CYCLIC CHEMICAL AND MORPHOLOGICAL CHANGES IN NOCARDIA RUBRA

Abstract

The morphological growth cycle of Nocardia rubra was related to cellular composition when the organism was grown in a biphasic system for varying lengths of time up to 96hr. The DNA, RNA, lipid, protein, and ash content were determined. The morphology of the organism progressed from long branched filaments in the lag phase of the growth curve to shorter and shorter filaments with decreasing branching during the logarithmic phase. In the stationary phase the N. rubra cells were bacillary, and gradually became coccoid in the declining or death phase.The DNA percentage of the dry cell weight increased during the logarithmic growth phase from 2.2% to 3.0%, and then decreased to 1.5% during the stationary and declining phase. The RNA content was at a maximum of 20.1% in the middle of the logarithmic phase, declined sharply to 10% at the end of this phase, and then decreased more slowly to 4.0% in the declining phase. The lipid content increased rapidly from 9.9% to 20% in the early logarithmic period, at which point it leveled off and increased more gradually to 30.8% in the declining phase. The protein percentage of dry cell weight decreased from 50% to 43% during the early logarithmic period and remained steady throughout the remainder of the logarithmic and stationary phases, and finally decreased in the declining growth phase to 31%. The ash content increased steadily from 8.2% to 9.5% during the incubation period.