Rhizobium common nod genes are required for biofilm formation.
In legume nitrogen-fixing symbioses, rhizobial nod genes are obligatory for initiating infection thread formation and root nodule development. Here we show that the common nod genes, nodD1ABC, whose products synthesize core Nod factor, a chitin-like oligomer, are also required for the establishment of the three-dimensional architecture of the biofilm of Sinorhizobium meliloti. Common nod gene mutants form a biofilm that is a monolayer. Moreover, adding Nod Factor antibody to S. meliloti cells inhibits biofilm formation, while chitinase treatment disrupts pre-formed biofilms. These results attest to the involvement of core Nod factor in rhizobial biofilm establishment. However, luteolin, the plant-derived inducer of S. meliloti's nod genes, is not required for mature biofilm formation, although biofilm establishment is enhanced in the presence of this flavonoid inducer. Because biofilm formation is plant-inducer-independent and because all nodulating rhizobia, both alpha- and beta-proteobacteria have common nod genes, the role of core Nod factor in biofilm formation is likely to be an ancestral and evolutionarily conserved function of these genes.
Fujishige
Nancy A
NA
Department of Molecular, Cell and Developmental Biology, University of California-Los Angeles, CA 90095-1606, USA.
Lum
Michelle R
MR
De Hoff
Peter L
PL
Whitelegge
Julian P
JP
Faull
Kym F
KF
Hirsch
Ann M
AM
D000907:Antibodies, Bacterial / Q000378:metabolism; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D047311:Luteolin / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009154:Mutation; D016962:Sinorhizobium meliloti / Q000235:genetics* / Q000502:physiology*; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*
D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D015534:Trans-Activators; D047311:Luteolin