Uptake of [14C]methylammonium by plankton communities: a comparative assay for ammonium transport systems in natural waters

1979 ◽  
Vol 25 (12) ◽  
pp. 1401-1407 ◽  
Author(s):  
Warwick F. Vincent
Keyword(s):  
Natural Waters ◽  
Competitive Inhibition ◽  
Eutrophic Lake ◽  
Transport Systems ◽  
Ammonium Transport ◽  
Transport Capacity ◽  
Diverse Range ◽  
Freshwater Plankton ◽  
Plankton Communities ◽  
Comparative Measure

A diverse range of freshwater plankton communities were tested for their ability to take up [14C]methylammonium. Uptake occurred at low substrate levels by high-affinity, energy-requiring, transport systems which were competitively inhibited by ammonium but not by L-amino acids or nicotinamide. A simple competitive inhibition model was used to examine the effects of increasing ammonium levels on uptake in a eutrophic lake. Apparent Kt values for the labelled substrate markedly increased with increasing ammonium. The transport systems had an approximately five-fold greater affinity for ammonium than for methylammonium. The Vmax for methylammonium uptake was relatively insensitive to large changes in ambient ammonium levels. This kinetic parameter may be a useful comparative measure of ammonium transport capacity in natural waters, particularly where low ambient ammonium concentrations preclude the use of 15N.

scholarly journals Isolation and Characterization of Two Ammonium Permease Genes, meaA and mepA, from Aspergillus nidulans

2002 ◽  
Vol 1 (1) ◽  
pp. 85-94 ◽  
Author(s):  
Brendon J. Monahan ◽  
James A. Fraser ◽  
Michael J. Hynes ◽  
Meryl A. Davis
Keyword(s):  
Deletion Mutant ◽  
Nitrogen Starvation ◽  
Expression Profiles ◽  
Optimal Growth ◽  
Gene Replacement ◽  
Transport Systems ◽  
Ammonium Transport ◽  
Isolation And Characterization ◽  
Multiple Copies ◽  
Starvation Conditions

ABSTRACT Ammonium and the analogue methylammonium are taken into the cell by active transport systems which constitute a family of transmembrane proteins that have been identified in fungi, bacteria, plants, and animals. Two genes from Aspergillus nidulans, mepA and meaA, which encode ammonium transporters with different affinities have been characterized. The MepA transporter exhibits the highest affinity for methylammonium (K m0, 44.3 μM); in comparison, the K m for MeaA is 3.04 mM. By use of targeted gene replacement strategies, meaA and mepA deletion mutants were created. Deletion of both meaA and mepA resulted in the inability of the strain to grow on ammonium concentrations of less than 10 mM. The single meaA deletion mutant exhibited reduced growth at the same concentrations, whereas the mepA deletion mutant displayed wild-type growth. Interestingly, multiple copies of mepA were found to complement the methylammonium resistance phenotype conferred by the deletion of meaA. The expression profiles for mepA and meaA differed; the mepA transcript was detected only in nitrogen-starved cultures, whereas meaA was expressed under both ammonium-sufficient and nitrogen starvation conditions. Together, these results indicate that MeaA constitutes the major ammonium transport activity and is required for the optimal growth of A. nidulans on ammonium as the sole nitrogen source and that MepA probably functions in scavenging low concentrations of ammonium under nitrogen starvation conditions.

scholarly journals Complex Analyses of Plankton Structure and Function

2001 ◽  
Vol 1 ◽  
pp. 119-132 ◽  
Author(s):  
Karl E. Havens
Keyword(s):  
Size Structure ◽  
Experimental Studies ◽  
Structure And Function ◽  
Size Spectrum ◽  
Phytoplankton Productivity ◽  
Resource Managers ◽  
Carbon Transfer ◽  
And Function ◽  
Freshwater Plankton ◽  
Plankton Communities

