Legionella is auxotrophic for seven amino acids: cysteine, leucine, methionine, valine, threonine, isoleucine, and arginine. Once inside the host cell, "Legionella" needs nutrients to grow and reproduce. Inside the vacuole, nutrient availability is low; the high demand of amino acids is not covered by the transport of free amino acids found in the host cytoplasm. To improve the availability of amino acids, the parasite promotes the host mechanisms of proteasomal degradation. This generates an excess of free amino acids in the cytoplasm of "L. pneumophila"-infected cells that can be used for intravacuolar proliferation of the parasite.