FEMS Microbiology Letters 100 (1992) 133-140 © 1992 Federation of European MicrobiologicalSocieties0378-1097/92/$05.00 Published by Elsevier 133 FEMSLE 80017 Molecular genetic studies of a 10.9-kb operon in Escherichia coli for phosphonate uptake and biodegradation Barry L. Wanner and William W. Metcalf Department of Biological Sciences, Purdue UniL~ersity,WestLafayette, Indiana, USA Received 5 June 1992 Accepted 18 June 1992 Key words: Escherichia coli; Phosphonate; C-P bond cleavage; Phosphite; Biodegradation; PHO regulon; Phosphate regulation 1. SUMMARY Bacteria that use phosphonates as a phospho- rus source must be able to break the stable car- bon-phosphorus bond. In Escherichia coli phos- phonates are broken down by a C-P lyase that has a broad substrate specificity. Evidence for a lyase is based on in vivo studies of product formation because it has been proven difficult to detect the activity in vitro. By using molecular genetic tech- niques, we have studied the genes for phospho- nate uptake and degradation in E. coli, which are organized in an operon of 14 genes, named phnC to phnP. As expected for genes involved in P acquisition, the phnC-phnP operon is a member of the PHO regulon and is induced many hun- dred-fold during phosphate limitation. Three gene products (PhnC, PhnD and PhnE) comprise a binding protein-dependent phosphonate trans- porter, which also transports phosphate, phos- phite, and certain phosphate esters such as phos- Correspondence to: B.L. Wanner, Department of Biological Sciences, Purdue University,West Lafayette, IN 47907, USA. phoserine; two gene products (PhnF and PhnO) may have a role in gene regulation; and nine gene products (PhnG, PhnH, PhnI, PhnJ, PhnK, PhnL, PhnM, PhnN, and PhnP) probably comprise a membrane-associated C-P lyase enzyme complex. Although E. coli can degrade many different phosphonates, the ability to use certain phospho- nates appears to be limited by the specificity of the PhnCDE transporter and not by the speci- ficity of the C-P lyase. 2. INTRODUCTION Escherichia coli uses many phosphorus (P) compounds for growth, however inorganic phos- phate (Pi) is preferred. Pi is transported by the low-affinity Pit transporter when in excess. Under conditions of Pi limitation, genes for the high-af- finity phosphate-specific transporter, Pst, and genes for the use of other, alternative P sources are induced several hundred-fold. Hence, these genes are collectively called the phosphate (PHO) regulon. Many years ago transcriptional fusions of the/3-galactosidase structural gene, lacZ, were Downloaded from https://academic.oup.com/femsle/article-abstract/100/1-3/133/562592 by guest on 08 June 2020