The effects of the ionic environment on the chromatin structures of bacteria.

Abstract

The aggregation of bacterial chromatin into compact masses under a variety of circumstances (exposure to high salt concentrations, low temperature, ultraviolet irradiation, metabolic inhibitors, and starvation) is a function of the concentration of electrolytes in the environment of the cell. This effect can be prevented or reversed in an environment deficient in salts. The observations indicate that chromatin aggregation is a consequence of interaction of cations (Na+ and K+, in particular) and polymerized desoxyribose nucleic acid, which behaves as an anionic gel. The organisms used (Shigella dysenteriae, Escherichia coli, Bacillus cereus, Caryophanon latum, a wild yeast, and a Geotrichum sp.) were able to maintain their "normal" configuration of chromatin in salt-deficient media and in media with up to 3% salt as long as their metabolism was intact. Disruption of metabolism by exposure to cold or metabolic inhibitors produced aggregation or dispersion of chromatin according to the ionic environment. This range of change in nuclear form can be produced in the living cell without apparent or permanent damage to viability. These studies indicate that bacterial and fungal cells share with cells of higher organisms the ability to regulate the influx and efflux of cations. Chromatin serves as a sensitive indicator of the integrity of these ion regulatory mechanisms. Some implications of these observations are discussed.