Articles
BACTERIOPHAGES AS BIOPESTICIDES: ROLE OF BACTERIAL EXOPOLYSACCHARIDES
Article number
896_65
Pages
449 – 455
Language
English
Abstract
Erwinia amylovora produces two types of exopolysaccharides (EPS), amylovoran and levan, which are responsible for disease symptoms in apple and pear.
PCR-based one step deletion of chromosomal genes, derived from the λ phage RED system, was used to generate amylovoran (rcsB–), levan (lsc–) and EPS (rcsB–, lsc–) deficient mutants.
These mutants were used to study the role of EPSs in bacteriophage attachment to the bacterial cell.
The EPS capsule may act as both a physical barrier and an attachment site for bacteriophage adsorption on the bacterial host. E. amylovora wild type isolates produce varying quantities of EPS. The isolates may be grouped as either high or low EPS producers, based on their colony appearance on nutrient agar supplemented with sugar.
Phage titres were determined for rcsB–, lsc– and wild type cells infected with phages and grown on sugar and non-amended medium.
The <i<E. amylovora hosts demonstrated considerable variation in final bacteriophage titres.
When Myoviridae, Podoviridae and Siphoviridae phages were grown on host cells with high EPS production; phage titres increased by 150-900%. Levan deficient cells did not vary titres of Myoviridae, Podoviridae or Siphoviridae bacteriophages except for Ea6-4 lsc– cells, which produced lower titres by 925%. Amylovoran deficient cells infected with Myoviridae bacteriophage did not affect total titres.
In contrast, amylovoran deficient cells resulted in the inhibition of infection by Podoviridae and Siphoviridae phages. Erwinia spp. bacteriophages have evolved to attack high EPS producing E. amylovora cells.
Experiments have demonstrated that increased EPS production lead to greater bacteriophage population propagation and amylovoran deficient bacterial mutants are resistant to bacteriophage attack.
The implications of these data on the use of bacteriophages as biopesticides in the field will be discussed.
PCR-based one step deletion of chromosomal genes, derived from the λ phage RED system, was used to generate amylovoran (rcsB–), levan (lsc–) and EPS (rcsB–, lsc–) deficient mutants.
These mutants were used to study the role of EPSs in bacteriophage attachment to the bacterial cell.
The EPS capsule may act as both a physical barrier and an attachment site for bacteriophage adsorption on the bacterial host. E. amylovora wild type isolates produce varying quantities of EPS. The isolates may be grouped as either high or low EPS producers, based on their colony appearance on nutrient agar supplemented with sugar.
Phage titres were determined for rcsB–, lsc– and wild type cells infected with phages and grown on sugar and non-amended medium.
The <i<E. amylovora hosts demonstrated considerable variation in final bacteriophage titres.
When Myoviridae, Podoviridae and Siphoviridae phages were grown on host cells with high EPS production; phage titres increased by 150-900%. Levan deficient cells did not vary titres of Myoviridae, Podoviridae or Siphoviridae bacteriophages except for Ea6-4 lsc– cells, which produced lower titres by 925%. Amylovoran deficient cells infected with Myoviridae bacteriophage did not affect total titres.
In contrast, amylovoran deficient cells resulted in the inhibition of infection by Podoviridae and Siphoviridae phages. Erwinia spp. bacteriophages have evolved to attack high EPS producing E. amylovora cells.
Experiments have demonstrated that increased EPS production lead to greater bacteriophage population propagation and amylovoran deficient bacterial mutants are resistant to bacteriophage attack.
The implications of these data on the use of bacteriophages as biopesticides in the field will be discussed.
Publication
Authors
D.R. Roach, D. Sjaarda, A.J. Castle, A.M. Svircev
Keywords
fire blight, bacteriophage, exopolysaccharide, EPS, phage resistance, recombineering
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