Nutrient-limited Growth Rates Research Articles

Carbon use efficiencies and allocation strategies in Prochlorococcus marinus strain PCC 9511 during nitrogen-limited growth.

We studied cell properties including carbon allocation dynamics in the globally abundant and important cyanobacterium Prochlorococcus marinus strain PCC 9511 grown at three different growth rates in nitrogen-limited continuous cultures. With increasing nitrogen limitation, cellular divinyl chlorophyll a and the functional absorption cross section of Photosystem II decreased, although maximal photosynthetic efficiency of PSII remained unaltered across all N-limited growth rates. Chl-specific gross and net carbon primary production were also invariant with nutrient-limited growth rate, but only 20% of Chl-specific gross carbon primary production was retained in the biomass across all growth rates. In nitrogen-replete cells, 60% of the assimilated carbon was incorporated into the protein pool while only 30% was incorporated into carbohydrates. As N limitation increased, new carbon became evenly distributed between these two pools. While many of these physiological traits are similar to those measured in other algae, there are also distinct differences, particularly the lower overall efficiency of carbon utilization. The latter provides new information needed for understanding and estimating primary production, particularly in the nutrient-limited tropical oceans where P. marinus dominates phytoplankton community composition.

Contrasting strategies of photosynthetic energy utilization drive lifestyle strategies in ecologically important picoeukaryotes.

The efficiency with which absorbed light is converted to net growth is a key property for estimating global carbon production. We previously showed that, despite considerable evolutionary distance, Dunaliella tertiolecta (Chlorophyceae) and Thalassiosira weissflogii (Bacillariophyceae) share a common strategy of photosynthetic energy utilization and nearly identical light energy conversion efficiencies. These findings suggested that a single model might be appropriate for describing relationships between measures of phytoplankton production. This conclusion was further evaluated for Ostreococcus tauri RCC1558 and Micromonas pusilla RCC299 (Chlorophyta, Prasinophyceae), two picoeukaryotes with contrasting geographic distributions and swimming abilities. Nutrient-dependent photosynthetic efficiencies in O. tauri were similar to the previously studied larger algae. Specifically, absorption-normalized gross oxygen and carbon production and net carbon production were independent of nutrient limited growth rate. In contrast, all measures of photosynthetic efficiency were strongly dependent on nutrient availability in M. pusilla. This marked difference was accompanied by a diminished relationship between Chla:C and nutrient limited growth rate and a remarkably greater efficiency of gross-to-net energy conversion than the other organisms studied. These results suggest that the cost-benefit of decoupling pigment concentration from nutrient availability enables motile organisms to rapidly exploit more frequent encounters with micro-scale nutrient patches in open ocean environments.

Comparison of factors limiting bacterial growth in different soils

Lack of carbon has been assumed to be the most common limiting factor for bacterial growth in soil, although there are reports of limitation by other nutrients, e.g. nitrogen and phosphorus. We have studied which nutrient(s) limited instantaneous growth rates of bacteria in 28 Swedish soils using the thymidine or leucine incorporation technique to measure increased growth rate after adding different combinations of organic carbon (glucose), nitrogen and phosphorus. The soils ranged in pH between 3.1 and 8.9, in organic matter content between 1% and 91% and in soil C/N ratio between 10 and 28. We also tested the effect of adding different amounts of carbon on the bacterial change in growth rate for two soils with different organic matter content. We found that bacterial growth in most of the 28 soils was limited by a lack of carbon, indicated by an increased bacterial growth rate 48 h after adding glucose. In some soils, adding carbon together with nitrogen increased the bacterial growth rates even further. In three soils no effects were seen upon adding nutrients separately, but adding carbon and nitrogen together increased bacterial growth rates. Nitrogen addition tended to decrease bacterial growth rates, while phosphorus addition had little effect in most soils. No correlations were found between the soil C/N ratio, ammonium or nitrate content in soil and bacterial growth limitation, indicating that even soils with a C/N ratio of 28 could be carbon limited. Although the interpretation of the effects of a single limiting nutrient was in most cases straightforward, an interaction between the amount of carbon added and the organic matter content of the soil confounded the interpretation of the extent of a second limiting nutrient.

Carbon isotopic fractionation by the marine diatom Phaeodactylum tricornutum under nutrient- and light-limited growth conditions

A theoretical model was developed to explain the characteristics of carbon isotopic fractionation ( ε P) by the marine diatom Phaeodactylum tricornutum under nutrient- and light-limited growth conditions. The model takes into consideration active transport and diffusion of inorganic carbon through the cell membrane and chloroplast membrane and the energetic tradeoff between production of Rubisco and operation of a carbon-concentrating mechanism to achieve a given growth rate. The model is able to explain 88% of the variance in experimental ε p data reported in this study and in previous work and is able to account for the observed pattern of Rubisco activity in nitrate-limited chemostats. Two important implications of the model include the fact that ε p is not a unique function of the ratio of growth rate to external CO 2 concentration (as opposed to the predictions of several previous models) and that changes in light-limited and nutrient-limited growth rates have opposite effects on the fraction of CO 2 taken up by the chloroplast that is lost to diffusion and hence on certain patterns of carbon isotopic fractionation.

