Ecophysiology, Cell Biology and Ultrastructure of a Benthic Diatom Isolated in the Arctic

Karsten, Ulf; Schumann, Rhena; Holzinger, Andreas

doi:10.1002/9781119370741.ch12

Cited by 3 publications

(7 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…minuta cultures exhibited ~20% dead cells after 1 month incubation (Karsten et al, 2019a). In contrast, after 5 months of dark exposure, >95% of Arctic Navicula directa cells were still alive as indicated by their intact membrane systems (Karsten et al, 2019b). This suggests that some diatom cells can cope better with long-term darkness than others, which we also confirmed after 10 months of dark-exposure of Antarctic strains.…”

Section: Membrane Integrity Differs Between Marine and Limnic Strainssupporting

confidence: 74%

“…As plastoglobules appear to actively participate in thylakoid biogenesis to senescence, it is possible that Antarctic diatoms "store" most of their thylakoids as plastoglobules during long-term darkness; as soon as light becomes they can be used as building blocks to restore the grana system, allowing to regain an appreciable photosynthetic performance. Degradation of the chloroplast seems to be a key mechanism in benthic diatoms to survive the polar night; dark exposure condenses the chloroplast in Antarctic diatoms (Wulff et al, 2008), and reduces the chloroplast lengths by up to 50% in Arctic diatoms (Karsten et al, 2012(Karsten et al, , 2019b, but recovery is possible after some hours in light. Even though strongly reduced, after 10 months of darkness, thylakoids are still visible in plastoglobules-rich chloroplasts, helping to explain why appreciable photosynthetic oxygen production is measurable immediately upon light exposure.…”

Section: Prominent Changes Of Chloroplast Ultrastructure After Dark A...mentioning

confidence: 99%

See 1 more Smart Citation

Antarctic benthic diatoms after 10 months of dark exposure: consequences for photosynthesis and cellular integrity

Handy,

Juchem,

Wang

et al. 2024

Front. Plant Sci.

Self Cite

View full text Add to dashboard Cite

Antarctic algae are exposed to prolonged periods of extreme darkness due to polar night, and coverage by ice and snow can extend such dark conditions to up to 10 months. A major group of microalgae in benthic habitats of Antarctica are diatoms, which are key primary producers in these regions. However, the effects of extremely prolonged dark exposure on their photosynthesis, cellular ultrastructure, and cell integrity remain unknown. Here we show that five strains of Antarctic benthic diatoms exhibit an active photosynthetic apparatus despite 10 months of dark-exposure. This was shown by a steady effective quantum yield of photosystem II (Y[II]) upon light exposure for up to 2.5 months, suggesting that Antarctic diatoms do not rely on metabolically inactive resting cells to survive prolonged darkness. While limnic strains performed better than their marine counterparts, Y(II) recovery to values commonly observed in diatoms occurred after 4-5 months of light exposure in all strains, suggesting long recovering times. Dark exposure for 10 months dramatically reduced the chloroplast ultrastructure, thylakoid stacking, and led to a higher proportion of cells with compromised membranes than in light-adapted cells. However, photosynthetic oxygen production was readily measurable after darkness and strong photoinhibition only occurred at high light levels (>800 µmol photons m-2 s-1). Our data suggest that Antarctic benthic diatoms are well adapted to long dark periods. However, prolonged darkness for several months followed by only few months of light and another dark period may prevent them to regain their full photosynthetic potential due to long recovery times, which might compromise long-term population survival.

show abstract

Section: Membrane Integrity Differs Between Marine and Limnic Strainssupporting

confidence: 74%

Section: Prominent Changes Of Chloroplast Ultrastructure After Dark A...mentioning

confidence: 99%

Antarctic benthic diatoms after 10 months of dark exposure: consequences for photosynthesis and cellular integrity

Handy,

Juchem,

Wang

et al. 2024

Front. Plant Sci.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Applying SYTOX Green to the Arctic benthic diatoms Surirella cf. minuta and Navicula directa during 5 months of darkness indicated that an increasing number of cells exhibited damaged membranes over time in the first species (Karsten et al, 2019a ), while the latter one was almost unaffected (Karsten et al, 2019b ). In the present study, SYTOX Green staining was applied for the first time to Antarctic benthic diatoms, and the results are comparable to those on both Arctic species.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, no long-term damage appears to have been caused by the partial decomposition of chloroplasts during the prolonged darkness. According to Karsten et al ( 2019b ), the degradation of chloroplast compounds seems to be a key mechanism in Arctic benthic diatoms to survive the polar night and generate energy for their maintenance metabolism. The results of this study confirm that this is also a survival strategy for the examined Antarctic benthic diatoms.…”

