The tail‐associated depolymerase of Erwinia amylovora phage L1 mediates host cell adsorption and enzymatic capsule removal, which can enhance infection by other phage

Abstract

The depolymerase enzyme (DpoL1) encoded by the T7-like phage L1 efficiently degrades amylovoran, an important virulence factor and major component of the extracellular polysaccharide (EPS) of its host, the plant pathogen Erwinia amylovora. Mass spectrometry analysis of hydrolysed EPS revealed that DpoL1 cleaves the galactose-containing backbone of amylovoran. The enzyme is most active at pH 6 and 50°C, and features a modular architecture. Removal of 180 N-terminal amino acids was shown not to affect enzyme activity. The C-terminus harbours the hydrolase activity, while the N-terminal domain links the enzyme to the phage particle. Electron microscopy demonstrated that DpoL1-specific antibodies cross-link phage particles at their tails, either lateral or frontal, and immunogold staining confirmed that DpoL1 is located at the tail spikes. Exposure of high-level EPS-producing Er. amylovora strain CFBP1430 to recombinant DpoL1 dramatically increased sensitivity to the Dpo-negative phage Y2, which was not the case for EPS-negative mutants or low-level EPS-producing Er. amylovora. Our findings indicate that enhanced phage susceptibility is based on enzymatic removal of the EPS capsule, normally a physical barrier to Y2 infection, and that use of DpoL1 together with the broad host range, virulent phage Y2 represents an attractive combination for biocontrol of fire blight.

Bacteriophages and Bacterial Plant Diseases

“…It is an attribute which has been shown to be involved in bacterial phytopathogen resistance to copper bactericides (Rodrigues et al, 2008). Phages have evolved to overcome this biofilm barrier through the use of depolymerase enzymes on their capsids but can also be released on host lysis, which allows them to degrade biofilm material, allowing the phage anti-receptor to gain access to the receptors on the surface of their host bacterium (Born et al, 2014). There is a growing demand by consumers for food produce that is free from chemicals biocides and preservatives.…”

Bacteriophage-encoded virion-associated enzymes to overcome the carbohydrate barriers during the infection process

“…Spectrometric measurement of reducing sugars allows to determine the EPS/CPS digestion (Yurewicz et al 1971; Rieger et al 1975; Hsu et al 2013). Other methods include examination of periodate oxidation of saccharides by determining the consumption of sodium periodate and the amount of formic acid formed (Kwiatkowski et al 1983), evaluation of decrease of turbidity of insoluble EPS precipitated by cetylpyridinium chloride (CPC complexes) (Born et al 2014; Majkowska-Skrobek et al 2016), or uronic acid release (Glonti et al 2010). Also, the crude separation of released sugars from polymer was analyzed by TLC chromatography (Glonti et al 2010).…”

The Genomes, Proteomes, and Structures of Three Novel Phages That Infect the Bacillus cereus Group and Carry Putative Virulence Factors

“…In addition, the JL genome encodes a putative tail lysin (gp104, 50%) that has similarity to cell wall-associated hydrolases as well as a protein containing an N-acetylmuramolyl domain (JL gp117) found in several Bacillus genomes and also encoded by phage SPBc2 (59% identity). Tailed double-stranded DNA (dsDNA) bacteriophages frequently harbor structural proteins displaying peptidoglycan hydrolases known to hydrolyze the amide bond between N-acetylmuramoyl and L-amino acids in certain cell wall glycopeptides (60)(61)(62). This suggests that both of these proteins aid in degradation of the Gram-positive cell wall, allowing phage access to the cell membrane.…”