Assessment of DMSP turnover reveals a non-bioavailable pool of dissolved DMSP in coastal waters of the Gulf of Mexico

2016 ◽  
Vol 13 (2) ◽  
pp. 266 ◽  
Author(s):  
Chengxuan Li ◽  
Gui-Peng Yang ◽  
David J. Kieber ◽  
Jessie Motard-Côté ◽  
Ronald P. Kiene
Keyword(s):  
Coastal Waters ◽  
Loss Rate ◽  
Small Volume ◽  
Accurate Determination ◽  
Tracer Technique ◽  
Marine Microbes ◽  
Tracer Method ◽  
Consumption Rates ◽  
Inhibitor Method

Environmental context DMSP is one of the most important substrates for marine bacteria and its cycling contributes substantially to fluxes of carbon and sulfur in the ocean. Accurate determination of the concentration of DMSP available to bacteria is essential to quantifying DMSP consumption rates, and this work improves those determinations by identifying non-bioavailable pools of DMSP that have previously gone unrecognised. Improved estimates of DMSP consumption rates will lead to better understanding of its role in ocean food web and biogeochemical dynamics. Abstract Dissolved dimethylsulfoniopropionate (DMSPd) is an important substrate for marine microbes and a precursor of sulfur gases. We compared DMSPd turnover flux rates in coastal seawater measured with a 35S-DMSPd tracer to those obtained with the DMSP-uptake inhibitor glycine betaine (GBT). The 35S-DMSP tracer method yielded DMSPd turnover fluxes (35.7–215nM day–1) that were 1.7 to 152 times higher than those obtained in parallel samples with the GBT inhibitor method (0.34–21.6nM day–1). Tests confirmed that GBT functioned as planned by strongly inhibiting DMSPd degradation and that 35S-DMSPd gave accurate estimates of DMSPd loss rate constants. This left the initial DMSPd concentrations, determined by small volume drip filtration (SVDF) through Whatman GF/F filters (0.7-μm nominal retention) ([DMSPd]SVDF), as a potential cause of the discrepancy in rate estimates. Indeed, GF/F filtrate incubations showed that the initial [DMSPd]SVDF overestimated the bioavailable DMSPd concentrations for at least two reasons: (1) a significant fraction (10–37%) of DMSP passing through GF/F filters was in particles >0.2μm (likely bacteria) and therefore not dissolved, and (2) a significant pool (0.44–1.0nM) of operationally dissolved, non-particle DMSP ([DMSPd]<0.2μm), comprising 40–99% of [DMSPd]SVDF, was refractory to degradation on a time scale of days. The nature of this refractory DMSP is currently unknown. Accounting for DMSP-containing particles and the refractory DMSP pool in GF/F filtrates is necessary to obtain the true bioavailable DMSPd concentrations, which we estimate to be very low (0.006–1.0nM; mean of 0.41nM) in the coastal waters examined, and to avoid overestimation of DMSPd turnover fluxes when using the 35S-DMSP tracer technique.

Isotopic non-stationary 13C gluconate tracer method for accurate determination of the pentose phosphate pathway split-ratio in Penicillium chrysogenum

2008 ◽  
Vol 10 (3-4) ◽  
pp. 178-186 ◽  
Author(s):  
Zheng Zhao ◽  
Karel Kuijvenhoven ◽  
Cor Ras ◽  
Walter M. van Gulik ◽  
Joseph J. Heijnen ◽  
...  
Keyword(s):  
Pentose Phosphate Pathway ◽  
Penicillium Chrysogenum ◽  
Accurate Determination ◽  
Pentose Phosphate ◽  
Tracer Method ◽  
Split Ratio

scholarly journals A modified sulphur hexafluoride tracer technique enables accurate determination of enteric methane emissions from ruminants

2014 ◽  
Vol 197 ◽  
pp. 47-63 ◽  
Author(s):  
Matthew H. Deighton ◽  
S. Richard O. Williams ◽  
Murray C. Hannah ◽  
Richard J. Eckard ◽  
Tommy M. Boland ◽  
...  
Keyword(s):  
Accurate Determination ◽  
Methane Emissions ◽  
Tracer Technique ◽  
Sulphur Hexafluoride ◽  
Enteric Methane ◽  
Enteric Methane Emissions

Dependence of microalgae culture specific endogenous loss rate and gross productivity on irradiance

2020 ◽  
pp. 8-16
Author(s):  
Anna L. Avsiyan ◽  
Alexander S. Lelekov
Keyword(s):  
Loss Rate ◽  
Accurate Determination ◽  
Arthrospira Platensis ◽  
Maintenance Respiration ◽  
Specific Loss ◽  
Microalgae Culture ◽  
Biomass Loss ◽  
Density Dynamics ◽  
The Difference

