IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

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17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Title Role of the Cpx two component regulatory system and a MFS transporter in the symbiosis between Sinorhizobium meliloti and leguminous plants Authors Mário R. Santos, Andreia T. Marques, Leonilde M. Moreira Poster Board Number 17 IBB-Institute for Biotechnology and Bioengineering, Centro de Engenharia Biológica e Química, Instituto Superior Técnico Sinorhizobium meliloti establishes a symbiotic nitrogen fixation relationship with Medicago sativa in a process involving signalling between rhizobia and the legume plant. There are several bacterial molecular determinants of symbiosis and we recently added protein TolC to those determinants [1]. A S. meliloti tolC mutant was strongly affected in the resistance to antimicrobial agents, presented higher susceptibility to osmotic/oxidative stresses and also had affected secretion of Ca 2+ -binding proteins, of exopolysaccharides and Nod-factors. Furthermore, S. meliloti tolC mutant induced a reduced number of nodules, which were unable to fix nitrogen in plant roots. The comparison of the transcriptome of the tolC mutant to that of the wild-type strain identified 1809 genes differently expressed, including those encoding proteins involved in central metabolism, protection against stresses and transport. From these genes, the ones with the highest expression in the tolC mutant included the homologues of the sensor histidine kinase CpxA, the response regulator CpxR and the MFS (Major Facilitor Superfamily) transporter encoded by genes SMc03167 and SMc03168 [2]. To determine whether these genes are involved in the symbiotic process, insertion mutants of cpx homologues and deletion mutants of the MFS genes were constructed. Phenotypic tests performed with cpx insertion mutants showed minor differences in motility and in symbiosis when compared to the wild-type strain. Deletion of MFS encoding genes had an effect in stress resistance, pH tolerance, and a slight effect in the number of nodules. Further studies are being conducted to determine other functions for these gene products in S. meliloti biology. 132 2011
17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Title Compatibility with rhizobia of polymer adhesives and colourants used in preinoculated legume pasture seed Authors Elizabeth Hartley, Greg Gemell & Jade Hartley Poster Board Number 18 Australian Inoculants Research Group, NSW Department of Primary Industries, Ourimbah Campus, University of Newcastle In recent years there has been an increase in commercially-produced preinoculated pasture legume seed. Nowadays, preinoculation is the incorporation of ingredients beneficial to seedlings, into a sticker solution containing rhizobia. Seed is coated then dried. Preinoculated seed is often stored for weeks or months before use. Data show that survival of rhizobia on preinoculated seed varies and is generally poor after a few weeks. Sowing preinoculated seed with nil or very few rhizobia may contribute to inadequate nodulation and possible crop failure costing the farmer in lost production. Many physical and chemical factors affect the ability of rhizobia to survive in high numbers when inoculated onto seed. This presentation focuses on ingredients such as polymers, stickers, dyes, pigments and insecticides and their compatibility with rhizobial strains when used in the commercial seed coating process. Chemical and agricultural companies who manufacture and supply such materials contributed 60 ingredients for assessment. To determine the compatibility with rhizobia, and their suitability as an ingredient in the seed coating process, each was applied at recommended rates to rhizobial broth cultures of 3 commercial strains, TA1 (white clover), WSM1325 (subterranean clover) and CB1809 (soybean). Viable rhizobia were counted after 0h, 3h, 24h and 72h incubation. 29 ingredients that were compatible with rhizobia were screened to determine their effect on survival of rhizobia when incorporated into peat slurries used to inoculate polyethylene beads as seed substitutes. Viable rhizobia on beads were counted 1h, 24h and 48h after coating. Results varied. The affect of each of the ingredients to rhizobial survival depended upon the strain, and the method of exposure of the cells to the ingredients. After 24h, 6 ingredient treatments supported better survival of rhizobia on beads than the control treatment. However, after 48h, only one ingredient promoted better survival than the control. 133 2011
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INVENTING THE FUTURE IN INOCULANTS
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17 ICNF Organising Committee Graham
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Cottesloe Beach © Tourism Western
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GeNeRAl INfoRmATIoN aTM’s Automat
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16:30 - 16:50 Felix Dakora Tshwane
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Thursday 1 December 2011 08:00 - 12
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IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

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