Changes in Escherichia coli cells starved in seawater or grown in seawater-wastewater mixtures

Some metabolic modifications of Escherichia coli cells during starvation in seawater were studied in laboratory microcosms. The apparent die-off of this bacterium under such conditions, as observed by comparing the enumeration of CFU in conventional freshwater media and direct epifluorescence counts, was partially prevented when cells were previously grown in salted organic medium or on seawater-wastewater agar. beta-Galactosidase activity of starved cells disappeared gradually with time, even though some other enzymatic activities, such as that of alkaline phosphatase, increased. Moreover, some modifications of sensitivity to antibiotics, heavy metals, and bacteriophages in seawater- and wastewater-grown cells suggested that the cells undergo structural changes under natural marine conditions. These results provide additional experimental data indicating the possible active adaptation of E. coli cells to seawater.     

A comparative study of the formation of extracellular proteins by Aeromonas salmonicida at two different temperatures

Aeromonas salmonicida was grown in a supplemented 3% (w/v) tryptone soya broth medium at 10 degrees C, a temperature at the lower end of the range over which furunculosis has been observed to occur in the field, and 25 degrees C, the optimum temperature for growth. Similar bacterial densities in the range 2.35 +/- 0.05 mg dry wt/ml were achieved in the two cultures at the beginning of the stationary phase of the growth cycle, after 125 h at 10 degrees C and 18 h at 25 degrees C. At this point, at the higher temperature 1.5 times more exoprotein was formed, 80 +/- 2.8 micrograms/ml compared with 54 +/- 1.7 micrograms/ml. Exoprotein contained the same proportion of haemolysin at both temperatures and twice as much protease at the higher temperature. The most marked difference was in an unidentified 100 kD protein which was formed in a 10-fold greater amount at 10 degrees C.     

Myofibrillar protein turnover and urinary N-tau-methylhistidine output. Response to dietary supply of protein and energy.

The urinary excretion of total N-tau-methylhistidine by the growing rat was measured to evaluate the effects of dietary protein and energy restriction on muscle protein turnover in vivo. 2. Young male rats (about 100 g initial wt.) were fed on one of three diets. Group I (controls) received an adequate 18% lactalbumin diet for 28 days, on which they sustained maximum growth. Group II (protein-depleted) was fed for 14 days on 0.5 lactalbumin diet, which caused loss of weight; this was followed by repletion for 14 days with the control diet. Group III (protein-energy restricted) received a 1% lactalbumin diet at one-half the food intake of group II for 14 days, and this was also followed by 14 days of repletion with the control diet. 3. The controls showed a progressive rise in the daily urinary output of N-tau-methylhistidine, which was proportionally slightly less rapid than the body-weight increase. 4. The protein-depleted group II showed a marked and progressive decrease in N-tau-methylhistidine excretion, which was proportionally greater than the fall in body weight; during repletion, N-tau-methylhistidine output rose in parallel with body-weight increase, but it did not reach the value attained by the control group. 5. Group III, restricted in both dietary protein and energy, showed an initial small increase in daily N-tau-methylhistidine output, which contrasted with the sharp loss of body weight during this period. After 11 days on this restricted diet, group III then underwent a decrease in N-tau-methylhistidine output, which persisted into the first 4 days of the repletion period, after which output of the methylated amino acid became the same as for group II. 6. Creatinine output, used as an additional metabolic measure of muscle metabolism, showed a fairly constant relationship to body weight in groups I and II during depletion and repletion. However, rats with protein-energy deficiency (group III) underwent a marked increase in output of creatinine per unit of body weight, which also persisited into the repletion period before it fell to more normal values relative to body weight. 7. Analysis of the N-tau-methylhistidine content of actin isolated from a group of protein-depleted rats revealed a small (5%) but significance (P less than 0.02) decrease relative to well-nourished controls. 8. Hence, the rate of muscle protein degradation, as indicated by changes in urinary N-tau-methylhistidine output, appears to respond sensitively and in opposite directions to insufficiency of protein of energy in the diet.     

