Studies of aerobic non-symbiotic nitrogen-fixing bacteria.

The occurrence of aerobic, non-symbiotic, nitroqen-fixing bacteria was determined in samples of soil collecte~l in the various soil zones of Allxrm and Saslcatchewan. Mannitol and sodiuttl betuoate dust-platrs. and mallnit01 solution cultures wiLh subsequent inoculation onto rnannitol agar demonstrated that Asolohnrtt-r were not wirlcspreatl in the Canadian prairie province soils. These r)n)ccrlurcs alm let1 to the isolation of smaller, aerobic, non-symbiotic, nitrogcnfixing organisms from all the Alberta ant1 Sas1;atchewan soils sturlietl. These smaller, nitro~en-iising Iracteria which de~~eloped as Ito 3-mm rircular, convex, unpigmentcd colonies on ~naitrlitol and glrrcose aEar were classified as Psmdomonos. Flag-ellation of the 0.75 to 1 p by 1.5to 2-p Gram-negative, corcoid rods was polar. Starch 1 ~ s hydroly7ecl; eelatin was not liqoified. Intlol, acid, and gas were not produced; litnlus milk was not reducetl, but hydrogen sr~lphitle was formed. The pseudomonads, capable of initiatin~ growth a t a pH of 1.9, could a150 grow a t 8" C, wllereav the rlrntobactrr rhroocorcu+n required higher temperatures and reartions above pH 6.2. Azolohurtrr chroucoccunt fixed up Lo 12 mg nitrogen F r r i m of carbohydrate. The smaller bacteria, rlassilied as Pseudomonuc aeolog~~tsis , fixed from 0.1 to 3.9 mg N per gram of mannitol.