Formation of extracellular gas balloons in colonies of some gram-negative bacteria

It was shown that some gram-negative bacteria of the genera Alcaligenes and Pseudomonas and also unidentified vibrioid bacteria form gas balloons (GBs ) similar in their properties to the GBs of gram-positive bacteria. A pecul iarity of the GBs of gram-negative bacterial is the compact arrangement of cells along the GB membrane, the tight contact between the GE and the cell wall outer membranes, and the association of a hemoglobin-like substance wi th the GB membrane. The formation of GBs is related to surface films on the colonies. These surface films form invaginations (gas channels) whose wall s can stick together with subsequent splitting of closed gas chambers-extra cellular gas balloons. In wet-mount specimens, artifactual GBs readily form due to the sticking together of gas channel walls. It is assumed that GBs and gas channels improve colony aeration; in liquid media, GBs favor cell f loatability.