MUCOID CLONES OF PSEUDOMONAS-AERUGINOSA P AO1 SURVIVING AFTER INDUCTION OF TRANSPOSABLE PROPHAGES

The origin and properties of mucoid clones were studied. The clones we re selected with high frequency after thermoinduction of Pseudomonas a eruginosa lysogenic for phagetransposons (PT). The production of algin ate does not promote the survival of lysogenic bacteria at 42 degrees C. Mucoid clones were shown to appear before thermoinduction; the freq uency bf their formation does not depend on the specificity of the mut ator effect intrinsic to different PT. Phenotypic differences typical of mucoid clones can be mediated by different mutations promoting clon e survival at 42 degrees C and by simultaneously arising additional mu tations. The SL21 mucoid clone selected among clones of P. aeruginosa PAO1 resistant to PT of B3 possesses an additional trait of phage resi stance at 42 degrees C. The presence of D3112 cts 15 prophage has no s ignificant effect on the frequency of SL21 reversion to nonmucoidness. This means that the mutator effect of PT has made-a slight contributi on to this process. The appearance of mutations promoting the survival of the thermoinducible lysogen SL21 (D3112 cts 15) does not affect. t he frequency of the loss of mucoidness. Nonmucoid derivatives of SL21 were shown to differ in phage resistance at 42 degrees C and in the ex tent of the residual mucoidness manifested under specific conditions. Consequently, nonmucoid clones appear as a result of pseudoreversions. Because some of these pseudorevertants cannot again be converted to t he mucoid form, it is concluded that they carry mutations in genes who se functions are obligatory for the production of alginate.