[Mucoid clones of Pseudomonas aeruginosa PAO1, surviving after induction of prophage transposons].

The origin and properties of mucoid clones were studied. The clones were selected with high frequency after thermo-induction of Pseudomonas aeruginosa lysogenic for phage transposons (PT). The production of alginate does not promote the survival of lysogenic bacteria at 42 degrees C. Mucoid clones were shown to appear before thermo-induction; the frequency of their formation does not depend on the specificity of the mutator effect intrinsic to different PT. Phenotypic differences typical of mucoid clones can be mediated by different mutations promoting clone survival at 42 degrees C and by simultaneously arising additional mutations. The SL21 mucoid clone selected among clones of P. aeruginosa PAO1 resistant to PT of B3 possesses an additional trait of phage resistance at 42 degrees C. The presence of D3112 cts 15 prophage has no significant effect on the frequency of SL21 reversion to nonmucoidness. This means that the mutator effect of PT has made a slight contribution to this process. The appearance of mutations promoting the survival of the thermoinducible lysogen SL21 (D3112 cts 15) does not affect the frequency of the loss of mucoidness. Nonmucoid derivatives of SL21 were shown to differ in phage resistance at 42 degrees C and in the extent of the residual mucoidness manifested under specific conditions. Consequently, nonmucoid clones appear as a result of pseudo-reversions. Because some of these pseudo-revertants cannot again be converted to the mucoid form, it is concluded that they carry mutations in genes whose functions are obligatory for the production of alginate.