Sensitivity of Escherichia coli to Viral Nucleic Acid, XII. Ca2+-or Ba2+-Facilitated Transfection of Cell Envelope Mutants

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Abstract
Using various envelope mutants of E. coli, the relationship between cell surface structure and Ca2+ or Ba2+-dependent competence for transfection was investigated. Unlike rough strains, smooth bacteria treated with Ca2+ or Ba2+ were incompetent for transfection by [phage] .vphi.A RF [double-stranded replicative form DNA]. In E. coli K12 D21 derivatives, Ca2+-dependent competence remarkably increased by lpsA1 mutation; highest level of competence was attained by further deficiency in glucose units of the LPS [lipopolysaccharide]. Upon treatment with BaCl2, strain D21 and its lpsA1 mutant became highly competent for .vphi.A RF. The effect of Ba2+ was weak for lpsA1 mutants 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 2 KDO [2-keto-3-deoxyoctonate] units, was nearly equal to that of wild type. The level of cellular competence induced by Ba2+ was not always parallel to that induced by Ca2+. In mutants deficient in outer membrane protein I, Ca2+- or Ba2+-dependent competence increased several-fold, but in mutants devoid of outer membrane [protein] II*, the competence decreased considerably. Unlike nucleoside transport, the uptake of DNA was not affected by tsx mutation.