scholarly journals Effects of an iron-light co-limitation on the elemental composition (Si, C, N) of the marine diatoms <i>Thalassiosira oceanica</i> and <i>Ditylum brightwellii</i>

2009 ◽  
Vol 6 (4) ◽  
pp. 7175-7205 ◽  
Author(s):  
E. Bucciarelli ◽  
P. Pondaven ◽  
G. Sarthou
Keyword(s):  
Growth Rate ◽  
Specific Growth ◽  
Growth Conditions ◽  
Marine Diatom ◽  
Carbon Export ◽  
Relative Variation ◽  
Ditylum Brightwellii ◽  
Interspecific Differences ◽  
Global Trend ◽  
C And N

Abstract. We examined the effect of iron (Fe) and Fe-light (Fe-L) co-limitation on cellular silica (BSi), carbon (C) and nitrogen (N) in two marine diatom species, Thalassiosira oceanica and Ditylum brightwellii. We showed that C and N per cell tend to decrease with increasing Fe and Fe-L co-limitation (i.e. decreasing growth rate). We observed an increase (T. oceanica, Fe-L co-limitation), no change (T. oceanica, Fe limitation) and a decrease (D. brightwellii, Fe and Fe-L limitations) in BSi per cell with increasing degree of limitation. When comparing our results to literature data, we noted that the trend in C and N per cell for other Fe limited diatoms was similar to ours. However there was no global trend in BSi, which suggests interspecific differences. The relative variations in C:N, Si:C and Si:N versus the relative variation in specific growth rate (i.e. μ:μmax) followed the same patterns for both species under Fe and Fe-L co-limitation. The variations of C:N under Fe limitation reported in the literature for other diatoms are contrasted, which may thus be more related to growth conditions than to interspecific differences. Si:C and Si:N ratios increased by more than 2-fold between 100% and 40% of μmax. Under more severe limitation (Fe or Fe-L), these ratios tend to decrease. To asses the field significance of our results, we compared them to those of artificial Fe fertilisation experiments. This comparison showed that Si:N increased between 100% and ~40% of μmax, but decreased between 40% and 20% of μmax, and increased again below 20% of μmax. Between ~15% and 30% of μmax, Si:N was even lower than under non limiting conditions. These results may have important biogeochemical implications on the understanding and the modeling of the oceanic biogeochemical cycles, e.g. carbon export.

scholarly journals Effects of an iron-light co-limitation on the elemental composition (Si, C, N) of the marine diatoms <I>Thalassiosira oceanica</I> and <I>Ditylum brightwellii</I>

2010 ◽  
Vol 7 (2) ◽  
pp. 657-669 ◽  
Author(s):  
E. Bucciarelli ◽  
P. Pondaven ◽  
G. Sarthou
Keyword(s):  
Growth Rate ◽  
Cell Volume ◽  
Growth Conditions ◽  
Marine Diatoms ◽  
Ditylum Brightwellii ◽  
Interspecific Differences ◽  
Coastal Species ◽  
Global Trend ◽  
C And N ◽  
First Time

Abstract. We examined the effect of iron (Fe) and Fe-light (Fe-L) co-limitation on cellular silica (BSi), carbon (C) and nitrogen (N) in two marine diatoms, the small oceanic diatom Thalassiosira oceanica and the large coastal species Ditylum brightwellii. We showed that C and N per cell tend to decrease with increasing Fe limitation (i.e. decreasing growth rate), both under high light (HL) and low light (LL). We observed an increase (T. oceanica, LL), no change (T. oceanica, HL) and a decrease (D. brightwellii, HL and LL) in BSi per cell with increasing degree of limitation. The comparison with literature data showed that the trend in C and N per cell for other Fe limited diatoms was similar to ours. Interspecific differences in C and N quotas of Fe limited diatoms observed in the literature seem thus to be mostly due to variations in cell volume. On the contrary, there was no global trend in BSi per cell or per cell volume, which suggests that other interspecific differences than Fe-induced variations in cell volume influence the degree of silicification. The relative variations in C:N, Si:C and Si:N versus the relative variation in specific growth rate (i.e. μ:μmax) followed the same patterns for T. oceanica and D. brightwellii, whatever the irradiance level. However, the variations of C:N under Fe limitation reported in the literature for other diatoms are contrasted, which may thus be more related to growth conditions than to interspecific differences. As observed in other studies, Si:C and Si:N ratios increased by more than 2-fold between 100% and 40% of μmax. Under more severe limitation (HL and LL), we observed for the first time a decrease in these ratios. These results may have important biogeochemical implications on the understanding and the modelling of the oceanic biogeochemical cycles, e.g. carbon and silica export.

