Bacteria from LB agar were scraped with a sterile loop and resuspended in 300 μl of 1× PBS. Subsequently, 30 μl of a 3% (vol/vol) suspension of Saccharomyces cerevisiae

(Sigma) or guinea pig red blood cells in PBS and an equal amount of bacterial cells to be tested were selleck screening library mixed on a glass slide [27]. Visible agglutination after gentle agitation indicated a positive reaction for type 1 fimbriae. The presence of mannose-sensitive yeast cell agglutination or mannose-sensitive guinea pig erythrocyte hemagglutination was determined by mixing the bacterial suspension with PBS containing 3% (w/v) α-methyl-D-mannoside (Sigma). Electron microscopy The bacterial strains tested were grown in static broth or on solid agar and resuspended in 1 × PBS. The bacterial cells were then negatively stained

with 2% phosphotungstic acid and observed with a AZD1152 cost Hitachi H-600 transmission electron microscope (Hitachi Ltd., Tokyo, Japan). Complementation test Primers used for the complementation test (stm0551-F and stm0551-R) are listed in Table 2 and were used to amplify genomic DNA of S. Typhimurium LB5010. The PCR product that possessed the full coding sequence of stm0551 was cloned into the pACYC184 vector using T4 DNA ligase (Fermentas). To construct a stm0551 allele with the glutamic acid at position 49 replaced with an alanine; stm0551-F and E49A-TOPO-R were used selleck chemicals llc to amplify

the first DNA fragment using Pfu DNA polymerase (Fermentas). The PCR conditions were: denaturing at 94°C for 3 min followed by 35 cycles of 94°C for 45 sec, 50°C for 45 sec and 72°C for 45 sec. The second DNA fragment was amplified using E49A-TOPO-F and stm0551-R with the same procedure described above. These two DNA fragments were purified by Montage Gel Extraction Kit (Millipore, Billerica, MA). Ligation of these two DNA fragments having next two overlapping ends was achieved with stm0551-F and stm0551-R primers as follows: denaturation at 94°C for 3 min, ligation at 50°C for 45 sec and elongation at 72°C for 45 sec, followed by 35 cycles of 94°C for 45 sec., 50°C for 45 sec, and 72°C for 45 sec. Amplified DNA fragment was digested with BamHI and EcoRV and cloned into pACYC184 vector to generate pSTM0551E49A. The mutated stm0551 allele of this plasmid was sequenced to confirm if the glutamic acid (E) at position 49 was replaced by alanine (A) before transforming into the S. Typhimurium Δstm0551 strain by electroporation. The pACYC184 cloning vector was also transformed into the S. Typhimurium Δstm0551 strain as a control. Quantitative RT-PCR analysis Total bacterial RNA was isolated using an RNeasy Mini Kit (Qiagen, Hilden, Germany) according to the manufacturer’s protocol. Subsequently, RNA was treated with RNase-free DNase (1 unit/1 μg RNA) to remove contaminating genomic DNA.