, 2012). One of the differences
between CYT ASW and LN ASW media is the presence of tryptone and yeast extract in CYT ASW. The importance of these factors was tested by adding tryptone or yeast extract at the same proportion (0.5 or 1.0 g L−1) as in CYT ASW medium. For those media (LN Ye ASW and LN Tryp ASW), iridescence profiles were similar to those observed on CYT ASW or MA. Gliding motility was visible for iridescent colonies after 72 h of growth. Cellulophaga lytica is potentially exposed to salinity variations and hypersaline conditions in its biotope. As shown in Table 2B, C. lytica’s iridescence was conserved even at high (sub-lethal) NaCl concentrations. As growth was inhibited under hypersaline conditions, red iridescence was more visible. Changes in agar Z-VAD-FMK datasheet concentration potentially affect several selleck chemicals physico-chemical parameters such as moisture, hydrostatic and osmotic pressures, and solidity of the surface. On soft agar plates (0.25–0.50%), colonies had a particular smooth aspect and no iridescence
was observed (Fig. 4). However, after 72 h of growth on 0.5% agar plate, iridescence could be observed on the inner part of the colony. In this specific condition, a second phase of growth and gliding motility may occur on older cells used as a support. The optimum agar concentration was 1.5%. At concentration higher than 2.0%, growth was lowered and Oxalosuccinic acid no iridescence was observed. These conditions were favorable for agarolysis but unfavorable for gliding motility. Natural or in vitro conditions that favor or inhibit the unique iridescence of C. lytica colonies are unknown. We thus examined the effect of key environmental factors to determine the possible conservation of the iridescence in the natural environment. Cellulophaga lytica is a nonphotosynthetic bacterium which potentially encounters a plethora of light or dark conditions in its natural habitats (tidal flats, rocks,
pelagic zones…). Accordingly, we found that C. lytica’s iridescence seems biologically uninfluenced by light exposure, even if light is physically essential for the phenomenon. Drop tests permitted to follow colors’ apparitions linked with population density level. Under growth-limited conditions (e.g. 24 h under hypoxia), low cell density colonies appeared red. A higher cell density was needed to generate bright green-dominant iridescence. However, iridescence could be lost in the inner parts of the colonies, may be owing to an altered physiology of the older cells or a too high cell density. As already described in higher organisms, changes in the color of iridescence are owing to modifications in structure dimensions. Such hypothesis is currently being investigated in C. lytica in our laboratory. Interestingly, seawater was required for iridescence. The only presence of seasalts with agar (LN ASW medium) allowed both growth and iridescence.