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

Abstract

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.

Global Nitrogen Cycle: Critical Enzymes, Organisms, and Processes for Nitrogen Budgets and Dynamics

“…106 To combat P limitation, C. watsonii can use a high affinity phosphate transporter to scavenge inorganic P as well as certain dissolved organic P sources. 177,178 Marine systems host a wide variety and distribution of noncyanobacterial diazotrophs. 179−181 These organisms, typically detected with molecular surveys of the dinitrogenase reductase gene nif H, 180 are thought to be predominantly heterotrophic Proteobacteria.…”

Elevated temperature relieves phosphorus limitation of marine unicellular diazotrophic cyanobacteria

“…These two N 2 fixers also differ in P metabolism. In contrast to Trichodesmium , C. watsonii is unable to utilize phosphonates, which roughly account for 25% of the dissolved organic P in the ocean (Clark et al 1998; Pereira et al 2019). In addition, due to its smaller cell size, C. watsonii has larger cell surface area to volume ratio for the uptake of P compared to Trichodesmium (Finkel et al 2009).…”

“…In addition, none of the previous relevant studies has studied the underlying molecular mechanisms (Hutchins et al 2007; Qu et al 2019). Various strategies for overcoming P limitation have been proposed in cyanobacteria (Pereira et al 2019), including high‐affinity scavenging for extracellular inorganic phosphate, utilizing organic P compounds, and lowering cellular P requirement by element substitution (Dyhrman and Haley 2006; Van Mooy et al 2006; Pereira et al 2019). It has also been reported that C. watsonii has versatile genetic potential of P acquisitions (Pereira et al 2019).…”

“…Various strategies for overcoming P limitation have been proposed in cyanobacteria (Pereira et al 2019), including high‐affinity scavenging for extracellular inorganic phosphate, utilizing organic P compounds, and lowering cellular P requirement by element substitution (Dyhrman and Haley 2006; Van Mooy et al 2006; Pereira et al 2019). It has also been reported that C. watsonii has versatile genetic potential of P acquisitions (Pereira et al 2019). However, it is uncertain whether/how temperature would affect the processes of P metabolism and hence mediate the physiological responses of C. watsonii to P limitation in a warming ocean.…”

Why Environmental Biomarkers Work: Transcriptome-Proteome Correlations and Modeling of Multi-Stressor Experiments in the Marine BacteriumTrichodesmium

“…As such, these proteins and their mRNA transcripts represent ideal environmental biomarkers to detect controls on ecosystem productivity. Biomarkers for nutritional stress in marine phytoplankton and bacteria that have been identified are shown in Table 2, including those for nitrogen 43,[48][49][50] , phosphorus [5][6][51][52][53] , iron [18][19][54][55][56][57][58][59][60][61] , vitamin B12 62,63 , and zinc 64 . Notably, proteins involved in adaptive responses in marine microbes are often distinct from those model organisms because of their very different environmental conditions.…”