Stages in the Life History of Phytomonas tumefaciens.

Phytomonas tumefaciens, the root nodule organisms, and other related bacterial species may produce, in the course of their life histories, peculiar, star-shaped aggregates of cells. Beijerinck (1890) and Beijerinck and van Delden (1902) were apparently the first to describe this phenomenon. Working with the root nodule bacteria and Alcaligenes radiobacter these investigators interpreted this phenomenon as being the result of a peculiar type of branching or division of a single bacterium. At the time when Lohnis (1921) was formulating his life cycle theory, he also observed these star-shaped bodies and concluded that they represented evidence of conjunction in the bacteria. In his first report on the subject Lieske (1926) did not attempt to interpret the phenomenon but later (1928) suggested that, superfically at least, it had the appearance of a sexual stage in the life history of the bacterium studied. Stapp and Bortels (1931) presented a detailed account of the different phases of the life cycle of Phytomonas tumefaciens. These investigators devised a simple medium which permitted the initiation and development of large numbers of bacterial stars and thus greatly facilitated their study. The medium consisted of dilute carrot juice and 70.01 per cent each of FeSO4. 7H20 and MnSO4.7H20. Recently Stapp (1942) has studied, with the aid of the Feulgen stain, the nuclear behavior within the aggregate. He has suggested that fusion of the nuclei of the individual members of the star results. Other investigators, however, have interpreted the phenomenon differently. Schatzel (1932) states that the aggregates result from an entangling of flagella of the individual members. Riker et al. (1946) suggest that further work is necessary to determine the possibility of the bacteria being attracted by a particle with an electric charge different from that of the organisms. Other workers believe that the bacterial stars represent an attempt by these organisms to form colonies such as are found in certain of the algae and protozoa. We have investigated, with the aid of an electron microscope, the various stages in the life history of Phytomonas tumefaciens when that organism developed in a special carrot medium. The chromatinic behavior within the star-shaped bodies was also studied by means of the Feulgen procedure and light microscopy. It is the purpose of the present paper to report our findings.