Abstract
The psychrotrophic Pseudomonad (4) of this study appears to be unique with regard to the production of a gel-like exopolymer (2, 3). If cells are repeatedly subcultured from the log phase, they produce minimal to no exopolymer upon inoculation of a permissive medium. However, if cells are allowed to reach maximum stationary phase during a particular growth cycle, and to persist for an appropriate period of time in this phase (the ‘aging’ period), the potential to make exopolymer accumulates and is expressed upon inoculation of a permissive medium. The nature of this potential is not known but a working hypothesis is that it is a regulatory compound that activates an enzyme (or enzymes) involved in exopolymer biosynthesis. This hypothesis stems from the following observations (2, 3): the accumulation of the potential during the aging period is time-, pH-, and temperature-dependent, and does not require new protein synthesis; there is a direct relationship between the amount of exopolymer produced and the number of aged cells in the inoculum; the potential accumulated in cells can be reduced by growth (cell divisions) in the nonpermissive medium prior to inoculation of a permissive medium; and exopolymer production occurs throughout the growth cycle of the bacterium and is not preceded by a lag period. In an attempt to understand the aging process at the molecular level, cell-free extracts from aged and unaged cells were prepared. This communication reports the stimulation of exopolymer production in unaged cells by adding portions of a cell-free extract to the permissive medium.
