FEMS Microbiology Letters 51 (1988) 33-36 33 Published by Elsevier FEM 03179 Iron-regulated outer membrane proteins and non-siderophore-mediated iron acquisition by Paracoccus denitrificans Sechan Wee, Sharon Hardesty, Murty V.V.S. Madiraju and Brian J. Wilkinson Microbiology Group, Department of Biological Sciences, lllinois State University, Normal IL, U.S.A. Received 29 January 1988 Accepted 10 February 1988 Key words: Paracoccus denitrificans; Iron-regulated protein; Iron uptake 1. SUMMARY Deprivation of Paracoccus denitrificans of iron in sodium molybdate-containing medium caused a slower rate of growth and lower final cell yield, in contrast to our previous studies in non-sodium molybdate-containing medium, where iron de- privation had little effect on growth rate. Five high M r outer membrane proteins and catechol production were induced in iron-deprived cul- tures. The fifth protein, M r 72 000, was produced later than the others. Growth of iron-deprived cells in medium containing 20 ~M ferric citrate repressed siderophore and iron deprivation-in- duced protein production, and led to production of an M r 23000 outer membrane protein (half maximum production after 5 h). Synthesis of the M r 23 000 and high M r proteins appeared to be mutaUy exclusive, and to be regulated by the cell's iron status. Cells inoculated into medium contain- ing 20 /~M ferric citrate took up 92% of the iron within 1 h, suggesting the occurrence of a non- siderophore mediated, 'low affinity' iron uptake pathway. 2. INTRODUCTION Iron deprivation of Paracoccus denitrificans in- duces the production of five high M r outer mem- brane proteins [1,2]. However, the production of a heat-modifiable 23000-M r protein, which is the second most abundant outer membrane protein, is dependent upon the addition of iron to a suc- cinate/salts (D) medium [1,2]. In this paper we describe some attempts to study the interrelation- ships of the iron-dependent and -repressible pro- teins. Additionally, measurement of the iron con- tent of growth medium and cells during growth revealed an apparently non-siderophore-mediated uptake of most of the medium iron within less than a generation. 3. MATERIALS AND METHODS Correspondence to: S. Wee, Microbiology Group, Department of Biological Sciences, Illinois State University, Normal, IL 61761, U.S.A. P. denitrificans ATCC 13543 was grown in suc- cinate/salts medium with and without ferric citrate, D. and D a media respectively, as described 0378-1097/88/$03.50 © 1988 Federation of European Microbiological Societies Downloaded from https://academic.oup.com/femsle/article/51/1/33/489444 by guest on 21 August 2023