Cryptic Plasmids in Glutamic Acid-producing Bacteria

Seven filamentous (fil) mutants were isolated from B. subtilis, and the mutations were mapped by means of lysed-protoplast transformation. Five of the mutations were linked to aroD and the others to pyrD. rgn mutations, which lead to a decrease in autolysin(s) and the formation of filaments, were also linked to aroD, and the mapping order was rgn-dnaE-aroD. On comparison with other reported filamentous mutations (lyt-1, lyt-2 and lyt-152), fil-1, fil-3 to -6, rgn and the above lyt mutations were determined to be in the same locus. All of the seven fil strains lacked flagella and showed decreased aμtolysin activity. Among them, only mutants having arod- linked mutations showed low competency. Protease assay results indicated that rgn mutants produce a several times higher amount of the enzyme than the parent strain, and the initiation time for the production in rgn mutants was two hours earlier than in the parent strain.