Resumo -Bactérias fixadoras de nitrogênio podem contribuir para o crescimento vegetal pela produção de auxinas. Os objetivos deste trabalho foram quantificar a produção de hormônios de crescimento por estirpes de bactérias fixadoras de nitrogênio e avaliar o efeito da inoculação destas estirpes em plântulas de milho e trigo. Todas as estirpes avaliadas começaram a produzir indóis no final da fase logarítmica. Houve efeito da adição de diferentes concentrações de triptofano ao meio de cultivo no aumento da produção de indóis até o nível de 200 µM. Nas estirpes de Azospirillum, as formas de N: NH 4 Cl, (NH 4 ) 2 SO 4 , NH 4 H 2 PO 4 e NH 4 NO 3 estimularam a produção de indóis em níveis baixos. A adição de KNO 3 , NaNO 3 e KNO 2 inibiu a produção de indóis em todas as bactérias testadas e no crescimento de células de Azospirillum. Os efeitos da inoculação foram também comparados com concentrações crescentes do ácido 3-indolacético, KNO 3 e triptofano. Em condições axênicas, a elevada produção de indóis reduz o comprimento das raízes e colmos na presença de triptofano, especialmente quando submetidas à inoculação de Azospirillum.Termos para indexação: bactérias diazotróficas, ácido 3-indolacético, fitormônios, fixação biológica de nitrogê-nio. Effect of inoculation with Azospirillum and Herbaspirillum on production of indolic compounds and growth of wheat and rice seedlingsAbstract -Nitrogen fixing bacteria can contribute to plant growth by the production of auxin. The objectives of this work were to quantify the production of plant growth hormones by different nitrogen-fixing bacteria and to evaluate the effect of this inoculation on growth of wheat and rice seedlings. All strains tested produced indoles during the late logarithmic phase. Increasing the amount of tryptophan in the medium enhanced the production of indoles by the bacteria up to the level of 200 µM. For the Azospirillum strains studied, the nitrogen sources: NH 4 Cl, (NH 4 ) 2 SO 4 , NH 4 H 2 PO 4 and NH 4 NO 3 stimulated indoles production in low levels. The addition of KNO 3 , NaNO 3 and KNO 2 inhibited the production of indole compounds for all bacteria tested as well as the Azospirillum growth. The effects of inoculation were also compared to those caused by increased concentrations of IAA, KNO 3 and tryptophan alone. In vitro conditions, the high amounts of indoles produced by the bacteria reduce the length of roots and stems in the presence of tryptophan, especially in the case of Azospirillum strains.Index terms: diazotrophic bacteria, indole-3-acetic acid, phytohormones, biological nitrogen fixation. IntroduçãoDurante a última década, várias bactérias capazes de reduzir N 2 foram descritas, sendo o gênero Azospirillum o mais estudado. Atualmente, este grupo engloba seis espécies diazotróficas, como o A. brasilense e o A. lipoferum. Além disso, algumas espécies foram descritas como endófitas porque não são capazes de sobreviver por longos períodos no solo (Baldani et al., 1997).A primeira espécie endófita a ser identificada foi o Herbaspirill...

