Molecular markers define progressing stages of phosphorus limitation in the nitrogen‐fixing cyanobacterium, <i>Crocosphaera</i>

Pereira, Nicole; Shilova, Irina N.; Zehr, Jonathan P.

doi:10.1111/jpy.12396

Cited by 17 publications

(38 citation statements)

References 45 publications

(75 reference statements)

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“…RNA extractions were carried out using a modified RNeasy Mini Kit protocol (Qiagen, Germantown, MD, USA) and converted to single stranded complementary DNA (cDNA) using the QuantiTect Reverse Transcription Kit (Qiagen) as previously outlined (Pereira et al. ). All cDNA was subsequently stored at −20°C.…”

Section: Methodsmentioning

confidence: 99%

“…The comparative (∆∆Ct) method was used to normalize the expression of pstS to a housekeeping gene ( rnpB ) previously used in Crocosphaera (Pereira et al. ). A single T 0 time point sample was used as a calibrator for calculating fold changes in each experiment.…”

Section: Methodsmentioning

confidence: 99%

“…, Pereira et al. ). Crocosphaera also lacks genes for assimilation of phosphonates as an alternative P substrate (Dyhrman and Haley ).…”

mentioning

confidence: 99%

“…, Pereira et al. ). The peak of basal pstS transcript levels occurs at the end of the light cycle, just prior to DNA replication in Crocosphaera (Shi et al.…”

mentioning

confidence: 99%

“…It has been previously shown that transcription of pstS in Crocosphaera is up‐regulated within 1 h of exposure to low external Pi (Pereira et al. ). However, pstS transcript levels have a diel cycle in Crocosphaera , thus elevated pstS transcript levels do not necessarily quantitatively reflect a decrease in external P availability (Shi et al.…”

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confidence: 99%

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Use of the high‐affinity phosphate transporter gene, pstS, as an indicator for phosphorus stress in the marine diazotroph Crocosphaera watsonii (Chroococcales, Cyanobacteria)

Pereira

Shilova

Zehr

2019

Journal of Phycology

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The marine diazotroph Crocosphaera watsonii provides fixed carbon (C) and nitrogen (N) to open‐ocean regimes, where nutrient deficiency controls productivity. The growth of Crocosphaera can be limited by low phosphorus (P) concentrations in these oligotrophic environments. Biomarkers such as the high‐affinity ABC transporter phosphate‐binding gene, pstS, are commonly used to monitor when such organisms are under P stress; however, transcriptional regulation of these markers is often complex and not well‐understood. In this study, we interrogated changes in pstS transcript levels in C. watsonii cells under P starvation, and in response to added dissolved inorganic phosphorus (DIP), dissolved organic phosphorus (DOP), and changing light levels. We observed elevated relative pstS transcript levels in C. watsonii WH8501 at DIP concentrations below 60 and above 20 nmol · L−1. Transcript levels were suppressed by both inorganic and bioavailable organic phosphorus; however, the P stress response was more sensitive to DIP than DOP sources. Increasing light intensity resulted in increased relative pstS transcript abundances independently of low external P, and seemed to exacerbate the physiological effects of P stress. The variable response to different P compounds and rapid and transient influence of high light on pstS transcript abundances suggests that pstS is an indicator of internal P status in Crocosphaera.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…, Pereira et al. ). Crocosphaera also lacks genes for assimilation of phosphonates as an alternative P substrate (Dyhrman and Haley ).…”

mentioning

confidence: 99%

“…, Pereira et al. ). The peak of basal pstS transcript levels occurs at the end of the light cycle, just prior to DNA replication in Crocosphaera (Shi et al.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Use of the high‐affinity phosphate transporter gene, pstS, as an indicator for phosphorus stress in the marine diazotroph Crocosphaera watsonii (Chroococcales, Cyanobacteria)

Pereira

Shilova

Zehr

2019

Journal of Phycology

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Elevated temperature relieves phosphorus limitation of marine unicellular diazotrophic cyanobacteria

Deng

Cheung

Kang

et al. 2021

Limnology & Oceanography

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The warming ocean is expected to be more phosphorus (P) limited due to increasing stratification. P is a major limiting nutrient of marine diazotrophs, while the interactive effect of temperature elevation and P limitation on marine unicellular diazotrophs is unknown. Here, we examined the physiology of a major unicellular diazotroph, Crocosphaera watsonii, grown under P‐limited and P‐replete conditions at 25°C, 28°C, and 31°C. Growth, N2, and CO2 fixation rates of C. watsonii increased with temperature under P limitation, and growth rates were similar between P‐limited and P‐replete treatments at 31°C. At high temperature, the P use efficiencies for N2 and CO2 fixation under P limitation were more than twice higher than under P‐replete conditions. Expression of genes involved in P acquisition, intracellular recycling, and substitution in C. watsonii was upregulated at higher temperature under P limitation. These results suggest that P limitation in C. watsonii was relieved with elevated temperature through various temperature‐dependent economic strategies on P metabolism. Through meta‐analysis of a field data set using general additive model, we found that C. watsonii abundance was correlated mainly with temperature and phosphate, and predicted to increase significantly with further warming.

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Heterotrophic bacteria outcompete diazotrophs for orthophosphate in the Mediterranean Sea

Rahav

Herut

Spungin

et al. 2021

Limnology & Oceanography

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Unicellular photoautotrophic diazotrophs such as Crocosphaera spp. are ubiquitous in many oligotrophic and N‐limited oceans, as they can reduce N2 into bioavailable ammonia. The Mediterranean Sea is potentially an ideal environment for photoautotrophic diazotrophic activity, and yet N2‐fixation rates measured in the last two decades are typically very low and no diazotrophic blooms have been recorded in its offshore waters. Previous studies suggest that diazotrophs, as well as nondiazotrophic phytoplankton and heterotrophic bacteria, may be P‐limited, hence their low biomass and activity. Here, we amended surface seawater from six stations across a nutrient gradient in the Mediterranean Sea (east to west transect) with dissolved inorganic phosphorus (DIP), and with seawater‐acclimated inocula of Crocosphaera watsonii, a unicellular cyanobacterial diazotroph, to examine if DIP can stimulate diazotrophy. Our results demonstrate that C. watsonii are poor competitors for DIP relative to native nondiazotrophic heterotrophic microbial populations, especially in the ultraoligotrophic eastern Mediterranean basin, resulting in low N2‐fixation rates. Moreover, the results indicate that when the ambient DIP concentrations are < 35 nmol L−1, unicellular photoautotrophic diazotrophs such as C. watsonii will likely be outcompeted for this macronutrient in the Mediterranean Sea, whereas above 35 nmol L−1 diazotrophy can be stimulated. Our findings support the “bypass theory” stating that photoautotrophs may be outcompeted by heterotrophic bacteria for DIP in nutrient‐poor regions such as the Mediterranean Sea.

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Molecular markers define progressing stages of phosphorus limitation in the nitrogen‐fixing cyanobacterium, Crocosphaera

Cited by 17 publications

References 45 publications

Use of the high‐affinity phosphate transporter gene, pstS, as an indicator for phosphorus stress in the marine diazotroph Crocosphaera watsonii (Chroococcales, Cyanobacteria)

Use of the high‐affinity phosphate transporter gene, pstS, as an indicator for phosphorus stress in the marine diazotroph Crocosphaera watsonii (Chroococcales, Cyanobacteria)

Elevated temperature relieves phosphorus limitation of marine unicellular diazotrophic cyanobacteria

Heterotrophic bacteria outcompete diazotrophs for orthophosphate in the Mediterranean Sea

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