Immunological and molecular probes to detect phytoplankton responses to environmental stress in nature

McKay, R. Michael L.; Boyd, Philip W.

doi:10.1007/978-94-011-4201-4_13

Cited by 24 publications

(28 citation statements)

References 148 publications

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“…4C and D). These differences are consistent with the understanding that inorganic N sources are preferred by photosynthetic microorganisms, although many of them have the ability to use a variety of organic N sources for growth (4,24,28). In contrast to the gradual N-dependent increase in bioluminescence, GS activities were mostly independent of inorganic N concentrations below 0.1 mM (Fig.…”

Section: Discussionsupporting

confidence: 85%

“…A chemical determination, as precise as it may be, presents only a shortterm profile of ambient N concentrations, without providing It is not surprising, therefore, that there is a constant search for alternative methods to assay N bioavailability as sensed by cells (28). One such approach is the use of enzymes associated with N assimilation, such as nitrate reductase, GS, and glutamate dehydrogenase, as possible indicators of N bioavailability (3).…”

Section: Discussionmentioning

confidence: 99%

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ASynechococcusPglnA::luxABFusion for Estimation of Nitrogen Bioavailability to Freshwater Cyanobacteria

Gillor

Harush

Hadas

et al. 2003

Appl Environ Microbiol

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In contrast to extensive studies of phosphorus, widely considered the main nutrient limiting phytoplankton biomass in freshwater ecosystems, there have been few studies on the role of nitrogen in controlling phytoplankton populations. This situation may be due partly to the complexity in estimating its utilization and bioavailability. In an attempt to provide a novel tool for this purpose, we fused the promoter of the glutamine synthetase-encoding gene, P glnA, from Synechococcus sp. strain PCC7942 to the luxAB luciferase-encoding genes of the bioluminescent bacterium Vibrio harveyi. The resulting construct was introduced into a neutral site on the Synechococcus chromosome to yield the reporter strain GSL. Light emission by this strain was dependent upon ambient nitrogen concentrations. The linear response range of the emitted luminescence was 1 mM to 1 M for the inorganic nitrogen species tested (ammonium, nitrate, and nitrite) and 10-to 50-fold lower for glutamine and urea. When water samples collected from along a depth profile in Lake Kinneret (Israel) were exposed to the reporter strain, the bioluminescence of the reporter strain mirrored the total dissolved nitrogen concentrations determined for the same samples and was shown to be a sensitive indicator of the concentration of bioavailable nitrogen.

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Section: Discussionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 99%

ASynechococcusPglnA::luxABFusion for Estimation of Nitrogen Bioavailability to Freshwater Cyanobacteria

Gillor

Harush

Hadas

et al. 2003

Appl Environ Microbiol

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Section: Centric Diatomsmentioning

confidence: 99%

“…Nonetheless, further studies using, for example, flow cytometric and/or molecular techniques (e.g. Gonzalez-Gil et al 1998, La Roche et al 1999, Scanlan & Wilson 1999) are needed to verify that the nutrient status of GBR phytoplankton grown within diffusion chambers approaches that of GBR phytoplankton growth under (non-contained) natural conditions.This study provides evidence to support the predictions of Raven (1986Raven ( , 1998) that marine picocyanobacteria achieve higher relative and absolute growth rates than nano-/microphytoplankton when DIN concentrations are low (< 0.05 µM). Our results extend previous studies on the growth rates of GBR phytoplankton (Furnas 1989(Furnas , 1991, which found no obvious difference between the relative growth responses (µ /µ max ) of both nano-/microphytoplankton and picocyanobacteria at DIN concentrations down to 0.1 µM.…”

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confidence: 99%

Net growth rates of picocyanobacteria and nano- microphytoplankton inhabiting shelf waters of the central (17S) and southern (20S) Great Barrier Reef

Crosbie¹,

Furnas²

2001

Aquat. Microb. Ecol.

