Motility of flagellated bacteria in viscous environments

The lowest viscosity that immobilized flagellated bacteria such as Psedomonas aeruginosa, Spirillum serpens, and Escherichia coli was 60 centipoise (cp). Much higher viscosities (1,000 cp and higher) were required to immobilize two flagellated bacteria selectively isolated from nature by methods based on their ability to migrate through agar gels. The latter finding indicates that certain flagellated bacteria have the ability to swim through environments of relatively high viscosity. It is suggested that these flagellated bacteria possess a specialized type of motility apparatus suited to viscous conditions present in their habitats.