METHOD FOR THE ISOLATION OF BACTERIA IN PURE CULTURE FROM SINGLE CELLS AND PROCEDURE FOR THE DIRECT TRACING OF BACTERIAL GROWTH ON A SOLID MEDIUM

Abstract

By a pure culture we understand, as is well-known, a culture consisting of individuals of which we know with certainty that all are descended from one single cell, and from one only. As all bacteriologic work, of whatever kind it may be, depends on our working with such reliable pure cultures, many efforts have, of course, been made in the course of time in order to devise reliable methods of isolating a single bacterium. The first investigator who solved the problem in a satisfactory wa,-although not in regard to the bacteria proper-was Emil Chr. Hansen. The principle of his method was, briefly stated, to observe directly under the microscope the growth of the individual yeast-cell until it has formed a small colony in a gelatin droplet on the lower surface of a coverglass in a moist chamber. Yeast-cells are however far bigger than most bacteria , and there is no possibility of tracing with any certainty the growth of a bacterium, as for instance a colon bacillus, in a similar way in gelatin. Of methods that have been proposed and employed for single cell cultivation of bacteria, the best known are those of Schouten, Barber and Malone, none of which have however attained any extensive application, no doubt partly owing to the intricate apparatus they require, and partly to the difficulty involved in picking up such minute objects as bacteria with such relatively coarse implements as pipettes and loops; and when Barber states that he is able to pick up successively each single one of four 537