Abstract
Biological characters of S-type of L.acidophilus were compared with those of R-type.
Standard strains of S-type and R-type were always stable on the standard medium of S. H. I. plate of PH. 5.0. On stained smears, S-type organism were seen to be moderate in size and rod shaped appearing either in single or in a chain of ?-3 bacilli. On the contrary, R-type bacilli were appeared to be long steady chains.
Homogeneous saline suspension was easily obtained from the S-type, but with the colony of R-type it was necessary to use glass-beads for grinding and keeping still for a while to obtain a turbid supernatant.
Behaviors of S-type were different from those of R-type, likewise the case of enteric bacteria, in the following reactions : salt sensitivity, Millon's reaction, heavy metal ion reaction, trypaflavin sensitivity, and growth in the broth.
However no appreciable difference was observed between S-type and R-type in the carbohydrate fermentation, final pH, reduction of nitrate, catalase reaction, bile resistance and in the reaction to the heating at 60°C for 30 minutes.
In general, S-type was stable in the acid side and unstable in the alkaline. In the alkaline side, it showed SR-or R-type appearance though there was some difference in the manner by the strain used and the kind of acids used to adjust the pH of the medium. R-type is unstable in the acid side, but stable in the alkaline side.
Relationship between S-type and R-type was observed on the plate added with immune serum. No remarkable change was observed in the appearance of colony between the plate added with homologous immune serum and that with heterologous immune serum except that both R-type and S-type showed a tendency to shift to SR-type on the plate added with heterologous immune serum.
From the above findings, it was concluded that S-type is quite different from R-type in various biological characters as is the case with enteric bacteria, furthermore, the designation of of type S- or R-should be made under the standard conditions stated already.
