Bacteriological studies: 1. The influence of immune serum on the biological properties of pneumococci.

  • Great Britain. Ministry of Health
Date:
1923
Catalogue details

Licence: Public Domain Mark

Credit: Bacteriological studies: 1. The influence of immune serum on the biological properties of pneumococci. Source: Wellcome Collection.

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    or it may subdivide into two portions, only one of which, either (a) or (0), is viable. I think this latter possibility is worth bearing in mind. Continuation of the influence which produced the mixture may result in elimination of the one form and survival of a pure culture of the other. (3) Starting with a pure strain of b as the “ normal,” it may be possible to grow it under conditions which cause it to throw off variants (c), all resembling each other and differing in the same respects from b. And this may not be the final limit to the possible number of variants. By appropriate treatment of c, another variant may be split off, and so on. But a multiplicity of variants does not mean that they are produced in a haphazard sort of way; they seem rather to emerge one at a time, as a series of consecutive reactions between the modified bacterium and its environment. (4) Under special conditions the characters of the variant recovered from 6 may be those of a, 7.e., reversion to the original type may occur. Such reversion is most commonly observed when the original influence which converted a into 6 was in operation only for a short time. (5) In the initiation of bacterial variation, a bacterium (A) may divide in such a way that one half (the variant) is not viable, whilst a fellow bacterium (B) may divide into halves which are each non-viable. If all the bacteria behaved like B, the production of variants would mean death of the culture. But suppose that, whilst a large majority of the bacteria behave like B, the remaining few behave like A; the result will be that disappearance of the variant is associated with scanty growth of the more resistant survivors of the normal individuals. This appears to be what happens in the production of “* autolysis ” associated with the growth of bacteria. It seems to be a special example of bacterial variation, due to an influence which is not an ordinary lysin, because it acts only on bacteria in active growth; it is a selective stimulus, the nature of which will be discussed later, causing the bacteria to subdivide into non-viable elements with the survival of some resistant individuals. For the sake of simplicity, I have stated the case as above; but there is usually an intermediate stage before the variants disappear entirely ; some of them are just viable, though tending to subdivide into non-viable forms; if removed from the lytic stimulus at this stage, they may be cultured as a variant charac- terised by its high sensitiveness to lytic influence. CORRELATION OF THE FACTS. _Is there any interrelationship between the data set out above ? Perhaps a clue may be found in considering the intimate way in which two essential processes of bacterial life are dependent
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