Loss Of Capsule Research Articles

Factors affecting the chain length of group A streptococci. I. Demonstration of a metabolically active chain-splitting system.

Group A streptococci which grew in long chains in the presence of homologous anti-M antibody were split into their original length by the addition of an excess of homologous M protein to the culture. The chain-splitting reaction showed temperature and pH optima (37 degrees C., 7.5) and was completely inhibited at 0 degrees C. or by heat-killing the long chains at 56 degrees C. prior to the addition of M protein. Addition of sublethal doses of HgCl(2), or of penicillin, inhibited the chain-splitting reaction. Pneumococci behaved in entirely comparable fashion to streptococci in similar experiments. Virulent strains of streptococci formed the shortest chains when broth media was enriched with serum. The chain-shortening effect of serum enrichment of the media was most apparent with encapsulated strains and under cultural conditions that favored capsule formation. Loss of capsules by mutation or by unfavorable growth conditions resulted in increase in chain length. The activity of the chain-splitting mechanism seemed to be independent of M protein, however, since encapsulated M-negative variants also formed very short chain in serum-enriched media. The physical presence of the capsule was not essential for chain shortening since enzymatic removal of the capsule with hyaluronidase during growth did not affect chain length. These results strongly suggest that chain-splitting of streptococci and pneumococci occurs by an active metabolic mechanism, presumably enzymatic, which is inhibited by the union of surface antigens with specific antibody.

Capsules and mucoid envelopes of bacteria

Methods have been described by which capsules and mucoid envelopes of bacteria can be fixed and stained positively and differentially, proving they are of different natures. The capsule is of definite shape and outline, the slime is amorphous. Some bacteria may have capsules, some may produce slime, and in others the capsulated organisms may be embedded in amorphous slime, as, for example, in the Fried-lander bacillus and in thePneumococcus,type III. These properties are probably more or less characteristic for certain organisms or groups of organisms. Of course, loss of capsules, and loss of slime production do occur.All bacteria which have capsules seem to possess special antigens (cp. Kauffmann's A-antigen). This was particularly shown for members of thecoli-oerosrenes-Friedlander groups andStreptococcus para-faecalis(Skadhauge). Organisms with L-antigens possess generally no capsular or mucoid envelopes of the type described, with one exception, viz. strain Bi 316/42.By means of the capsule- and slime-staining methods here described, a densely staining edge was demonstrated in the bacteria examined, which—it is suggested—may comprise the cell wall and its adjoining cytoplasmic layer. Organisms supposed to have no cell walls (Myxococci) do not show this appearance.The so-called ‘swelling reaction’ is a reaction between antiserum and homologous bacteria, by which the capsule becomes easily demonstrable. It seems doubtful that actual swelling takes place.