Microbial Activity in the Bovine Rumen

MICROBIAL ACTIVITY IN BOVINE RUMEN bengal, asparagus agar (Allen, 1951), asparagus agar plus 1:80,000 crystal violet, and asparagus agar plus 1:15,000 rose bengal.The addition of dyes decreased the number of contaminants but also appeared to inhibit the development of the rhizobia.All plates were examined daily for 2 weeks.Smears of colonies which resembled rhizobia were examined.Pure cultures were obtained by the use of both pour and streak plates.These pure cultures were inoculated into Bacto-MR-VP Medium', alkaline, and very alkaline broth (Hofer, 1935).At the same time, known pure cultures of rhizobia were inoculated into the same media.The reactions of the isolates are given in table 1.After 1 to 2 years' storage under mineral oil at room temperature or refrigerator temperature, all nodules were dark and soft.No typical rhizobia were isolated from nodules stored under mineral oil.The 1 Difco Laboratories, Inc., Detroit, Michigan.nodules stored in the deep freeze cabinet appeared unchanged after storage.All the isolates studied were from frozen nodules.The majority of the isolates appear to be rhizobia.SUMMARY Nodules of leguminous plants can be preserved by freezing for as long as 2 years; they cannot be pre- served by storage under mineral oil at room or re- frigerator temperatures.