This paper critically evaluates some complex methods that have been used to characterize the structure and function of freshwater plankton communities. The focus is on methods related to plankton size structure and carbon transfer. The specific methods reviewed are 1) size spectrum analysis, 2) size-fractionated phytoplankton productivity, 3) size-fractionated zooplankton grazing, 4) plankton ecological transfer efficiency, and 5) grazer effects on phytoplankton community structure. Taken together, these methods can provide information on community ecological properties that are directly related to practical issues including water quality and fisheries productivity. However, caution is warranted since application without a complete understanding of assumptions and context of the manipulations could lead to erroneous conclusions. As an example, experimental studies involving the addition or removal of zooplankton, especially when coupled with nutrient addition treatments, could provide information on the degree of consumer vs. resource control of phytoplankton. Resource managers subsequently could use this information in developing effective measures for controlling nuisance algal biomass. However, the experiments must be done critically and with sufficient safeguards and other measurements to ensure that treatments (e.g., zooplankton exclosure by screening of water) actually are successful and do not introduce other changes in the community (e.g., removal of large algae). In all of the methods described here, the investigator must take care when generalizing results and, in particular, carry out a sufficient number of replications to encompass both the major seasonal and spatial variation that occurs in the ecosystem.

scholarly journals Regulation by light of ammonium transport systems in Chlamydomonas reinhardtii

2010 ◽  
Vol 33 (6) ◽  
pp. 1049-1056 ◽  
Author(s):  
ELENA V. ERMILOVA ◽  
ZHANNETA M. ZALUTSKAYA ◽  
MAXIM M. NIKITIN ◽  
TATYANA V. LAPINA ◽  
EMILIO FERNÁNDEZ
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Transport Systems ◽  
Ammonium Transport

scholarly journals Biomass Distribution in Freshwater Plankton Communities

1995 ◽  
Vol 146 (1) ◽  
pp. 135-152 ◽  
Author(s):  
Paul A. del Giorgio ◽  
Josep M. Gasol
Keyword(s):  
Biomass Distribution ◽  
Freshwater Plankton ◽  
Plankton Communities

scholarly journals Dynamics of biodegradable DOC produced by freshwater plankton communities

2000 ◽  
Vol 23 ◽  
pp. 73-83 ◽  
Author(s):  
M Søndergaard ◽  
NH Borch ◽  
B Riemann
Keyword(s):  
Freshwater Plankton ◽  
Plankton Communities

scholarly journals Ontogenesis of epithelial phosphate transport systems in goats

2003 ◽  
Vol 284 (2) ◽  
pp. R413-R421 ◽  
Author(s):  
Korinna Huber ◽  
Uta Roesler ◽  
Alexandra Muscher ◽  
Kathrin Hansen ◽  
Irkham Widiyono ◽  
...  
Keyword(s):  
Rapid Development ◽  
Membrane Vesicle ◽  
Phosphate Transport ◽  
Transport Systems ◽  
Transport Capacity ◽  
Parotid Glands ◽  
Rumen Microbes ◽  
Age Related ◽  
Small Intestines ◽  
Uptake Studies

The rapid development of precocial goats in the first weeks after birth requires an adequate adaptation of phosphate transport systems to maintain the P homeostasis at each developmental stage. Here we examined the age-related development of Na+-Pitransport systems in small intestines, kidneys, and parotid glands of goats. Kinetic parameters were determined by brush-border membrane vesicle uptake studies, and relative expression of NaPi type II mRNA and protein was recorded by molecular biological methods. High intestinal Pi transport capacity was already present on the first day of life. Within the first 3 wk of life there seemed to be a change in the type of Na+-dependent Pitransporter, and NaPi IIb was expressed increasingly up to the fifth month of life. Renal Na+-Pi transport capacity was also high at birth, and this was associated with high expression levels of NaPi IIa mRNA, indicating the important role of this transporter for renal Pi reabsorption. At weaning an increase in both intestinal and renal Na+-Pitransport balanced the increasing requirements for Pi to establish the endogenous Pi cycle. Salivary Piconcentration and parotid NaPi II mRNA rose markedly to guarantee an adequate Pi supply for rumen microbes. We concluded that the high demand for Pi in young goats was assured by high basal Na+-Pi transport capacity of small intestines and kidney expressed continuously during ontogenesis.

Considerations on transport capacity of natural gas pipelines and its limits

2013 ◽  
Vol 24 (2) ◽  
pp. 67-72 ◽  
Author(s):  
Sorin Neacşu ◽  
Silvian Suditu ◽  
Doru Stoica
Keyword(s):  
Natural Gas ◽  
Transport Systems ◽  
Transport Capacity ◽  
Gas Pipelines ◽  
Natural Gas Pipelines ◽  
Working Parameters

AbstractThe paper deals with the transport capacity of the pipeline and shows its variation in accordance with working parameters. The most drastic limitation occurs when the sonic choke is reached. This should be avoided during the operation of transport systems.

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