Starch counteracts the inhibitory action of Bacto-peptone and bile salts in media for the growth of halobacteria

It has been reported that Halobacterium sodomense requires the presence of either starch or bentonite in its growth medium. The present work shows this requirement to be attributable to Bacto-peptone as a component of the medium. When Bacto-peptone is omitted or replaced by other nutrients, no starch is required. Starch (and to a lesser extent bentonite) was shown to effectively protect Halobacterium cells from lysis by Bacto-peptone, and by bile salts, which have been identified as the lytic factor in the peptone.