Polymorphism in a marine bacterium in relation to population growth.

Greenfield, Leonard J. (University of Miami, Miami, Fla.), Janet J. Hines, and Linda L. Boral. Polymorphism in a marine bacterium in relation to population growth. J. Bacteriol. 84:357-363. 1962.-A marine pseudomonad, MB-1, from South Florida waters, exists in three forms: orange (y), lemon-yellow (xy), and white (x), each of which is polymorphic. Replicate growth curves of each form were obtained by culturing at 25 C in 1% peptone-sea water using a controlled inoculum. The controlled inoculum was obtained by growing an isolate on a 1% peptone-sea water agar (1.5%) slant for 24 hr at 25 C, transferring a wire loopful of culture to 50 ml of 1% peptone-sea water in a 125-ml flask, and incubating at 25 C for another 24 hr. The resulting bacterial suspension in 0.5-ml amounts was used to inoculate 50 ml of 1% peptone-sea water broths in which growth was measured. The logarithmic growth phase occurred in x and xy between 12 and 18 hr of incubation; in y, this period was between 18 and 24 hr. The stage of growth could also be characterized by the percentage of cell types present at a given period. In late lag phase, single cells outnumbered binary types by about two to one. During logarithmic growth, the single cells predominated by 2.5 or 2.4 to 1. In the stages following this ratio increased, but all cells showed considerable variation in size. Chains of cells were present in all stages but were reduced in number during the logarithmic phase.