Supernatants (300 μL) were extracted twice with 600 μL of ethylacetate; the resulting ethylacetate phases were pooled and evaporated to dryness. When needed, samples of the supernatant
were diluted with water. Dried extracts were solved in 100 μL of water, mixed with orcinol (1.6% w/v in water), 800 μL H2SO4 (60%) and heated to 80 °C for 30 min. The concentration of rhamnose was measured spectrophotometrically at a wavelength of 421 nm and compared with rhamnose reference standards. Bacterial cells were grown in LB medium for 18 h at 37 °C. Cell harvesting, protein isolation, two-dimensional gel electrophoresis and bioinformatic analysis were carried out Trichostatin A as described previously using large IPG strips (17 cm, pH 5–8) (Schreiber et al., 2006). Pseudomonas aeruginosa cells are motile rods with a single flagellum inserted at one pole of the cell. On semi-solid surfaces such as low concentrated agar (0.2–0.4% w/v) Selleck Tyrosine Kinase Inhibitor Library plates, cells swim through water-filled channels (Rashid & Kornberg, 2000) and this swimming motility is driven by the intact flagellum and requires various cellular functions. Compared with the wild type, swimming motility was absent in the lipC mutant, but could be restored by plasmid pBBLCH (Fig. 1). This type
of motility can be distinguished from swimming by the appearance of dendritic patterns in the bacterial growth that Carnitine dehydrogenase elongate and branch from a central colony. Swarming has been described for various Gram-negative pathogens, and like swimming, it requires flagellar function. As expected from the results of the swimming assays, the P. aeruginosa lipC mutant also failed to swarm (Fig. 1). Swarming motility was restored when the lipC mutant was complemented with plasmid pBBLCH providing functional LipC, although this complementation was not complete (Fig. 1). In contrast to the swimming defect observed for the lipC mutant, no significant residual swarming motility was detected. On solid surfaces,
P. aeruginosa is capable of twitching motility, a mode of translocation dependent on type IV pili (Mattick, 2002). Cells that are stabbed to the plastic bottom of an agar-filled Petri dish start colony expansion on the interstitial surface between the agar layer and the Petri dish, which is visible as a faint turbid zone. Compared with twitching wild-type cells, the spatial extension of this twitching zone was sharply reduced for the lipC mutant (Fig. 1). However, when compared with a pilus-deficient pilD mutant, the twitching defect of the lipC mutant was less drastic (data not shown). The motility defects of the lipC mutant could all be restored by the expression of functional LipC from plasmid pBBLCH excluding the polar effects of this mutation. Therefore, we conclude that all three forms of motility require functional LipC in P. aeruginosa. Examination of the P.