title: Direct single-cell biomass estimates for marine bacteria via Archimedes' principle.
abstract: Microbes are an essential component of marine food webs and biogeochemical cycles, and therefore precise estimates of their biomass are of significant value. Here, we measured single-cell biomass distributions of isolates from several numerically abundant marine bacterial groups, including Pelagibacter (SAR11), Prochlorococcus and Vibrio using a microfluidic mass sensor known as a suspended microchannel resonator (SMR). We show that the SMR can provide biomass (dry mass) measurements for cells spanning more than two orders of magnitude and that these estimates are consistent with other independent measures. We find that Pelagibacterales strain HTCC1062 has a median biomass of 11.9±0.7 fg per cell, which is five- to twelve-fold smaller than the median Prochlorococcus cell's biomass (depending upon strain) and nearly 100-fold lower than that of rapidly growing V. splendidus strain 13B01. Knowing the biomass contributions from various taxonomic groups will provide more precise estimates of total marine biomass, aiding models of nutrient flux in the ocean.
authors.affiliation: Program in Computational and Systems Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Nathan
authors.initials: N
authors.lastname: Cermak
authors.affiliation: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Jamie W
authors.identifier: 0000-0001-5308-1818
authors.initials: JW
authors.lastname: Becker
authors.affiliation: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Knudsen
authors.affiliation: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.|Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Sallie W
authors.initials: SW
authors.lastname: Chisholm
authors.affiliation: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.|Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Manalis
authors.affiliation: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Martin F
authors.initials: MF
authors.lastname: Polz
mesh_terms: D001419:Bacteria / Q000145:classification*; D018533:Biomass; D020387:Food Chain; D046210:Microfluidic Analytical Techniques; D008954:Models, Biological; D012623:Seawater / Q000382:microbiology; D014871:Water Microbiology