Method of temperature-gradient incubation and its application to microbiological examinations.

Nakae, Toshitaka (Tohoku University, Sendai, Japan). Method of temperature-gradient incubation and its application to microbiological examinations. J. Bacteriol. 91:1730-1735. 1966.-An apparatus for incubating organisms by means of a temperature-gradient system under steady-state conduction of liquid was devised. This "temperature-gradient bath" consists of a cylindrical temperature-gradient compartment mounted between two circulating water compartments which are regulated separately at constant temperature, the upper compartment being warmer than the lower compartment. A series of different, constant temperatures in the temperature-gradient compartment can be established simultaneously. Water is a suitable heat-transfer liquid for this purpose. Incubation tubes containing solid media are inserted vertically into the temperature-gradient bath and incubated. Visible growth of the organism appears in a definite portion of the agar column, corresponding to its temperature range for growth. The apparatus was successfully applied to the rapid and simultaneous estimation of maximal, minimal, and optimal temperatures for microbial growth, as well as for the simultaneous isolation of psychrophiles, mesophiles, and thermophiles.