Penicillin was originally purified from the fungus Penicillium and acts by interfering directly with the turnover of the bacteria cell wall and indirectly by triggering the release of enzymes that further alter the cell wall. Streptomycin was originally purified from Streptomyces griseus. Streptomycin acts by binding to the 30S subunit of the bacterial ribosome leading to inhibition of protein synthesis and death in susceptible bacteria. Amphotericin B is an antifungal agent that prevents the growth of fungi and yeast by causing an increase in fungal plasma membrane permeability.