DEVELOPMENT OF IMMUNOASSAYS FOR THE IRON‐REGULATED PROTEINS FERREDOXIN AND FLAVODOXIN IN POLAR MICROALGAE<sup>1</sup>

Pankowski, Andrew; McMinn, Andrew

doi:10.1111/j.1529-8817.2009.00687.x

Cited by 21 publications

(18 citation statements)

References 46 publications

(120 reference statements)

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“…Multiple diatom ISIP2A and flavodoxin encoding ORFs were not repressed 24 h after iron addition. These ORFs may have been repressed by iron addition on a different timescale, or it may be that some Antarctic diatoms constitutively express these genes, as observed previously for flavodoxin (24). Nitrate uptake rates were elevated after iron addition, in line with observed up-regulation of diatom Fig.…”

Section: Resultssupporting

confidence: 79%

Phytoplankton–bacterial interactions mediate micronutrient colimitation at the coastal Antarctic sea ice edge

Bertrand

McCrow

Moustafa

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

220

247

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Southern Ocean primary productivity plays a key role in global ocean biogeochemistry and climate. At the Southern Ocean sea ice edge in coastal McMurdo Sound, we observed simultaneous cobalamin and iron limitation of surface water phytoplankton communities in late Austral summer. Cobalamin is produced only by bacteria and archaea, suggesting phytoplankton-bacterial interactions must play a role in this limitation. To characterize these interactions and investigate the molecular basis of multiple nutrient limitation, we examined transitions in global gene expression over short time scales, induced by shifts in micronutrient availability. Diatoms, the dominant primary producers, exhibited transcriptional patterns indicative of co-occurring iron and cobalamin deprivation. The major contributor to cobalamin biosynthesis gene expression was a gammaproteobacterial population, Oceanospirillaceae ASP10-02a. This group also contributed significantly to metagenomic cobalamin biosynthesis gene abundance throughout Southern Ocean surface waters. Oceanospirillaceae ASP10-02a displayed elevated expression of organic matter acquisition and cell surface attachment-related genes, consistent with a mutualistic relationship in which they are dependent on phytoplankton growth to fuel cobalamin production. Separate bacterial groups, including Methylophaga, appeared to rely on phytoplankton for carbon and energy sources, but displayed gene expression patterns consistent with iron and cobalamin deprivation. This suggests they also compete with phytoplankton and are important cobalamin consumers. Expression patterns of siderophore-related genes offer evidence for bacterial influences on iron availability as well. The nature and degree of this episodic colimitation appear to be mediated by a series of phytoplankton-bacterial interactions in both positive and negative feedback loops.colimitation | Southern Ocean primary productivity | metatranscriptomics | phytoplankton-bacterial interactions | cobalamin P rimary productivity and community composition in the Southern Ocean play key roles in global change (1, 2). The coastal Southern Ocean, particularly its shelf and marginal ice zones, is highly productive, with mean rates approaching 300-450 mg C m −2 ·d −1 (3). As such, identifying factors controlling phytoplankton growth in these regions is essential for understanding the ocean's role in past, present, and future biogeochemical cycles. Although irradiance, temperature, and iron availability are often considered to be the primary drivers of Southern Ocean productivity (1, 4), cobalamin (vitamin B 12 ) availability has also been shown to play a role (5, 6). Cobalamin is produced only by select bacteria and archaea and is required by most eukaryotic phytoplankton, as well as many bacteria that do not produce the vitamin (7). Cobalamin is used for a range of functions, including methionine biosynthesis and one-carbon metabolism. Importantly, phytoplankton that are able to grow without cobalamin preferentially use it when available; growth...

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Section: Resultssupporting

confidence: 79%

Phytoplankton–bacterial interactions mediate micronutrient colimitation at the coastal Antarctic sea ice edge

Bertrand

McCrow

Moustafa

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

220

247

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“…The maximum growth rate of Fragilariopsis cylindrus (0.57 d -1 ) in trace-metal-buffered media was similar to that observed by Fiala & Oriol (1990) under equivalent light and temperature conditions in f medium, and identical to the rate observed in f /2 medium for this strain (Pankowski & McMinn 2009). Growth of F. curta in this medium was 75% of that observed for this strain in f /2 medium under similar light intensity (Pankowski & McMinn 2009).…”

Section: Growthsupporting

confidence: 80%

“…Growth of F. curta in this medium was 75% of that observed for this strain in f /2 medium under similar light intensity (Pankowski & McMinn 2009). …”

Section: Growthmentioning

confidence: 50%

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Iron availability regulates growth, photosynthesis, and production of ferredoxin and flavodoxin in Antarctic sea ice diatoms

Pankowski¹,

McMinn

2009

Aquat. Biol.

