Bibliography: leaves 121-160. / xiv, 180 leaves, [14] l. of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1994

Bibliography: leaves 121-160.

Thesis (Ph. D.)--University of Adelaide, 1994. / Includes bibliographical references (leaves 121-160).

Regensburg, Univ., Diss., 2003. / Erscheinungsjahr an der Haupttitelstelle: 2002. Computerdatei im Fernzugriff.

Regensburg, Univ., Diss., 2004. / Computerdatei im Fernzugriff.

Regensburg, Universiẗat, Diss., 2003. / Erscheinungsjahr an der Haupttitelstelle: 2002.

Regensburg, Universiẗat, Diss., 2004.

Sinorhizobium meliloti maintains a complex lifestyle, including saprotrophy, rhizophere colonization and root hair infection leading to the formation of root nodules in which the plant provides sustenance in return for nitrogen fixation. S. meliloti cells use a variety of carbon substrates for growth; this omnivory probably contributes to competitive ability in the soil. Several candidates for contribution to the catabolic capacity are found within the family of short chain dehydrogenases /reductases (SDR), which catalyze NAD(P)(H) dependent oxidation / reduction reactions. The 6.7 Mb genome of S. meliloti contains 78 SDR-encoding genes distributed on all three replicons. In this work each of these genes were disrupted by single crossover mutagenesis. These mutants were screened for growth on 93 different compounds as carbon source, and phenotypes were found for 17 of the mutants, providing suggestions for potential substrates of the corresponding enzymes. Carbon sources for which phenotype was observed include sugar alcohols, leucine, lysine, ornithine, galactitol, rhamnose, arabinose, mono-methyl succinate and ribono-γ-lactone. In addition, one of the mutants was found to be a proline auxotroph. In several cases, the phenotypes were consistent with the phenotypes of deletion mutants in which large sections of pSymB were absent. Eight of the mutants exhibited symbiotic deficiency after inoculation of alfalfa, while viable cells of three of the mutants could not be isolated from the nodules even though nitrogen fixation occurred. The results suggest that the corresponding SDR enzymes are involved in a pathway that is required for maintenance of viability by cells throughout infection and nodule development. This work demonstrates that members of the SDR family contribute to both the catabolic capacity and the symbiotic interactions of S. meliloti. Further experiments will address the details of the biochemical pathways involved. Knowledge of the substrate specificities of these enzymes should also prove informative in the description and annotation of orthologs that are identified in other genome sequences.

Sinorhizobium meliloti maintains a complex lifestyle, including saprotrophy, rhizophere colonization and root hair infection leading to the formation of root nodules in which the plant provides sustenance in return for nitrogen fixation. S. meliloti cells use a variety of carbon substrates for growth; this omnivory probably contributes to competitive ability in the soil. Several candidates for contribution to the catabolic capacity are found within the family of short chain dehydrogenases /reductases (SDR), which catalyze NAD(P)(H) dependent oxidation / reduction reactions. The 6.7 Mb genome of S. meliloti contains 78 SDR-encoding genes distributed on all three replicons. In this work each of these genes were disrupted by single crossover mutagenesis. These mutants were screened for growth on 93 different compounds as carbon source, and phenotypes were found for 17 of the mutants, providing suggestions for potential substrates of the corresponding enzymes. Carbon sources for which phenotype was observed include sugar alcohols, leucine, lysine, ornithine, galactitol, rhamnose, arabinose, mono-methyl succinate and ribono-γ-lactone. In addition, one of the mutants was found to be a proline auxotroph. In several cases, the phenotypes were consistent with the phenotypes of deletion mutants in which large sections of pSymB were absent. Eight of the mutants exhibited symbiotic deficiency after inoculation of alfalfa, while viable cells of three of the mutants could not be isolated from the nodules even though nitrogen fixation occurred. The results suggest that the corresponding SDR enzymes are involved in a pathway that is required for maintenance of viability by cells throughout infection and nodule development. This work demonstrates that members of the SDR family contribute to both the catabolic capacity and the symbiotic interactions of S. meliloti. Further experiments will address the details of the biochemical pathways involved. Knowledge of the substrate specificities of these enzymes should also prove informative in the description and annotation of orthologs that are identified in other genome sequences.

Four Sinorhizobium meliloti mutants with IPTG-dependent phenotypes were isolated via random Tn5tac1 mutagenesis. The growth phenotypes of Rm30192 (pheT), Rm30193 (ffh ), and Rm300196 (unmapped) were conditional on the presence of IPTG, while that of Rm30194 was conditional on its absence. The insertion in Rm30194 is upstream of tacA, which appears to be under conditional control of the Tn5tac1 Ptac. While all four strains formed root nodules on alfalfa, Rm300192 and Rm30193 attained only 53% and 36% respectively, of the wild-type shoot dry weight value. / Five previously isolated Tn5tac1 mutants were also characterized. Significantly, Rm30044 (bhbA) was able to use arabinose but not glutamate as sole carbon source, a novel finding. Finally, Rm30047 (gpsA), which lacks NADPH-dependent glycerol-3-phosphate dehydrogenase (G3PDH) activity, was found to have an NADH-dependent G3PDH activity that was repressed by IPTG, possibly due to conditional expression by the Tn5tac1 P tac of genes downstream of gpsA.