In the early online edition of the Proceedings of the National Academy of Sciences, researchers from the University of Arizona and Brown University explain how flagella allow these algae to get the energy they need to multiply and create colonies – the critical secret that allowed them to evolve into multicellular organisms.
Munching in motion
The beating flagella of a Volvox colony creates a flow of water around it, visible here through the use of miniscule, illuminated plastic beads. The coordinated beating of flagella creates a nutrient-rich environment for the colony. Image: University of Arizona
“This is the first evidence that flagella not only help organisms move, but can help them feed at a rate that allowed them to evolve to a larger size,” said Thomas Powers, an assistant professor of engineering at Brown who studies microorganisms in motion. “This is a critical piece of information, since understanding how one-celled life forms evolve into many-celled ones is a fundamental question in biology.”
The team studied a group of green algae known as the volvocines, organisms so common they can be found in puddles of rain. Biologists study the group, which runs the gamut from single-celled organisms to teeming colonies, to understand how cells differentiate and multiply. But how did the volvocines jump from solo cells to Volvox, a colony of as many as 50,000 cells?
It’s a puzzler of a question, given the size of a Volvox colony and the laws of physics. Bigger organisms need more energy – a lot more energy – to survive. And Volvox is the largest colony that the volvocines make, a giant ball of flagella-waving body guards protecting a small cluster of reproductive cells. When the radius of the spherical colony increases by a factor of two, the area of the sphere increases by a factor of four. So it follows that the energy demands for Volvox would quadruple, too, as it grows.
Yet microscopic organisms such as volvocines get nutrients through diffusion, a process by which bits of food bump into the cell and pass through the cell membrane. Doubling the radius of the colony doubles – not quadruples – the colony’s food intake rate. So a large organism such as a Volvox colony shouldn’t survive because it would demand more energy than passive feeding could supply, a conundrum that researchers refer to as the “bottleneck problem.”
The research team had a hunch that flagella somehow played a role in bringing in nutrients needed for Volvox to grow and survive. Raymond Goldstein, a professor of physics and applied mathematics at the University of Arizona, gathered together a group of scientists with expertise in physics, mathematics, engineering and biology to work on the problem.
The team created a mathematical model that allowed them to calculate how the flagella created a flow of water around the colony and verified this prediction with experimental measurements. Then they used the model to show that the coordinated beating of the flagella concentrated the nutrients just ahead of the moving colony. The colony plows into this nutrient-rich region and leaves a plume of waste in its wake.
So a Volvox colony doesn’t just passively feed, it actively increases the concentration of nutrients around it using its flagella. Put another way, these tiny protein whips not only acts as legs, but also as arms, gathering in food the colony needs to grow and thrive.
Powers, brought in to help with biomechanical theory, said the surprise in the finding is that the nutrient current created by Volvox was proportional to the surface area of the colony. In other words, Volvox met its rapidly increasing demand for nutrients through flagellar beating, allowing the organism to make the multicellular leap.
“Previous models would have predicted that the nutrient demands of Volvox would outstrip the supply,” Powers said. “But we showed that metabolic supply can, in fact, keep up with metabolic demand. The colony beat the bottleneck problem. Its increasing size is actually an advantage, allowing it to create a faster flow of nutrients.”
The National Science Foundation funded the work.
Wendy Lawton | EurekAlert!
Link Discovered between Immune System, Brain Structure and Memory
26.04.2017 | Universität Basel
Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
26.04.2017 | Materials Sciences
26.04.2017 | Agricultural and Forestry Science
26.04.2017 | Physics and Astronomy