A strain of Gluconacetobacter diazotrophicus (Gd) characterised by the presence of at least one nucleic acid sequence selected from SEQ ID NOS 1-10 or variants or paralogues thereof and/or the presence of a single plasmid of about 17566 bp in size. Such strains, exemplified by IMI504853, are useful in agriculture, in particular as they are able to colonise plants intracellularly.