Sorption of Water Vapour and Nitrogen Gas by Bacterial Spores

Abstract

As a result of their high refractility and their resistance to stains and to lethal agents such as heat and chemicals, it has long been thought that bacterial spores are relatively dry and impermeable. There is conflicting evidence, however, about the degree of desiccation and impermeability which may exist. Refractive index measurements on spores in aqueous suspensions indicate very low water contents1, and the surface area of lyophilized spores available to adsorption of nitrogen gas is so small that little or no internal porosity can be postulated2. On the other hand, it has been demonstrated that spores have a significant affinity for water3. In aqueous media it is known that germinants enter spores rapidly and evidence has been presented for considerable porosity and a water content as high as 75 per cent of the dry weight4. In an effort to account for these discrepancies, we have employed standard gas adsorption techniques to measure water vapour sorption of intact and crushed spores and the nitrogen gas adsorption of spores which were dried in various ways. The results confirm the hydrophilic nature of spores and indicate that a considerable fraction of the volume occupied by water in wet spores can be preserved in the dry state by employing dehydration methods which minimize the collapse of hydrophilic, macromolecular structures.