Phenotypic and Genotypic Criteria for the Screening of Highly Active S-Type Pyocins Pseudomonas aeruginosa Producers

Abstract

Bacteriocins of Pseudomonas aeruginosa, especially S-type pyocins, show high efficiency as analogs of antimicrobial drugs. Various screening methods can be used to identify producers of highly active pyocins, but there are no clear criteria for selecting perspective strains. The aim of this work was to determine criteria that can be used during phenotypic and genotypic screening for the selection of perspective highly active S-type pyocin P. aeruginosa producers. Methods. The objects of investigation were 40 P. aeruginosa strains. Pyocins were obtained from each culture, relative coefficients of activity spectrum and sensitivity were determined for all the strains used. The obtained results of the phenotypic screening were compared with the data of the genotypic screening. Results. The use of the proposed method of activity assessment according to the lysis intensity made it possible to phenotypically assess the expression of pyocin genes. It was established that according to the new criteria, only one strain — P. aeruginosa UCM B-333 — can be included in the group of the most active pyocin producers that inhibit the growth of more than 75% of indicator cultures. The majority of representatives of maximally and highly active producers were characterized by high resistance to the action of other pyocins, which can be considered as an additional criterion for the selection of perspective strains. During genotypic screening, it was established that the quantity of pyocin genes in the genome cannot be interpreted as a clear criterion of the producer’s perspective. However, 50% of representatives of maximally and highly active pyocin producers were characterized by the presence of two pyocin genes, while in 47.7% of moderately active and 54.5% of low active producers, one pyocin gene was detected more often. It was established that with widening the bacteriocin activity spectrum, the detection frequency of pyocin S1 and S5 genes increases, and for pyocin S2 and S3 genes — decreases. Thus, among the producers of maximally and highly active bacteriocins, pyocin S1 and S5 genes were identified with the highest frequency — 42.8% and 78.6%, and pyocin S2 and S3 genes — with the lowest one — 28.6% and 7.1%, respectively. Gene of pyocin S4 with tRNase activity were detected with equally high frequency in all groups of producers. Conclusions. The method of activity assessment by the lysis intensity allows not only to determine the presence of pyocins, but also to phenotypically evaluate the level of their expression, which is an important criterion for the selection of perspective producers. Bacteriocins with a wider activity spectrum are synthesized by P. aeruginosa strains with higher resistance to the action of pyocins from other cultures. The most optimal genotypic criterion for the selection of a highly perspective pyocin producer, detection of genes combination of bacteriocins with different mechanisms of action — with DNase activity (pyocin S1) and the ability to pore formation (pyocin S5) — can be considered.