The diatomChaetoceros socialis: spore formation and preservation

Virus‐induced spore formation as a defense mechanism in marine diatoms

“…3c,d). To contextualize these findings, we tested the ability of both APC12 and L‐4 to form spores under nitrogen (N) limitation, a treatment known to induce a shift from vegetative cells to resting stages in most diatoms, including C. socialis (Pelusi et al ., 2019). Less than 1% of the cells of strain L‐4 formed spores after 5 d in an N‐limited medium, compared to 99% ± 0.69 in strain APC12 (Supporting Information Fig.…”

“…Chaetoceros socialis strain APC12 was isolated in 2015 from a single short chain of cells that had germinated during incubations of surface sediments collected in the Gulf of Naples (Mediterranean Sea, Italy). The strain is preserved as dormant spores (Pelusi et al ., 2019), and freshly established cultures were used for all experiments. Strain L‐4 (identified as C. socialis f. radians ) was isolated in 2005 from Hiroshima Bay, Japan and kindly provided by Yuji Tomaru (National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency).…”

Density‐dependent mechanisms regulate spore formation in the diatom Chaetoceros socialis

“…The use of nitrogen‐deplete culture media has been shown to induce spore production in various Chaetoceros species (French III and Hargraves 1985; Kuwata et al 1993; McQuoid and Hobson 1996) including C. socialis , where different strains isolated from the Gulf of Naples responded in the same way, all turning into spores within a few days (Pelusi et al 2019). We have now convincingly shown that spore formation occurs also in control conditions when nutrients are not limiting, and this suggests that their depletion in the medium does not represent the only trigger for this transition.…”

“…Strain isolation, maintenance, and genetic characterization are illustrated in Pelusi et al (2019). Culture media were prepared with artificial seawater at salinity of 36 (Sea salts, Sigma‐Aldrich; Pelusi et al 2019); ventilated tissue culture flasks (Corning) were used. Experiments were carried out at controlled temperature (18°C ± 1°C) and irradiance (~ 90 μ mol photons·m −2 ·s −1 daily average) obtained with a sinusoidal cool‐white illumination system at 12 : 12 h light : dark photocycle.…”

“…We addressed the issue using the marine colonial diatom Chaetoceros socialis , which produces endogenous spores (Pelusi et al 2019) and is abundant in many coastal areas (De Luca et al 2019). We tested nitrogen depletion, traditionally the most effective environmental factor, but explored also the possible role of biological cues related to cell density indicative of a coordinated response at the level of the whole population.…”