scholarly journals A minimalistic resource allocation model to explain ubiquitous increase in protein expression with growth rate

2015 ◽  
Author(s):  
Uri Barenholz ◽  
Leeat Keren ◽  
Eran Segal ◽  
Ron Milo
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Specific Growth ◽  
Growth Conditions ◽  
Cellular Growth ◽  
Biological Research ◽  
Base Line ◽  
Allocation Model ◽  
Growth Environment ◽  
Active Regulation

Most proteins show changes in level across growth conditions. Many of these changes seem to be coordinated with the specific growth rate rather than the growth environment or the protein function. Although cellular growth rates, gene expression levels and gene regulation have been at the center of biological research for decades, there are only a few models giving a base line prediction of the dependence of the proteome fraction occupied by a gene with the specific growth rate. We present a simple model that predicts a widely coordinated increase in the fraction of many proteins out of the proteome, proportionally with the growth rate. The model reveals how passive redistribution of resources, due to active regulation of only a few proteins, can have proteome wide effects that are quantitatively predictable. Our model provides a potential explanation for why and how such a coordinated response of a large fraction of the proteome to the specific growth rate arises under different environmental conditions. The simplicity of our model can also be useful by serving as a baseline null hypothesis in the search for active regulation. We exemplify the usage of the model by analyzing the relationship between growth rate and proteome composition for the model microorganism E.coli as reflected in two recent proteomics data sets spanning various growth conditions. We find that the fraction out of the proteome of a large number of proteins, and from different cellular processes, increases proportionally with the growth rate. Notably, ribosomal proteins, which have been previously reported to increase in fraction with growth rate, are only a small part of this group of proteins. We suggest that, although the fractions of many proteins change with the growth rate, such changes could be part of a global effect, not requiring specific cellular control mechanisms.

scholarly journals Influence of Carbon Source on Nitrate Removal by Nitrate-TolerantKlebsiella oxytoca CECT 4460 in Batch and Chemostat Cultures

1998 ◽  
Vol 64 (8) ◽  
pp. 2970-2976 ◽  
Author(s):  
Guadalupe Piñar ◽  
Karin Kovárová ◽  
Thomas Egli ◽  
Juan L. Ramos
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Specific Growth ◽  
Nitrate Removal ◽  
Dry Weight ◽  
Specific Rate ◽  
Continuous Cultures ◽  
Batch Cultures ◽  
Chemostat Cultures ◽  
C And N

ABSTRACT The nitrate-tolerant organism Klebsiella oxytoca CECT 4460 tolerates nitrate at concentrations up to 1 M and is used to treat wastewater with high nitrate loads in industrial wastewater treatment plants. We studied the influence of the C source (glycerol or sucrose or both) on the growth rate and the efficiency of nitrate removal under laboratory conditions. With sucrose as the sole C source the maximum specific growth rate was 0.3 h−1, whereas with glycerol it was 0.45 h−1. In batch cultures K. oxytocacells grown on sucrose or glycerol were able to immediately use sucrose as a sole C source, suggesting that sucrose uptake and metabolism were constitutive. In contrast, glycerol uptake occurred preferentially in glycerol-grown cells. Independent of the preculture conditions, when sucrose and glycerol were added simultaneously to batch cultures, the sucrose was used first, and once the supply of sucrose was exhausted, the glycerol was consumed. Utilization of nitrate as an N source occurred without nitrite or ammonium accumulation when glycerol was used, but nitrite accumulated when sucrose was used. In chemostat cultures K. oxytoca CECT 4460 efficiently removed nitrate without accumulation of nitrate or ammonium when sucrose, glycerol, or mixtures of these two C sources were used. The growth yields and the efficiencies of C and N utilization were determined at different growth rates in chemostat cultures. Regardless of the C source, yield carbon (YC) ranged between 1.3 and 1.0 g (dry weight) per g of sucrose C or glycerol C consumed. Regardless of the specific growth rate and the C source, yield nitrogen (YN) ranged from 17.2 to 12.5 g (dry weight) per g of nitrate N consumed. In contrast to batch cultures, in continuous cultures glycerol and sucrose were utilized simultaneously, although the specific rate of sucrose consumption was higher than the specific rate of glycerol consumption. In continuous cultures double-nutrient-limited growth appeared with respect to the C/N ratio of the feed medium and the dilution rate, so that for a C/N ratio between 10 and 30 and a growth rate of 0.1 h−1 the process led to simultaneous and efficient removal of the C and N sources used. At a growth rate of 0.2 h−1the zone of double limitation was between 8 and 11. This suggests that the regimen of double limitation is influenced by the C/N ratio and the growth rate. The results of these experiments were validated by pulse assays.

