Nucleic acid and protein content during the growth cycle ofPseudomonas fluorescens, Methanomonas methanicaand of a sporing bacillus

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Abstract
The variations in the cell size and in the RNA, DNA and protein content during the growth cycles of Pseudomonas fluorescens, Methanomonas methanica and of a sporing bacillus ("C") which has some of the characteristics of Bacillus coaqulans (Hammer), are reported. The results are discussed in terms of those obtained previously with Bacterium lactis aerogenes (Aerobacter aerogenes). The most striking behavior is found in the DNA/mass which not only remains relatively constant during the major part of the growth cycle of all the strains but varies little from strain to strain. With P. fluorescens the cell size is nearly constant during the growth cycle so that here DNA/cell is also relatively constant. With M. methanica and with "C" the cell size passes through a maximum early in the cycle. The addition of a complete mixture of amino-acids to the growth medium speeds up the rate of growth of P. fluorescens the cell size and the DNA/cell now pass through maxima, but DNA/mass is hardly affected although the maxima in RNA/mass and protein/mass are augmented. This pattern of behavior of DNA/mass is also seen with B. lactis aerogenes when supplements such as amino-acids, vitamins or metabolites are added to the growth medium. Here again, although the levels of the cell size, RNA/mass and protein/mass were affected to varying degrees, DNA/mass was practically normal. In the unsupplemented medium the levels of RNA/mass and protein/mass for P. fluorescens, M. methanica and "C" agree more closely with the equilibrium (continuous culture) levels for B. lactis aerogenes than with the values obtained during a growth cycle.