Genome sequences and characterization of the related Gordonia phages GTE5 and GRU1 and their use as potential biocontrol agents

Abstract

Activated sludge plants suffer frequently from the operational problem of stable foam formation on aerobic reactor surfaces, which can be difficult to prevent. Many foams are stabilized by mycolic acid-containing Actinobacteria, the mycolata. The in situ biocontrol of foaming using phages is an attractive strategy. We describe two polyvalent phages, GTE5 and GRU1, targeting Gordonia terrae and Gordonia rubrupertincta, respectively, isolated from activated sludge. Phage GRU1 also propagates on Nocardia nova. Both phages belong to the family Siphoviridae and have similar-size icosahedral heads that encapsulate double-stranded DNA genomes (∼65 kb). Their genome sequences are similar to each other but markedly different from those of other sequenced phages. Both are arranged in a modular fashion. These phages can reduce or eliminate foam formation by their host cells under laboratory conditions.

Fig 1

Electron micrographs of GTE5 (A) and GRU1 (B). Scale bars, 50 nm.

Fig 2

Pairwise alignment and genetic maps of the GTE5 and GRU1 phage genomes. (A) Pairwise LAGAN alignment of GTE5 and GRU1. (B and C) Genetic maps of GTE5 (B) and GRU1 (C). The lines at the bottom indicate the modular regions. The arrows representing genes are shaded similarly if their protein products have similar functions.