Cellular microcystin content in N-limited Microcystis aeruginosa can be predicted from growth rate.

Cell quotas of microcystin (Q(MCYST); femtomoles of MCYST per cell), protein, and chlorophyll a (Chl a), cell dry weight, and cell volume were measured over a range of growth rates in N-limited chemostat cultures of the toxic cyanobacterium Microcystis aeruginosa MASH 01-A19. There was a positive linear relationship between Q(MCYST) and specific growth rate (mu), from which we propose a generalized model that enables Q(MCYST) at any nutrient-limited growth rate to be predicted based on a single batch culture experiment. The model predicts Q(MCYST) from mu, mu(max) (maximum specific growth rate), Q(MCYSTmax) (maximum cell quota), and Q(MCYSTmin) (minimum cell quota). Under the conditions examined in this study, we predict a Q(MCYSTmax) of 0.129 fmol cell(-1) at mu(max) and a Q(MCYSTmin) of 0.050 fmol cell(-1) at mu = 0. Net MCYST production rate (R(MCYST)) asymptotes to zero at mu = 0 and reaches a maximum of 0.155 fmol cell(-1) day(-1) at mu(max). MCYST/dry weight ratio (milligrams per gram [dry weight]) increased linearly with mu, whereas the MCYST/protein ratio reached a maximum at intermediate mu. In contrast, the MCYST/Chl a ratio remained constant. Cell volume correlated negatively with mu, leading to an increase in intracellular MCYST concentration at high mu. Taken together, our results show that fast-growing cells of N-limited M. aeruginosa are smaller, are of lower mass, and have a higher intracellular MCYST quota and concentration than slow-growing cells. The data also highlight the importance of determining cell MCYST quotas, as potentially confusing interpretations can arise from determining MCYST content as a ratio to other cell components.

Nitrogen limitation of North Atlantic phytoplankton: analysis of physiological condition in nutrient enrichment experiments

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 11:53-64 (1996) - doi:10.3354/ame011053 Nitrogen limitation of North Atlantic phytoplankton: analysis of physiological condition in nutrient enrichment experiments Graziano LM, Geider RJ, Li WKW, Olaizola M Nutrient enrichment experiments were conducted in May and June of 1993 at 8 stations along a North Atlantic transect, from Morocco to Nova Scotia, Canada. Variable fluorescence (Fv/Fm) was measured in order to estimate the health or physiological state of the population as a whole. Low values across the transect indicated nutrient limited photosynthetic efficiency and probable growth rates ranging from 10 to about 50% of μmax. Where the lowest value was measured, over the Grand Banks of Newfoundland, Canada, nitrogen addition to incubated samples resulted in large, significant increases in photochemical efficiency. Numbers and cell-specific fluorescence of 3 major groups of picophytoplankton were studied using flow cytometry, in order to further quantify the physiological response to nutrient additions. Results indicated nitrogen limitation of physiology and/or abundance of small eukaryotes, cyanobacteria, and prochlorophytes. Abundance (cell numbers) and cellular fluorescence of the 3 groups responded differently to nutrient additions. Prochlorophytes showed the greatest response to incubation in terms of cell numbers, responding especially to nitrogen addition. By contrast, cyanobacterial numbers did not change from initial values or with treatment, although cell pigment content did. Cellular fluorescence as measured by the flow cytometer reflected cell pigment content in most experiments. Increased cellular fluorescence of all groups in nitrogen-amended treatments relative to unamended controls indicated physiological limitation by nitrogen. Nitrogen limitation · Physiology · Fluorescence Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 11, No. 1. Publication date: August 29, 1996 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 1996 Inter-Research.

