Water Relations of Staphylococcus Aureus At 30°C

Abstract

Fourteen food-poisoning strains of Staphylococcus aureus have been grown in various media of known water activity at 30�C. Aerobic growth was observed atwater activities between 0.999 and 0.86. The rate of growth and the yield of cells were both reduced substantially when the water activity was less than c. 0.94. The lower limits for growth in dried meat, dried milk, and dried soup were similar to those in liquid media. Aerobic growth proceeded at slightly lower water activities than anaerobic growth. All cells were capable of forming colonies on agar media with water activities as low as 0.92. The 14 strains proved to be a homogeneous group with similar water equirements.

On the nature of the relationship between water activity and % moisture in honey

“…However, it is not the water content but the water activity (a w ) of a food which controls microbial growth (Beuchat, 1987;Chirife, Zamora, & Motto, 2005;Christian, 1963;Scott, 1953;Troller & Christian, 1978). The limiting water activity for growth of osmotolerant yeasts (naturally found in honey) is about a w = 0.61/0.62 ; knowledge of water activity of honey is also needed to predict moisture exchange with the environment, since water activity is the driving force behind water transfer from/to honey .…”

The correlation between water activity and % moisture in honey: Fundamental aspects and application to Argentine honeys

“…Water activity is a major factor in preventing or limiting microbial growth and in several cases a w is the primary parameter responsible for food stability, modulating microbial response and determining the type of microorganisms encountered in food. Of all other factors affecting microbial growth in food products (temperature, pH, oxygen, nutrient availability, etc) the influence of water activity on vegetative microorganisms and spores is one of the most complex and fascinating and for this reason has been extensively studied by food microbiologists (Beuchat, 1981(Beuchat, , 1983(Beuchat, , 1987Brown, 1974;Christian, 1963;Scott, 1953). …”

Novel Staphylococcus sp. isolated from wall scrapings of a historical building in India

“…Staphylococci are known to adapt a second strategy to thrive in a low water activity niche. Staphylococcus aureus can grow in foods of water activity 0.86, equivalent to 3.5 mols −1 NaCl (Scott 1953) due its ability to efficiently osmoregulate. It uses glycine, betaine, and proline as its osmolytes, which accumulate to a high intracellular concentration when the organism is subjected to high osmotic stress (Graham and Wilkinson 1992).…”