Oscillating conditions for influencing the composition of mixed biological cultures

1998 ◽  
Vol 37 (4-5) ◽  
pp. 259-262 ◽  
Author(s):  
Bjarne R. Horntvedt ◽  
Morten Rambekk ◽  
Rune Bakke
Keyword(s):  
Growth Rate ◽  
Specific Growth ◽  
Heterotrophic Bacteria ◽  
Bacterial Species ◽  
Rate Reduction ◽  
Similar Strategy ◽  
Sinusoidal Oscillations ◽  
Specific Growth Rates ◽  
Rate Limiting ◽  
Concentration Levels

This paper presents a strategy in which mixed biological cultures are exposed to oscillating concentration levels, to improve the potential for coexistence of desired bacterial species. A mechanistic mathematical model is constructed to investigate and illustrate this strategy. This paper is focused on competition between nitrifying, denitrifying and aerobic heterotrophic bacteria in a CSTR with sludge recycle. For nitrifying and aerobic heterotrophic cultures, the effect of sinusoidal oscillations in DO levels with an amplitude of 1.0 mg/l is a 16% specific growth rate reduction compared to that at a constant DO level. The denitrifiers growth rate is increased by an average of 59%, compared to the constant DO level situation. A similar strategy has been tested in a pilot plant. It is concluded that the influence on specific growth rates is a function of the amplitude of the oscillations. The effects are greatest when concentrations fluctuate around the half saturation concentration of the rate limiting component(s).

scholarly journals Understanding the Interaction Effects between Dietary Lipid Content and Rearing Temperature on Growth Performance, Feed Utilization, and Fat Deposition of Sea Bass (Dicentrarchus labrax)

Animals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 392
Author(s):  
Lydia Katsika ◽  
Mario Huesca Flores ◽  
Yannis Kotzamanis ◽  
Alicia Estevez ◽  
Stavros Chatzifotis
Keyword(s):  
Growth Rate ◽  
Body Weight ◽  
Specific Growth ◽  
Dicentrarchus Labrax ◽  
Sea Bass ◽  
Dietary Lipid ◽  
Lipid Levels ◽  
Final Body Weight ◽  
Temperature Regimes ◽  
Fish Group

This study was conducted to elucidate the interaction effects of temperature and dietary lipid levels (2 × 2 factorial experiment) on the growth performance, muscle, and liver composition in adult farmed European sea bass (Dicentrarchus labrax). Two groups of fish (190 g; 60 fish per group) were distributed in 12 tanks in triplicates and kept at two different temperature regimes; one starting at 23 °C and then changed to 17 °C for 61 days, and the other starting at 17 °C and then changed to 23 °C for 39 days. Two commercial diets containing both ~44% crude protein but incorporating different dietary lipid levels, 16.5% (D16) and 20.0% (D20) (dry matter (DM)), were fed to the fish to apparent satiation; the type of diet fed to each fish group remained constant throughout the experiment. Final body weight, weight gain, and specific growth rate were significantly higher for the fish group held at 23 °C compared to the fish group at 17 °C (before the temperature changes), while the dietary fat content did not have any profound effect in both groups. Furthermore, the different temperature regimes did not affect muscle or liver composition, but, on the contrary, dietary lipids affected hepatosomatic, perivisceral fat, and visceral indexes. Feed conversion ratio and specific growth rate were not affected by the dietary lipid level. An interaction of temperature and dietary lipid content was observed in daily feed consumption (DFC) and final body weight (FBW).

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