Potential nitrogen-fixing freshwater photosynthetic bacteria of 32 isolates from the Aswan High Dam Lake were investigated using the acetylene reduction technique to ascertain the magnitude of their contribution of fixed nitrogen to the ecosystem. The superior nitrogen-fixing Rhodospirillaceae were Rhodocyclus gelatinosus and Rhodomicrobium vannielii followed by Rhodobacter capsulatus, Rhodopseudomonas viridis and Rhodopseudomonas palustris. High and moderate nitrogenase activities (534 to 1528 nmol ethylene produced/4 ml/h) were found in 56% of the isolates, while the remainder showed low activities (76 to 477 nmol ethylene produced/4 ml/h).

Six strains and a commercial inoculant of Bradyrhizobium japonicum were evaluated in association with Glycine max (L.) cultivar Clark. Inoculated and uninoculated plants were grown in pot and field experiments. Nodules were counted and weighed and roots and shoots were separated and analysed for total nitrogen. In pot experiments, two of six bacterial strains were superior to the other four, and to the commercial inoculant (Nitragin) in promoting greater root and top growth and plant nitrogen accumulation. In the field experiment, there were indications that environmental conditions may have affected nodulation by the bacteria. The strains could be divided into three groups according to nodule efficiencies, accumulation of plant dry matter, and total nitrogen content. The greater variations in nodule efficiencies of the tested strains could be attributed to the quantities of bacteroid, cytosol protein and leghaemoglobin in the nodules.

ABSTRACT. Azotobacter chroococcum was isolated from straw-amended soil and found to utilize 4-hydroxybenzoic acid, resorcinol, pyrocatechol and vanillic acid as sole carbon source. Growth and nitrogenase activity ofA. chroococcum were supported by 8, 6 and 4 mmol/L of 4-hydroxybeazoie acid, rcsorcinoi and pyrocatechol, respectively, The generation time of 1.71 h in 4-hydroxybenzoie acid did not significantly differ from the generation time of 1.64 h, observed when grown in mannitol. 4-Hydroxybenzoic acid was utilized rapidly. However, the decomposition of other tested phenolic compounds set in only slowly. It was concluded that this isolate has good potential to utilize some phenolic compounds released during biodegradation of plant wastes

ABSTRACT. Seeds of three species of lupine (Lupinus tennis, L. triticale and L. albus) were tested to determine if the seed contains diffusable substances toxic to bradyrhizobia. L. albus seeds were less toxic to bradyrhizobia, followed by L. triticale. Six strains of Bradyrhizobium were evaluated for their resistance to the toxic substances in lupine seeds. Zones of growth inhibition were determined on yeast-mannitol-agar medium surrounding surface-sterilized seed. The effect of surface sterilization of seeds by different chemical treatments on seed toxicity was assessed. Seeds soaked in water for 1 h before placing on agar surface significantly decreased the inhibition zone. Also, the effect of soaking seeds in water for 4 h before planting and inoculation on nodulation, nitrogen fixation and plant growth were investigated. Addition of seed diffusate to soaked seeds significantly decreased nodulation and plant growth. Autoclaving the seed diffusate had no effect on the toxicity of the seed diffusate. Addition of the absorbent polyvinylpolypyrrolidone (PVPP) to seed diffusates significantly decreased the inhibitory effect of seed diffusate on nodulation and plant growth. Seed diffusate substances were water-soluble, heat-stable and partially bound to PVPP.

The effect of four bacterial and six fungal species on nodulation and growth of Vicia faba cv. Giza 3 inoculated with Rhizobium leguminosarum biovar viceae strain RCR 1001 were assessed in a pot experiment. Bacillus cereus, Pseudomonasfluorescens, Aspergillus niger and ,4. quadriliniatus either alive cells or sterile filtrate significantly promoted nodulation, growth and nitrogen accumulation. Heat-killed cells had no effect.

Pyrano[2,3-d]thiazoline-7-spiro-3
-(1
-substitutedindoline-2
-ones) 5a,b has been synthesized and reacted with some nucleophile reagents to afford new spirothiazolino[4,5:2
,3
]pyrano[6
,5
-d]pyrimidine derivatives 6a,b–13a,b, which are analogues of some reported biologically active spiroheterocyclic compounds

Pyrano[2,3-d]thiazoline-7-spiro-3
-(1
-substitutedindoline-2
-ones) 5a,b has been synthesized and reacted with some nucleophile reagents to afford new spirothiazolino[4,5:2
,3
]pyrano[6
,5
-d]pyrimidine derivatives 6a,b–13a,b, which are analogues of some reported biologically active spiroheterocyclic compounds

Pyrano[2,3-d]thiazoline-7-spiro-3
-(1
-substitutedindoline-2
-ones) 5a,b has been synthesized and reacted with some nucleophile reagents to afford new spirothiazolino[4,5:2
,3
]pyrano[6
,5
-d]pyrimidine derivatives 6a,b–13a,b, which are analogues of some reported biologically active spiroheterocyclic compounds

Pyrano[2,3-d]thiazoline-7-spiro-3
-(1
-substitutedindoline-2
-ones) 5a,b has been synthesized and reacted with some nucleophile reagents to afford new spirothiazolino[4,5:2
,3
]pyrano[6
,5
-d]pyrimidine derivatives 6a,b–13a,b, which are analogues of some reported biologically active spiroheterocyclic compounds

Azotobacter chroococcum was grown on cultures containing five carbon sources alone and also in co-cultures with three cellulolytic fungi (Aspergillus niger, Penicillium funiculosum and Trichoderma harzianum). In the absence of fungal species, nitrogenase activity was relatively low. The best nitrogenase activity was recorded in cultures containing faba bean straw followed by that in cultures havingwheat straw, sugar cane leaves, carboxymethyl cellulose (CMC) or cellulose. In co-cultures with fungi, Azotobacter showed substantial nitrogenase activity on all tested substrates. Azotobacter-Trichoderma association showed thg highest nitrogenase activity.