Determining chemotactic responses by two subsurface microaerophiles using a simplified capillary assay method.

A simplified capillary chemotaxis assay utilizing a hypodermic needle, syringe, and disposable pipette tip was developed to measure bacterial tactic responses. The method was applied to two strains of subsurface microaerophilic bacteria. This method was more convenient than the Adler method and required less practice. Isolate VT10 was a strain of Pseudomonas syringae, which was isolated from the shallow subsurface. It was chemotactically attracted toward dextrose, glycerol, and phenol, which could be used as sole carbon sources, and toward maltose, which could not be used. Isolate MR100 was phylogenetically related to Pseudomonas mendocina and was isolated from the deep subsurface. It showed no tactic response to these compounds, although, it could use dextrose, maltose, and glycerol as carbon sources. The chemotaxis results obtained by the new method were verified by using the swarm plate assay technique. The simplified technique may be useful for routine chemotactic testing.