Microalgal growth rate is determined by the difference between gross productivity and endogenous biomass loss rate. Gross productivity is a function of surface irradiance and reaches the maximal value under saturating light intensity. Endogenous biomass consumption of microalgal cells is mainly due to the respiration which can be sub-divided into growth and maintenance respiration. The paper proposes equations for calculating microalgae culture gross productivity and specific loss rate based on production characteristics. Verification of the obtained equations was performed for Arthrospira platensis and Dunaliella salina cultivated under constant illumination with different irradiance. It was demonstrated that gross productivity and specific loss rate increase linearly with increasing irradiance. Specific loss rate varied from 0,01 to 0,58 h-1 in A. platensis and from 0,04 to 0,35 day-1 in D. salina. Specific maintenance respiration rate was determined to be 0,01 h-1 in A. platensis and 0,01–0,04 day-1 in D. salina. The proposed calculation method enables a sufficiently accurate determination of productivity and loss rates based on culture density dynamics measures.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

Fast calibration of CBED patterns for quantitative analysis

1993 ◽  
Vol 51 ◽  
pp. 674-675
Author(s):  
M.A. Gribelyuk ◽  
M. Rühle
Keyword(s):  
Reciprocal Lattice ◽  
Accurate Determination ◽  
Incident Beam ◽  
Crystal Thickness ◽  
Structure Model ◽  
Beam Direction ◽  
Transmitted Beam ◽  
Reciprocal Vector ◽  
On Line

A new method is suggested for the accurate determination of the incident beam direction K, crystal thickness t and the coordinates of the basic reciprocal lattice vectors V1 and V2 (Fig. 1) of the ZOLZ plans in pixels of the digitized 2-D CBED pattern. For a given structure model and some estimated values Vest and Kest of some point O in the CBED pattern a set of line scans AkBk is chosen so that all the scans are located within CBED disks.The points on line scans AkBk are conjugate to those on A0B0 since they are shifted by the reciprocal vector gk with respect to each other. As many conjugate scans are considered as CBED disks fall into the energy filtered region of the experimental pattern. Electron intensities of the transmitted beam I0 and diffracted beams Igk for all points on conjugate scans are found as a function of crystal thickness t on the basis of the full dynamical calculation.

Computer-Assisted High-Re Solution TEM

1990 ◽  
Vol 48 (1) ◽  
pp. 162-163
Author(s):  
F.A. Ponce ◽  
H. Hikashi
Keyword(s):  
Signal To Noise Ratio ◽  
Accurate Determination ◽  
Computer Software ◽  
Video Camera ◽  
Image Contrast ◽  
Objective Lens ◽  
Computer Assisted ◽  
Optical Parameters ◽  
Astigmatism Correction

The determination of the atomic positions from HRTEM micrographs is only possible if the optical parameters are known to a certain accuracy, and reliable through-focus series are available to match the experimental images with calculated images of possible atomic models. The main limitation in interpreting images at the atomic level is the knowledge of the optical parameters such as beam alignment, astigmatism correction and defocus value. Under ordinary conditions, the uncertainty in these values is sufficiently large to prevent the accurate determination of the atomic positions. Therefore, in order to achieve the resolution power of the microscope (under 0.2nm) it is necessary to take extraordinary measures. The use of on line computers has been proposed [e.g.: 2-5] and used with certain amount of success.We have built a system that can perform operations in the range of one frame stored and analyzed per second. A schematic diagram of the system is shown in figure 1. A JEOL 4000EX microscope equipped with an external computer interface is directly linked to a SUN-3 computer. All electrical parameters in the microscope can be changed via this interface by the use of a set of commands. The image is received from a video camera. A commercial image processor improves the signal-to-noise ratio by recursively averaging with a time constant, usually set at 0.25 sec. The computer software is based on a multi-window system and is entirely mouse-driven. All operations can be performed by clicking the mouse on the appropiate windows and buttons. This capability leads to extreme friendliness, ease of operation, and high operator speeds. Image analysis can be done in various ways. Here, we have measured the image contrast and used it to optimize certain parameters. The system is designed to have instant access to: (a) x- and y- alignment coils, (b) x- and y- astigmatism correction coils, and (c) objective lens current. The algorithm is shown in figure 2. Figure 3 shows an example taken from a thin CdTe crystal. The image contrast is displayed for changing objective lens current (defocus value). The display is calibrated in angstroms. Images are stored on the disk and are accessible by clicking the data points in the graph. Some of the frame-store images are displayed in Fig. 4.

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