Relevant UOPs play a number of specific, in some cases highly economically relevant ecological roles. Fully understanding and thereby gaining an ability to efficiently work with or against these phenomena requires more than just a molecular understanding of UOP-host interactions. Horizontal transfer of genetic material is very important with regard to various crucial problems of the modern world such as antibiotic resistance in pathogens and the potential for breakout of the products of biotechnology. Unicellular organisms can serve as hosts for parasites also capable of infecting and causing disease in multicellular organisms. That is, some UOPs are etiological agents for zoonotic diseases having unicellular reservoirs.
Bacteriophage serve as indicators of fecal pollution.
Bacteriophage serve as models for studies of viral disinfection.