✦ LIBER ✦

Nutritional control of pigment and isoprenoid compound formation in extremely halophilic bacteria

✍ Scribed by Gochnauer, M. B. ;Kushwaha, S. C. ;Kates, M. ;Kushner, D. J.

No coin nor oath required. For personal study only.

✦ Synopsis

Cells of the extremely halophilic bacteria, Halobacterium cutirubrum and H. halobium grown in a chemically defined medium (BSMK) were red due to the presence of baeterioruberins (maxima, 370, 388, 494 and 527 nm). Adding 0.1 ~ glycerol to BSMK stimulated growth, but cells rapidly lost bacterioruberins becoming greyish purple in the stationary phase. Acetone extracts of these cells were yellow with a broad absorption band at 360--390 nm, partly attributable to retinal. In BSMK medium with or without glucose, the bacterioruberin concentration increased until maximal growth was reached, then fell rapidly.
In complex medium (CM) cells formed less bacterioruberins than in BSMK. Adding 0.1 ~ glycerol to CM stimulated growth but did not change pigmentation; adding glucose only slightly stimulated growth but greatly increased bacterioruberin formation. Exposure to visible light did not affect growth or pigmentation.
Addition of glycerol or glucose to BSMK increased the formation (relative to squalene) of dihych'osqualene, tetrahydrosqualene, and vitamin MK s. Higher levels of these compounds were found in cells grown in CM than in BSMK. Though glycerol decreased the formation of bacterioruberins it increased the formation of /~-carotenes. Glucose increased the formation both of bacterioruberins and fl-carotene. A preliminary hypothesis to account for the effects of nutrients on pigmentation is presented.