Very slow growth of Escherichia coli

W Chesbro, T Evans, R Eifert
1979 Journal of Bacteriology  
A recycling fermentor (a chemostat with 100% biomass feedback) was used to study glucose-limited behavior of Escherichia coli B. The expectation from mass transfer analysis that growth would asymptotically approach a limit mass determined by the glucose provision rate (GPR) and the culture's maintenance requirement was not met. Instead, growth proceeded at progressively lower rates through three distinct phases. After the fermentor was seeded, but before glucose became limiting, growth followed
more » ... ng, growth followed the usual, exponential path (phase 1). About 12 h postseeding, residual glucose in the fermentor fell below 1 jig-ml" and the growth rate (dx/dt) became constant and a linear function of GPR (phase 2). The specific growth rate, ,I, therefore fell continuously throughout the phase. Biomass yield and glucose assimilation (13%) were near the level for exponential growth, however, and independent of GPR over a broad range. At a critical specific growth rate (0.04 h-1 for this strain), phase 2 ended abruptly and phase 3 commenced. In phase 3, the growth rate was again constant, although lower than in phase 2, so that,u continued to fall, but growth rates and yields were paraboloid functions of GPR. They were never zero, however, at any positive value of GPR. By inference, the fraction of metabolic energy used for maintenance functions is constant for a given GPR, although different for phases 2 and 3, and independent of biomass. In both phases 2 and 3, orcinol, diphenylamine, and Lowry reactive materials were secreted at near-constant rates such that over 50% as much biosynthetic mass was secreted as was retained by the cells. ment of the requirements for the Ph.D.). MATERIALS AND METHODS Culture, medium, and fermentor seeding. E. coli B was maintained on Davis and Mingioli (5) minimal medium slants containing 1.25 mg of glucose. 625 on May 9, 2020 by guest
doi:10.1128/jb.139.2.625-638.1979 fatcat:i7chlf4mmfb2zffogrvchb4sky