SOME BIOCHEMICAL CHARACTERISTICS OF FRESHLY ISOLATED STRAINS OF THE GENUS SERRATIA

SUMMARY: Many of 110 strains of Serratia , isolated from soil, water, milk and dairy equipment, were biochemically closely related to the coli-aerogenes bacteria. Acid and gas was formed from glucose in 14 days at 30° by 53% and from lactose and MacConkey's broth by about 40%. All except one strain gave——++ IMViC reactions.
An inverse relationship was observed between depth of pigmentation and carbohydrate fermentation. Complete loss of pigment in mutant strains was not uncommon, and was associated with loss of proteolytic properties and increase of saccharolytic activity.
The majority of the strains had psychrophilic characteristics: 75% grew at 3–5°. Most strains showed moderate growth at 37°, but only 7 formed red pigment at that temperature.
All strains resembled Serratia marcescens in morphology, containing minute coccoid rods smaller than those of coli-aerogenes bacteria.