Relationships between the cell volume and the carbon content of bacteria

The bacterial biomass is an essential point in microbial ecology. The dry weight and carbon content of microorganisms are traditionally used for the calculation of the fluxes of carbon and energy in aquatic ecosystems. Since direct measurements of these parameters in natural conditions are rather difficult, a certain biomass-carbon converting factor is used, which is determined experimentally or by empirical calculations. However, the relationship between the cell volume and its dry weight (in particular, carbon) does not depend only on the cell size and the conditions of its growth but also on the fixation and staining methods used. We made an attempt to summarize all the present data on the relationships between the cell volume, its dry weight, and the carbon content. Thus, the principal goal of the present study was searching for a generally applicable or methodology-dependent converting factor for the bacterial biomass calculation. Thereto, all the data available were grouped according to the dye used, as well as to the methods of fixation and the dry weight determination. The data on the most frequent combinations of dies and fixatives are insufficient for precise calculations; therefore, we suggest a relationship generalized for different methods of carbon and cell volume recalculations and applicable for bacterial cells larger than 0.025 mu m(3), as fgC cell(-1) = 133.754 x V (0.438).