Gas Vesicles in Actinomycetes: Not Simply a Case of Flotation in Water-Logged Soil

Abstract

Gas vesicles are gas-filled prokaryotic organelles that provide buoyancy in many planktonic (cyano)bacteriaand halophilic archaea. Remarkably, more and more genomes of soil bacteria, especially those of actinomycetes,show gas vesicle gene (gvp) clusters often encoding homologues of atleast the eight gvp genes essential for gas vesicle formation in archaea.Here, I discuss characteristics specific to actinomycete Gvp proteins, their expression under stress conditions,and the apparent absence of a buoyancy phenotype in gvp mutant strains.Alternative functions for gas vesicles in actinomycetes are discussed in relation to their unusually complexdevelopmental life cycle.