Nutrient Requirements of Renibacterium salmoninarum on Agar and in Broth Media

In well-aerated broth cultures, good growth of Renibacterium salmoninarum was obtained in a serum-free medium consisting of 1% peptone, 1% yeast extract, and 0.1% l-cysteine (PYC broth). In contrast, serum or charcoal is required for growth on agar medium. Charcoal treatment of broth media, either before bacterial inoculation or during growth, increased the growth of R. salmoninarum, whereas the surfactants Tween 20 and Tween 80 inhibited growth. l-Cysteine was essential for optimal growth. Other organic sulfur compounds, such as d-cysteine, l-methionine, homocysteine, homocysteine thiolactone, and reduced glutathione, supported only lower levels of growth, while cystine and dithiothreitol did not allow growth.