. Cell heredity. Cytogenetics. 208 CELL HEREDITY From pump controlling input from reservoir. Overflow FIGURE A chemostat in operation. overflow. In this steady state the total number of bacteria in the chamber remains constant in accordance with the concentration of Hmiting nutrient in the input; the rate of growth is also constant and equal to the rate of turnover of the medium which is a function of the rate of in- put. In a closed system such as a test tube, the concentration of nu- trients falls during growth while the concentration of waste products rises. In the open system of the c
. Cell heredity. Cytogenetics. 208 CELL HEREDITY From pump controlling input from reservoir. Overflow FIGURE A chemostat in operation. overflow. In this steady state the total number of bacteria in the chamber remains constant in accordance with the concentration of Hmiting nutrient in the input; the rate of growth is also constant and equal to the rate of turnover of the medium which is a function of the rate of in- put. In a closed system such as a test tube, the concentration of nu- trients falls during growth while the concentration of waste products rises. In the open system of the chemostat, since the bacteria im- mediately use up the incoming nutrient and since waste products are continually lost in the overflow, a steady state of the chemical environ- ment is maintained. In this way, then, the conditions of growth may be accurately controlled and varied at will. When a mutant arises in the chemostat, it may multiply at the same rate as the parents. If so, its proportion in the population will not in- crease through growth alone because mutants as well as parents are lost as fast as they are formed. But the proportion of mutants will increase as new mutations occur, and in a linear fashion as long as the number of mutants, M, is so small that it is unnecessary to take back mutation into account. If the growth rate of the mutants is equal to that of the parents, whose number is N, then so long as N is very large relative to M, the rate of increase of mutants will be: dM dt aN () where a is the chance of mutation per parent bacterium per Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Sager, Ruth; Ryan, Francis J. (Francis Joseph), 1916-. New York, Wiley
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