Psychrotrophic Clostridia

摘要

Of 287 strains of clostridia of 23 different species 96 grew well at 6°, 77 of which wereClostridium carnofoetidumvar.amylolyticumand 16 wereCl. perfringens.The water of polluted wells seems to be the normal habitat ofCl. carnofoetidumvar.amylolyticum. This species is both proteolytic and saccharolytic and is not pathogenic for mice or guinea pigs. Spores survive at 80° for 40 min. Mg is essential to obtain sporulation of the strains in artificial environments.Growth temperatures vary between 6 and 37° with an optimum at 30°. At 6° strains untrained to grow at this temperature grow in about 5 days in Rosenow medium. Trained stains have a lag phase of 24 h. Growth curves show a longer logarithmic phase at 6° than at 30°. At the end of this phase the bacterial count is the same at both temperatures.Cl. carnofoetidumvar.amylolyticumis, therefore, a true psychrotrophic species.Glucose and pyruvate breakdown studied by Warburg's method confirms the slowing down of metabolism at 6°. A study of amino acid degradation indicates that serine is the substance most rapidly attacked at 37°, but at 6° the activity against serine disappears completely.In Rosenow medium at the first inoculation 8 strains ofCl. perfringensout of 24 failed to grow at 6° after 30 days. They were all enterotoxic types. Among the other 16 strains none survived beyond the tenth transfer at 6° and it was not possible to train any strain to grow at this temperature. An examination of the growth curves shows that they are not truly psy