| Popis: |
Ten types of bacteria isolated from soil are described for which vitamin B12acts as an essential nutrilite. In addition to vitamin B12, thiamine was found to be essential for the growth of all, and biotin for eight, of the 10 forms; in two cases riboflavin acted as a growth antagonist. For nine of the organisms thymidine, with or without the addition of purine and pyrimidine bases, was unable to replace vitamin B12in promoting growth; with one organism but slight response was noted. Methionine was equally ineffective as a substitute for B12. Three of the organisms were observed to be cocci and one a pleomorphic, curved, unbranched, filamentous form producing cocci in older culture. The remaining six types, representing approximately 80% of the isolates studied, were considered to belong to the genus Arthrobacter, the findings providing further evidence of the importance of this group as members of the indigenous soil microflora. |
