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1. Extraction and Characterization of Lipids from Macroalgae

   https://doi.org/10.1007/978-1-4939-9484-7_7  

   Nobles DR Jr, Manning SR (January 2019, Methods in molecular biology)

   Although most algal biofuel research has focused on microalgae, macroalgae are also potential sources of lipid for the production of biodiesel and other liquid fuels. Reliable, accurate methods for assessing the lipid composition of biomass are essential for the development of macroalgae in this area. The conventional methods most commonly used to evaluate lipid composition, such as those of Bligh and Dyer and Folch, do not provide complete extraction of lipids in photosynthetic cells/tissues and therefore do not provide an accurate accounting of lipid production. Here we present a 2-EE lipid extraction protocol, a method which has been demonstrated to be superior to conventional lipid extraction methods for microalgae, adapted for use with macroalgae. 

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2. Cooperative motility, force generation and mechanosensing in a foraging non-photosynthetic diatom

   https://doi.org/10.1098/rsob.230148  

   Zheng, Peng; Kumadaki, Kayo; Quek, Christopher; Lim, Zeng Hao; Ashenafi, Yonatan; Yip, Zhi Ting; Newby, Jay; Alverson, Andrew J; Jie, Yan; Jedd, Gregory (October 2023, Open Biology)

   Diatoms are ancestrally photosynthetic microalgae. However, some underwent a major evolutionary transition, losing photosynthesis to become obligate heterotrophs. The molecular and physiological basis for this transition is unclear. Here, we isolate and characterize new strains of non-photosynthetic diatoms from the coastal waters of Singapore. These diatoms occupy diverse ecological niches and display glucose-mediated catabolite repression, a classical feature of bacterial and fungal heterotrophs. Live-cell imaging reveals deposition of secreted extracellular polymeric substance (EPS). Diatoms moving on pre-existing EPS trails (runners) move faster than those laying new trails (blazers). This leads to cell-to-cell coupling where runners can push blazers to make them move faster. Calibrated micropipettes measure substantial single-cell pushing forces, which are consistent with high-order myosin motor cooperativity. Collisions that impede forward motion induce reversal, revealing navigation-related force sensing. Together, these data identify aspects of metabolism and motility that are likely to promote and underpin diatom heterotrophy. 

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3. Reduction-dependent siderophore assimilation in a model pennate diatom

   https://doi.org/10.1073/pnas.1907234116  

   Coale, Tyler H.; Moosburner, Mark; Horák, Aleš; Oborník, Miroslav; Barbeau, Katherine A.; Allen, Andrew E. (November 2019, Proceedings of the National Academy of Sciences)

   Iron uptake by diatoms is a biochemical process with global biogeochemical implications. In large regions of the surface ocean diatoms are both responsible for the majority of primary production and frequently experiencing iron limitation of growth. The strategies used by these phytoplankton to extract iron from seawater constrain carbon flux into higher trophic levels and sequestration into sediments. In this study we use reverse genetic techniques to target putative iron-acquisition genes in the model pennate diatom Phaeodactylum tricornutum . We describe components of a reduction-dependent siderophore acquisition pathway that relies on a bacterial-derived receptor protein and provides a viable alternative to inorganic iron uptake under certain conditions. This form of iron uptake entails a close association between diatoms and siderophore-producing organisms during low-iron conditions. Homologs of these proteins are found distributed across diatom lineages, suggesting the significance of siderophore utilization by diatoms in the marine environment. Evaluation of specific proteins enables us to confirm independent iron-acquisition pathways in diatoms and characterize their preferred substrates. These findings refine our mechanistic understanding of the multiple iron-uptake systems used by diatoms and help us better predict the influence of iron speciation on taxa-specific iron bioavailability. 

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4. Efficient zinc/cobalt inter‐replacement in northeast Pacific diatoms and relationship to high surface dissolved Co : Zn ratios

   https://doi.org/10.1002/lno.11471  

   Kellogg, Riss M.; McIlvin, Matthew R.; Vedamati, Jagruti; Twining, Benjamin S.; Moffett, James W.; Marchetti, Adrian; Moran, Dawn M.; Saito, Mak A. (June 2020, Limnology and Oceanography)

   Abstract The importance of zinc (Zn) as a nutrient and its ability to be substituted for by cobalt (Co) have been characterized in model marine diatoms. However, the extent to which this substitution capability is distributed among diatom taxa is unknown. Zn/Co metabolic substitution was assayed in four diatom species as measured by the effect of free ion concentrations of Zn²⁺and Co²⁺on specific growth rate. Analysis of growth responses found substitution of these metals can occur within the northwest Atlantic isolateThalassiosira pseudonanaCCMP1335, the northeast Atlantic isolatePhaeodactylum tricornutumCCMP632, and within the northeast Pacific isolatesPseudo‐nitzschia delicatissimaUNC1205 andThalassiosirasp. UNC1203. Metabolic substitution of Co in place of Zn in the Atlantic diatoms supports their growth in media lacking added Zn, but at the cost of reduced growth rates. In contrast, highly efficient Zn/Co substitution that supported growth even in media lacking added Zn was observed in the northeast Pacific diatoms. We also present new data from the northeast Pacific Line P transect that revealed dissolved Co and Zn ratios (dCo : dZn) as high as 3.52 : 1 at surface (0–100 m) depths. We posit that the enhanced ability of the NE Pacific diatoms to grow using Co is an adaptation to these high surface dCo : dZn ratios. Particulate metal data and single‐cell metal quotas also suggest a high Zn demand in diatoms that may be partially compensated for by Co. 

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5. The Importance of Protein Phosphorylation for Signaling and Metabolism in Response to Diel Light Cycling and Nutrient Availability in a Marine Diatom

   https://doi.org/10.3390/biology9070155  

   Tan, Maxine H.; Smith, Sarah R.; Hixson, Kim K.; Tan, Justin; McCarthy, James K.; Kustka, Adam B.; Allen, Andrew E. (July 2020, Biology)

   null (Ed.)

   Diatoms are major contributors to global primary production and their populations in the modern oceans are affected by availability of iron, nitrogen, phosphate, silica, and other trace metals, vitamins, and infochemicals. However, little is known about the role of phosphorylation in diatoms and its role in regulation and signaling. We report a total of 2759 phosphorylation sites on 1502 proteins detected in Phaeodactylum tricornutum. Conditionally phosphorylated peptides were detected at low iron (n = 108), during the diel cycle (n = 149), and due to nitrogen availability (n = 137). Through a multi-omic comparison of transcript, protein, phosphorylation, and protein homology, we identify numerous proteins and key cellular processes that are likely under control of phospho-regulation. We show that phosphorylation regulates: (1) carbon retrenchment and reallocation during growth under low iron, (2) carbon flux towards lipid biosynthesis after the lights turn on, (3) coordination of transcription and translation over the diel cycle and (4) in response to nitrogen depletion. We also uncover phosphorylation sites for proteins that play major roles in diatom Fe sensing and utilization, including flavodoxin and phytotransferrin (ISIP2A), as well as identify phospho-regulated stress proteins and kinases. These findings provide much needed insight into the roles of protein phosphorylation in diel cycling and nutrient sensing in diatoms. 

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