- Volume 7, Issue 3-4, 1952

Concentrated culture fitrates from Bacillus subtilis, with high gelatinase activity, disintegrated hide powder although unable to attack native collagen; they also haemolysed the red blood cells of a number of species. The concentrated filtrates were dermonecrotic in rabbits and lethal on intravenous injection into mice. There was no conclusive evidence that the factors responsible for any of these effects were autigenic. Although each of the in vitro and in vivo activities was destroyed by heat, the haemolytic activity was more resistant than the others. Fresh normal sera from many species inhibited each of the three properties shown in vitro. Tests with gelatinase showed that inhibition occurred rapidly and in multiple proportions. The inhibitory action was diminished by heat and storage and was distinct from the antitryptic property of serum.

Proteus vulgaris, suspended in meat extract broth or in a defined medium, bound cobalt to an extent dependent on the cell concentration and on the concentration of cobalt in the medium. An increase in concentration of cobalt or a decrease in the number of cells per unit volume resulted in a greater amount of cobalt ion bound per unit of cellular material. The composition of the suspending medium with regard to the cobalt combining groups present, as well as the availability of other metallic ions, markedly affected the amount of cobalt bound by the cells. Magnesium was particularly effective in diminishing the cobalt-combining capacity of the cells. An exposure time of 15 min. was sufficient for the major portion of the ion to be taken up by the cells. In an anaerobic medium, the cells-bound approximately one-half as much cobalt as in an aerobic medium. Raising the pH value of the medium from 5·0 to 7·0 resulted in an increased uptake of the metal by the cells. Cobalt taken up by the cells could be removed to an extent of 70–80% by dilution in distilled water and almost completely by 0·1 n-HCl. A derived strain of Proteus, capable of growth in relatively high concentrations of cobalt, bound smaller quantities of the ion at each level tested than did the parent strain. However, at the growth inhibitory level peculiar to each strain, the resistant form took up a much greater quantity of the metal than did the sensitive strain. This fact indicates that resistance to cobalt cannot be explained merely on the basis of the cobalt-concentrating ability of the cells.