Progoitrin is a thioglycoside present in high concentration in the seeds of most Brassicaceous plants and in the edible parts of some, particularly rutabaga and turnip. I t is hydrolyzed by enzymes (myrosinases) in these plants to yield goitrin, a potent antithyroid compound ( 1,2,3) (Fig. 1 ).Although it had been assumed for many years that hydrolysis of thioglycosides similar to progoitrin could be accomplished only through the action of myrosinase of plant origin, recent studies have indicated that this view is incorrect. Reese et aZ(4) reported that the fungus Aspergillus s y d m * produced a P-thioglycosidase (termed "sinigrinase") active on the mustard oil thioglycosides sinigrin, sinalbin, and progoitrin; however, the enzyme could not be obtained from other fungal genera or from the bacteria, Bacillus subtilis or Pseudomonas aeruginosa, which also were found to "consume" sinigrin on prolonged (14-day) incubation with this compound. Thioglycosidase activity hydrblyzing several purinyl thioglycosides has been reported by Goodman et aZ(5) to be widespread in mammalian species, and to occur in the microorganisms Tetrahymena pyriformis and Escherichia coli.Because of the possible importance of goitrin derived from commonly ingested vegetables in the production of human non-toxic goiter, studies were undertaken of the metabolic fate of pure crystalline progoitrin in man after oral ingestion. It was found that in such cases goitrin could be demonstrated * Supported by grants from U.S.P.H.S. in blood and urine(6). These results suggested that the conversion of progoitrin to goitrin might have been carried out by thioglycosidase activity of bacteria in the gastrointestinal tract. This hypothesis was reinforced by the finding that incubation of rat or human feces with progoitrin resulted in goitrin formation( 3 ) . This myrosinase activity in feces was destroyed by boiling, filtration, or sonoration, and was markedly reduced by prior oral administration of Amphotericin B and Neomycin(3), a regimen which has been shown to effect a striking decrease in viable fecal bacterial flora (7).The data reported here concern experiments on the isolation and identification of fecal bacteria with myrminase activity, comparison of such organisms with stock strains of various bacterial species, and conditions necessary for formation and activity of bacterial myrosinase.MateriaZs and methods. Progoitrin was prepared from rutabaga seed by the method of Greer (2). Bacterial cell suspensions were obtained by growing the organisms, unless otherwise stated, in nutrient broth containing 1 % glucose for 18 hours a t 37°C without shaking. The cells were harvested by centrifugation, washed once with water, and resuspended in water at a concentration between 1.0 and 2.0 mg bacterial nitrogen per ml. The cell suspensions were incubated with progoitrin and buffer at concentrations noted in the legends, in a total volume of 5.0 ml contained in 50 ml Erlenmeyer flasks which were shaken in a water bath at 37°C. Length

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Group A streptococci strain C203S, grown in heart infusion broth with 0.3% maltose, produce two cellular hemolysins related to extracellular streptolysin S (SLS). Enzymatic lysis of the streptococci by group C streptococcal phageassociated lysin results in release of low titer, labile hemolysin, which can be stabilized by ribonucleic acid (RNA)-core (RNA preparation from yeast). This labile hemolysin can be detected only after the higher titer cellular streptolysin 0 is removed by erythrocyte membranes or inactivated by N-ethylmaleimide. The other cellular SLS-related hemolysin is released in a latent state (potential hemolysin) which can be activated.to high-titer hemolysin by sonication with RNA-core. The titer of such activated hemolysin depends upon the intensity of sonic energy, duration of sonication, and amount of RNA-core. RNA obtained from the streptococci is far less effective than RNA-core. When the cocci are disrupted by sonication or grinding, potential hemolysin and/or activated form may be released, depending upon the conditions employed. The potential hemolysin material is large and heterogeneous; activation appears to involve, in part, disaggregation or fragmentation. Labile hemolysin, potential hemolysin, and the activated form of potential hemolysin can all be converted to hemolysin having the same hemolytic and physical properties as RNA-core SLS, suggesting that all have the same hemolytic moiety. The presence of glucose in heart infusion broth prevents formation of both potential hemolysin and RNA-core SLS by log-phase cells, whereas addition of glucose to a culture in heart infusion broth with 0.3% maltose stops accumulation of potential hemolysin but does not affect continuation of RNA-core SLS release. These results suggest that potential hemolysin is a cellular precursor to RNA-core SLS.

The susceptibility of a marine bacterium, designated isolate c-Al, to lysis in distilled water and in salt solutions has been found to be a function of Na+ concentration. Optical densities of cells pre-exposed to 0.05 M MgCl2 were maintained in 1.0 M KCl, whereas those of cells pre-exposed to 1.0 M NaCl were not maintained at any KCl concentration tested. Cells transferred from MgCl2 to low concentrations of NaCl underwent more extensive lysis than did those transferred to distilled water. The degree of disruption of cells transferred to distilled water from mixtures of 0.05 M MgCl2 and NaCl (0 to 1.0 M) was dependent on the concentration of NaCl; similar results were obtained with LiCl, but not with KCI. In electron micrographs of thin sections, c-Al cell envelopes consisted of two double-track layers which fractured and peeled apart on lysis after pre-exposure to NaCl-MgCl2 mixtures. Envelope eruptions or "hernias" occurred only in lysed cells pre-exposed to NaCl alone. No evidence for a functional lytic enzyme was found. Comparative studies on a terrestrial pseudomonad with a multilayered envelope indicated that preexposure to NaCl did not enhance the susceptibility of this cell to lysis in distilled water. The lytic susceptibility of the marine bacterium is considered to be the consequence of competition between specific monovalent cations and Mg++ for electrostatic interactions with components of the cell envelope of this organism.

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