Role of an ABC importer in mycobacterial drug resistance

Phosphate specific transporter (Pst) in bacteria is involved in phosphate t ransport. Pst is a multisubunit system which belongs to the ABC family of t ransporters. The import function of this transporter is known to be operati ve at media phosphate concentrations below the millimolar range. However, w e found amplification of this transporter in a laboratory generated ciprofl oxacin resistant Mycobacterium smegmatis colony (CIP1) which was grown in a condition when phosphate scavenging function of this operon was inoperativ e. Our results therefore argue the role of this ABC importer in conferring high level of fluoroquinolone resistance in CIP1.