Cooperative Motility, Force Generation and Mechanosensing in a Foraging Non-Photosynthetic Diatom
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Abstract
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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he inset photo-graph shows Sargassum (yellow tag) at the Sentosa, Singapore collection site.(which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.The copyright holder for this preprintthis version posted April 12, 2023.;https://doi.org/10.1101/2023.03.27.533254doi:bioRxiv preprint
Thank you for including this information!!! Being able to see the actual collection site / environment provides a lot of information that is often never publicly reported and gets lost with time!
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Cooperative Motility, Force Generation and Mechanosensingin a Foraging Non-Photosynthetic Diatom
This is really fun work! Thank you for sharing all of the neat images/movies! Very exciting observations that will surely bring about a ton more questions!
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Here, trails are not seen because the EPS is not at the airinterface.
Is the EPS trail visible after the seawater is removed / dried up? My limited understanding is that the EPS is a sort of mucusal "slip-n-slide" but if the entire surface is wet, there'd be no need for EPS trails, right?
Also, did you notice any changes in the directionality of these cells at the different substrates?
Did the cells at the SW-air interface also show a bump-induced cooperative motility mechanism?
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The relationship between runners and blazers leads tocooperative motility
Has this type of cooperative motility between clonal diatoms been shown before?
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nterestingly,diatoms are also observed gliding in a monolayer at theseawater-air interface, indicating that N. sing1 motility isnot strictly dependent on substratum attachment (
This is wild! How do you distinguish between gliding movement and simply drifting in the liquid?
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The graph shows thespeed of diatoms shown in (C). The bar shows the average with stand-ard deviation indicated. Related to Supplementary Movies 1, 2 and 3.(which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.The copyright holder for this preprintthis version posted April 12, 2023.;https://doi.org/10.1101/2023.03.27.533254doi:bioRxiv preprint
Very interesting! Was the difference between agar & SW-air in the SW-overlay statistically significant?
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Theprojections show diatom motility under the indicated conditions. Totaltime = 305 seconds. Scale bar = 100 μm.
Is this on the 1 or 2% agarose medium?
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DAPI
Did the DAPI staining not work? It isn't included in any of the figures.
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3: Environmental control of EPS and motility.
Just curious, do motile Nitzschia cells move on glass or inorganic substrates?
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Related to Figure S5
Should this be referencing Figure S4? Also, is Fig S5 just showing more examples of this? If so, Awesome and thank you for providing these images!! If not, its unclear to me what additional information is shown in Figure S4.
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) Lipiddroplet accumulation of N. sing1-1 and N. putrida on seawater agarosemedia in the presence (+) and absence (-) of glucose. The dotted linetraces the cell periphery. Scale bar = 10 μm. Related to Figure S5
Is this stained with BODIPY like cells in Figure S4?
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F-actin staining of N. sing1-1. The arrows point to the approximate posi-tion of proximal raphe ends. A bright-field (BF) image of N. putrida isshown for comparison. Scale bar = 10 μm.(which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.The copyright holder for this preprintthis version posted April 12, 2023.;https://doi.org/10.1101/2023.03.27.533254doi:bioRxiv preprint
Very cool! In the bright-field image, is the structure on the left an EPS trail? or a pipette tip like in Fig 6?
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For solid media, salt solutions I and II wereprepared as 4X stock solutions, while polysaccharides were prepared at 2Xconcentrations.
What are the components of these solutions? or if unknown, what is the source?
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