Population Dynamics between Erwinia amylovora, Pantoea agglomerans and Bacteriophages: Exploiting Synergy and Competition to Improve Phage Cocktail Efficacy

Abstract

Bacteriophages are viruses capable of recognizing with high specificity, propagating inside of, and destroying their bacterial hosts. The phage lytic life cycle makes phages attractive as tools to selectively kill pathogenic bacteria with minimal impact on the surrounding microbiome. To effectively harness the potential of phages in therapy, it is critical to understand the phage–host dynamics and how these interactions can change in complex populations. Our model examined the interactions between the plant pathogen Erwinia amylovora, the antagonistic epiphyte Pantoea agglomerans, and the bacteriophages that infect and kill both species. P. agglomerans strains are used as a phage carrier; their role is to deliver and propagate the bacteriophages on the plant surface prior to the arrival of the pathogen. Using liquid cultures, the populations of the pathogen, carrier, and phages were tracked over time with quantitative real-time PCR. The jumbo Myoviridae phage ϕEa35-70 synergized with both the Myoviridae ϕEa21-4 and Podoviridae ϕEa46-1-A1 and was most effective in combination at reducing E. amylovora growth over 24 h. Phage ϕEa35-70, however, also reduced the growth of P. agglomerans. Phage cocktails of ϕEa21-4, ϕEa46-1-A1, and ϕEa35-70 at multiplicities of infections (MOIs) of 10, 1, and 0.01, respectively, no longer inhibited growth of P. agglomerans. When this cocktail was grown with P. agglomerans for 8 h prior to pathogen introduction, pathogen growth was reduced by over four log units over 24 h. These findings present a novel approach to study complex phage–host dynamics that can be exploited to create more effective phage-based therapies.

Function and Application of the CRISPR-Cas System in the Plant PathogenErwinia amylovora

“…With Ea6-4 confirmed to have CRISPR-Cas activity through plasmid transformation, CRISPR-Cas activity was tested using phage Kolesnikvirus Erwinia virus Ea214 (ΦEa21-4). ΦEa21-4 was first isolated on Ea6-4 and is a candidate for phage biocontrol of E. amylovora ( 26 – 30 ). To this end, characteristics about the lytic replication cycle (i.e., adsorption rate, burst size, and time to lysis) have been previously described on this bacterial host through quantitative, real-time PCR (qPCR) ( 31 ).…”

Classification of In Vitro Phage–Host Population Growth Dynamics

“…This study presents the classification of bacterial growth dynamics in the presence of lytic phages using two statistical data mining techniques: NMDS and PCA. OD as the input is a fast and data-rich screening method for in vitro phage-host growth dynamics [35]. This approach captures the ongoing dynamics and produces a quantitative high-throughput data to determine the phage-host range, phage virulence/infectivity, and bacterial phage resistance development [16,32,36].…”

Limitations of Phage Therapy and Corresponding Optimization Strategies: A Review

“…To prevent the emergence of phage resistance, we should prioritize the use of phage mixtures [ 96 ] when using PT. Gayder found that competition and synergy between bacteriophages can be used to enhance the antibacterial efficacy of bacteriophage mixtures [ 97 ]. We should take advantage of the interactions between bacteriophages and bacteria to improve our battle against bacteria.…”