Bacteriorhodopsin induces a light-scati’ering change in Halobacterium Halobium

Abstract

When suspensions of Halobacterium halobium are exposed to bright light, the light-scattering properties of the bacteria change. This light-scattering response can produce a transmission decrease of about 1 throughout the red and nearinfrared region. The action spectrum for the light-scattering response appropriately matches the absorption spectrum of bacteriorhodopsin. The response is eliminated by cyanide p-trifluoro-methoxyphenylhydrazone, a proton ionophore, and by triphenylmethylphosphonium, a membrane permanent cation. A mild hypertonic shock induces a similar light-scattering change, suggesting that bright light causes the bacteria to shrink about 1 in volume, thereby producing the light-scattering response. © 1978, Rockefeller University Press., All rights reserved.