Are bacteria more like plants or animals? Growth rate and resource dependence of bacterial C : N : P stoichiometry

Abstract

Summary 1.We examined the relative importance of resource composition (carbon : phosphorus molar ratios which varied between 9 and 933) and growth rate (0·5-1·5 h − 1 ) to biomass carbon : nitrogen : phosphorus stoichiometry and nucleic acid content in Escherichia coli grown in chemostats, and in other heterotrophic prokaryotes using published literature. 2. Escherichia coli RNA content and the contribution of RNA-P to total cellular P increased with increasing growth rate at all supply C : P ratios. Growth rate had a much stronger effect on biomass C : P than did supply C : P, and increased RNA content resulted in low biomass C : P and N : P ratios. 3. However, we observed only twofold variations in biomass C : P and N : P ratios in the experiments, despite a difference of two orders of magnitude in C : P and N : P supply. The response of biomass C : P and N : P ratios to alteration of the supply C : P and N : P ratios revealed that E. coli was strongly homeostatic in its elemental composition. 4. This result, and a literature survey, suggest that each heterotrophic bacterial strain regulates its elemental composition homeostatically within a relatively narrow range of characteristic biomass C : P and N : P ratios. 5. Thus shifts in the dominance of different bacterial strains in the environment are probably responsible for the large variation in bacterial biomass C : P, as has been suggested for crustacean zooplankton. These findings indicate that bacteria are more like animals than plants in terms of biomass C : P and N : P homeostasis.

Biological stoichiometry of Daphnia growth: An ecophysiological test of the growth rate hypothesis

“…4C, p Ͻ 0.05, R and P contents with growth rate in the N-limited experiment should be interpreted cautiously, since our N-limited growth conditions did not induce a very wide range of growth rates in the animals, especially when compared to the P-limited case. Our data on Daphnia in the N-limited experiment have been placed in a broader context in the analyses of , who noted a decoupling of growth, RNA, and P contents in other biota under certain conditions: in bacteria when substrate C : P ratios are low (Makino et al 2003), under very low food conditions in Daphnia (Sterner unpubl. data), as well as in cyanobacteria and eukaryotic algae (Rhee 1978;Healey 1985).…”

Coupling of growth rate and body stoichiometry in Daphnia: a role for maintenance processes?

“…Indeed, strong couplings between l, RNA and P have been documented in various daphnids (DeMott et al, 1998;Vrede, Andersen & Hessen, 1999;Acharya, Kyle & Elser, 2004), the bacterium Escherichia coli (Makino et al, 2003), cyanobacteria (Lepp & Schmidt, 1998), yeast (Aiking & Tempest, 1976), algae (Rhee, 1978) and other biota . While there are consistent general patterns within species and groups of species, considerable variation in the relationships of RNA and P contents with growth does exist among taxa.…”

Aquatic heterotrophic bacteria have highly flexible phosphorus content and biomass stoichiometry

“…Past work has shown that heterotrophic bacteria, a group of organisms that process terrestrial inputs of organic carbon, nitrogen (N) and phosphorus (P) , are C-poor and P-rich (Makino et al, 2003) relative to terrestrial inputs characterized by high C:P ratios. As a result, bacterial assemblages in freshwater ecosystems should experience elemental imbalance and act as efficient exporters of organic carbon to downstream ecosystems.…”

“…The range of P content measured in the assemblage cultures was nearly equal to the range of existing data in the literature, particularly for P relative to dry mass (Supplementary Table 6). Single-cell measurements from plankton environments indicated the potential for even lower phosphorus quotas (Norland et al, 1995;Cotner et al, 2010), although many of those cells may not be actively growing, potentially decreasing their demand for P-rich RNA, where much of the P resides in bacterial cells (Makino et al, 2003). The P relative to dry mass values measured here were lower than those reported for a bacterium grown in the absence of added phosphate and high concentrations of arsenate (0.012% of dry mass as P, Wolfe-Simon et al, 2010).…”