Improving Dispersion of Bacterial Endospores for Enumeration

Abstract

Precise enumeration of spores is crucial for accurate evaluation of spore survival in the presence of inactivating agents or extreme environmental conditions. Bacterial endospores tend to agglomerate, leading to low estimates of spore numbers. We have shown that addition of SDS to diluent used in counting bacterial endospores better disperses spores, leading to a ten-fold increase in counts. We attribute this effect to steric hindrance and electrostatic repulsion between micellar structures of SDS adsorbed at spore surfaces. We have also demonstrated that use of a low surface energy material (Teflon) improves spread-plate counts, an effect we attribute to lesser hold-up of liquid on Teflon versus glass.