Bradyrhizobiumjaponicum FN1 produces an inhibitory substance that affects competition for nodule occupancy.

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From: Canadian Journal of Microbiology(Vol. 68, Issue 4)
Publisher: NRC Research Press
Document Type: Report
Length: 6,135 words
Lexile Measure: 1390L

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Abstract :

Bacteriocins are narrow-spectrum antibiotics of bacterial origin that can affect competition in resource-limited environments, such as the rhizosphere. Therefore, bacteriocins may be good candidates for manipulation to generate more competitive inocula for soybean. In this study, Bradyrhizobium japonicum FN1, along with other Bradyrhizobia in our culture collection, was screened for bacteriocin-like activity. Five distinct inhibitory effects were observed. FN1 genes putatively involved in bacteriocin production were computationally identified. These genes were mutagenized, and the subsequent strains were screened for loss of inhibitory activity. Mutant strain BRJ-48, with an insert in bjfn1_01204, displayed a loss of ability to inhibit an indicator strain. This loss can be complemented by the introduction of a plasmid expressing bjfn1_01204 in trans. The strain carrying the mutation did not affect competition in broth cultures but was less competitive for nodule occupancy. Annotation suggests that bjfn1_01204 encodes a carboxymuconolactone decarboxylase; however, the direct contribution of how this enzyme contributes to inhibiting the tester strain remains unknown. Key words: Bradyrhizobium, bacteriocin, competition, root nodules, symbiosis. Les bacteriocines sont des antibiotiques a spectre etroit d'origine bacterienne qui peuvent affecter la competition dans des environnements a ressources limitees comme la rhizosphere. Par consequent, les bacteriocines peuvent etre de bons candidats a la manipulation afin de generer des inoculums plus competitifs pour le soja. Dans cette etude, Bradyrhizobiumjaponicum FN1 ainsi que d'autres Bradyrhizobia de la collection de cultures des auteurs ont ete examines quant a leur activite de type bacteriocine. Un total de cinq activites inhibitrices distinctes a pu etre observe. Les genes de FN1 supposement impliques dans la production de bacteriocines ont ete identifies par informatique. Ces genes ont ete mutagenises et les souches qui en ont resulte ont ete examinees en matiere de perte d'activite inhibitrice. La souche mutante BRJ-48, avec un insert dans bjfn1_01204, montrait une perte de la capacite d'inhiber une souche indicatrice. Cette perte pouvait etre complementee par l'introduction d'un plasmide exprimant bjfn1_01204 en trans. La souche portant la mutation n'affectait pas la competition en cultures en milieu liquide, mais se montrait moins competitive pour l'occupation des nodules. L'annotation suggere que bjfn1_01204 code une carboxymuconolactone decarboxylase, cependant la contribution directe de cette enzyme a l'inhibition de la souche de controle reste inconnue. [Traduit par la Redaction] Mots-cles : Bradyrhizobium, bacteriocine, competition, raciness nodules, symbiose.

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Gale Document Number: GALE|A700067501