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Growth rates of diffusion cultures of nano-and microphytoplankton from Great Barrier Reef shelf water, especially diatoms (µ max = 3.2 doublings d -1), exceeded those of picocyanobacteria (Prochlorococcus and Synechococcus) when DIN (NH 4 + + NO 2 -+ NO 3 -) concentrations were ≥ 0.05 µM. The picocyanobacteria (µ max = 1.1 and 1.6 doublings d -1 for Prochlorococcus and Synechococcus respectively) achieved higher relative and absolute growth rates when time-averaged DIN concentrations were < 0.05 µM. Most estimates (71%) of in situ growth rates of nano-/microphytoplankton were ≤ 0.25 of µ max when DIN concentrations were < 0.1 µM, while only 18% of in situ picocyanobacteria growth rates were ≤ 0.25 of µ max when DIN concentrations were < 0.1 µM, the majority being ≥ 0.50 of µ max at such DIN concentrations. Thus growth rates of Synechococcus and Prochlorococcus populations did not appear to be significantly nutrient (nitrogen)-limited under ambient concentrations, and were of similar order to those measured in the equatorial Pacific Ocean, where NO 3 -concentrations (> 2 µM) are far above growth-saturating levels, and in the oligotrophic North Pacific Gyre. In contrast, for those nano-/microphytoplankton for which in situ or simulated in situ growth rates were estimated, growth rates appeared to be nitrogen-limited at DIN concentrations < 0.1 µM. The results provide further support for the hypothesis that picocyanobacteria dominate oligotrophic marine water columns because of their superior ability to grow at low nutrient concentrations. KEY WORDS: Synechococcus · Prochlorococcus · Tropical nano-/microphytoplankton · Growth ratesResale or republication not permitted without written consent of the publisher Aquat Microb Ecol 24: 209-224, 2001 levels. As such, phytoplankton growth rates measured under existing conditions can be used to predict changes to phytoplankton standing stocks and primary productivity that might occur following increased nutrient concentrations and other changes to growth conditions. Bulk biochemical measurements provide one estimation of production, but cells, rather than carbon per se, are the major currency of phytoplanktonbased food webs (Banse 1992(Banse , 1994. Additionally, the extrapolation of biochemical measurements to phytoplankton growth rates is notoriously difficult and the resulting estimates can be substantially different from the true in situ growth rates (Furnas 1990).Picocyanobacteria-and diatom-based food chains co-exist in shelf waters of the Great Barrier Reef (GBR), but their relative importance varies in time and space (Furnas & Mitchell 1997). Resident phytoplankton populations have the capacity to develop significant blooms within 1 to 2 d when significant amounts of nutrients, particularly nitrogen, are introduced into shelf waters (Furnas & Mitchell 1997). During the months of monsoonal rainfall (November-April), the GBR shelf system may experience broad-scale, elevated water column nutrient concentrations (more than 10 times greater than 'normal') a...

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“…As pointed out by others (31,41,50), before a gene or protein can be used in field studies, its pattern of expression must be rigorously studied in relation to appropriate environmental factors under controlled laboratory conditions. In this study we focus on the response of ntcA gene expression to ecologically relevant nitrogen conditions, and we develop a protocol for the investigation of the nitrogen status of cyanobacterial field populations using ntcA gene expression.…”

mentioning

confidence: 99%

Ecological Aspects of ntcA Gene Expression and Its Use as an Indicator of the Nitrogen Status of Marine Synechococcus spp

Lindell

Post

2001

Appl Environ Microbiol

106

136

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Nitrogen nutrition in cyanobacteria is regulated by NtcA, a transcriptional activator that is subject to negative control by ammonium. Using Synechococcus sp. strain WH7803 as a model organism, we show that ntcA expression was induced when cells were exposed to nitrogen stress but not when they were subjected to phosphorus or iron deprivation. Transcript levels accumulated in cells grown on a variety of inorganic and organic nitrogen sources, with the sole exception of ammonium. ntcA transcription was induced when ammonium levels dropped below 1 M and reached maximal levels within 2 h. Furthermore, the addition of more than 1 M ammonium led to a rapid decline in ntcA mRNA. The negative effect of ammonium was prevented by the addition of Lmethionine-D,L-sulfoximine (MSX) and azaserine, inhibitors of ammonium assimilation. Thus, basal ntcA transcript levels are indicative of ammonium utilization. Conversely, the highest ntcA transcript levels were found in cells lacking a nitrogen source capable of supporting growth. Therefore, maximal ntcA expression would indicate nitrogen deprivation. This state of nitrogen deprivation was induced by a 1-h incubation with MSX. The rapid response of ntcA gene expression to the addition of ammonium and MSX was used to design a protocol for assessing relative ntcA transcript levels in field populations of cyanobacteria, from which their nitrogen status can be inferred. ntcA was basally expressed in Synechococcus at a nutrient-enriched site at the northern tip of the Gulf of Aqaba, Red Sea. Therefore, these cyanobacteria were not nitrogen stressed, and their nitrogen requirements were met by regenerated nitrogen in the form of ammonium.

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Immunological and molecular probes to detect phytoplankton responses to environmental stress in nature

Cited by 24 publications

References 148 publications

ASynechococcusPglnA::luxABFusion for Estimation of Nitrogen Bioavailability to Freshwater Cyanobacteria

ASynechococcusPglnA::luxABFusion for Estimation of Nitrogen Bioavailability to Freshwater Cyanobacteria

Net growth rates of picocyanobacteria and nano- microphytoplankton inhabiting shelf waters of the central (17S) and southern (20S) Great Barrier Reef

Ecological Aspects of ntcA Gene Expression and Its Use as an Indicator of the Nitrogen Status of Marine Synechococcus spp

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