Micro-photographs of <i>P. phosphoreum</i> ANT-2200 cells by electron microscopy.

<p>Observation at 0.1 MPa (A1 on dehydrated samples, A2 on freeze-dried samples) and 22 MPa (B1 on dehydrated samples, B2 on freeze-dried samples) using SEM and at 0.1 MPa (A3) and 22 MPa (B3) using TEM. Intracellular inclusions are indicated by arrows.</p

Example of logistic model fitting empirical growth data of <i>P. phosphoreum</i> ANT-2200.

<p>Experiments were done at pressures of 0.1, 10, 22, 30 and 40 MPa and at temperatures of 13°C and 30°C. The logistic model (line) improves the r and K parameter estimation on empirical growth data (dots). Dashed lines are levels of confidence for the 0.05 and 0.95 quantile curves and the 0.25 and 0.75 quantile curves. Mean +/− standard deviation for growth rate (r, h⁻¹) and maximum population density (K, OD_{600 nm}) parameters are indicated. The dotted frame is the growth curve under optimum pressure and temperature conditions using both r and K parameters. The solid line frame is the growth curve under <i>in situ</i> conditions, at 22 MPa and 13°C. N is the number of replicates done for the same pressure and temperature conditions.</p

Cross diagram of the temperature-pressure dependence of <i>P. phosphoreum</i> ANT-2200.

<p>(A) Extrapolated-contour diagram of the temperature-pressure dependence for both the growth rate (r, h⁻¹) and the maximum population density (K, OD_{600 nm}) for <i>P. phosphoreum</i> ANT-2200. The cross coefficient C_r–K is defined as: 0r–K<1. (B) Standard deviation associated to the C_r–K coefficient. The grey circles indicate parameter values used to extrapolate the contours. Size is proportional to their values. The black circle corresponds to the <i>in situ</i> conditions for the strain. Isolines define zones with same level of values.</p

Bioluminescence and growth of <i>P. phosphoreum</i> ANT-2200.

<p>(A) Bioluminescence (photons sec⁻¹) of <i>P. phosphoreum</i> ANT-2200 at 0.1 MPa (blue lines) and 22 MPa (red lines). (B) Fitted logistic growth curves for 0.1-MPa experiments (blue lines) and 22-MPa experiments (red lines). The dashed lines represent levels of confidence for the 0.05, 0.95 and 0.25, 0.75 quantile curves. Cell number is estimated using <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066580#pone.0066580.e001" target="_blank">equation (1</a>). On (A) and (B) blue and red dotted lines represent the mean time of the bioluminescence peak for both pressure conditions.</p

Relative total fatty-acid composition (%) of <i>P. phosphoreum</i> ANT-2200.

<p>Strain ANT-2200 is grown at 0.1 (black bar) and 22 MPa (grey bar). Others: sum of C17:0, C18:2 and C 19:1 fatty acids; UFA: unsaturated fatty acids; SFA: saturated fatty acids.</p

Time series of oceanographic parameters measured at the Lacaze-Duthiers Canyon (LDC) and the open-sea convection region in the Gulf of Lion (LION) from January 2008 to June 2010.

<p>(<b>a</b>) Potential temperature at 500 and 1,000 m depth at the LDC mooring site and (<b>b</b>) from various water depths at the LION site, jointly with (<b>c</b>) salinity at 2,300 m depth, (<b>d</b>) horizontal current speed and (<b>e</b>) vertical current speed from various water depths at the LION site. The four levels of temperature measurements at LION presented here are a sub-set of measurement depths (see Fig. S1). Essentially stable temperatures in the deepest layers in 2008 show that open-sea convection reached only 700 m and did not modify the deep water in the study area. In contrast, strong convection events, reaching 2,300 m depth, occurred during February-March 2009 and 2010 with an abrupt cooling of the upper water column and an increase in temperature and salinity in the deep layers. A concurrent increase in current speed was also noticed in winter 2009 and 2010. The 5-month long data gap in 2009 is due to a damaging of the mooring line during the April 2009 recovery, which induced a postponement of its redeployment to September 2009.</p

Links between bioluminescence, current speed and the modification of the properties of the Western Mediterranean Deep Water (WMDW).

<p>Box-and-whisker plot of median PMT counting rates (log scale) versus current speed classes for salinities higher (red) or lower (grey) than 38.479 for data recorded in (<b>a</b>) 2008, (<b>b</b>) 2009 and (<b>c</b>) between January and June 2010. The salinity threshold of 38.479 is used as a marker of the intrusion of newly formed deep water at the ANTARES site. While bioluminescence increases with current speed, it is also enhanced by the modification of WMDW (red box-plots). The top and bottom of each box-plot represent 75% (upper quartile) and 25% (lower quartile) of all values, respectively. The horizontal line is the median. The ends of the whiskers represent the 10^th and 90^th percentiles. Outliers are not represented. The statistical comparison between the two box-plots (red and grey) in each current class is given by the Kruskal-Wallis test: the observed difference between the two samples is significant beyond the 0.05 (*), the 0.01 (**) and the 0.001 (***) levels. The absence of an asterisk in some current classes indicates that the difference between the two box-plots is not significant. The number of measurements for salinity lower or higher than 38.479 is given in black or in red, respectively. Note the different scales of figures a, b and c.</p