Merriam-Webster Collegiate Dictionary - proteus

 noun  Etymology: Latin, from Greek Proteus  Date: 15th century a Greek sea god capable of assuming different forms PROTEUS  noun  (plural protei)  Etymology: New Latin, from Latin, Proteus  Date: 1896 any of a genus (Proteus) of aerobic usually motile enterobacteria that include saprophytes in decaying organic matter and a common causative agent (P. mirabilis) of urinary tract infections