, 2001). This appearance has been well studied in higher organisms particularly in Insecta (Ghiradella, 1991; Vukusic et al., 2004;

Seago et al., 2009), Aves (Greenewalt et al., 1960; Prum & Torres, 2003; Doucet et al., 2006), and in fishes (Land, 1972; Lythgoe & Shand, 1989). Iridescence is also encountered in viruses (Williams & Smith, 1958) and in marine organisms such as ctenophore (Welch et al., 2006) and diatoms (Noyes et al., 2008). Iridescence ABT-888 in vivo has been poorly studied in the prokaryote kingdom. Both direct illumination and trans-illumination have been used to observe colonies’ iridescence on solid media (Pijper, 1923; Nogrady & Guérault, 1964; Zierdt, 1971). Recently (Kientz et al., 2012), a comparison of a wide range of bacterial strains

permitted to defined four classes of iridescence: rainbow-diffuse and rainbow-edge iridescences under trans-illumination and, metallic appearance and intense glitter-like iridescence under direct illumination. Cellulophaga lytica was the unique bacterium belonging to the latter class. As this type of iridescence occurred under direct natural light exposure, it was described ZD1839 as a more natural coloration effect. The visual appearance corresponds to sub-millimeter-sized centers of color of varying brightness distributed across the biofilm giving a glitter-like character. Iridescent green is the dominant color, but red and blue-violet are also observed at the colonies’ edges on classical marine

media. Though the physiology of C. lytica has never been thoroughly characterized, some microbiological features (Johansen et al., 1999) and genomic data (Pati et al., 2011) suggest that the bacterium is well adapted to extreme conditions. Moreover, C. lytica is frequently isolated from coastal shore. In this biotope, high variations of temperature, salinity, or light exposure are common. It is still unknown whether C. lytica’s iridescence can occur under such conditions, in vitro or in natural habitats. In the present work, we examine the effect of key abiotic factors on C. lytica’s iridescence. Several stress conditions that mimic the natural Flavopiridol (Alvocidib) biotope of the bacterium were preferentially employed. Unless otherwise specified, agar concentration was 1.5%. Ready-to-use media marine agar (MA), nutrient agar (NA), tryptic soy agar (TSA), and Luria–Bertani (LB) were purchased from Dutscher (France). Cytophaga agar (CYT ASW) and low nutrient (LN ASW) media were made with artificial seawater (ASW) Instant Ocean© (30 g L−1 in pure water). CYT ASW medium contained 1 g tryptone, 0.5 g yeast extract, 0.5 g CaCl2·2H2O, 0.5 g MgSO4·7H2O, and 15 g agar in 1 L of ASW (Johansen et al., 1999). Casein was replaced by tryptone because C. lytica does not degrade casein (Kientz et al., 2012). LN ASW medium only contained agar (15 g) in 1 L of ASW (Jensen et al., 1996).