Interrelations between glycogen, poly-β-hydroxybutyric acid and lipids during accumulation and subsequent utilization in a Pseudomonas

Abstract

A pleomorphic pseudomonad, V-19, was isolated from activated sludge on the basis of its floc-forming capacity in 0.1% casitone −0.035% yeast extract (CYE) −0.2% glycerol medium. In the late exponential phase of growth morphological changes and flocculation phenomena took place accompanied by a massive deposition of reserve granules in the cell.

Chemical and electron-microscopical examination revealed 3 types of storage products: glycogen, poly-β-hydroxybutyric acid (PHB) and ether-extractable lipids. These products were isolated and chemically characterized.

In CYE medium supplied with 0.5% glucose or glycerol as the carbon source mainly ether-soluble lipids and glycogen were synthesized. On continued incubation these materials were slowly utilized, which enabled the cells to survive for long periods of time.

Growth in inorganic salts medium (0.1% ammonium sulfate; 1% carbon source) yielded cells containing different accumulated products, depending on the carbon source used. Glycerol-grown cells contained mainly glycogen, but also ether-soluble lipid, and no PHB. Glucose was largely converted into gluconic acid and excreted into the medium before being deposited in the form of PHB as the primary product of assimilation. Subsequently, PHB was metabolized thereby being partly transformed into glycogen and ether-soluble lipid.

Addition of ammonium sulfate to nitrogen-starved cells caused a ready mobilization of the accumulated products, resulting in a net synthesis of reservefree cell material and an increase in the number of cells.