Application of Adaptive Evolution to Improve the Stability of Bacteriophages during Storage.

Kelvin K Kering,Raphael Nyaruaba,Xiaoxu Zhang,Hongping Wei,Junping Yu

doi:10.3390/v12040423

Kelvin K Kering, Raphael Nyaruaba + Show 3 more

Open Access

https://doi.org/10.3390/v12040423

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Abstract

Phage stability is important for the successful application of bacteriophages as alternative antibacterial agents. Considering that temperature is a critical factor in phage stability, this study aimed to explore the possibility of improving long-term phage stability through adaptive evolution to elevated temperature. Evolution of three wild-type ancestral phages (Myoviridae phage Wc4 and Podoviridae phages CX5 and P-PSG-11) was induced by subjecting the phages to heat treatment at 60 °C for five cycles. The adapted phages showed better stability than the wild-type ancestral phages when subjected to heat treatment at 60 °C for 1 h and after 60 days of storage at 37 °C. However, the adapted phages could not withstand thermal treatment at 70 °C for 1 h. The infectivity and the lytic properties of the phages were not changed by the evolution process. Whole-genome sequencing revealed that single substitutions in the tail tubular proteins were the only changes observed in the genomes of the adapted phages. This study demonstrates that adaptive evolution could be used as a general method for enhancing the thermal stability of phages without affecting their lytic activity. Sequencing results showed that bacteriophages may exist as a population with minor heterogeneous mutants, which might be important to understand the ecology of phages in different environments.

Highlights

Bacteriophages are viruses that replicate within bacteria, often resulting in the lysis of the bacterial cell
Sequencing results showed that bacteriophages may exist as a population with minor heterogeneous mutants, which might be important to understand the ecology of phages in different environments
The interest in phages as antibacterial agents is attributed to their specificity, self-replication, minimum disruption of normal flora, low inherent toxicity, biofilm clearance, and counteractive adaptation against resistant bacteria [15]

Summary

Introduction

Bacteriophages (phages) are viruses that replicate within bacteria, often resulting in the lysis of the bacterial cell. With an estimated total world-wide number of 1031 , phages are considered the most abundant forms of life on earth [1,2,3]. They are present in every environment where bacteria can be found: animals, humans, plants, water, soil, and sewage [4,5,6,7]. Research on phage ecology has shown that desert soil (Sahara and Namib) contains abundant and diverse phage populations [8,9]. The interest in phages as antibacterial agents is attributed to their specificity, self-replication, minimum disruption of normal flora, low inherent toxicity, biofilm clearance, and counteractive adaptation against resistant bacteria [15]

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