Rapid selection of mutants of <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis> for carbohydrate and fatty acid metabolism by fourier transform infrared spectroscopy and gas chromatography combined with multivariate analysis

Transgene-tagged mutants of Chlamydomonas reinhardtii were generated by random insertional mutagenesis for screening of mutants of carbohydrate and fatty acid metabolism. Approximately 2,500 insertion mutants tagged with the aph7″ gene were produced from one mutagenesis in three weeks. To establish a rapid screening system for numerous insertional lines, whole cell extracts of 100 insertional lines were subjected to Fourier transform infrared spectroscopy (FT-IR) and gas chromatography (GC) analysis combined with multivariate analysis. Mutant lines 28, 67, and 90 showed dramatic differences in the carbohydrate (1,000∼1,200 cm⁻¹) and amide (1,500∼1,700 cm⁻¹) regions of the FT-IR spectrum compared to wild type strain CC-124. Separate GC analysis also showed that 16:0 iso, palmitic acid (16:0), and oleic acid (18:1) were the major fatty acids in the wild type strain. In mutant 80, the relative content ratio of 16:0 iso in total fatty acids was significantly lower than in wild type, whereas the ratios of palmitic acid and oleic acid to 16:0 iso were higher. In mutant 95, the ratio of 16:0 iso to total fatty acids was increased, whereas ratios of palmitic acid and oleic acid to 16:0 iso were decreased. In particular, mutant 57 showed remarkably different fatty acid patterns with novel peaks of long-chain fatty acids having more than 20 carbon atoms. The results of this study show that FT-IR and GC combined with multivariate analysis enable rapid selection of mutants of carbohydrate and fatty acid metabolism in C. reinhardtii.