Variation of carbon content among bacterial species under starvation condition

To explore the variability of bacterial biomass conversion factors in aquatic environments, 5 manne and 5 non-marine bacterial strains were exposed to nutrient deprivation in artificial seawater and physiological (NaC1, 9 g I-') water, respectively. Carbon content per cell (C,) and per volume (C,) were estimated from total cell number, particulate organic carbon and cell volume (V) measurements after 0. 7, 15 and 28 d of starvation. While Cc appeared to be rather constant (26.02 * 1.08 fg C cell-'; mean k standard error. n = 50) during starvation, C, showed a significant increase. In general, C, increased more rapidly in marine strains than in nonmarine strains. Cc and V were not correlated, but a highly significant relationship between C, and V was found. The non-linear relation was well fitted by a power function model (r2 = 0.847, p < 0.0001). Parameters of the power function adjusted to marine or non-marine strains were not significantly different. We conclude that C, and, to a lesser extent, Cc were dependent on species and physiological status. However, it seems that the differences in C, between marine and non-marine bacteria observed in this study and by others are not the consequence of different relationships between C, and volume, but, more Ilkely, of the low cell volume of marine bacteria and their ability to reduce their water content faster than can non-marine bactena.