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the haem agglutinin, in the form seen after ether treatm ent, does not represent a structure which is present as such in the virus particle before sp litt ing, but a m odification of a po rtio n of the outer coat.T he G antigen, on the co n trary , is alm ost cer tainly present in the form observed after ether sp litt ing. T he only question in doubt is the total length of G antigen in the particle, and w hether it is in the form of several sho rt pieces, or of one long piece which is d isrupted by the ether treatm ent. The m ost significant outcom e of these findings is th at they confirm the pred ictio n of S c h ä f e r 11 (1957) that the G antigen w ould be found to correspond, as a stru ctu re, to the w hole particle of the sm aller RNA viruses. A typical sm all " sph erical" virus (m ouse encephalom yelitis (M E) virus) has been sprayed with som e G antigen of K P virus, and the two to gether exem plify the two com m on form s of arra n g e m ent of subunits, i. e. the helical and the polyhedral, e. g. icosahedral or dodecahedral. It is the G antigen which contains the RNA. and which presum ably alone 11 W . S c h ä f e r , in: T he N ature of Viruses (Ed. A. E. W . W o ls t e n h o l m e and E. C. P. M i l l a r ) , p. 100, London 1957.carries the genetic in fo rm atio n of the particle, and which has p ro tein su b u n its sym m etrically arran g ed (a sym m etry of form which is not seen in the intact p a rtic le ).As fa r as the von M agnus incom plete form s are concerned, it is clear th at the sim ilarity of K P to influenza extends also to the phenom enon of p ro d u c tion of incom plete viru s by passage of larg e inocula and th at th ere a re sim ilarities betw een the incom plete form s of th e two viruses ( W a t e r s o n and H o r n e 12, 1 9 6 1 ; R o t t and S c h ä f e r 9 , 1 9 6 0 ). The particles of v iru s N show much m ore v ariatio n in shape and size th a n do those of K P, although it is fa ir to p o in t out th at in som e passages of K P virus alm ost as much v aria tio n m ay be found.T2-infected cells of E. coli B synthesize an enzyme whose role it is eventually to lyse the cell from within, whereby the new crop of T2-phage is released from it. Procedures for isolating this enzyme in pure form are described. The enzyme is characterized as a lysozyme. It has a m olecular weight of 15 2 0 0 . Die erste B eobachtung über ein anscheinend n u r von phageninfizierten Zellen synthetisiertes, lytisches Enzym stam m t von S e r t i c 1. E r beschreibt einen "Lysinzonen b ild e n d en " P hagen Fez (W irtsbakte rium ist der m ucoide E. co/t-Stam m Fb) und fü h rt die E rscheinung der Z onenbildung, d. h. das A uf treten eines H ofs rin g s um einen P hagen-P laque, auf ein lytisches, im A gar diffundibles Agens zurück, das die infizierte Zelle zusam m en m it den neugebil deten Phagenteilchen verläßt. Es kann von diesen abgetrennt w erden. 1 V. S e r t i c , Zbl. Bakteriol., Parasitenkunde Infektionskrankh.. Abt. I, Orig. 110, 125 [1929]. 2 A. G r a t ia , C. R. Seances Soc. Biol. Filiale...

A cell-bound bacteriocin was extracted from a Bacteroidesfragilis BF-11 strain by treating the cells with a low-molarity buffer (0.01 M Tris-hydrochloride, pH 8.0). Sucrose osmotic shock experiments and ultrasonic lysis of whole cells indicated that the majority of the bacteriocin was located at the cell surface. Culture supernatants contained no significant bacteriocin activity. The bacteriocin was purified by DEAEcellulose and Sephacryl S200 chromatography and had an apparent molecular weight of approximately 7,000. It was relatively heat stable and was inactivated by proteases. There was a delay of approximately 3.5 h before DNA, RNA, and protein synthesis were inhibited by the bacteriocin. Inhibition of macromolecular synthesis coincided with lysis of the susceptible indicator strain.There are numerous reports on the characterization of bacteriocins produced by aerobic bacteria (7,9,11,22) Since the production of more than one bacteriocin by a single bacterial strain is not uncommon (22), we investigated the production of a cell-bound bacteriocin by a derivative of the B. fragilis Bf-1 strain Bf-11 which had lost the ability to produce the cell-free bacteriocin described by Mossie et al. (12). MATERIALS AND METHODSBacterial strains. A derivative of B. fragilis Bf-1 (designated Bf-11) which had lost the ability to produce the cell-free bacteriocin which was studied by Mossie et al. (12-14) was used for the production of the bacteriocin. The susceptible indicator strain (Bf-2) and the 10 rifampin-resistant Bf-2 mutants have been described previously (13).Media and bacteriocin assay. The bacteriocin was produced in a complex medium which contained, in grams per liter, Difco tryptic soy broth, 24; Difco yeast extract, 10; glucose, 1; and L-cysteine-hydrochloride 0.5. The bacteriocin was assayed with porcelain beads (18) containing 20-,ul samples which were placed on the surface of a 3-ml seeded soft agar overlay on brain heart infusion agar plates which contained, in grams per liter, Difco brain heart infusion, 37; Difco yeast extract, 5; L-cysteine-hydrochloride, 0.5; and agar, 15. Bacteriocin titers in arbitrary units (AU) were expressed as the reciprocal of the highest doubling dilution that gave a zone of inhibition surrounding the bead. The minimal medium of Varel and Bryant (23) analysis of macromolecular synthesis. Hemin and menadione (Sigma Chemical Co.) were added to all the media (5 and 0.5 mg/liter, respectively). Protein concentrations were estimated by the method of Bradford (2).Bacteriocin purification. Overnight cultures (100 ml) of B. fragilis Bf-11 were harvested by centrifugation, and the cells were suspended in 10 ml of extraction buffer (0.01 M Trishydrochloride, pH 8.0) for 30 min at 20°C. The bacteriocin was also extracted by the sucrose osmotic shock method of Willis et al. (24). The cells were disrupted by ultrasonication (Heat Systems-Ultrasonics Inc.) at 4°C. All subsequent operations were performed at 4°C. The supernatant obtained after centrifugation was dialyzed in dialysis tubing w...