Nutrient-limited growth rates: quantitative benefits of stress responses and some aspects of regulation

Young sunflower plants (Helianthus annuus L.) under stress of low nitrate or phosphate availability exhibited increases in root: shoot ratio and in kinetic parameters for uptake. They showed no significant changes in photosynthetic utilization of either nutrient. Increases in root: shoot ratio were achieved by early and persistent suppression of shoot growth, but not root growth. Affinity for phosphate uptake, 1/K m (P), increased with phosphate stress, as did affinity for nitrate uptake, 1/K m (N), with nitrate stress. Maximal uptake rate, V maX , for phosphate uptake increased with phosphorus stress; V maX for nitrate did not increase with nitrogen stress. Phosphate V maX was related strongly to root nutrient status. Decreases in V maX with plant age were not well explained by changes in age structure of roots. Estimated benefits of acclimatory changes in root: shoot ratio and uptake kinetics ranged up to 2-fold increases in relative growth rate, RGR. The relation of RGR to uptake physiology followed predictions of functional balance moderately well, with some systematic deviations. Analyses of RGR using growth models imply no significant growth benefit from regulating V maX , specifically, not from down-regulating it at high nutrient availability. Quantitative benefits of increases in root:shoot ratio and uptake parameters are predicted to be quite small under common conditions wherein nutrient concentrations are significantly depleted by uptake. The root: shoot response is estimated to confer the smallest benefit under non-depleting conditions and the largest benefit under depleting conditions. Even then, the absolute benefit is predicted to be small, possibly excepting the case of heterogeneous soils. Depleting and non-depleting conditions are addressed with very different experimental techniques. We note that a theoretical framework is lacking that spans both these cases, other than purely numerical formulations that are not readily interpreted.

Nutrient-Limited Growth Rates: Roles of Nutrient-Use Efficiency and of Adaptations to Increase Uptake Rate

When stressed by low nutrient availability, young sunflower plants (Helianthus annuus) showed responses seen in many other species: increases in root uptake capacity (V max , I/K m ), root: shoot ratio, and putative nutrient-use efficiency, nUE=1/(tissue nutrient content). A straightforward mechanistic model is derived for relative growth rate (RGR) in solution culture in terms of these factors. A linear regression based on the model indicates a negative role for nUE, which violates a premise of the model

A theoretical and experimental examination of the predictions of two recent models of phytoplankton growth

An analysis of the theoretical models of phytoplankton growth developed independently by Bannister (1979) and Shuter (1979) shows that the models are mathematically identical in their predictions regarding steady-state light limited growth rates, respiration rates and chlorophyll: carbon ratios if one takes n = 1 and m = ∞ in the Bannister model. The chief advantages of the Bannister model are its ability to predict short-term photosynthesis versus light curves, and its adaptability to L : D cycle growth conditions. The latter capability of the model is greatly facilitated if n = 1. The principal advantages of the Shuter model are its ability to describe nutrient-limited steady-state nitrogen: carbon and phosphorus: carbon ratios, and its ability to predict the interactive effects of temperature, light and nutrient limitation on phytoplankton composition. A comparison of the models with nutrient and light limited growth rate and composition data for the marine diatom Thalassiosira weissflogii shows good agreement in all cases except for RNA: C and ATP: C data. The latter two composition ratios do not appear amenable to description by the model. An examination of the Shuter model shows that it predicts a hyperbolic relationship between nitrogen :carbon (or phosphorus: carbon) ratios and nutrient-limited growth rate of exactly the form proposed on empirical grounds by Caperon & Meyer (1972), and that the hyperbolic function reduces to the form earlier proposed by Droop (1968) in the limit of high light intensity. The predicted light and temperature dependences of the parameters in the hyperbola are shown to be in qualitative agreement with recent experimental data.

On the theory of control of microbial growth kinetics by limiting nutrient concentrations

Abstract Some formulations relating nutrient concentration to nutrient transport and to nutrient-limited growth rate are derived. Experimental examples are given in which transport restricts maximal growth rate in some cases and does not affect it in others. It is demonstrated that normal variations in cell yield from substrate consumed at various growth rates can generate curvature in growth kinetic curves unrelated to saturation phenomena. Nutrient uptake and growth rate versus concentration curves are diagrammed for a range of situations, and the kinetic constants for these curves are discussed. The definition of a previously introduced term, the affinity, is sharpened and literature values compiled. It is suggested that this is one of the more useful kinetic constants for describing the kinetics of aquatic microbial processes.

Nitrogen-limited growth of marine phytoplankton—I. changes in population characteristics with steady-state growth rate

Steady-state growth of Coccochloris stagnina, Cyclotella nana, Monochrysis lutheri and Dunaliella tertiolecta in nitrate limiting medium and of Dunaliella and Monochrysis in ammonium limiting medium is examined in continuous culture experiments. Growth rate can not be directly related to observed nutrient concentration in a chemostat environment except perhaps in a long-term average sense. Nitrate-limited growth rate is related to internal nitrogen per unit population by a hyperbolic expression. These results are consistent with an internal reservoir nutritional mechanism. Steady-state ammonium limited growth takes place without evidence of an internal reservoir, and nitrogen per cell remains constant over all growth rates studied. The relative variability of population carbon, nitrogen, chlorophyll- a, cell volume and cell concentration with steady-state growth rate is examined in the context of using these indicators of the physiological state of the population, rather than environmental parameters, to determine steady-state nutrient-limited growth rate.