Section: Discussionmentioning

confidence: 99%

“…In order to maintain viability, not only organelles but also membranes and DNA must remain intact (McMinn and Martin, 2013 ). Benthic diatoms with intact plasmalemma can be distinguished from those with permeabilized membranes using the nucleic acid stain SYTOX Green, which only passes through compromised or damaged membranes, and stains the nucleus, leading to enhanced fluorescence under blue light excitation (Karsten et al, 2019a , b , and references therein). Application of the SYTOX Green stain to dark-incubated Arctic Navicula directa (W. Smith) Brébisson indicated that >95% of all cells exhibited intact membranes, even after 5 months of darkness, and hence, the high degree of membrane integrity contributed to long-term dark tolerance (Karsten et al, 2019a , b ).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Lipid degradation and photosynthetic traits after prolonged darkness in four Antarctic benthic diatoms, including the newly described species Planothidium wetzelii sp. nov.

Juchem,

Schimani,

Holzinger

et al. 2023

Front. Microbiol.

Self Cite

View full text Add to dashboard Cite

In polar regions, the microphytobenthos has important ecological functions in shallow-water habitats, such as on top of coastal sediments. This community is dominated by benthic diatoms, which contribute significantly to primary production and biogeochemical cycling while also being an important component of polar food webs. Polar diatoms are able to cope with markedly changing light conditions and prolonged periods of darkness during the polar night in Antarctica. However, the underlying mechanisms are poorly understood. In this study, five strains of Antarctic benthic diatoms were isolated in the field, and the resulting unialgal cultures were identified as four distinct species, of which one is described as a new species, Planothidium wetzelii sp. nov. All four species were thoroughly examined using physiological, cell biological, and biochemical methods over a fully controlled dark period of 3 months. The results showed that the utilization of storage lipids is one of the key mechanisms in Antarctic benthic diatoms to survive the polar night, although different fatty acids were involved in the investigated taxa. In all tested species, the storage lipid content declined significantly, along with an ultrastructurally observable degradation of the chloroplasts. Surprisingly, photosynthetic performance did not change significantly despite chloroplasts decreasing in thylakoid membranes and an increased number of plastoglobules. Thus, a combination of biochemical and cell biological mechanisms allows Antarctic benthic diatoms to survive the polar night.

show abstract

Freezing stress tolerance of benthic freshwater diatoms from the genus Pinnularia: Comparison of strains from polar, alpine, and temperate habitats

Hejduková,

Kollár,

Nedbalová

2024

Journal of Phycology

View full text Add to dashboard Cite

Diatoms are among the most important primary producers in alpine and polar freshwaters. Although temperate diatoms are sensitive to freezing, polar diatoms often exhibit more resistance. This is particularly true for members of the (predominantly terrestrial) Pinnularia borealis species complex. However, it remains unclear to what extent this resistance applies to other representatives of the genus. Here, we compare the freezing‐stress tolerance of 11 freshwater, benthic strains representing different species of Pinnularia (including Caloneis) from polar, alpine, and temperate habitats. As vegetative cells, strains were exposed to freezing temperatures of −4, −10, −20, −40, −80, and −196°C. Survival was assessed by light microscopy and photosynthetic measurements. We observed vegetative cells to be sensitive to low freezing temperatures; only “mild” freezing was survived by all tested strains, and most tested strains did not survive treatments ≤−10°C. However, individual strain sensitivities appeared related to their original habitats. For example, polar and alpine strains better withstood “mild” and “moderate” freezing (−4 and −10°C, respectively); although temperate strains were significantly affected by the “mild” freezing treatment, polar and alpine strains were not. The −10°C treatment was survived exclusively by polar strains, and only P. catenaborealis survived all treatments. Interestingly, this species exhibited the lowest survival in the −10°C treatment, potentially implying some metabolic activity even at freezing temperatures. Thus, despite more extensive sampling throughout the genus and finer temperature scaling compared to previous studies, the remarkable freezing‐stress tolerance of the P. borealis species complex remains unique within the genus.

show abstract

Ecophysiology, Cell Biology and Ultrastructure of a Benthic Diatom Isolated in the Arctic

Cited by 3 publications

References 44 publications

Antarctic benthic diatoms after 10 months of dark exposure: consequences for photosynthesis and cellular integrity

Antarctic benthic diatoms after 10 months of dark exposure: consequences for photosynthesis and cellular integrity

Lipid degradation and photosynthetic traits after prolonged darkness in four Antarctic benthic diatoms, including the newly described species Planothidium wetzelii sp. nov.

Freezing stress tolerance of benthic freshwater diatoms from the genus Pinnularia: Comparison of strains from polar, alpine, and temperate habitats

Contact Info

Product

Resources

About