parameters has shown that they differ only slightly. The generating function for this model was found by Bartlett in 1978 and is where μ is the mutation rate (assumed to be constant), with β as the cellular growth rate (also assumed to be constant) and t as the time. The determination of μ from this equation has proved difficult but a solution was discovered in 2005. Differentiation of the generating function with respect to μ allows the application of the Newton–Raphson method which together with the use of a score function allows one to obtain confidence intervals for μ. Molecular biology The mechanism of resistance to the phage T1 appears to have been due to mutations in the fhuA gene - a membrane protein that acts as the T1 receptor. The tonB gene product is also required for infection by T1. The FhuA protein is actively involved in the transport of ferrichrome, albomycin and rifamycin. It also confers sensitivity to microcin J25 and colicin M and acts as a receptor for the phages T5 and phi80 as well as T1. The FhuA protein has a beta-barrel domain (residues 161 to 714) that is closed by a globular cork domain (residues 1 to 160). Within the cork domain is the TonB binding region (residues 7 to 11). The large membrane spanning monomeric β-barrel domains have 22 β-strands of variable length, several of which extend significantly beyond the membrane hydrophobic core into the extracellular space. There are 11 extracellular loops numbered L1 to L11. The L4 loop is where the T1 phage binds. References External links On Mutation lab Profiles in Science: The Salvador E. Luria Papers Information on Salvador Luria from the National Library of Medicine Biology experiments Genetics experiments Statistical genetics Bacteria 1943 in biology