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  • The genus Micromonospora is widespread in legume root nodules: the example of Lupinus angustifolius.

The genus Micromonospora is widespread in legume root nodules: the example of Lupinus angustifolius.

The ISME journal (2010-05-07)
Martha E Trujillo, Pablo Alonso-Vega, Raúl Rodríguez, Lorena Carro, Eugenia Cerda, Pilar Alonso, Eustoquio Martínez-Molina
ABSTRACT

Our current knowledge of plant-microbe interactions indicate that populations inhabiting a host plant are not restricted to a single microbial species but comprise several genera and species. No one knows if communities inside plants interact, and it has been speculated that beneficial effects are the result of their combined activities. During an ecological study of nitrogen-fixing bacterial communities from Lupinus angustifolius collected in Spain, significant numbers of orange-pigmented actinomycete colonies were isolated from surface-sterilized root nodules. The isolates were analysed by BOX-PCR fingerprinting revealing an unexpectedly high genetic variation. Selected strains were chosen for 16S rRNA gene sequencing and phylogenetic analyses confirmed that all strains isolated belonged to the genus Micromonospora and that some of them may represent new species. To determine the possibility that the isolates fixed atmospheric nitrogen, chosen strains were grown in nitrogen-free media, obtaining in some cases, significant growth when compared with the controls. These strains were further screened for the presence of the nifH gene encoding dinitrogenase reductase, a key enzyme in nitrogen fixation. The partial nifH-like gene sequences obtained showed a 99% similarity with the sequence of the nifH gene from Frankia alni ACN14a, an actinobacterium that induces nodulation and fixes nitrogen in symbiosis with Alnus. In addition, in situ hybridization was performed to determine if these microorganisms inhabit the inside of the nodules. This study strongly suggests that Micromonospora populations are natural inhabitants of nitrogen-fixing root nodules.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
REDExtract-N-Amp Plant PCR Kit, sufficient for 1000 extractions, sufficient for 1000 amplifications
Sigma-Aldrich
REDExtract-N-Amp Plant PCR Kit, sufficient for 100 extractions, sufficient for 100 amplifications
Sigma-Aldrich
REDExtract-N-Amp Plant PCR Kit, sufficient for 10 extractions, sufficient for 10 amplifications