The exbD mutant of P. luminescens TT01. A) The exbD locus on the genome of P. luminescens TT01 (taken from Colibase at http://xbase.bham.ac.uk/colibase). B) Siderophore production by P. temperata K122, P. temperata K122 exbD::Km, P. luminescens TT01 and P. luminescens TT01 ΔexbD. The bacteria were cultured overnight at 30°C in LB broth and the OD600 of the culture was adjusted to 1. An aliquot of 10 μl of each cell suspension was inoculated onto the surface of an LB agar plate containing CAS solution and the plate was incubated at 30°C for 48 h. Siderophore production is observed as the orange halo surrounding the growing colony. C) The growth of P. luminescens TT01 ΔexbD is sensitive to the levels of iron in the medium. TT01 (diamonds) and the ΔexbD mutant (circles) were grown in fresh LB (open symbols) or LB broth supplemented with 50 μM 2'2'-dipyridyl (filled symbols). Growth curves were done in triplicate and a representative curve is shown.