Characterization of pEC01, a Novel Plasmid Required for Phosphate Taxis in Enterobacter cloacae IFO 3320

概要

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Enterobacter cloacae IFO 3320 exhibits chemotactic responses to inorganic phosphate (P_i) when starved of P_1. One Tnl737KH-induced mutant failed to exhibit P_i taxis even under conditions of P_i limitation. The mutant showed normal chemotactic responses to amino acids and citrate, suggesting that it is specifically defective in P_i taxis. Southern blot analysis revealed that the insertion Tnl737KH was located in the indigenous plasmid pEC01. The pEC01-cured strain of IFO 3320 did not show P_i taxis even under conditions of P_i limitation, indicating that pEC01 is required for P_i taxis in E. cloacae IFO 3320. This plasmid is 5002 bp long, consisting of four mobilization genes, mbeCABD, and an origin of replication homologous to ColEl-type plasmids. pEC01 contains no open reading frame (ORF) encoding a protein with a highly conserved motif of methyl-accepting chemotaxis proteins (MCPs), suggesting that a gene encoding a MCP responsible for P_i taxis is located on the chromosome. An ORF encoding a putative protein of 102 amino acids was responsible for the complementation of the pEC01-cured strain. The putative protein had a helix-turn-helix motif, suggesting that it is involved in the gene regulation of the Pi taxis MCP gene.
日本微生物生態学会の論文