Leucine Incorporation as a Measure of Biomass Production by Heterotrophic Bacteria

2018 ◽  
pp. 509-512 ◽  
Author(s):  
David L. Kirchman
Keyword(s):  
Biomass Production ◽  
Heterotrophic Bacteria ◽  
Leucine Incorporation

scholarly journals Empirical Leucine-to-Carbon Conversion Factors for Estimating Heterotrophic Bacterial Production: Seasonality and Predictability in a Temperate Coastal Ecosystem

2009 ◽  
Vol 75 (10) ◽  
pp. 3216-3221 ◽  
Author(s):  
Alejandra Calvo-D�az ◽  
Xos� Anxelu G. Mor�n
Keyword(s):  
Protein Synthesis ◽  
Bacterial Production ◽  
Heterotrophic Bacteria ◽  
Spatiotemporal Variability ◽  
Leucine Incorporation ◽  
Carbon Conversion ◽  
Conversion Factors ◽  
Production Studies ◽  
Favorable Conditions

ABSTRACT Leucine-to-carbon conversion factors (CFs) are needed for converting substrate incorporation into biomass production of heterotrophic bacteria. During 2006 we performed 20 dilution experiments for determining the spatiotemporal variability of empirical CFs in temperate Atlantic coastal waters. Values (0.49 to 1.92 kg C mol Leu−1) showed maxima in autumn to early winter and minima in summer. Spatially averaged CFs were significantly negatively correlated with in situ leucine incorporation rates (r = −0.91) and positively correlated with phosphate concentrations (r = 0.76). These relationships, together with a strong positive covariation between cell-specific leucine incorporation rates and carbon contents (r = 0.85), were interpreted as a strategy to maximize survival through protein synthesis and low growth rates under nutrient limitation (low CFs) until favorable conditions stimulate cell division relative to protein synthesis (high CFs). A multiple regression with in situ leucine incorporation rates and cellular carbon contents explained 96% of CF variance in our ecosystem, suggesting their potential prediction from more easily measurable routine variables. The use of the theoretical CF of 1.55 kg C mol Leu−1 would have resulted in a serious overestimation (73%) of annual bacterial production rates. Our results emphasize the need for considering the temporal scale in CFs for bacterial production studies.

scholarly journals Biomass Production and Assimilation of Dissolved Organic Matter by SAR11 Bacteria in the Northwest Atlantic Ocean

2005 ◽  
Vol 71 (6) ◽  
pp. 2979-2986 ◽  
Author(s):  
Rex R. Malmstrom ◽  
Matthew T. Cottrell ◽  
Hila Elifantz ◽  
David L. Kirchman
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Atlantic Ocean ◽  
Dissolved Organic Matter ◽  
Biomass Production ◽  
Growth Rates ◽  
Bacterial Biomass ◽  
Leucine Incorporation ◽  
Northwest Atlantic ◽  
Specific Growth Rates

ABSTRACT Members of the SAR11 clade often dominate the composition of marine microbial communities, yet their contribution to biomass production and the flux of dissolved organic matter (DOM) is unclear. In addition, little is known about the specific components of the DOM pool utilized by SAR11 bacteria. To better understand the role of SAR11 bacteria in the flux of DOM, we examined the assimilation of leucine (a measure of biomass production), as well as free amino acids, protein, and glucose, by SAR11 bacteria in the Northwest Atlantic Ocean. We found that when SAR11 bacteria were >25% of total prokaryotes, they accounted for about 30 to 50% of leucine incorporation, suggesting that SAR11 bacteria were major contributors to bacterial biomass production and the DOM flux. Specific growth rates of SAR11 bacteria either equaled or exceeded growth rates for the total prokaryotic community. In addition, SAR11 bacteria were typically responsible for a greater portion of amino acid assimilation (34 to 61%) and glucose assimilation (45 to 57%) than of protein assimilation (≤34%). These data suggest that SAR11 bacteria do not utilize various components of the DOM pool equally and may be more important to the flux of low-molecular-weight monomers than to that of high-molecular-weight polymers.