Resumo -Foi analisada a produção de compostos indólicos por Azospirillum brasilense Cd, A. lipoferum Br 17, Herbaspirillum seropedicae Z 67, H. rubrisubalbicans M4 e a estirpe 34 isolada de arroz, que não se enquadra em nenhuma das espécies de Herbaspirillum já descritas, em relação a diferentes condições de aeração e concentrações de sais. A maior aeração do meio propiciou aumento na produção de compostos indólicos pelas bactérias testadas. Foi verificado aumento desses compostos, em culturas estáticas, em meio sem nitrogênio no caso de Azospirillum, e na presença de N para as estirpes de Herbaspirillum. O aumento da concentração de sais no meio de cultivo inibiu a produção de compostos indólicos, embora tenha sido observado um pequeno aumento quando a concentração de CaCl 2 foi de 1 g L -1 . O efeito mais deletério da salinidade foi observado com a presença de NaHCO 3 , seguido de NaCl e Na 2 SO 4 . Azospirillum produziu mais compostos indólicos em meio semi-sólido e Herbaspirillum em meio líquido, mas em menor nível.Termos para indexação: Azospirillum, Herbaspirillum, auxina, ácido-3-indol acético, compostos indólicos. Aeration and salt effects on indol acetic production by diazotrophic bacteriaAbstract -The production of indolic compounds by Azospirillum brasilense Cd, A. lipoferum Br 17, Herbaspirillum seropedicae Z 67, H. rubrisubalbicans M4, and strain 34 isolated from rice, which does not fit into the described Herbaspirillum species, was measured under aeration ratio and salt concentrations. Aeration of the medium increased growth and production of indole compounds by these bacteria. Under static condition, the production was higher both in nitrogen-free medium for Azospirillum, and in amended N medium for the Herbaspirillum strains. Increasing salt concentration into the medium inhibited the production of indole compounds, although a small increase in production was observed, when CaCl 2 concentration was raised above 1 g L -1. Deleterious effect of salinity was more pronounced in the presence of NaHCO 3 , followed by NaCl and Na 2 SO 4 . Azospirillum produced more indolic compounds in semi-solid cultures, and Herbaspirillum in liquid medium, but at lower levels.

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T3SS is an important virulence factor of Pseudomonas aeruginosa and has a central role in the infection process. However, the functional regulation of the T3SS by environmental signals is poorly understood. In our lab, we use fluorescence microscopy to study protein kinetics in real-time in live cells. In P. aeruginosa, results have shown that T3SS appears as bright foci at the cell membrane with no specific arrangement. In addition, T3SS is tightly controlled as it appears under a limited time period with the highest intensity at 3 h then disappears. Surprisingly, only 2.5% of the all assembled T3SS in the population have detectable ExoS synthesis. While T3SS assembly and ExoS synthesis increased under high salt concentration, they unexpectedly were not affected by different cyclic di-GMP levels. On the other hand, T3SS itself has an effect on the cyclic di-GMP levels inside the cell. Data have shown that despite T3SS in P. aeruginosa and Yersinia enterocolitica belong to the same the group, the two systems differentiate greatly in activity and regulation. We can conclude that every T3SS is unique and thus further studies are needed to elucidate the functional regulation of each system to better help effective inhibitor design.

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Two field experiments were carried out at The Experimental Farm, faculty of Agricultural at Dar El Ramed, Fayoum University, Egypt, during two winter seasons of 2015/2016 and 2016/2017. The objectives of experiments were to assess the effect of replacing part of chemical N fertilizers through the organic, bio, and foliar application of organic stimulants on growth parameters (fresh weight of shoots per plant (g), fresh weight of roots per plant (g), dry weight of shoots per plant (g), dry weight of roots per plant (g), Plant height (cm) and chemical composition (plant pigments), macro elements content and enzymatic activities (dehydrogenase activity (μg TPF/ g dry soil/ day) & Nitrogenase activity (μ mole C2H4 / g rhizosphere /h)}, of wheat plants (Triticum aestivum L.) cv. Sids12. The experiment comprising eleven treatments in three replications was laid out in a randomized block design. Results indicated that, wheat growth criteria (fresh weight of shoots per plant (g), fresh weight of roots per plant (g), dry weight of shoots per plant (g), dry weight of roots per plant (g), Plant height (cm), chlorophyll content of leaves, N, P, and K uptakes in the flag leaf of wheat plants with all treatments receiving bio-fertilizer + 50% N-compost + 50% N-mineral treatment showed the highest significant increase in growth criteria followed by 50% N-mineral +50%N-compost + foliar application of mix organic acids. Combined inoculation of mixture bio-fertilizers with 50% N-mineral +50%N-compost (T9) gave the highest nitrogenase and dehydrogenase activities in the rhizosphere as well as the macronutrient uptakes in the flag leaf of wheat plants. The highest significant increases for all growth characters and yield components of wheat plants were also recorded by the same treatment (T9). It could be concluded that there is a possibility of using microbial inoculations (Azotobacter and Azospirillium) with the addition of organic manure to soil in order to reduce the amount of mineral fertilizers and to produce a good yield and quality of wheat in addition to improve the biological properties of the soils.