Acoustic Streaming, The “Small Invention” of Cianobacteria?

Abstract

RESUMEN: Los mecanismos de bombeo en microingeniería aparecieron al principio de la década de los 90. El principio detrás de esto es el de flujo acústico. ¿Ha descubierto laABSTRACT: Micro-engineering pumping devices without mechanical parts appeared "way back" in the early 1990's. The working principle is acoustic streaming. Has Nature "rediscovered" this invention 2.7 Gyr ago? Strands of marine cyanobacteria Synechococcus swim 25 diameters per second without any visible means of propulsion. We show that nanoscale amplitude vibrations on the S-layer (a crystalline shell outside the outer membrane present in motile strands) and frequencies of the order of 0.5-1.5 MHz (achievable by molecular motors), could produce steady streaming slip velocities outside a (Stokes) boundary layer. Inside this boundary layer the flow pattern is rotational (hence biologically advantageous). In addition to this purported "swimming by singing", we also indicate other possible instantiations of acoustic streaming. Sir James Lighthill has proposed that acoustic streaming occurs in the cochlear dynamics, and new findings on the outer hair cell membranes are suggestive. Other possibilities are membrane vibrations of yeast cells, enhancing its chemistry (beer and bread, keep it up, yeast!), squirming motion of red blood cells along capillaries, and fluid pumping by silicated diatoms.

Dancing with the Cells: Acoustic Microflows Generated by Oscillating Cells

“…One example is streaming flows generated in the mammalian inner ear upon a perturbation caused by an incident sound wave . Similarly, the self‐propulsion mechanism of some flagella‐less microorganisms, such as the cyanobacterium Synechococcus, is hypothesized to be acoustic streaming . This hypothesis is also inspiring the development of autonomous microswimmers propelled by acoustic streaming .…”

Could cell membranes produce acoustic streaming? Making the case for Synechococcus self-propulsion

“…Experiments. We refer to the companion paper [22] for recent biological findings. The "holy grail" is identifying the molecular motor.…”

“…Moreover, acoustic streaming entails a mixing flow in the Stokes boundary layer, and this additional feature is biologically advantageous. For additional biological information we refer to the companion article [22].…”

“…While photosynthetic as every cyanobacteria, motile strains of Synechococcus do not show a phototactic or photophobic response to light, but do show a chemotactic response to certain nitrogenous compounds. For more biological details, see [22].…”

Nature of acoustic nonlinear radiation stress

“…Aeroacoustics of jet engines, acoustic tweezers, and uses of ultrasonics as active elements are just a few applications where nonlinear radiation (NLR) is a core mechanism. As Nyborg 5 already pointed out, a significant number of biological processes are being explained by acoustic streaming, 17 including cyanobacteria propulsion mechanisms, yeast mechanisms, or hearing mechanisms by the cochlea. 18 Applications to medical engineering have also been envisaged recently, for instance, for nanofluidics, [19][20][21][22] acoustic tweezers, or acoustic radiation force elastography, 23 where efforts are currently required in accurately simulating the exerted radiation force responsible for generating the shear waves that propagate through tissue and correctly quantify its shear modulus.…”