Substrate characteristic bacterial fatty acid production based on amino acid assimilation and transformation in marine sediments

2019 ◽  
Vol 95 (10) ◽  
Author(s):  
Rebecca F Aepfler ◽  
Solveig I Bühring ◽  
Marcus Elvert
Keyword(s):  
Marine Sediments ◽  
Stable Carbon Isotopes ◽  
Heterotrophic Bacteria ◽  
Dissolved Inorganic Carbon ◽  
Carbon Sources ◽  
Leucine Incorporation ◽  
Fatty Acid Production ◽  
Coastal Marine ◽  
Multiple Species ◽  
Precursor Molecules

ABSTRACT Polar lipid-derived fatty acids (PLFAs) and their stable carbon isotopes are frequently combined to characterize microbial populations involved in the degradation of organic matter, offering a link to biogeochemical processes and carbon sources used. However, PLFA patterns derive from multiple species and may be influenced by substrate types. Here, we investigated such dependencies by monitoring the transformation of position-specifically 13C-labeled amino acids (AAs) in coastal marine sediments dominated by heterotrophic bacteria. Alanine was assimilated into straight-chain FAs, while valine and leucine incorporation led to the characteristic production of even- and odd-numbered iso-series FAs. This suggests that identical microbial communities adjust lipid biosynthesis according to substrate availability. Transformation into precursor molecules for FA biosynthesis was manifested in increased 13C recoveries of the corresponding volatiles acetate, isobutyrate and isovalerate of up to 39.1%, much higher than for PLFAs (<0.9%). A significant fraction of 13C was found in dissolved inorganic carbon (up to 37.9%), while less was recovered in total organic carbon (up to 17.3%). We observed a clear discrimination against the carboxyl C, whereby C2 and C3 positions were preferentially incorporated into PLFAs. Therefore, position-specific labeling is an appropriate tool for reconstructing the metabolic fate of protein-derived AAs in marine environments.

scholarly journals Contrasting effects of ocean acidification on the microbial food web under different trophic conditions

2015 ◽  
Vol 73 (3) ◽  
pp. 670-679 ◽  
Author(s):  
M. M. Sala ◽  
F. L. Aparicio ◽  
V. Balagué ◽  
J. A. Boras ◽  
E. Borrull ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Microbial Communities ◽  
Heterotrophic Bacteria ◽  
Phytoplankton Bloom ◽  
Extracellular Enzyme ◽  
Nutrient Concentrations ◽  
Leucine Incorporation ◽  
Negative Effects ◽  
Trophic Conditions ◽  
Positive Effects

AbstractWe investigated the effects of an increase in dissolved CO2 on the microbial communities of the Mediterranean Sea during two mesocosm experiments in two contrasting seasons: winter, at the peak of the annual phytoplankton bloom, and summer, under low nutrient conditions. The experiments included treatments with acidification and nutrient addition, and combinations of the two. We followed the effects of ocean acidification (OA) on the abundance of the main groups of microorganisms (diatoms, dinoflagellates, nanoeukaryotes, picoeukaryotes, cyanobacteria, and heterotrophic bacteria) and on bacterial activity, leucine incorporation, and extracellular enzyme activity. Our results showed a clear stimulation effect of OA on the abundance of small phytoplankton (pico- and nanoeukaryotes), independently of the season and nutrient availability. A large number of the measured variables showed significant positive effects of acidification in summer compared with winter, when the effects were sometimes negative. Effects of OA were more conspicuous when nutrient concentrations were low. Our results therefore suggest that microbial communities in oligotrophic waters are considerably affected by OA, whereas microbes in more productive waters are less affected. The overall enhancing effect of acidification on eukaryotic pico- and nanophytoplankton, in comparison with the non-significant or even negative response to nutrient-rich conditions of larger groups and autotrophic prokaryotes, suggests a shift towards medium-sized producers in a future acidified ocean.

scholarly journals Fine scale variability in methanol uptake and oxidation in the micro-layer and near-surface waters of the Atlantic

2012 ◽  
Vol 9 (4) ◽  
pp. 4513-4542
Author(s):  
J. L. Dixon ◽  
P. D. Nightingale
Keyword(s):  
Methanol Oxidation ◽  
Surface Waters ◽  
Significant Relationship ◽  
Heterotrophic Bacteria ◽  
Energy Generation ◽  
Cellular Growth ◽  
Leucine Incorporation ◽  
Marine Microbes ◽  
Near Surface ◽  
Uptake Rates

