Action of Bacteriophage on Psychrophilic Organisms

Abstract

Additional species of bacteria which are susceptible to bacteriophagy are being reported from time to time, and the list at the present time appears to be far from complete. It seemed of interest, in view of the report of Koser 1 on transmissible lysis of a thermophilic bacterium to determine whether the same phenomenon would be evident in the group of psychrophilic organisms which are capable of growth at low temperatures. A preliminary communication regarding the action of the bacteriophage on psychrophiles has appeared 2 and additional data will be presented here. The cultures selected for investigation were originally isolated from samples of diluted aerobic sewage which had been held at 2 C. for three weeks. Sixty cultures, all of which grew quite well at 4 C. but would not grow at 37 C. were included in this study. From the sixty cultures first selected six which appeared to grow more rapidly at 4 C. than any of the others were selected for bacteriophage experiments. Attempts were made to find an active lytic principle against each of these organisms by means of the method of alternate feeding and filtration. A lytic principle was obtained by incubation of a filtrate of sewage-polluted water with small amounts of the young culture 9 in broth. Beef infusion peptone broth, PH 7.4 to 7.6, was used in all the experiments. Continued alternate feedings and filtrations failed to produce a lytic principle for any of the other five organisms. The lytic principle for culture 9 developed rapidly. The third filtrate showed some evidence of lytic power and the sixth filtrate gave a complete clearing when a drop of the culture was brought in contact with an agar slant previously inoculated with the culture. The psychrophilic lytic principle was shown to be filtrable, produced lysis which was transmissible in series and produced plaques on agar; it therefore fulfilled the common requirements of bacteriophagy.