SerA and DnaK fusions also have localization patterns in C. crescentus similar to those observed in E. coli. SerA, which catalyzes the first reaction dedicated to serine biosynthesis, was localized to a focus that was frequently at the stalked pole or near mid-cell. DnaK, a protein chaperone, was found concentrated at both cell poles. Two proteins, CoxA and CC2362, were found around the periphery of the cell. CoxA is an integral membrane protein, and is localized to the cell periphery in E. coli. CC2362 is predicted to be a peripheral membrane protein, and the transposon-generated fusion confirms this prediction. These data indicate that the transposon mutagenesis strategy is capable of identifying 2-O-beta-L-galactopyranosylorientin proteins expected to be localized. Seven independent fusions to RsaA, the S-layer protein, were localized to a single focus at the cell pole. These results were unexpected, because RsaA is secreted by a dedicated type I transporter, and the mature form of the protein is extracellular. However, the polar localization of C-terminal GFP fusions was not inconsistent with previous studies of RsaA transport. Cterminal truncations of RsaA are not exported because the extreme C terminus contains the export signal, but it has been proposed that the N-terminal region of the protein contains Quizalofop-p-ethyl information to target RsaA to the transporter sites. The localization of RsaA-GFP to the cell poles may indicate that the transporter complex is located at the cell poles. Two of the localized GFP fusions were to proteins with known functions but for which no intracellular localization had been reported. AhpC, a subunit of alkyl hydroperoxide reductase, was localized to a single focus at the stalked pole or mid-cell when fused to GFP. AhpC is involved in oxidative stress response, and there is no obvious reason why it would be localized to a subdomain of the cytoplasm. To confirm the epifluorescence results and ensure that truncation of the protein was not responsible for the localization pattern, immunofluorescence microscopy was used to observe the localization of full-length AhpC with an M2 epitope at the C terminus.