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Iron availability affects the growth of not only phytoplankton, but also sea ice diatoms. Iron availability had a clear effect on the growth rates of Fragilariopsis cylindrus and F. curta. Maximum growth rates were 0.57 d -1 for F. cylindrus and 0.28 d -1 for F. curta; K m (half-saturation growth constant) was 0.51 × 10 -12 and 1.3 × 10 -12 M for F. cylindrus and F. curta, respectively. For both F. cylindrus and F. curta, F v /F m (quantum yield of fluorescence) was highest and lowest for the cultures grown with the highest and lowest concentrations of iron, respectively. For both species there was also a reduction in both rETR max (maximum relative electron transfer rate) and α (photosynthetic efficiency) with decreasing iron concentration. For F. cylindrus grown with the least iron, rETR max was half of the iron-replete value, while α was reduced by 65%. Changes in E k (light-adaptation parameter) were not well defined. Immunoassays were developed for the proteins ferredoxin and flavodoxin in Antarctic pack ice. Iron availability had different effects on the expression of flavodoxin and ferredoxin in the 2 Fragilariopsis species tested. Cultures of F. cylindrus grown at high iron concentration produced predominantly ferredoxin, with a small amount of flavodoxin. Ferredoxin was sequentially replaced by flavodoxin for cultures grown with less iron, although the response was not a simple switch from one protein to the other. The ability to produce ferredoxin is apparently absent in F. curta, with relatively constant levels of flavodoxin produced at all iron concentrations. These results strongly imply that the presence of flavodoxin alone cannot be used as evidence of ironlimited growth.

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“…Axenic cultures of Fragilariopsis cylindrus, Thalassiosira antarctica and Entomoneis kjellmanii isolated from sea ice of the Mertz Glacier region of the Southern Ocean (Pankowski and McMinn 2009) are maintained in the Antarctic Culture Facility at the University of Tasmania. Batch cultures of each species were incubated in f2 media (Guillard 1975) under constant light conditions (41 ± 13 lmol photons m -2 s -1 ) at 2°C ± 0.5°C for approximately 2 weeks.…”

Section: Experimental Set-upmentioning

confidence: 99%

The effect of prolonged darkness on the growth, recovery and survival of Antarctic sea ice diatoms

2011

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While global climate change in polar regions is expected to cause significant warming, the annual cycle of light and dark will remain unchanged. Cultures of three species of Antarctic sea ice diatoms, Fragilariopsis cylindrus (Grunow) Krieger, Thalassiosira antarctica Comber and Entomoneis kjellmanii (P.T. Cleve) Poulin and Cardinal, were incubated in the dark and exposed to differing temperatures. Maximum dark survival times varied between 30 and 60 days. Photosynthetic parameters, photosynthetic efficiency (a), maximum quantum yield (Fv/ Fm), maximum relative electron transport rate (rETRmax) and non-photochemical quenching (NPQ), showed that dark exposure had a significant impact on photoacclimation. In contrast, elevated temperatures had a relatively minor impact on photosynthetic functioning during the dark exposure period but had a considerable impact on dark survival with minimal dark survival times reduced to only 7 days when exposed to 10°C. Recovery of maximum quantum yield of fluorescence (Fv/Fm) was not significantly impacted by temperature, species or dark exposure length. Recovery rates of Fv/Fm ranged from -5.06E-7 ± 2.71E-7 s -1 to 1.36E-5 ± 1.53E-5 s -1 for monthly experiments and from -9.63E-7 ± 7.71E-7 s -1 to 2.65E-5 ± 2.97E-5 s -1 for weekly experiments. NPQ recovery was greater and more consistent than Fv/Fm recovery, ranging between 5.74E-7 ± 8.11E-7 s -1 to 7.50E-3 ± 7.1E-4 s -1 . The concentration of chl-a and monosaccharides remained relatively constant in both experiments. These results suggest that there will probably be little effect on Antarctic microalgae with increasing water temperatures during the Antarctic winter.

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DEVELOPMENT OF IMMUNOASSAYS FOR THE IRON‐REGULATED PROTEINS FERREDOXIN AND FLAVODOXIN IN POLAR MICROALGAE¹

Cited by 21 publications

References 46 publications

Phytoplankton–bacterial interactions mediate micronutrient colimitation at the coastal Antarctic sea ice edge

Phytoplankton–bacterial interactions mediate micronutrient colimitation at the coastal Antarctic sea ice edge

Iron availability regulates growth, photosynthesis, and production of ferredoxin and flavodoxin in Antarctic sea ice diatoms

The effect of prolonged darkness on the growth, recovery and survival of Antarctic sea ice diatoms

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DEVELOPMENT OF IMMUNOASSAYS FOR THE IRON‐REGULATED PROTEINS FERREDOXIN AND FLAVODOXIN IN POLAR MICROALGAE1

Cited by 21 publications

References 46 publications

Phytoplankton–bacterial interactions mediate micronutrient colimitation at the coastal Antarctic sea ice edge

Phytoplankton–bacterial interactions mediate micronutrient colimitation at the coastal Antarctic sea ice edge

Iron availability regulates growth, photosynthesis, and production of ferredoxin and flavodoxin in Antarctic sea ice diatoms

The effect of prolonged darkness on the growth, recovery and survival of Antarctic sea ice diatoms

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DEVELOPMENT OF IMMUNOASSAYS FOR THE IRON‐REGULATED PROTEINS FERREDOXIN AND FLAVODOXIN IN POLAR MICROALGAE¹