Michael J. Dilworth

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1. The finding that the plant is the genetic determinant of leghaemoglobin production in legume nodules was further tested by inoculating snake beans with two strains of Rhizobium selected to give large genetic differences. Carbohydrate requirement patterns, immunological techniques and DNA base ratio determinations were used to demonstrate genetic(More)
The enzymes involved in the assimilation of ammonia by free-living cultures of Rhizobium spp. are glutamine synthetase (EC. 6.o.I.2), glutamate synthase (L-glutamine:2-oxoglutarate amino transferase) and glutamate dehydrogenase (ED I.4.I.4). Under conditions of ammonia or nitrate limitation in a chemostat the assimilation of ammonia by cultures of R.(More)
Cassettes have been developed that contain an antibiotic resistance marker with and without a promoterless gusA reporter gene. The nptII (encoding kanamycin resistance) or aacCI (encoding gentamicin resistance) genes were equipped with the tac promoter (Ptac) and the trpA terminator (TtrpA) and then cloned between NotI sites to construct the CAS-Nm(More)
This chapter aims to survey the problems faced by bacteria found in environments of adverse pH, to review strategies used to combat those problems and to ask how those strategies are implemented. At acid or alkaline pH, bacteria are challenged not just by excess of H+ or OH- but also by excess of metal ions (aluminium, heavy metals at acidic pH, Na+ at(More)
Medicago truncatula (barrel medic) A17 is currently being sequenced as a model legume, complementing the sequenced root nodule bacterial strain Sinorhizobium meliloti 1021 (Sm1021). In this study, the effectiveness of the Sm1021-M. truncatula symbiosis at fixing N(2) was evaluated. N(2) fixation effectiveness was examined with eight Medicago species and(More)
Biological nitrogen fixation, especially via the legume Rhizobium symbiosis, is important for world agriculture. The productivity of legume crops and pastures is significantly affected by soil acidity; in some cases it is the prokaryotic partner that is pH sensitive. Growth of Rhizobium is adversely affected by low pH, especially in the 'acid stress zone'.(More)
Strains of Gram-negative, rod-shaped, non-spore-forming bacteria were isolated from nitrogen-fixing nodules of the native legumes Listia angolensis (from Zambia) and Lupinus texensis (from Texas, USA). Phylogenetic analysis of the 16S rRNA gene showed that the novel strains belong to the genus Microvirga, with ≥ 96.1% sequence similarity with type strains(More)
An acid-sensitive mutant, TG5-46, derived from Rhizobium meliloti WSM419 by Tn5 mutagenesis, fails to grow below pH 6.0 whereas the parent strain grows at pH 5.7. The DNA sequence of a 2.2 kb rhizobial DNA region flanking Tn5 in TG5-46 contains two open reading frames, ORF1 (designated actS) and ORF2 (designated actR), having high similarity to the(More)
Nineteen strains of root nodule bacteria were grown under various iron regimes (0.1, 1.0 and 20 μM added iron) and tested for catechol and hydroxamate siderophore production and the excretion of malate and citrate. The growth response of the strains to iron differed markedly. For 12 strains (Bradyrhizobium strains NC92B and 32H1, B. japonicum USDA110 and(More)