Dual host specificity of phage SP6 is facilitated by tailspike rotation

Abstract

Bacteriophage SP6 exhibits dual-host adsorption specificity. The SP6 tailspikes are recognized as important in host range determination but the mechanisms underlying dual host specificity are unknown. Cryo-electron tomography and sub-tomogram classification were used to analyze the SP6 virion with a particular focus on the interaction of tailspikes with host membranes. The SP6 tail is surrounded by six V-shaped structures that interconnect in forming a hand-over-hand hexameric garland. Each V-shaped structure consists of two trimeric tailspike proteins: gp46 and gp47, connected through the adaptor protein gp37. SP6 infection of Salmonella enterica serovars Typhimurium and Newport results in distinguishable changes in tailspike orientation, providing the first direct demonstration how tailspikes can confer dual host adsorption specificity. SP6 also infects S. Typhimurium strains lacking O antigen; in these infections tailspikes have no apparent specific role and the phage tail must therefore interact with a distinct receptor to allow infection.

Morphologically Different Pectobacterium brasiliense Bacteriophages PP99 and PP101: Deacetylation of O-Polysaccharide by the Tail Spike Protein of Phage PP99 Accompanies the Infection

“…The overall genome layout of PP99 follows the general features of SP6-like phages, including the presence of a pronounced set of early genes preceding the gene-encoding phage RNA polymerase, several apparently non-coding regions, and a holin/muramidase lysis module. Many SP6-like phages, including PP99, share a unified two-component structure of a tail spike (Gebhart et al, 2017;Tu et al, 2017). The gene encoding an adaptor protein providing an attachment of the spike to the tail is separated from the gene encoding the spike in the genome.…”

The Genetic Basis of phage susceptibility, cross-resistance and host-range in Salmonella

“…Four of the phages tested (P22Lys, SP6, Reaper_GE, Savina_GE) displayed strict requirements for full O4 [5] antigen biosynthesis despite being unrelated ( Figure 2BCD). This was expected for both P22Lys and SP6 since the O4 [5] antigen is the established receptor for their respective tail fibers 17,19,43 . SP6 and P22Lys had the most stringent LPS and O-antigen requirements, requiring 19 and 18 of the 25 LPS and O-antigen biosynthesis genes respectively across liquid and solid fitness experiments.…”

“…Only 4 of the phages investigated here have well-studied host-requirement characterization: Chi, FelixO1, P22Lys (a clear-plaque, obligately lytic mutant of P22), and S16 15,16,18,28,31,32 . An additional 3 have suspected, but not extensively studied, host-factor requirements: Br60, Ffm, and SP6 19,32,33 . We additionally isolated and subsequently investigated 4 bacteriophages from a commercial Intesti bacteriophage preparation in Georgia (see Methods): Aji_GE_EIP16 (Aji_GE), Reaper_GE_8C2 (Reaper_GE), Savina_GE_6H2 (Savina_GE), and Shishito_GE_6F2 (Shishito_GE).…”

“…Historically, S. typhimurium played a critical role in the identification of phage receptors, yielding critical insights into the genetics of complex receptors such as LPS and O-antigen and their structural composition [14][15][16][17][18][19] . However, mapping many phage-resistant mutations was a laborious process for a single phage, nonetheless for multiple diverse phages.…”

A Smooth-Type, Phage-Resistant Klebsiella pneumoniae Mutant Strain Reveals that OmpC Is Indispensable for Infection by Phage GH-K3

“…Moreover, the binding mode of podovirus with the host outer membrane has also been characterized by cryoelectron microscopy (cryo-EM). SP6 infection of Salmonella enterica serovars Typhimurium and Newport leads to the rotation of the tail spikes, providing direct proof of dual host adsorption specificity of the phage (37). Nevertheless, GH-K3 belongs to the family Siphoviridae, and knowledge gained from T4 or SP6 may not be relevant.…”