The lysis of dead bacteria by bacteriophage.

Abstract

There is no difference of opinion that only young and actively growing bacteria are subject to transmissible lysis. Old or dead bacteria do not undergo lysis and do not contribute to the increase in concentration of the active lytic substance, but rather, on the contrary, bring about a measurable reduction of it.

Recently, Twort 1 has stated (somewhat similar to the evidence offered a year earlier by Gratia 2 , 3 ) that dead staphylococcus may undergo lysis if, in addition to a suitable bacteriophage, there is also present live staphylococcus. We have confirmed these observations, and in addition have endeavored to ascertain the explanation of the mechanism of this phenomenon. We found that in order to elicit the phenomenon it is necessary to control the numbers of live and dead bacteria in the mixture. An excess of dead bacteria interferes with lysis by adsorbing the active lytic substance before it has the opportunity to initiate lysis of the live bacteria, and thus all solution is prevented. The phenomenon is specific, that is, the lysis of live bacteria will initiate lysis of dead bacteria of the same species only. In its extent and completeness, lysis of dead bacteria occurs best with stapylococcus, the organism which easily undergoes autolysis under appropriate conditions. In the case of colon bacillus, which undergoes autolysis very slowly, the lysis of the dead bacteria is less regular and less complete.

If the experiment is performed so that a suitable semi-permeable membrane is interposed between the dead and live bacteria, dead bacteria are never dissolved, in spite of the lysis of living bacteria on the other side of the membrane. The active substance determining the lysis of dead bacteria is not diffusible, while the principle initiating the lysis of live bacteria diffuses freely and is demonstrably present on both sides of the membrane.