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The ahility of the Rhizobium sp., isolated from the root nodules of the leguminous pulse yielding shrub Cajanus cujan. to produce extracellular polysacccharides (EPS) was checked. A large amount of EPS (1,128 p d m l ) WAS produced by the bacteria in yeast extract mannitol medium. Growth and EPS production started simultaneously, hut the production reached its maximum level in the stationary phase of growth at 28 h. The EPS production by this Rhizobium sp. was much higher than by many other strains from nodules of Cajanus cajan which took a much longer time to reach maximum EPS production than this strain. The maximum EPS production (2.561 pg/ml) was obtained when the medium was supplemented with mannitol (l%), cetyl pyridinium chloride (2 pdml) and KN03 (0.2%), in which the Production was increased by 276% compared to the control.The EPS production rose in the period up to 65 h with increased mannitol concentration. The EPS contained arahinose, xylose and rhamnose monomers. The possible role of rhizobial EPS production in root nodule symbiosis is discussed.

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The Rhizobium sp., isolated from the root nodules of the leguminous fodder herbMefiforus alba, produced large amounts of extracellular polysaccharides (EPS) (963.5 pdml) in a y e a t extract mannitol medium. Growth and EPS production started simultaneously, but EPS production reached its maximum during the stationary phase of growth of the bacteria, at 20 hours. EPS production was increased with all of the thirteen sugars tested. Different nitrogen sources, such as nitrates, glutamic acid, casamino acid and L-asparagine, increased the EPS production although i t was inhibited by glycine, nitrite and ammonium salts. Among the vitamins and metal ions only pyridoxal phosphate and ZnS04 promoted EPS production. Attempts were made to optimize the cultural requirements for growth and maximum EPS production. Maximum EPS production (1457.0 p d m l ) was obtained when the medium was supplemented with glucose (1%). pyridoxal phosphate (2 p dml), ZnS04 X 7 H20 (10 pdml) and gluumic acid (0.1%). Under these conditions, the production was increased by 254.3% compared to the control. The EPS contained arabinose, xylose and rhamnose monomers. The presence of arabinose and xylose in the EPS produced by il Rhizobium sp. wils uncommon.

The root nodules of Melilotus alba DESR., a fodder legume, contained high amounts of IAA. A tryptophan pool present in the nodule might serve as a source of IAA production. Presence of IAA oxidase and peroxidase in the nodules indicated the metabolism of IAA, at least in part, in the nodules. The Rhizobium species isolated from the root nodules produced a high amount of IAA (190 pglml) from L-tryptophan supplemented basal medium. IAA production and microbial growth were coincident. The production of IAA by the Rhizobiurn sp. was increased by 315% when the medium was supplemented with lactose (I%), NiClz (10 pglml), cetyl pyridinium chloride (0.5 pglml) and glutamic acid (0.4%). in addition to L-tryptophan (3 mglml). The possible role of the rhizobial production of IAA on the rhizobia-legume symbiosis is discussed.