Unusual nucleotide sequence heterogeneity of small multicopy pHSB plasmid from Halobacterium strain SB3, an archaebacterium.

A small multicopy plasmid, pHSB, from the Halobacterium strain SB3 is present in the cell as a population of molecules differing from each other by one or several point nucleotide substitutions. At least three sequence versions of the plasmid coexist in the cell. The pHSB primary structure heterogeneity may be a reflection of high genetic instability of the host organism.