Expression of H1 outer-membrane protein of Pseudomonas aeruginosa in relation to sensitivity to EDTA and polymyxin B.
During growth in magnesium (Mg++)-deficient mineral media, Pseudomonas aeruginosa cells synthesise large amounts of H1 outer-membrane protein and are resistant to polymyxins and EDTA. It has been suggested that H1 protein replaces Mg++ as an outer-membrane-stabilising component in Mg++-deprived cells, thereby removing the EDTA target and blocking an adsorption site for polymyxins. Induction of H1 protein synthesis also occurred in P. aeruginosa cells grown in Antibiotic No. 3 Broth (Ab3B), although this medium is not Mg++-deficient. Generally, significant induction of H1 protein did not occur in P. aeruginosa cultures grown in other complex media such as Proteose Peptone and Nutrient Broth, which contained less Mg++ than Ab3B, nor in Isosensitest Broth or Mueller Hinton Broth, which contained higher Mg++ concentrations. H1-protein-induced P. aeruginosa cells from Ab3B cultures, unlike those from Mg++-deficient mineral-broth culture, remained fully sensitive to polymyxin B and, with one exception, to EDTA. It is concluded that induction of H1 protein does not itself confer resistance to polymyxin B, and has no more than a minor role in EDTA resistance. Other cell-wall changes, such as phospholipid modifications and the absence of Mg++, probably account for the resistance of Mg++-deprived cells.
Said
A A
AA
Department of Medical Microbiology, London Hospital Medical College.
Livermore
D M
DM
Williams
R J
RJ
D001425:Bacterial Outer Membrane Proteins / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D003470:Culture Media; D004352:Drug Resistance, Microbial; D004492:Edetic Acid / Q000494:pharmacology*; D008274:Magnesium / Q000378:metabolism; D008970:Molecular Weight; D011112:Polymyxin B / Q000494:pharmacology*; D011113:Polymyxins / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000502:physiology
D001425:Bacterial Outer Membrane Proteins; D003470:Culture Media; D011113:Polymyxins; D004492:Edetic Acid; D008274:Magnesium; D011112:Polymyxin B; D002118:Calcium