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.

Efficient expression of the yeast metallothionein gene in Escherichia coli.

Abstract: The yeast metallothionein gene CUP1 was cloned into a bacterial expression system to achieve efficient, controlled expression of the stable, unprocessed protein product. The Escherichia coli-synthesized yeast metallothionein bound copper, cadmium, and zinc, indicating that the protein was functional. Furthermore, E. coli cells expressing CUP1 acquired a new, inducible ability to selectively sequester heavy metal ions from the growth medium.

The removal of alkylation products from the DNA of Escherichia coli cells treated with the carcinogens N-ethyl-N-nitrosourea and N-methyl-N-nitrosourea: influence of growth conditions and DNA repair defects.

Abstract: Cultures of Escherichia coli were treated with alkylnitrosoureas. The rates of removal of methylation and ethylation products from the DNA of strains defective in various repair pathways were compared with those of their respective wild-type strains. It was found that the removal of O6-methylguanine did not depend upon xth gene function or the uvr endonuclease. However, the rate of elimination of this product was markedly decreased in polA strains. O6-Ethylguanine (in contrast to its methyl analogue) was removed more slowly from the DNA of uvrA(-) than from that of uvrA(+) strains, indicating that the removal of O6-ethylguanine can be initiated by the uvr endonuclease. The composition of the medium in which methylated cells were resuspended following treatment with N-methyl-N-nitrosourea was also found to influence the rate at which O6-methylguanine was removed from the DNA of treated bacteria. No significant removal of this product from bacterial DNA occurred during treatment of cells in buffer, or when treated bacteria were resuspended in salts medium or in growth medium containing chloramphenicol. The results indicate that the elimination of O6-methylguanine, but not of 3-methyladenine, requires protein synthesis. Only very limited constitutive activity capable of removing O6-MeGua was detected.

Uptake of 14C -streptomycin by some Micro-organisms and its Relation to their Streptomycin Sensitivity

Abstract: SUMMARY: The uptake of radioactivity from 14C-streptomycin, in a form which cannot be displaced from the organisms by unlabelled streptomycin, was determined in several species of bacteria and one yeast growing under standard conditions. This uptake showed a good correlation with the sensitivity of the organism to streptomycin, and in streptomycin-resistant organisms was about 1 % of that in a highly sensitive organism, Bacillus megaterium. The quantity of streptomycin taken up when growth ceased represented an intracellular concentration 10- to 50-fold higher than that in the growth medium. Environmental factors, such as anaerobiosis or presence of carbon monoxide, which increased the resistance of Staphylococcus aureus to streptomycin also resulted in decreased rates of uptake of 14C-streptomycin. When Bacillus subtilis grew in medium containing the streptomycin antagonist 2-n-heptyl-4-hydroxyquinoline N-oxide, the rate of uptake of radioactivity was reduced to about 30 % of that in absence of the antagonist; the rate at which harvested organisms oxidized succinate and malate was reduced to a similar extent.

Growth inhibition of Clostridium cellulolyticum by an inefficiently regulated carbon flow.

Abstract: Carbon flow in Clostridium cellulolyticum was investigated either in batch or continuous culture using a synthetic medium with cellobiose as the sole source of carbon and energy. Previous experiments carried out using a complex growth medium led to the conclusion that the carbon flow was stopped by intracellular NADH. In this study, results showed that cells cultured in a synthetic medium were better able to control electron flow since the NADH/NAD+ ratios were in the range 0.3-0.7, whereas a ratio as high as 57 was previously found in cells cultured on a complex medium. Furthermore, a specific rate of cellobiose consumption of 2.13 mmol (g cells)-1 h-1 was observed on synthetic medium whereas the highest value obtained on complex medium was 0.68 mmol (g cells)-1 h-1. When C. cellulolyticum was grown in continuous culture and cellobiose in the feed medium was increased from 5.84 to 17.57 mM in stepwise fashion, there was an increase in cellobiose utilization without growth inhibition. In contrast, when the reactor was fed directly with 14.62 mM cellobiose, residual cellobiose was observed (4.24 mM) and growth was limited. These data indicate that C. cellulolyticum is not able to optimize its growth and carbon flow in response to a sudden increase in the concentration of growth substrate cellobiose. This interpretation was confirmed (i) by the study of cellobiose batch fermentation where it was demonstrated that growth inhibition was not due to nutritional limitation or inhibition by fermentation products but was associated with carbon excess and (ii) by the growth of C. cellulolyticum in dialysis culture where no growth inhibition was observed due to the limitation of carbon flow by the low rate of cellobiose diffusion through the dialysis tubing.

Effects of Addition of Sucrose and Salt, and of Starvation upon Thermotolerance and Survival During Storage of Freeze-dried Lactobacillus delbrueckii ssp bulgaricus

Abstract: Increased survival of freeze-dried cells of Lactobacillus bulgaricus was observed when the drying medium was supplemented with sucrose; however, the magnitude of such protection was dependent on the growth medium used. Supplementing the growth medium with NaCl markedly increased survival of dried cells, and only a small effect was exerted by the composition of the drying medium or prior to starvation of cells. The D57 values of Lactobacillus bulgaricus cells grown in MRS were about half of those of cells grown in MRS supplemented with sucrose, with sucrose plus NaCl, or with NaCl.