Differential staining of bacteria: flagella stain

Abstract

Bacterial flagella are appendages used for motility. Their presence is a useful tool for identification and differentiation of prokaryotes. Since flagella are too thin to be seen by compound light microscopy, staining methods employ the use of a mordant (often tannic acid) to make them thick enough to see using an oil immersion objective. Two protocols are described. Basic Protocol 1 is a modified Leifson method and is the one that many microbiologists have adapted. Basic Protocol 2 is a wet-mount stain using a Ryu stain and is included because the stain is stable at room temperature. Both of these methods are fairly time-consuming, taking from 15 to as long as 60 min to perform.