Effects of external osmolality on polyamine metabolism in HeLa cells

The polyamine content of Escherichia coli is inversely related to the osmolality of the growth medium. The experiments described here demonstrate that a similar phenomenon occurs in mammalian cells. When grown in media of low NaCl concentration, HeLa cells and human fibroblasts were found to contain high levels of putrescine, spermidine, and spermine. The putrescine content of HeLa cells was a function of the osmolality of the medium, as shown by growing cells in media containing mannitol or additional glucose. External osmolality per se had no effect on the contents of spermidine and spermine. For all media, the total cellular polyamine content could be correlated with the activity of ornithine decarboxylase, the first enzyme in polyamine biosynthesis. Different levels of enzyme activity appear to result solely from variations in the rate of enzyme degradation.A sudden increase in NaCl concentration produced rapid loss of ornithine decarboxylase activity and a gradual loss of putrescine and spermidine. A sudden decrease in NaCl concentration led to rapid and substantial increases in ornithine decarboxylase activity and putrescine.     

Effects of external osmolality on polyamine metabolism in HeLa cells.

The polyamine content of Escherichia coli is inversely related to the osmolality of the growth medium. The experiments described here demonstrate that a similar phenomenon occurs in mammalian cells. When grown in media of low NaCl concentration, HeLa cells and human fibroblasts were found to contain high levels of putrescine, spermidine, and spermine. The putrescine content of HeLa cells was a function of the osmolality of the medium, as shown by growing cells in media containing mannitol or additional glucose. External osmolality per se had no effect on the contents of spermidine and spermine. For all media, the total cellular polyamine content could be correlated with the activity of ornithine decarboxylase, the first enzyme in polyamine biosynthesis. Different levels of enzyme activity appear to result solely from variations in the rate of enzyme degradation. A sudden increase in a NaCl concentration produced rapid loss of ornithine decarboxylase activity and a gradual loss of putrescine and spermidine. A sudden decrease in NaCl concentration led to rapid and substantial increases in ornithine decarboxylase activity and putrescine.     

The presence of two GDP-L-fucose: glycoproteine fucosyltransferases in human serum

Two soluble fucosyltransferases have been demonstrated in human serum. One enzyme transfers l-fucose from GDP-l-fucose to the terminal galactose residues of lactose, N-acetyllactosamine, and sialidase-treated α₁-acid glycoprotein, to form the blood group H determinant, α-l-fucosyl-(1 → 2)-β-d-galactosyl-R. The second enzyme transfers fucose to the terminal N-acetylglucosamine residue of sialidase-, β-galactosidase-treated α₁-acid glycoprotein. Serum from a donor with the rare “Bombay” O_h blood group (genotype hh) cannot transfer fucose to terminal galactose residues but has normal levels of the enzyme acting on sialidase-, β-galactosidase-treated α₁-acid glycoprotein. This observation, as well as mixed substrate experiments, demonstrate that the two fucosyltransferase activities are due to two separate enzymes. The GDP-l-fucose:galactoside fucosyltransferase has a pH optimum of 5.5 and the following K_m values: lactose, 31 mm; N-acetyllactosamine, 7.5 mm; sialidase-treated α₁-acid glycoprotein, 6.4 mm. The GDP-l-fucose: N-acetylglucosaminide fucosyltransferase has a pH optimum of 5.0 and a K_m for sialidase-, β-galactosidase-treated α₁-acid glycoprotein of 1.2 mm. The serum GDP-l-fucose: N-acetylglucosaminide fucosyltransferase is distinct from the blood group Lewis-dependent enzyme in milk since the serum enzyme is present in serum from Le (a-b-)donors and since the Le-dependent fucosyltransferase could not be demonstrated in serum from donors carrying the Le gene.