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Abstract
SUMMARY: Both laboratory-cultured bacteria and the bacteroid forms of Rhizobium lupini (strain wu8) isolated from serradella root nodules synthesize haem from [14C]-δ-aminolaevulinic acid (ALA) and release the product into the incubation medium. Laevulinic acid, an inhibitor of haem synthesis in other organisms, effectively inhibits this synthesis in Rhizobium. When compared on the basis of fresh weight, protein or numbers, the laboratory-grown bacteria are more active in the incorporation of [14C]-ALA than are the bacteroid forms, either when intact or when disrupted by sonication. A synergistic effect between cytoplasmic (plant) and particulate (bacteroid) extracts from serradella nodules is observed which is greater than that for soybean nodules. It is proposed that the haem synthesis for leghaemoglobin in serradella root nodules is a co-operative effort between plant and bacteroid.
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