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A novel intracellular nitrogen‐fixing symbiosis made by U stilago maydis and B acillus spp.
Author(s) -
RuizHerrera José,
LeónRamírez Claudia,
VeraNuñez Antonio,
SánchezArreguín Alejandro,
RuizMedrano Roberto,
SalgadoLugo Holjes,
SánchezSegura Lino,
PeñaCabriales Juan José
Publication year - 2015
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.13359
Subject(s) - bacteria , ustilago , biology , bacillus pumilus , intracellular , nitrogenase , microbiology and biotechnology , fungus , 16s ribosomal rna , botany , nitrogen fixation , biochemistry , gene , genetics
Summary We observed that the maize pathogenic fungus Ustilago maydis grew in nitrogen (N)‐free media at a rate similar to that observed in media containing ammonium nitrate, suggesting that it was able to fix atmospheric N 2 . Because only prokaryotic organisms have the capacity to reduce N 2 , we entertained the possibility that U. maydis was associated with an intracellular bacterium. The presence of nitrogenase in the fungus was analyzed by acetylene reduction, and capacity to fix N 2 by use of 15 N 2 . Presence of an intracellular N 2 ‐fixing bacterium was analyzed by PCR amplification of bacterial 16S r RNA and nifH genes, and by microscopic observations. Nitrogenase activity and 15 N incorporation into the cells proved that U. maydis fixed N 2 . Light and electron microscopy, and fluorescence in situ hybridization ( FISH ) experiments revealed the presence of intracellular bacteria related to Bacillus pumilus , as evidenced by sequencing of the PCR ‐amplified fragments. These observations reveal for the first time the existence of an endosymbiotic N 2 ‐fixing association involving a fungus and a bacterium.