Abstract. The aim of this research was to make the first depth profiles of the microbial assimilation of methanol carbon, and its oxidation to carbon dioxide and use as an energy source from the micro-layer to 1000 m. Some of the highest reported methanol oxidation rate constants of 0.5–0.6 d−1 were occasionally found in the micro-layer, and immediately underlying waters (10 cm depth), albeit these samples also showed the greatest heterogeneity compared to other depths down to 1000 m. Methanol uptake into the particulate phase was exceptionally low in micro-layer samples, suggesting that any methanol utilised by microbes in this environment is for energy generation. The sea surface micro-layer and 10 cm depth also showed a higher proportion of bacteria with a low DNA content, and bacterial leucine uptake rates in surface micro-layer samples were either less than, or the same as those in the underlying 10 cm layer. The average methanol oxidation and particulate rates were however statistically the same throughout the depths sampled, although the later were highly variable in the near surface 0.25–2 m compared to deeper depths. The statistically significant relationship demonstrated between uptake of methanol into particles and bacterial leucine incorporation suggests that heterotrophic bacteria use methanol carbon for cellular growth, but the lack of relationships observed with methanol oxidation, perhaps suggest that a wider group of marine microbes use methanol for energy generation. Whilst the statistically significant relationship observed between the uptake of methanol into cell particles and the numbers of Prochlorococcus during diel experiments could also suggest that this abundant group of marine cyanobacteria are capable of mixotrophy, using methanol as a carbon source for growth. We conclude that microbial methanol uptake rates, i.e., loss from seawater are highly variable, particularly close to the seawater surface, which could significantly impact upon seawater concentrations and hence the air-sea flux.

scholarly journals Factors limiting heterotrophic bacterial production in the southern Pacific Ocean

2008 ◽  
Vol 5 (3) ◽  
pp. 833-845 ◽  
Author(s):  
F. Van Wambeke ◽  
S. Bonnet ◽  
T. Moutin ◽  
P. Raimbault ◽  
G. Alarcón ◽  
...  
Keyword(s):  
Bacterial Production ◽  
Heterotrophic Bacteria ◽  
Leucine Incorporation ◽  
Limiting Factor ◽  
Labile Carbon ◽  
Longitudinal Gradients ◽  
Eastern Border ◽  
Potential Factors ◽  
Seawater Samples ◽  
Enrichment Experiments

Abstract. The role of potential factors limiting bacterial growth was investigated along vertical and longitudinal gradients across the South Eastern Pacific Gyre. The effects of glucose, nitrate, ammonium and phosphate additions on heterotrophic bacterial production (using leucine technique) were studied in parallel in unfiltered seawater samples incubated under natural daily irradiance. The enrichments realized on the subsurface showed three types of responses. From 141° W (Marquesas plateau) to approx 125° W, bacteria were not bottom-up controlled, as confirmed by the huge potential of growth in non-enriched seawater (median of enhancement factor×39 in 24 h). Within the Gyre (125° W–95° W), nitrogen alone stimulated leucine incorporation rates (median×4.2), but rapidly labile carbon (glucose) became a second limiting factor (median×37) when the two elements were added. Finally from the border of the gyre to the Chilean upwelling (95° W–73° W), labile carbon was the only factor stimulating heterotrophic bacterial production. Interaction between phytoplankton and heterotrophic bacterial communities and the direct versus indirect effect of iron and macronutrients on bacterial production were also investigated in four selected sites: two sites on the vicinity of the Marquesas plateau, the centre of the gyre and the Eastern border of the gyre. Both phytoplankton and heterotrophic bacteria were limited by availability of nitrogen within the gyre, but not by iron. Iron limited phytoplankton at Marquesas plateau and at the eastern border of the gyre. However 48 h enrichment experiments were not sufficient to show any clear limitation of heterotrophic bacteria within Marquesas plateau and showed a limitation of these organisms by labile carbon in the eastern border of the Gyre.

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