Abstract: The subject invention relates in part to novel uses of bacteriophage tail spike proteins (TSPs). Some preferred uses are therapeutic uses in animals, such as chickens, against pathogenic bacteria, such as Salmonella. Fragments of the TSPs can also be used according to the subject invention, particularly protein fragments comprising the phage receptor binding domains (PRBDs), which recognize their hosts and facilitate infection. The binding domains are specific to unique surface structures on bacteria and may be used for a variety of applications according to the subject invention. We have shown that by utilizing these PRBDs, it is possible to exploit the long-established evolutionary relationship between bacteria and their viruses (ie bacteriophages) that specifically infect them. The subject invention also relates in part to novel, synthetic forms of tail spike proteins. In some preferred embodiments, these are hexamers.