The photographic examination of giant colonies.

Recently (1949) we recorded particulars of giant colonies of Acetobacter species which had been grown on a semi-solid medium. In such conditions certain species, e.g., A . aceti (Kiitzing) Beijerinck, form highly characteristic colonies. Other species, including the majority of the known species of Acetobacter, characterized by colonies of a particular type, can be classified in a number of groups. Species which form cellulose, e.g. A. xylinum (Brown) Holland, A. kutzingianum (Hansen) Bergey et al., A . acetigenum (Henneberg) Bergey et al. belong to one group. Again, the giant colonies of A . acetosum (Henneberg) Bergey et al., A . ascendens (Henneberg) Bergey et al., and A . rancens Beijerinck, though differing from each other in size, are similar in general appearance and form another group. A third group comprises A . subozydans Kluyver & de Leeuw, and a number of species all of which are highly motile and form colonies with zones of motile cells. These various characteristic features are brought out particularly well in photographs taken under conditions which we have devised, and since the technique may prove of service to others, we describe i t below.