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The opening of the SPP1 bacteriophage tail, a prevalent mechanism in Gram-positive-infecting siphophages.

ABSTRACT: The SPP1 siphophage uses its long non-contractile tail and tail tip to recognize and infect the Gram-positive bacterium Bacillus subtilis. The tail-end cap and its attached tip are the critical components for host recognition and opening of the tail tube for genome exit. In the present work, we determined the cryo-electron microscopic (cryo-EM) structure of a complex formed by the cap protein gp19.1 (Dit) and the N terminus of the downstream protein of gp19.1 in the SPP1 genome, gp21(1-552) (Tal). This complex assembles two back-to-back stacked gp19.1 ring hexamers, interacting loosely, and two gp21(1-552) trimers interacting with gp19.1 at both ends of the stack. Remarkably, one gp21(1-552) trimer displays a "closed" conformation, whereas the second is "open" delineating a central channel. The two conformational states dock nicely into the EM map of the SPP1 cap domain, respectively, before and after DNA release. Moreover, the open/closed conformations of gp19.1-gp21(1-552) are consistent with the structures of the corresponding proteins in the siphophage p2 baseplate, where the Tal protein (ORF16) attached to the ring of Dit (ORF15) was also found to adopt these two conformations. Therefore, the present contribution allowed us to revisit the SPP1 tail distal-end architectural organization. Considering the sequence conservation among Dit and the N-terminal region of Tal-like proteins in Gram-positive-infecting Siphoviridae, it also reveals the Tal opening mechanism as a hallmark of siphophages probably involved in the generation of the firing signal initiating the cascade of events that lead to phage DNA release in vivo.

SUBMITTER: Goulet A

PROVIDER: S-EPMC3137110 | biostudies-literature | 2011 Jul

REPOSITORIES: biostudies-literature

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The opening of the SPP1 bacteriophage tail, a prevalent mechanism in Gram-positive-infecting siphophages.

Goulet Adeline A Lai-Kee-Him Joséphine J Veesler David D Auzat Isabelle I Robin Gautier G Shepherd Dale A DA Ashcroft Alison E AE Richard Eric E Lichière Julie J Tavares Paulo P Cambillau Christian C Bron Patrick P

The Journal of biological chemistry 20110526 28

The SPP1 siphophage uses its long non-contractile tail and tail tip to recognize and infect the Gram-positive bacterium Bacillus subtilis. The tail-end cap and its attached tip are the critical components for host recognition and opening of the tail tube for genome exit. In the present work, we determined the cryo-electron microscopic (cryo-EM) structure of a complex formed by the cap protein gp19.1 (Dit) and the N terminus of the downstream protein of gp19.1 in the SPP1 genome, gp21(1-552) (Tal ...[more]

PMID: 21622577

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Project description:Bacteriophages play critical roles in impacting microbial community succession both ecologically and evolutionarily. Although the majority of phage genetic diversity has been increasingly unveiled, phages infecting members of the ecologically important genus Alteromonas remain poorly understood. Here, we present a comprehensive analysis of a newly isolated alterophage, vB_AcoS-R7M (R7M), to characterize its life cycle traits, genomic features, and putative evolutionary origin. R7M harbors abundant genes identified as host-like auxiliary metabolic genes facilitating viral propagation. Genomic analysis suggested that R7M is distinct from currently known alterophages. Interestingly, R7M was found to share a set of similar characteristics with a number of siphophages infecting diverse aquatic opportunistic copiotrophs. We therefore proposed the creation of one new subfamily (Queuovirinae) to group with these evolutionarily related phages. Notably, tail genes were less likely to be shared among them, and baseplate-related genes varied the most. In-depth analyses indicated that R7M has replaced its distal tail with a Rhodobacter capsulatus gene transfer agent (RcGTA)-like baseplate and further acquired a putative receptor interaction site targeting Alteromonas. These findings suggest that horizontal exchanges of viral tail adsorption apparatuses are widespread and vital for phages to hunt new hosts and to adapt to new niches. IMPORTANCE The evolution and ecology of phages infecting members of Alteromonas, a marine opportunistic genus that is widely distributed and of great ecological significance, remain poorly understood. The present study integrates physiological and genomic evidence to characterize the properties and putative phage-host interactions of a newly isolated Alteromonas phage, vB_AcoS-R7M (R7M). A taxonomic study reveals close evolutionary relationships among R7M and a number of siphophages infecting various aquatic copiotrophs. Their similar head morphology and overall genetic framework suggest their putative common ancestry and the grouping of a new viral subfamily. However, their major difference lies in the viral tail adsorption apparatuses and the horizontal exchanges of which possibly account for variations in host specificity. These findings outline an evolutionary scenario for the emergence of diverse viral lineages of a shared genetic pool and give insights into the genetics and ecology of viral host jumps.

Dataset Information

The opening of the SPP1 bacteriophage tail, a prevalent mechanism in Gram-positive-infecting siphophages.

Publications

The opening of the SPP1 bacteriophage tail, a prevalent mechanism in Gram-positive-infecting siphophages.

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