Figure 7

Biosynthesis rates of the various components of the bacterial cell during the division cycle [48]. The curves are drawn proportional to their relative contributions to the cell, using the results of Neidhardt [54] for E. coli grown in minimal glucose medium. The percentages of dry weight are as follows: peptidoglycan, 2.5%; DNA, 3.1%; lipopolysaccharide, 3.4%; other (including polyamines, salts, glycogen, etc.), 6.4%; lipid, 9.1%; RNA, 20.5%; and protein, 55.0%. The RNA, protein, and other materials were assumed to have an exponential increase. The synthesis rates of lipid, lipopolysaccharide, and peptidoglycan were presumed to be proportional to the peptidoglycan synthesis rate [42, 44-47]. The rate for DNA synthesis was assumed to be linear with a doubling in rate in the middle of the division cycle [3, 25, 27]. The dotted line is an exponential increase; it indicates the difference between the calculated mass increase and exponential mass increase. The two panels are the same graphs but differ in scale to illustrate the biosynthesis rates of the less prominent material.