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.

Effect of growth rate on plasmid maintenance by Escherichia coli HB101(pAT153).

Abstract: Summary: The effects of changing the composition of the growth medium, the dilution rate and the source of the bacterial host on maintenance of the plasmid pAT153 in Escherichia coli HB101 have been studied. In a medium supplemented with Casamino acids, the plasmid was maintained longer during phosphate-limited growth at a dilution rate of 0·3 h−1 than at 0·15 h−1. In contrast, phosphate-limited growth was not achieved when the Casamino acids were replaced by proline, leucine and thiamin to satisfy the auxotrophic requirements of the host. Although 100% of the bacteria were still ampicillin resistant after 72 generations of growth at a dilution rate of 0·15 h−1, the original plasmid had almost totally been replaced by a structurally modified plasmid which lacked a functional tet gene. Further experiments confirmed that neither the host nor the plasmid was retained unchanged in the minimal medium. The changes were highly reproducible and reflected periodic selection of sub-populations which were either plasmid-free or carried a structurally modified plasmid, which had reverted to Leu+ or Pro+, or had acquired other chromosomal mutations which gave them a selective advantage. We conclude that in complex media the plasmid is maintained longer by E. coli HB101 at a high than at a low growth rate and that different results reported from different laboratories are largely due to differences in analytical techniques and the growth medium rather than to differences in the bacterial host or the plasmid used. A fermenter-adapted strain was isolated which reproducibly maintained the plasmid longer during phosphate-limited continuous growth than the original strain which had been cultured on laboratory media.

Estrogen Synthetase (Aromatase) Activity in Primary Culture of Human Term Placental Cells: Effects of Cell Preparation, Growth Medium, and Serum on Adenosine 3′,5′-Monophosphate Response*

Abstract: The establishment of human term trophoblast cells in culture is dependent on the method of cell preparation, growth medium used, and presence of serum. Using freshly isolated term placental cells, we investigated 1) the effects of two different methods of removal of nontrophoblast cells and two culture media on trophoblast aromatase specific activity, cellular morphology, and hCG secretion over 72 h; and 2) the sensitivity of these hormonal parameters to cAMP added 24 h after the initiation of culture. Under conditions in which aromatase is responsive to cAMP, we studied the effect of removing serum after 24 h in culture with serum. After trypsin digestion of placental villi, isolated trophoblast cells were either treated with ammonium chloride (A) or purified on Percoll density gradients (P) and then grown in monolayer culture with medium 199 plus 10% fetal bovine serum (M) or Dulbecco’s Modified Eagle’s Medium (DMEM) plus 20% fetal bovine serum (D). Regardless of the method of treatment or growth medium...

Observations on the Regulation of Glutamate Dehydrogenase Activity in Coprinus lagopus

Abstract: Extracts of the mycelium of Coprinus lagopua (sensu Buller) contain two glutamate dehydro genases with different optimum pH values. One is assayed with nicotinamide adenine dinucleotide (NAD-GDH) and the other with nicotinamide adenine dinucleotide phosphate (NADP-GDH). Changes in specific activity of the enzymes were investigated during the growth of both a monokaryon (H9) and a dikaryon (H9 x TO) in different media and after the transfer of mycelium from one growth medium into another. In the latter case the magnitude of the changes in enzyme activity could be altered by modification of either the carbon or the nitrogen source in the transfer medium. It is concluded from the results obtained that neither glutamate nor the ammonium ion seems to regulate directly the synthesis of either enzyme. However, some of the results are in accordance with the view that a product of glucose metabolism represses the synthesis of the NAD-GDH and derepresses or induces that of the NADP-GDH and evidence that this regulator is 2-oxoglutarate was obtained. It is also concluded that the complete system of regulation must involve more than one molecule.