Abstract
Five isolates of Bdellovibrio bacteriovorus obtained from paddy field soils of Japan were tested on their ability and mode of multiplication in media composed of autoclaved susceptible or resistant bacteria. The isolate Bd-N6801 successively transferred on Xanthomonas oryzae living cell medium was commonly used in this experiment.
Bd-N6801 multiplied in media composed of autoclaved cells of susceptible and also of some species of resistant bacteria. The multiplication was slightly retarded in the autoclaved cell (AC) medium than in the living cell (LC) medium. Autoclaved cytoplasm fraction of the bacteria also supported the multiplication of Bd-N6801. Bd-N6801 grew well on AC-agar plate, forming light yellowish colonies. Lytic zone appeared around each colony on AC-agar plate prepared from susceptible bacteria, in contrast to negative results with plate prepared from resistant bacteria.
Since the plaque forming units (PFU) on LC-agar medium closely corresponded with the colony forming units (CFU) on AC-agar medium, it is concluded that every cell of Bd-N6801 either in the plaque on LC-agar or in the colony on AC-agar possesses both parasitic and saprophytic propagation abilities. The morphological characteristics of the cells from the colony were identical with those from the plaque.
The other isolates of B. bacteriovorus, Bd-N6802, Bd-N6804, Bd-N6805, and Bd-N6806, also formed colonies on AC-agar medium. The ratio of CFU to PFU, however, varied much with different isolates.
