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.

Structure and function of the lysosomes of human fibroblasts in culture: dependence on medium pH.

Abstract: Extract: Histochemical and ultrastructural consequences of pH variations in growth media were studied using three normal human fibroblast strains. Histochemical staining for acid phosphatase indicated increased amounts of enzyme activity in cells grown at higher pH. The ultrastructural consequences of an increase in growth medium pH was dramatic. A picture resembling storage disease developed in these cells within a few days. The cells became filled with bodies which could roughly be divided into two types. Type I had a homogeneous matrix, stained slightly with ruthenium red, was usually not membrane bound, and exhibited no acid glycerophosphatase activity. The nature and origin of these bodies is unclear. Type II bodies contained whorles of membranes and inhomogeneous matrix which was acid phosphatase positive but did not stain with ruthenium red. This type was always membrane bound and qualifies as lysosomes. Normal cells thus grown at higher pH were morphologically similar to cells cultured at neutral pH from patients with I-cell disease. These morphologic changes did not affect cell viability or cell growth. Speculation: A morphologic picture of severe storage disease can be induced in normal fibroblasts simply by increasing the medium pH. This is in agreement with our earlier observation that the lysosomal function of mucopolysaccharide degradation is progressively inhibited as pH of the growth medium increases. When attempting to diagnose genetic disease in cultured cells it is important to realize that intracellular lysosomal function is sensitive to extracellular pH. The observation of such pH sensitivity might also be a useful tool in studies on the general nature of lysosomal function.

Glycine-induced extracellular secretion of a recombinant cytochrome expressed in Escherichia coli.

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.

Influence of growth conditions on heat-stable phospholipase activity in Pseudomonas.

Abstract: Many psychrotrophic bacteria contaminating raw milk produce phospholipase that withstands pasteurization and UHT treatments. This enzyme acts on the milk fat globule membrane and exposes triacylglycerides to the action of lipase. Phospholipase production by various isolates of Pseudomonas was investigated. The isolates were cultured aerobically at 8 °C in nutrient broth, McKellar's minimal salts medium, Chrisope's medium, and skim milk. Each strain produced phospholipase during the 50 h incubation. Enzyme production varied significantly (P < 0·001) with strain and growth medium. Strains varied significantly (P < 0·001) in their enzyme production in each medium and during the incubation time as well. Strain, incubation time, and the growth medium significantly influenced (P < 0·001) heat stability of the enzyme activity. Pasteurization reduced the activity, but did not eliminate it in skim milk.