IRON STARVATION OF BORDETELLA-AVIUM STIMULATES EXPRESSION OF 5 OUTER-MEMBRANE PROTEINS AND REGULATES A GENE INVOLVED IN ACQUIRING IRON FROMSERUM

Iron starvation of Bordetella avium induced expression of five outer m embrane proteins with apparent molecular masses of 95, 92, 91.5, 84, a nd 51 kDa, Iron-responsive outer membrane proteins (FeRPs) of similar sizes were detected in six of six strains of B, avium, suggesting that the five FeRPs are common constituents of the outer membrane of most, if not all, strains of B. avium. Iron-regulated genes of B, avium wer e targeted for mutagenesis with the transposon TnphoA, Two mutants wit h iron-responsive alkaline phosphatase activities were isolated from t he transposon library. The transposon insertion did not alter the iron -regulated expression of the five FeRPs in mutant Pho-6, The mutant Ph o-20 exhibited a loss in expression of the 95-kDa FeRP and the 84-kDa FeRP. Both Pho-6 and Pho-20 were able to use free iron as a nutrient s ource. However, Pho30 was severely compromised in its ability to use i ron present in turkey serum. The data indicated that the mutation in P ho-20 affected expression of one or more components of an uptake machi nery that is involved in acquisition of iron from organic ferricomplex es.