Membranes of Bacillus stearothermophilus : Factors Affecting Protoplast Stability and Thermostability of Alkaline Phosphatase and Reduced Nicotinamide Adenine Dinucleotide Oxidase

Abstract

Protoplasts of Bacillus stearothermophilus NCA 1503-4R are resistant to osmotic rupture and are not sensitive to mechanical manipulation. Protoplast stability is maintained by divalent cations. The thermostability of protoplasts is enhanced when the cells are grown at elevated temperatures. The membrane content of the cell and the protein-to-lipid ratio of the membrane increases as the growth temperature is increased. The membrane-bound nicotinamide adenine dinucleotide (reduced form) oxidase system from cultures grown at 70 C was more thermostable than the same enzyme system from cultures grown at 55 C. Alkaline phosphatase was resistant to thermal inactivation in the intact protoplast. The extent of this protection is dependent on protoplast stability. 1336

Toxicity of methoprene as assessed by the use of a model microorganism

“…Oxygen consumption was measured with protoplasts prepared from cells from cultures harvested in the middle of the exponential growth phase, by incubation with lysosyme, essentially as described by Wisdom and Welker (1973). The protein content of the protoplasts was determined by the Biuret method, calibrated with bovine serum albumin (Gornal et al, 1949).…”

The effect of growth rate on the viability of Bacillus stearothermophilus

“…In the literature there are several reports on the effects of growth rate on the viability of a bacterial culture ([ 17] and references therein). The observation that the growth rate of the culture at the time of sampling can affect viability of the culture could explain the results of Baillie and Holms [8] and Wisdom and Welker [9]. Baillie and Holms found that Bacillus subtilis cells growing exponentially in peptone plus glucose medium lost viability rapidly on transfer-ring to a buffer, whereas cells growing in peptone medium showed no such loss of viability on transfer to a buffer.…”

Influence of Divalent Cations on the Growth and Morphology of Bacillus stearothermophilus

“…E. coli grown in a medium deficient in divalent cations showed structural modifications in the cytoplasmic membrane following a presumed lipid phase transition, not observed in bacteria grown in control medium containing 1 mM-Mg2+ (Arancia et al, 1980). The structural integrity of protoplast membranes of B. stearothermophilus was also shown to be maintained by divalent cations (Wisdom & Welker, 1973). Studies are now in progress with liposomes and protoplasts of B. stearothermophilus to ascertain the effect of Ca2+, Mg2+ and Sr2+ on the biophysical properties of their membranes.…”