Mikrobiologi

A research group is studying a bactrium X that binds to muosal cells in the lungs and invades host cells. Wildtype X has an LD₅₀ value of 10 bacteria when administered to mice by inhalation. Using transposon mutagenesis, the researchers have isolated two mutants of X that they call Xmut1 and Xmut2, both of which have LD₅₀ values of 10⁵ when inhaled by mice. However, in tissue culture cells, Xmut1 can invade the cells just as well as wildtype X, while Xmut2 cannot. Provide a possible explanation for these results. 

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