, 2006), are indicated. Vibrio shilonii is a monoflagellated marine bacterium that has been postulated to be the causative agent of bleaching of the coral O. patagonica

(Kushmaro et al., 1997; Banin et al., 2000; Kushmaro et al., 2001; Rosenberg et al., 2009). It has also been shown that this species resides during the winter season in the marine worm Hermodice carunculata (Sussman et al., 2003). Therefore, motility becomes an important issue in understanding how this Gram-negative bacterium moves about in the various environments that it encounters in the coral reef. In this work, the swimming behavior of V. shilonii was analyzed under various agar Y-27632 in vitro concentrations in the presence or absence of the sodium channel blocker amiloride. Our results show that the formation of lateral flagella appears to increase with a higher density of soft agar in plates. At agar concentrations of 0.5%, we observed that cells start to elongate, reaching an average length of twice the size of the planktonic cells. Possibly, as the polar

flagellum slows down, swarmer cell differentiation occurs as has been shown previously in V. parahaemolyticus (Belas et al., 1986; McCarter et al., 1988). At a higher agar concentration (0.7%), V. shilonii cells lose their flagella, and most of the cells become round. This morphological transformation does not mean that the cells become sick or unviable, given that the growth of cells obtained from this condition was observed in either solid or liquid growth media. These results indicate that V. shilonii Selleck Romidepsin has a constitutive polar flagellum for swimming and inducible lateral flagella whose presence is associated with morphological changes. Furthermore, the drastic morphological change observed at 0.7% agar could be related to an uncharacterized stress response that this bacterium may undergo when it is exposed to this condition, which may be related to its life style.

Several bacterial species differentiate upon contact with a surface such as V. parahaemolyticus, Aeromonas caviae and A. hydrophila. Many of these are water-borne bacteria involved in different animal and human infections. In these species, 4-Aminobutyrate aminotransferase the polar flagellum is important for motility in liquid media. Upon host attachment, lateral flagella are induced, contributing to microcolony formation, also allowing bacteria to adhere more firmly and facilitate biofilm formation (Belas & Colwell, 1982; Kirov et al., 2002). It will be interesting to determine whether the lateral flagella identified in this work contribute to the adherence of V. shilonii cells and whether this behavior is related to its ability to invade a host in its marine environment. According to our observations, the filament of the polar flagellum has a diameter of c. 30 nm and what we believe are lateral flagella are c. 15 nm in diameter (Fig. 2).