putida) bacteria were selected and modified here to contain different type of conjugative plasmids that belong to different incompatibility groups (including lncP-1 α, IncP-1 ε and lncA/C2 respectively). The objective of this study was to investigate whether and how the presence of plasmids in bacterial hosts could affect phage isolation and infectivity. Given the surging interest in therapeutic use of phage as alternative antimicrobial agents, there is a knowledge gap in investigating the potential roles of plasmids towards different phage aspects, such as isolation and infectivity.
Despite the known role of plasmid-mediated phage defence and plasmid encoded sex-apparatus, information with regards to interactions of plasmids towards phage isolation and infectivity is scarce. coli Inoviruses targeting the F sex pilus and broad host-range Tectiviridae-like PRD1 targeting conjugative pili of plasmids. pilus) that led to isolation of plasmid dependent phage such as E. Apart from the known anti-phage immunity associated with plasmids, previous studies have also reported the association of plasmid and its encoded plasmid sex apparatus (i.e. Plasmid-mediated phage defence that leads to phage abortive infection systems was reported to be linked to the presence of a plasmid encoded toxin-antitoxin pair system, which is able to interfere with phage replication through reduced cell metabolism or active promotion of programmed cell death. Independent of bacterial chromosomal DNA, plasmids are circular, extrachromosomal DNA molecules that can encode accessory genes that confer selective advantage for bacterial survival such as antibiotic resistance, production of toxins as well as utilization of specific substrates for growth. In addition, plasmids present in bacterial hosts are also found to be able to mediate the development of phage resistance. Common phage resistance mechanisms include blocking of phage adsorption entry, interference of phage genome entry and replication.
The development of phage resistance by bacteria represents an intrinsic defence mechanism against phages. Despite these advantages, phage therapy also has certain limitations, including host range specificity and development of phage resistance. Indeed, previous studies have shown that phage therapy offers promising antimicrobial efficiencies with several added advantages compared to antibiotics. The surging interest in phage therapy observed globally coincides with the rise of antibiotic resistance, a major health crisis caused by abuse and misuse of antibiotics. Owing to the intrinsic properties of phage capable of infecting and killing bacteria, increasing studies have been utilizing phages as alternative antimicrobial agents for treatment of bacterial infections, also known as phage therapy. Given their vast abundance and diversity, phages also play an important role in regulating different populations within bacterial communities in both natural and engineered ecosystems. With a total estimated global abundance of 10 31 particles, phages represent the most abundant entities found on Earth and can be found in every living habitat where bacteria reside. Given the diverse and ubiquitous nature of plasmids, our findings highlight the need to consider plasmids as factors that can influence both phage isolation and infectivity.īacteriophages or phages, are viruses that specifically infect and kill bacteria. Furthermore, the presence of plasmids was found to alter the expression of bacteria membrane protein, which correlates with bacterial cell surface receptors recognized by phages, thus affecting phage isolation and infectivity. In particular, the isolated phages exhibited different phage plaquing infectivity towards the same bacterial species containing different plasmids. We found that plasmids can influence both the phage isolation process and phage infectivity. In this study, using both Escherichia coli and Pseudomonas putida bacteria containing different plasmids, eight phages were isolated and characterized in terms of phage morphology and host range analysis, in conjunction with DNA and protein sequencing. However, it remains unknown about the influence of plasmids present in bacterial hosts on phage isolation and subsequent infectivity. Antibiotic resistance genes are often carried by plasmids, which spread intra- and inter genera bacterial populations, and also play a critical role in bacteria conferring phage resistance.