Morphological, host range, and genetic characterization of two coliphages

Abstract

Two coliphages, AR1 and LG1, were characterized based on their morphological, host range, and genetic properties. Transmission electron microscopy showed that both phages belonged to the Myoviridae; phage particles of LG1 were smaller than those of AR1 and had an isometric head 68 nm in diameter and a complex contractile tail 111 nm in length. Transmission electron micrographs of AR1 showed phage particles consisting of an elongated isometric head of 103 by 74 nm and a complex contractile tail 116 nm in length. Both phages were extensively tested on many strains of Escherichia coli and other enterobacteria. The results showed that both phages could infect many serotypes of E. coli. Among the enterobacteria, Proteus mirabilis, Shigella dysenteriae, and two Salmonella strains were lysed by the phages. The genetic material of AR1 and LG1 was characterized. Phage LG1 had a genome size of 49.5 kb compared to 150 kb for AR1. Restriction endonuclease analysis showed that several restriction enzymes could degrade DNA from both phages. The morphological, genome size, and restriction endonuclease similarities between AR1 and phage T4 were striking. Southern hybridizations showed that AR1 and T4 are genetically related. The wide host ranges of phages AR1 and LG1 suggest that they may be useful as biocontrol, therapeutic, or diagnostic agents to control and detect the prevalence of E. coli in animals and food.

FIG. 1.

Transmission electron micrographs of bacteriophages LG1 (A) and AR1 (B). Bars, 100 nm. Magnifications, ×377,910.

FIG. 2.

Structures of the five known outer core OSs from the LPS of E. coli. The genes whose products catalyze formation of each linkage (the waa operon) are indicated. The figure was adapted from the work of Amor et al. (2).

FIG. 3.

Agarose (0.8%) gel (left) and corresponding Southern blots (right) of AR1, T4 ATCC 11303B4, and LG1 NdeI-digested genomic DNA. Whole-genomic, digoxigenin-labeled, NdeI-digested AR1 DNA was used as the probe for the Southern analysis. Lanes 1, lambda HindIII molecular size markers (2.0 to 23.0 kb); lanes 2, NdeI-digested AR1 genomic DNA; lanes 3, NdeI-digested T4 ATCC 11303B4 genomic DNA; lanes 4, NdeI-digested LG1 genomic DNA.