The present invention is directed to chitosan-derivative compounds and structures, methods of making chitosan-derivative compounds and methods for controlling, inhibiting and enhancing microbial populations in a variety of environments. The present invention is also directed to the control, inhibition and enhancement of microbial populations in animals, particularly humans. The microbial populations include bacteria, viruses and other pathogens where control of microbial populations are a necessity. The chitosan-derivative compounds of the present invention include chitosan-arginine compounds, related chitosan-L/D unnatural amino acid compounds, chitosan-acid amine compounds, chitosan-L/D natural amino acid derivative compounds, co-derivatives of the chitosan-derivative compounds, salts of the chitosan derivative compounds, and chitosan-guanidine compounds.