Identification of a novel fatty acid in the cell membrane of Chryseobacterium frigidisoli PB4T isolated from an East Antarctic glacier forefield

Abstract

The cell membrane phospholipid fatty acid (PLFA) inventory of Chryseobacterium frigidisoli PB4T, a psychrotolerant, non-motile, gram-negative, aerobic bacterium isolated from ice free permafrost deposits in continental Antarctica contains a FA with a novel methyl ester mass spectrum. In a temperature cultivation experiment of C. frigidisoli at 0°C this unknown FA was the dominant PLFA. The molecular mass indicates a C17 FA with two double bond equivalents (DBEs). A 3-pyridylcarbinol derivatization experiment as well as hydrogenation of the double bonds allowed structural assignment of the respective FA as 14-methyl-hexadeca-9,13-dienoic acid (anteiso-heptadeca-9,13-dienoic acid or ai-17:2Δ9,13) an unusual anteiso-ω3-FA with bis-methylene interrupted double bonds (ai-17:2ω3,7 or ai-17:2n-3,7). The iso-counterpart of this unsaturated FA also occurred in trace amount. The close vicinity of the ω3 double bond to the anteiso branch and also to the iso branch seems to be responsible for a shift in the gas chromatography retention times of these compounds, resulting in elution shortly after the saturated counterparts. The dominance of the ai-17:2ω3,7 at 0°C cultivation temperature suggests its importance for cell membrane adaptation of C. frigidisoli with respect to low ambient temperature conditions.