ISOLATION AND CHARACTERIZATION OF A SPECIES-SPECIFIC MULTICOPY DNA-SEQUENCE FROM ENTAMOEBA-HISTOLYTICA

A genomic library of Entamoeba histolytica (pathogenic strain HM-1:IMS S) was screened to detect repetitive DNA clones other than those from the highly abundant ribosomal DNA (rDNA). One such clone (HMc) had a 2 .3 kb insert which hybridized with the main genome and not the rDNA ci rcle. Southern hybridization of E. histolytica genomic DNA, digested w ith EcoR I and probed with HMc, showed multiple bands. The banding pat tern was identical in all axenic pathogenic strains tested. Difference s, however, existed when the banding pattern of a pathogenic strain wa s compared with that of a non-pathogenic strain. HMc was present in ab out 25-30 copies per genome in strain HM-1:IMSS. Nucleotide sequence a nalysis of HMc revealed a partial open reading frame which hybridized with a 1.35 kb poly Af transcript in Northern blots. The deduced amino acid sequence did not, however, show significant homology with known proteins. The HMc sequence was found only in E. histolytica as it hybr idized with 5 different axenic strains off. histolytica but did not re cognize other closely related species of Entamoeba. It has thus the po tential to be used as a species-specific DNA probe.