Growth Characteristics of Rough and Smooth Acid Fast Bacteria Living in Microculture

Abstract

While studying the growth of a number of acid fast bacteria in microculture a series of micro motion pictures has been made of a strain of organisms pathogenic to frogs. This mycobacterium, M. ranae I, was provided by the Phipps Institute which obtained it several years ago from E. R. Baldwin. Planted at room temperature on the usual media it gives a rich white growth which at first often has the consistency of very thick cream but with age assumes the wrinkled growth more familiar in acid fast bacterial cultures. Both young and old growths are completely acid fast when stained by the Cooper modification of the Ziehl-Neelson technique. Dissociation was readily brought about by following Petroff's procedure of dilution platings on egg medium containing sodium taurocholate. The rough strain gives the usual wrinkled surface growth on fluid media. Streaked on solid it yields a coarse mealy mass. The smooth strain clouds glycerinated broth and produces a luxuriant mucoid growth on solid media. By transplantation from old Petroff bottles 2 S strains have recently been isolated which differ greatly from one another in their mucosity, one being so fluid that it will almost drip from the surface of an inverted Petri dish. Micro motion picture records show that these R and S dissociants grow in very different ways. The completely dissociated R organisms lie closely packed together as they multiply. They show little tendency to spread over the medium and commence early to overlie one another, forming thereby a thick tangled mass of bacilli. Micro colonies of the S organisms thus far photographed, on the other hand, strikingly resemble those of highly capsulated pneumococci. Several bacilli placed close together when seeding a micro field will not elongate for the first day or two.