Formation of submicron colloidal particles from marine bacteria by viral infection

We tested the hypothesis that viral lytic infection leads to the formation of submicron-sized colloidal particles originating from marine bacteria. Laboratory experiments were performed using a marine bacterium, Vibrio alginolyticus, and and its infectious phage. A particle counter was used to determine abundance and size distribution of particles. We found that the non-living submicron sized particles (size range from 0.38 to 0.7 mu m in diameter) increased rapidly along with a decrease of bacteria and an increase of phage, indicating that these particles are cell debris originating from bacteria. These particles were stained faintly by acridine orange but were not countable due to the amorphous shape. These results show that amorphous submicron particles are produced by viral lysis of bacteria. This process maybe one of the major pathways of colloid formation associated with microbial food webs in the sea.