Cationic polypeptides interact with bacterial cells of E. coli and B. anthracis. They confer upon the cells some of the characteristics of cationic particles. Since bacterial cells usually behave as anions, acidic dyes at high pH levels differentiate between cells which have and those which have not interacted with cationic polypeptides. Under the conditions of these experiments it appeared that cationic polypeptides tend to be sorbed in highest concentration in the surface layers of the cells. Electrovalent binding to anionic cell components and detergent action are probably among the mechanisms involved in the interaction between the polypeptides such as histones and bacterial cells.
The differential staining of bacterial cells which have interacted with cationic polypeptides is feasible and reasonably selective. It should be useful in determining whether bacterial cells interact with host cationic polypeptides in vitro.