-related to 3HD structure, while no 3HD was detected in the growth media inoculated with wild type E. coli HB101 and recombinant E. coli HB101 harboring vector pBluescript SK− only. 3HD production by E. coli HB101 (pLZZGPp) harboring phaG from fructose was 587 mg/l, approximately three times that from cultivation in glucose under same culture conditions. 3HD production was affected by timing of fructose addition and fructose concentration in the culture. As an inhibitor of fatty acid de novo synthesis, the presence of triclosan in the culture could increase 3HD production by E. coli HB101 (pLZZGPp) by about 20–40%. The results further confirmed that (R)-3-hydroxydecanoyl-ACP:CoA transacylase (PhaG) provides 3HD precursors for medium-chain-length polyhydroxyalkanoate synthesis. At the same time, this phenomenon showed that recombinant organisms can be used for production of certain fine chemicals such as hydroxyalkanoic acids.