Horak, R. | bioRxiv Science

bioRxiv2024

Isolation and characterization of a phage collection against Pseudomonas putida

The environmental bacterium Pseudomonas putida has a wide range of metabolic pathways and thus entails great promise both as cell factories in biotechnological production and for bioremediation approaches to degrade various aromatic pollutants. To thrive in the environment, P. putida has to be able to endure the constant threat posed by bacteriophages. Surprisingly, up until now, only a few phages have been isolated for the common laboratory strain P. putida KT2440, and no phage defence mechanisms have been characterized yet. Here, we introduce a novel Collection of Environmental Pseudomonas putida Phages from Estonia (CEPEST), consisting of 67 dsDNA phages that belong to 22 phage species and nine phage genera. We show that most of the phages in the CEPEST collection are more infectious at lower temperatures, have a narrow host range, and require intact LPS for P. putida infection. Additionally, we demonstrate that cryptic prophages in the P. putida chromosome strongly protect against the infection of many phages, whereas the chromosomal toxin-antitoxin systems play no role in phage defence of P. putida.

microbiology↗

bioRxiv2020

Pseudomonas putida chromosomal toxin-antitoxin systems carry neither clear fitness benefits nor big costs

Chromosomal toxin-antitoxin (TA) systems are widespread genetic elements among bacteria, yet, despite extensive studies in the last decade, their biological importance remains ambivalent. The ability of TA-encoded toxins to affect stress tolerance supports the hypothesis of TA systems being associated with stress adaptation. However, the deletion of TA genes has usually no fitness consequences, supporting the selfish elements hypothesis. Here, we aimed to evaluate the cost and benefits of chromosomal TA systems to Pseudomonas putida. We show that multiple TA systems do not confer fitness benefits to this bacterium as deletion of 13 TA loci does not influence stress tolerance, persistence and biofilm formation. Our results instead show that TA loci are costly and decrease the competitive fitness of P. putida. Still, the cost of multiple TA systems is low and detectable in certain conditions only. Construction of antitoxin deletion strains showed that only five TA systems code for toxic proteins, while other TA loci have evolved towards reduced toxicity and encode non-toxic or moderately potent proteins. Analysis of P. putida TA systems homologs among fully sequenced Pseudomonads suggests that the TA loci have been subjected to purifying selection and that TA systems spread among bacteria by horizontal gene transfer.

microbiology↗