Some nutritive aspects of proteinase biosynthesis by non-proliferating cells of Streptococcus liquefaciens, strain 31, were investigated by substituting constituents in a basal medium containing casein, lactose, purines, pyrimidines, vitamins, and salts. The casein of the medium could be replaced by a mixture of 12 "essential" amino acids (glutamic acid, histidine, valine, serine, methionine, leucine, isoleucine, arginine, cystine, lysine, tryptophane, and threonine), thus demonstrating that proteinase synthesis can occur in a medium devoid of protein. Proteinase biosynthesis appeared to depend upon an inordinately high concentration of arginine, required a fermentable carbohydrate, and occurred optimally at pH 6.3. Sodium fluoride and iodoacetate did not inhibit the proteinase activity but radically curbed its synthesis.
Osmotically fragile bodies which may be t r~~e protoplasts of the group D S~rcptococcus faecalls vat. I%c/~~c'f'~cii~zs have been produced b y use of a lytic enzynle derived fro111 phage-infected cultures of the group D S. f(~ecalis vat.cy~t~ogcnes. 'These bodies may be held in 1.1 ilc sucrose a n d are lysetl almost q~iantitatively upon removal illto \\rater a t root11 ternperat~ire or a t 37" C. T h e phage-associatetl lysin, in the presence of 0.7 i M cysieine, causes almost complete lysis of the sensitive organism by the end of 1 hour a t 37" C and effects complete removal of cell-wall materials (rhamnose-~ont:~i11i1ig moieties and phage-receptor sitcs) in that time.Osniotically fragile bodies which may be termed spheroplasts of S. filccalis var. lig~rcfhcie~zs have been produced by the use of lysozyme on cells previously gr0u.n in penicillin ( 5 ~~n i t s / r n l ) .Lysis to the extent of 50% iii 1 hour a t 37' C occurs in the aqueous suspensions. whereas 17% sucrose with 0.2% MgS0.,.71-120 or 0.27Z0 '04gS0~.71-1?0 alor~e elfects almost complcte stabilization. T h e stabilized bodies are Iysed almost q~~a n t i t a t i v e l y upon re~noval to water a t 56' C. Cellwall material containing rhamnose reruai~is on these forms, indicating that they are spiieroplasts rather than protoplasts.
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, AND L. N. Zini-MIERMAN. New mode of genetic transfer in Str-eptococcius faecalis var. liquefaciens. J. Bacteriol. 87:799-801. 1964.-When chloramphenicol-resistant mutants are grown in mixed culture with the sensitive wild type of Streptococcus faecalis var.
Survival of Serratia marcescens after freezedrying or aerosolization at unfavorable humidity. I. Effects of sugars. J. Bacteriol. 84:1297-1302. 1962.-Suspensions of Serratia marcescens were subjected to freeze-drying or to aerosolization at unfavorable humidity levels. The survival of the cells during one or the other of these treatments was markedly improved in the presence of common sugars, but no one sugar stabilized the cells against both stresses. The protective effects of the sugars were correlated with their penetrability into cells; minimally penetrable sugars stabilized cells against aerosolization, and freely penetrable sugars stabilized cells during freeze-drying. These results were attributed to the modifications of intracellular water content induced by the presence of the sugars in the cell suspensions.
Neutral solutions of ascorbic acid were antibacterial to Serratia marcescens at low but not at high population densities. The toxicity of ascorbate was eliminated by metalsequestering treatments, and was restored only by the addition of trace amounts of copper salts. Copper-ascorbate was equally toxic under aerobic or anaerobic conditions; its toxicity was abolished by (i) chelating agents that sequestered the copper, (ii) metal-complexing agents that bound to the cells but did not sequester copper, and (iii) iron salts in the presence of air. On the basis of these observations, the toxic effects of copper-ascorbate were attributed to its reaction with vital Fe-containing cellular components. Neutralized 1% ascorbic acid is one of the solutes that enhances the survival of Serratia marcescens during freeze-drying (12) of suspensions containing 1010 to 1011 cells per milliliter.
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