The mobile phase A contained 2% acetonitrile in water, 0.1% formic acid. The organic phase B contained 2% water in acetonitrile with 0.1% formic acid. Peptides were eluted

with a linear gradient of a 5–60% mobile GSK-J4 phase B over 60 min at 0.2 μL min−1. Spectra were acquired in the automated mode using Information Dependent Acquisition. Precursor ions were selected in Q1 using the enhanced MS (EMS) mode as a survey scan. The EMS was followed by an enhanced resolution scan of the three most intense ions at a low speed of 250 AMU s−1 to determine the ion charge states and then by an enhanced product ion scan. The precursor ions were fragmented by collisionally activated dissociation in the Q2 collision cell. The fragment ions generated were captured and mass analyzed in the Q3 linear ion trap. Protein identifications find more were obtained from the MS/MS spectra data sets using mascot (version 1.6b9, Matrix Science, London, UK, available at http://www.matrixscience.com). Mass tolerances of 0.5 Da for the precursor and 0.3 Da for the fragment ion masses were used. Carbamidomethyl-cysteine was the fixed modification and one missed cleavage for trypsin was allowed. Searches were conducted using the Bacteria subset of the NCBInr database (http://www.ncbi.nih.gov). Wild-type V. shilonii AK-1 cells were taken directly from swimming plates at different soft agar concentrations

and suspended in 10 mM HEPES buffer, pH 8.0. Cell samples were stained negatively with 1% uranyl acetate, isolated hook–basal bodies (HBB) were stained with 2% ammonium hepta-molibdate, pH 8.0, and observed using a JEM-1200EXII electron microscope (JEOL, Tokyo, Japan). Micrographs were taken at an accelerating voltage of 80 and 120 kV for cells and HBB, respectively. Vibrio shilonii displays a constitutive single-sheathed polar flagellum when grown in a liquid Pyruvate dehydrogenase lipoamide kinase isozyme 1 medium. Figure 1a shows an electron micrograph of a typical swimmer bacterial cell grown in a liquid culture. We tested the effect of amiloride, a sodium channel blocker, on the ability of this marine bacterium to swim on soft agar plates (0.3% agar).

Figure 1b shows that in the presence of 2 mM amiloride dissolved in 2% DMSO, the swimming capacity of V. shilonii in soft agar plates is diminished as compared with cells swimming under the same conditions in the absence of amiloride. Consistent with this result, we detected that amiloride reduces swimming drastically in cells growing in liquid cultures that were observed using high-intensity dark-field microscopy. The effect of amiloride on the growth rate of V. shilonii in liquid cultures was also tested. Figure 1c shows that the growth rate of control cells is indistinguishable from a culture to which a volume of 2% DMSO was added. However, in the presence of 2 mM amiloride, a slight decrease in the growth rate of V. shilonii that recovers after a few hours was observed.