Phylogenetic Analysis of phn Transporters of Achromobacter insolitus LCu2

Abstract

Phosphonates are alternative phosphorus sources for bacteria. The genome of Achromobacter insolitus strain LCu2 contains three predicted phn clusters of ABC-type phosphonate transporters into the cell. To understand the functional, evolutionary, and ecological role of the phn clusters, phylogenetic analysis of substrate-binding PhnD proteins from strain LCu2 with their homologs in other Achromobacter species and in closely related genera of the family Alcaligenaceae was carried out. The PhnD transporters formed three separate clusters, which indicated the differences in their structural composition. PhnD₁ and PhnD₂ were present in the genomes of all Achromobacter species and grouped separately from those of other members of the family Alcaligenaceae, which indicated vertical inheritance of the phnD₁ and phnD₂ genes and their involvement in the life-supporting processes. PhnD₃ was found in the genomes of seven Achromobacter species. The phnD₃ gene was probably acquired via horizontal transfer or duplication and is induced during adaptation to changing environmental conditions. Maintenance of three structurally different phn clusters of transporters is probably ecologically advantageous to A. insolitus LCu2, providing for phosphorus retrieval from synthetic and natural organophosphonates as well as other sources.