Heterotrophy by Plankton in Three Lakes of Different Productivity

Monheimer, Richard H.

doi:10.1038/236463a0

Cited by 9 publications

(4 citation statements)

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“…Previous investigators do suggest that substrates utilizable by heterotrophic algae will be maintained by bacterial uptake at concentrations too low to provide an effective energy source for phytoplankton (e.g., Allen 1969). The only exception appears to be Monheimer ( 1972) , who claimed that phytoplankton may conduct up to 50% of the heterotrophic activity in the dark, based on experiments measuring the uptake of labeled organic sulfur compounds. His logic is incomplete, however, as these compounds might have been added in greater than tracer amounts.…”

Section: Sulfate Uptakementioning

confidence: 99%

“…It may thus be feasible to measure 35 S0 4 uptake by natural populations of chemolithotrophic and chemoorganotrophic bacteria in the dark and obtain a direct, sensitive estimate of net bacterial productivity. Monheimer (1972) was apparently the first to apply this technique in situ in estimating the importance of heterotrophy in several lakes. The present study was undertaken to test the applicability and precision of dark 35 S0 4 uptake as a production measurement for planktonic bacterial communities, and to conduct a lengthy series of in situ production estimates.…”

Section: Introductionmentioning

confidence: 99%

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Dark Sulfate Uptake and Bacterial Productivity in a Subalpine Lake

Jassby¹

1975

Ecology

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Dark uptake of 35SO4 was investigated as a possible method for estimating bacterial production rates in Castle Lake, California. Assuming a fixed cellular sulfur; carbon ratio, bacterial productivities determined in this manner ranged from 2.5 to 28 mg C°m.—3°day—1 in 48 in situ measurements in the summer of 1972. Average production rates increased throughout the sampling period and corresponded in part to increasing levels of dissolved organic carbon. Production rates were stimulated by addition of NH4Cl and vitamin B12 to water samples, but not by thiamine, biotin, SO4, NO3, PO4 or a trace metal mix. Further studies on the sulfur content of bacteria and the role of phytoplankton in SO4 uptake are required before dark 35SO4 uptake is used for routine field measurements.

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Section: Sulfate Uptakementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dark Sulfate Uptake and Bacterial Productivity in a Subalpine Lake

Jassby¹

1975

Ecology

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“…Une autre méthode proposée par MONHEIMER (1972MONHEIMER ( , 1974 consiste à mesurer le taux d'incorporation de 35 S-sulfate dans les protéines ; en connaissant la teneur en soufre des protéines bactériennes, le taux de synthèse protéique peut Être calculé (JORDAN et PETERSON, 1978 ;JORDAN et LIKENS, 1980 ;CUHEL et al, 1981CUHEL et al, , 1982PEDROS-ALIO et BROCK, 1982). Cette méthode soulève un certain nombre de problêmes et d'incertitudes, tels que : la spécificité vis-à-vis des bactéries (la contribution alguale à l'incorporation de sulfate n'est pas négligeable), la difficulté d'évaluer la contribution des composés organiques soufrés aux besoins en soufre des bactéries (ROBERTS et al, 1955), la variabilité du rapport C/S des bactéries (ZOBELL, 1963 ;JORDAN et PETERSON, 1978).…”

Section: -Les Méthodes De Mesure De La Production Bactérienneunclassified

Mesure de la production bactérienne par incorporation de thymidine tritiée

Servais¹

2005

rseau

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Au cours des dix dernières années, de nombreuses méthodes ont été proposées dans la littérature, afin de mesurer l'activité des bactéries hétérotrophes en milieu aquatique. Parmi celles-ci, la mesure de l'incorporation de thymidine tritiée dans le DNA bactérien semble être, à l'heure actuelle, la méthode la plus utilisée. Elle offre, en effet, l'avantage de sa spécificité et d'un protocole expérimental simple. Néanmoins, la conversion des résultats expérimentaux en production de biomasse bactérienne pose un certain nombre de problèmes quant à l'interprétation correcte de cette méthode. Cet article fait le point sur les réponses théoriques et expérimentales qui peuvent être apportées à ces problèmes, ainsi que sur les diverses possibilités d'utilisation de cette méthode.During the fast ten years, numerous methods have been proposed in the literature to mesure the activity of heterotrophic bacteria in aquatic ecosystems. Among these methods, the measurement of tritiated thymidine incorporation proposed by FUHRMAN and AZAM (1980) seems to be, at the present time, the most useful. It offers in fact the advantage of its specificity for bacteria and its simple experimental procedure.This method is based on the fact that, in bacteria, DNA synthesis is directly proportional to the division rate. The close relation between growth and DNA synthesis means that measurement of the rate of DNA synthesis is a good way to measure the bacterial growth rate. The DNA synthesis rate is estimated from the incorporation rate of methyl-3H thymidine. Thymidine is one of the four nucleoside precursors of DNA, but it is not a precursor of RNA. At the nanomolar concentrations of (methyl-3H) thymidine used in this experiment only heterotrophic bacteria utilize exogenous thymidine and all active heterotrophic bacteria utilize thymidine. The usual experimental procedure used by the various authors working with this method is that of the FUHRMAN and AZAM (1982). A 5 nM thymidine concentration has been recommended by these authors for the marine environment, but it has been shown that in more eutrophic ecosystems higher concentrations are needed to saturate the incorporation process.In fact, the conversion of experimental data into bacterial production raises some problems. Among these, two questions are important :- Which is the relative part of exogenous and endogenous thymidine used for DNA synthesis? In other words, which is the isotopic dilution factor?- The cold trichloroacetic acid (TCA) fraction collected in this experiment includes, besides DNA, proteins and RNA. As some catabolic products of thymidine could be incorporated into RNA or proteins, how mach radioactivity is really incorporated into DNA?Some theoretical and experimental answers can be given to these questions.- Comparing their results of thymidine and H32PO4= incorporation in DNA of marine bacteria, FUHRMAN and AZAM (1982) found an isotopic dilution factor in the 3-7 range. MORIARTY and POLLARD (1981) have proposed a kinetic approach for estimating the internal pool of thy...

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“…Bacteria are suspected, at least in Gnotuk because of the presence from time to time of bacterial-eating ciliates in the plankton and the high levels of bacteriochlorophyll (values 3.45 greater than those for chlorophyll-a) (Hussainy, 1972). However high algal heterotrophy (Monheimer, 1972) and dark carboxylation (Fogg, 1969) could be contributing in all three lakes. Total yearly 'dark' production (expressed as gC/ m 2 ) was 4.0 in Purrumbete, 24.8 in Bullenmerri and 22.2 in Gnotuk.…”

Section: 'Dark' Carbon Assimilationmentioning

confidence: 99%