*2.1. Fatty Acid Compositions*

Fatty acid compositions of *P. salina* strains LD40H and SL540T are reported in Table 1. A total of 22 fatty acids were detected. Saturated fatty acids (SFA) were lauric acid (12:0), myristic acid (14:0), pentadecylic acid (15:0), palmitic acid (16:0), margaric acid (17:0), stearic acid (18:0), arachidic acid (20:0), and behenic acid (22:0). Altogether, 16:0 and 18:0 were the most abundant SFA and contributed in average 23 ± 3 and 4 ± 1% to total fatty acids (TFA), respectively. Mono-unsaturated fatty acids (MUFA) were myristoleic acid (14:1*n*-5), palmitoleic acid (16:1*n*-7), hypogeic acid (16:1*n*-9), 17:1*n*-7, 17:1*n*-9, vaccenic acid (18:1*n*-7), oleic acid (18:1*n*-9), and 20:1*n*-9. Across all treatments, 18:1*n*-9 was the most abundant MUFA (28 ± 4% of TFA). Measured poly-unsaturated fatty acids (PUFA) were 16:2*n*-4, 16:2*n*-6, 17:2*n*-5, Linoleic acid (18:2*n*-6), alpha-linolenic acid (18:3*n*-3), and 20:2*n*-9. Linoleic acid was the most abundant PUFA as well as the most abundant fatty acid with 40 ± 3% of TFA.


**Table 1.** Fatty acids

concentrations

 (μg g−1) in the extracts of

endophytic *P. salina*

isolated from *L. digitata* (LD) or *S. latissima* (SL) and grown at different salinities



112

Concentrations of the most abundant fatty acids were compared according to temperature and salinity treatments. Figure 1 shows the differences between temperatures for each of these fatty acids per salinity treatment and algal host. For both LD and SL temperature changes induced few modifications of fatty acids concentrations at 23.5 practical salinity units (PSU). Significant changes were observed only for minor fatty acids such as 16:1*n*-7 or 18:3*n*-3 whereas most compounds (including major *P. salina* ones) showed significant changes with temperature at 50 and 70 PSU.

**Figure 1.** Concentrations (μg g−1) of the 7 most abundant fatty acids. (**a**) Higher concentrations and (**b**) lower concentrations of endophytic *P. salina* isolated from *L. digitata* (LD) or *S. latissima* (SL) and grown at different salinities (23.5, 50 and 70 PSU) and temperatures (10, 18 and 25 °C). One-way Welch ANOVA (W) or One-way ANOVA (A) has been performed depending on the result of Bartlett test: n.s. = not significant, \* *p* < 0.05, \*\* *p* < 0.01, and \*\*\* *p* < 0.001.
