Sensitivity of Escherichia coli to viral nucleic acid, XII. Ca2+- or Ba2+-facilitated transfection of cell envelope mutants.

Using various envelope mutants of Escherichia coli, the relationship between cell surface struc­ ture and the Ca2*or Ba2+-dependent competence for transfection was investigated. In contrast with rough strains, smooth bacteria treated with Ca2+ or Ba2+ were incompetent for the trans­ fection by 0 A RF. In E. coli K12 D21 derivatives, Ca2+-dependent competence remarkably in­ creased by IpsA l mutation and the highest level of competence was attained by further deficiency in glucose units of the LPS. Upon treatment with BaCl2 , strain D21 and its Ip sA l mutant became highly competent for 0 A RF. The effect of Ba2* was, however, feeble for Ip sA l mutants further deficient in heptose units and/or glucose units. Among different LPS mutants of E. coli B, variation of the Ca2*or Ba2+-dependent competence was relatively small and even the competence of strain BB12, whose LPS core contained only two KDO units, was nearly equal to that of wild type bacteria. However, the level of cellular competence induced by Ba2+ was not allways parallel to that induced by Ca2+. In mutants deficient in outer membrane protein I, either Ca2*or Ba2+-dependent competence increased several-fold, whereas in mutants devoid of outer membrane II*, the com­ petence decreased considerably. Unlike nucleoside transport, the uptake of DNA was not affected by tsx mutation.