PHYSIOLOGY OF EXOPOLYMER PRODUCTION BY A PSYCHROTROPHIC BACTERIUM

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Cells of the psychrotrophic Pseudomonas species grown and ‘aged’ at 20°C in the nonpermissive medium Boylen and Brock broth then inoculated into the permissive medium half-strength. Trypticase Soy broth produced no exopolymer at 10°C, a minimal amount at 15°C, a maximal amount at 25°C, and a reduced amount at 30°C. Cells grown and aged at 10°C, produced exopolymer at 20°C but not at 10°C. Cells grown and aged at 5°C, produced no exopolymer at 5°C, but produced exopolymer at 20°C when the aging period was increased from 48 to 72h. The accumulation of potential for exopolymer production during the aging period was affected by temperature; it occurred when buffer or saline were substituted for spent medium, and in the ‘packed’ cell condition; it was affected by pH; and it did not involve the selection of cells capable of exopolymer production. Exopolymer-producing cells assimilated considerably more ¹⁴C-glucose than nonexopolymer-producing cells even though growth rates and total cell yields were the same. All of the carbon sources tested promoted growth and exopolymer production by suitably aged cells.