I am aware that bile salts (or crystal violet) is used in agars to inhibit the growth of Gram-positive bacteria but I am wondering what the mechanism is. From my biological understanding, the fact that bile emulsifies lipids to grant access for lipid-degrading enzymes leads to the conclusion that Gram-negative bacteria - due to its lipids in their outer membrane - should be more susceptible to bile salts.
How can bile salts inhibit Gram-positive bacteria instead of Gram- negative organisms.
And if they inhibit Gram-positives, why can gram-positive bacteria like Ruminococcus and Clostridium survive in human intestines??
Thank you very much for your help in this interesting field!