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Presented as Thesis (Ph. D.)--University of Wisconsin--Madison, 1929. / "Sonderabdruck aus dem Zentralblatt für Bakteriologie, parasitenkunde und Infektionskrankheiten. II. Abteilung. 1929, Bd. 79." Includes bibliographical references.

Thesis (M.S.)--University of Kentucky, 2008. / Title from document title page (viewed on December 10, 2008). Document formatted into pages; contains: vii, 56 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 47-55).

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Soybean (Glycine max L. Merr.) and Bradyrhizobium japonicum can form a nitrogen fixing symbiosis. This symbiosis is important for most sustainable agriculture systems. This thesis examines two ways to enhance nodulation and nitrogen fixation by this symbiosis: coinoculation of plant growth promoting bacteria (PGPB) with B. japonicum, and addition of RNA to a bradyrhizobial culture medium. The optimal coinoculation dose of Serratia proteamaculans 1--102 and S. liquefaciens 2--68 was determined as 108 cells per plant under both optimal and suboptimal root zone temperatures (RZTs). Nodulation dynamics studies indicated that coinoculation of these two PGPB caused earlier nodule initiation and a higher nodulation rate, contributing to the higher nodule number and nodule weight. The coinoculation also increased nitrogen fixation efficiency under both optimal and suboptimal RZTs. A novel inducible activator only produced by the bacteria after addition of flavonoids to the culture system was prepared and evaluated in greenhouse and field experiments. Fourteen non-bradyrhizobial endophytic bacteria (NEB) were isolated from the surface sterilized root nodules, and three of these, designated NEB4, NEW and NEB17, showed soybean plant growth promotion under both greenhouse (with controlled RZTs) and field conditions. Alone, they were neither nodule inducers nor nitrogen fixers. Biolog tests and partial 16S rRNA gene sequence analyses placed the three strains in genus Bacillus: NEB4 and NEB5 are B. subtilis and NEB17 B. thuringiensis. Bradyrhizobium species grow slowly, making the culture process long and the cost of inoculant production higher. Addition of commercial yeast RNA to the bacterial culture medium accelerated the bacterial growth rate, shortened the culture time and increased the lipo-chitooligosaccharide (LCO) yield in flask cultures. Inoculation experiments in the greenhouse also showed that bradyrhizobial inoculant produced in the presence of RNA had better symb

[Truncated abstract] Some plants, such as legumes, are able to use atmospheric nitrogen as a nitrogen source due to the nitrogen-fixing bacteria residing in specialised root structures called nodules. The exchange of carbon and nitrogen between the host plant (legume) and the nitrogen- fixing micro-symbiont is vital for biological nitrogen fixation. In particular, transport of C4-dicarboxylates, mainly malate, from the plant to the micro-symbiont, and the reverse transport of fixed nitrogen in the form of ammonium are essential for symbiotic nitrogen fixation. In the legume nodule, the symbiosome membrane (SM) surrounds the bacteroid and all exchanges of metabolites and nutrients that occur between the plant and the micro-symbiont must cross this membrane. Recently it has been established that cycling of amino acids across the SM is also critical for optimal symbiotic nitrogen fixation. Therefore to fully understand this agriculturally significant phenomenon, the mechanisms facilitating these exchanges need to be investigated. The major aim of this study was to increase the understanding of nutrient exchange within the nodule at the molecular level by isolating and characterising genes encoding transporters responsible for malate and amino acids transport in soybean (Glycine max, L.), with particular interest in genes significantly or highly expressed in nodules. A combination of molecular and biochemical techniques was used to achieve this. ... Southern blot analysis showed that a small gene family of up to five members encodes these proteins in soybean. A full-length cDNA, designated GmAAP5, was isolated that encodes a novel, putative amino acid transporter. Molecular characterisation of this cDNA and that of GmAAP1 (GenBank Accession no: AY029352), a previously identified putative amino acid transporter gene, was done. Expression analyses showed relatively high expression of GmAAP5 in soybean nodules compared to that in leaf and root tissues, while GmAAP1 showed uniformly high expression in root, leaf and nodule tissues. Phylogenetic analysis of the deduced amino acid sequences of known functional AAPs from dicotyledonous plants revealed that GmAAP1 is most closely related to AAP2 from V. faba, while GmAAP5 is more closely related to AAPs from non-leguminous plants than from leguminous plants. Based on the functional characterisation of the AAPs with which GmAAP1 and GmAAP5 cluster, it is likely that both transporters are neutral and acidic amino acid transporters within the AAP subfamily.