Pace, D. A. | Search bioRxiv

bioRxiv2024

Aquavert: Imaging and Microfluidics for Vertical Swimming of Microorganisms

Investigating aquatic microorganisms swimming and feeding behaviors under well-controlled conditions is of great interest across multiple disciplines. Thus, broader access to resources that enable these investigations is desirable. Given the organisms microscopic dimensions, an ideal system should combine microscopy to visualize and fluidics to control and modulate their environments. We report an integrated device (Aquavert) that combines DIY microscopy and microfluidics for biomechanical investigations of marine microorganisms, emphasizing vertical swimming. The DIY microscope was developed for modularity, and imaging chambers were secured in vertical orientations (either in portrait or landscape mode). Fluid channels were used to introduce flow and fluid segmentation while remaining upright. Fluid segmentation established two distinct environments (e.g., with and without algae) in neighboring regions inside a chamber. System application with multiple marine larvae (sand dollars, sea urchins, and starfish) and introduction of unicellular algae were demonstrated. Finally, the devices capabilities were extended to fluorescence imaging to visualize tracer beads. The role of gravity is often ignored in conventional plate or microfluidic experiments. Beyond the current application, Aquavert enables investigations of the behavior and physiology of microorganisms where the role of gravity is critical.

biophysics↗

bioRxiv2020

Different protein metabolic strategies for growth during food-induced physiological plasticity

Food-induced morphological plasticity, a type of developmental plasticity, is a well-documented phenomenon in larvae of the echinoid echinoderm, Dendraster excentricus. A recent study in our lab has shown that this morphological plasticity is associated with significant physiological plasticity for growth. The goal of the current study was to measure several aspects of protein metabolism in larvae growing at different rates to understand the mechanistic basis for this physiological growth plasticity. Larvae of D. excentricus were fed rations of 1,000 (low-fed) or 10,000 (high-fed) algal cells mL−1. Primary measurements of protein growth, algal ingestion, aerobic metabolism, alanine transport and protein synthesis were used to model growth and protein metabolism. Relative protein growth rates were 6.0 and 12.2 % day−1 for low- and high-fed larvae, respectively. The energetic cost of protein synthesis was similar between both treatments at 4.91 J (mg protein synthesized)−1. Larvae in both treatments used about 50% of their metabolic energy production to fuel protein synthesis. Mass-specific rates of protein synthesis were also similar. The most important difference between low- and high-fed larvae were mass-specific rates of protein degradation. Low-fed larvae had relatively low rates of degradation early in development that increased with larval age, surpassing high-fed degradation rates at 20 days post-fertilization. Changes in protein depositional efficiency during development were similar to those of larval growth efficiency, indicating that differences in protein metabolism are largely responsible for whole-organism growth plasticity. Mass-specific alanine transport rates were about 2-times higher in low-fed larvae, demonstrating that the longer arms of low-fed larvae may be a mechanism for acquiring more dissolved nutrients from their environment. In total, these results provide an explanation for the differences in growth efficiency between low- and high-fed larvae and demonstrate the importance of protein degradation pathways in establishing these growth differences. These observations, together with previous studies measuring morphological and physiological plastic responses, allow for a more integrated understanding of developmental plasticity in echinoid larvae.AbbreviationsDPFdays post-fertilizationPOpostoral armAEassimilation efficiencyGGEgross growth efficiencyNGEnet growth efficiencyPGEprotein growth efficiencyPDEprotein depositional efficiencyMBLmidline body lengthFAAfree amino acid poolRGRrelative growth rateBCAbicinchoninic assayBSAbovine serum albuminTCAtrichloroacetic acidBODbiological oxygen demandTORtarget of rapamycinDOMdissolved organic materialView Full Text

physiology↗