Biomedical subjects

J L INGRAHAM

Publications and source records attributed to J L INGRAHAM.

10 recordsLinked to original sources

PubMed1965

FACTORS AFFECTING THE RATE OF KILLING OF ESCHERICHIA COLI BY REPEATED FREEZING AND THAWING.

Packer, Elliot L. (University of California, Davis), John L. Ingraham, and Stanley Scher. Factors affecting the rate of killing of Escherichia coli by repeated freezing and thawing. J. Bacteriol. 89:718-724. 1965.-Repeated freezing and thawing of cultures of Escherichia coli grown in a minimal medium and frozen in the same medium without carbon source resulted in a linear decrease in the log of the number of surviving cells as a function of the number of freeze-thaw cycles. The slope of this curve, which can be determined accurately, is an index of susceptibility of a culture to death by freezing and thawing. The effect of the physiological state of the culture on the killing rate was determined. Contrary to previous reports, the phase of growth, the state of aerobiosis, and the density of the culture had no effect on the degree of susceptibility to death by freezing and thawing. However, presence of spent growth medium (a filtrate of a stationary culture) in the freezing medium protected cells against death by freezing and thawing. Protection by spent growth medium is effective at high dilutions (1:10(5)), and is lost if spent growth medium is heated in the presence of alkali. It is suggested that the protection afforded by spent growth medium accounts for differences between our results and those reported in the literature.

Cold Temperature↗

PubMed1964

EFFECT OF THE TEMPERATURE OF GROWTH OF ESCHERICHIA COLI ON THE FORMATION OF BETA-GALACTOSIDASE.

Marr, Allen G. (University of California, Davis), John L. Ingraham, and Craig L. Squires. Effect of the temperature of growth of Escherichia coli on the formation of beta-galactosidase. J. Bacteriol. 87:356-362. 1964.-The synthesis of beta-galactosidase was measured during exponential growth of Escherichia coli in a succinate-minimal medium over a temperature range of 10 to 43 C for the following: (i) a constitutive strain, and (ii) an inducible cryptic strain, induced maximally with isopropyl-thio-beta-d-galactopyranoside (IPTG), or induced submaximally with IPTG. The differential rates of synthesis of beta-galactosidase were identical for the constitutive strain and for the fully induced strain; the rates were constant from 20 to 43 C, and decreased progressively with a decrease in temperature below 20 C. Thus, in the absence of specific repression, the ability of E. coli to produce beta-galactosidase decreases at low temperature. The differential rate of the submaximally induced culture was minimal between 20 and 30 C, and increased progressively with temperature both above 30 C and below 20 C. That the repressor concentration is maximal at 20 C was established by measuring the rate of induced synthesis of beta-galactosidase as a function of the concentration of IPTG; the relative concentrations of repressor were 1.00:3.28:0.25 at 40, 20, and 10 C, respectively. After an abrupt change in temperature, the differential rate of a submaximally induced culture changed gradually to the rate of the steady state, which is in agreement with the proposal that the effect of temperature is on the concentration of repressor and not on the equilibrium between repressor and its site of action. The effect of temperature on catabolic repression was determined by comparing the differential rate of synthesis of beta-galactosidase by a constitutive strain grown in succinate-minimal medium with the rate in glucose-minimal medium at various temperatures; the ratio of the rates in the two media decreased progressively and approached 2.0 as the temperature of growth was increased.

Cold Temperature↗

PubMed1962

Damage and derepression in Escherichia coli resulting from growth at low temperatures.

Ng, Henry (University of California, Davis), John L. Ingraham, and Allen G. Marr. Damage and derepression in Escherichia coli resulting from growth at low temperatures. J. Bacteriol. 84:331-339. 1962.-Exponentially growing cultures of Escherichia coli ML30 were subjected to abrupt changes in temperature. If the change in temperature was made within the range of temperature in which the temperature characteristic, mu, is constant, exponential growth resumed immediately at a rate characteristic of the new temperature. But, if the shifts were made to or from a temperature below the range of constant mu, the initial growth rate was intermediate to the rates normal for the initial and final temperatures. The results indicate that growth at low temperature alters or damages the cell in a way that reduces the growth rate. A period of growth at higher temperature is required to correct the damage. Release from glucose repression of the induction of beta-galactosidase occurs at a temperature coincident with low-temperature damage. Derepression may be the damage that results from growth at low temperature.

Cold Temperature↗

PubMed1961