FYFD

Tag: bacteria

  • Understanding Cyanobacteria

    Understanding Cyanobacteria

    Over 2 billion years ago, cyanobacteria emerged as Earth’s first photosynthesizing organisms. Today they are widespread and critical contributors to both carbon and nitrogen cycles. Colonies can form large mats, like those pictured above, but, even at the microscale, cyanobacteria are actively forming patterns among individual bacteria. A recent study considers cyanobacteria as active matter.

    At the microscopic scale, cyanobacteria form different patterns.
    At the microscopic scale, cyanobacteria form different patterns, depending on their density.

    By simulating the cyanobacteria as filaments that interact through a series of simple rules, the researchers were able to reproduce the complex patterns bacterial colonies form. Their physical model also offered an explanation — based on the relative importance of advective and diffusive transport — for the characteristic length scales found in the bacterial patterns. (Image credit: Yellowstone – B. Cappellacci, patterns – M. Faluweki et al.; research credit: M. Faluweki et al.; via APS Physics)

  • Bacterial Turbulence

    Bacterial Turbulence

    Conventional fluid dynamical wisdom posits that any flows at the microscale should be laminar. Tiny swimmers like microorganisms live in a world dominated by viscosity, therefore, there can be no turbulence. But experiments with bacterial colonies have shown that’s not entirely true. With enough micro-swimmers moving around, even these viscous, small-scale flows become turbulent.

    That’s what is shown in Image 2, where tracer particles show the complex motion of fluid around a bacterial swarm. By tracking both the bacteria motion and the fluid motion, researchers were able to describe the flow using statistical methods similar to those used for conventional turbulence. The characteristics of this bacterial turbulence are not identical to larger-scale turbulence, but they are certainly more turbulent than laminar. (Image credits: bacterium – A. Weiner, bacterial turbulence – J. Dunkel et al.; research credit: J. Dunkel et al.; submitted by Jeff M.)

  • Reducing Viscosity With Bacteria

    Reducing Viscosity With Bacteria

    Conventional wisdom – and the Second Law of Thermodynamics – require all fluids to have viscosity, with the noted and bizarre exception of superfluids, which can flow with zero viscosity. In essence, you cannot have work (i.e. flow) for free. Some effort has to be lost to resistance.

    But scientists have discovered, bizarrely, that adding bacteria to water can result in zero or even negative viscosities – meaning that effort is required to keep the flow from accelerating. Before you ask, no, this is not a recipe for a perpetual motion machine. What happens when the bacteria-filled fluid is sheared is that the bacteria align and start collectively swimming. The local effects of each bacteria combine en masse to create a fluid that seemingly flows on its own. In the end, though, it’s the bacteria that are supplying that work. It certainly raises interesting prospects, though, for harnessing the power of bacterial superfluids. See the links below for more. (Image credit: M. Copeland, source; research credit: S. Guo et al., A. Loisy et al.; via Quanta; submitted by Kam-Yung Soh)