title: Online analysis of single cyanobacteria and algae cells under nitrogen-limited conditions using aerosol time-of-flight mass spectrometry.
abstract: Metabolomics studies typically perform measurements on populations of whole cells which provide the average representation of a collection of many cells. However, key mechanistic information can be lost using this approach. Investigating chemistry at the single cell level yields a more accurate representation of the diversity of populations within a cell sample; however, this approach has many analytical challenges. In this study, an aerosol time-of-flight mass spectrometer (ATOFMS) was used for rapid analysis of single algae and cyanobacteria cells with diameters ranging from 1 to 8 μm. Cells were aerosolized by nebulization and directly transmitted into the ATOFMS. Whole cells were determined to remain intact inside the instrument through a combination of particle sizing and imaging measurements. Differences in cell populations were observed after perturbing Chlamydomonas reinhardtii cells via nitrogen deprivation. Thousands of single cells were measured over a period of 4 days for nitrogen-replete and nitrogen-limited conditions. A comparison of the single cell mass spectra of the cells sampled under the two conditions revealed an increase in the dipalmitic acid sulfolipid sulfoquinovosyldiacylglycerol (SQDG), a chloroplast membrane lipid, under nitrogen-limited conditions. Single cell peak intensity distributions demonstrate the ability of the ATOFMS to measure metabolic differences of single cells. The ATOFMS provides an unprecedented maximum throughput of 50 Hz, enabling the rapid online measurement of thousands of single cell mass spectra.
authors.affiliation: ‡Department of Chemistry and Biochemistry, University of California, La Jolla, California 92093, United States.
authors.forename: John F
authors.initials: JF
authors.lastname: Cahill
authors.affiliation: †nanoComposix, San Diego, California 92111, United States.
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Darlington
authors.affiliation: †nanoComposix, San Diego, California 92111, United States.
authors.forename: Christine
authors.initials: C
authors.lastname: Fitzgerald
authors.affiliation: ‡Department of Chemistry and Biochemistry, University of California, La Jolla, California 92093, United States.
authors.forename: Nathan G
authors.initials: NG
authors.lastname: Schoepp
authors.affiliation: ‡Department of Chemistry and Biochemistry, University of California, La Jolla, California 92093, United States.
authors.forename: Joris
authors.initials: J
authors.lastname: Beld
authors.affiliation: ‡Department of Chemistry and Biochemistry, University of California, La Jolla, California 92093, United States.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Burkart
authors.affiliation: ‡Department of Chemistry and Biochemistry, University of California, La Jolla, California 92093, United States.|§Scripps Institution of Oceanography, University of California, La Jolla, California 92093, United States.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Prather
mesh_terms: D000336:Aerosols / Q000737:chemistry*; D049108:Cell Enlargement; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D000460:Chlorophyta / Q000737:chemistry*; D000458:Cyanobacteria / Q000737:chemistry*; D009862:Online Systems; D059010:Single-Cell Analysis; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000336:Aerosols