Comparative genomics of CEV2, a T5-family bacteriophage infecting Escherichia coli O157:H7.

ARISTIMUÑO FICOSECO MARIA CECILIA; MARÍA J. OLAYA PASSARELL; HEBERT ELVIRA MARIA; ELIZABETH KUTTER ; RAÚL R. RAYA

Olympia

Congreso; 2017 Evergreen International Phage Meeting; 2017

The Evergreen State College

Escherichia coli phage CEV2, a siphovirus (phage with longnon-contractile tails) of the T5-like family, possesses a 118,347 bp genome (39.3mol GC%) which encodes 160 ORFs and 22 tRNAs. Phages CEV2 and T5 showed similarhost ranges, but only CEV2 infects virtually all tested E. coli O157: H7 strains. In their irreversible final step of phagebinding to their hosts, both phages recognize, through their PB5(oad gene; 99% identity) proteins, theouter cell membrane FhuA protein as receptor. However, their LTF proteins,responsible for the reversible interaction that occurs between the phage andthe LPS (antigen O) of the bacterium, presented only 46% identity. Theseresults could explain the difference in host range observed between thesephages. A comparative genomic study of eight T5-like phages [T5(AY543070.1 and NC_005859.1); CEV2; SPC35 (HQ406778.1); DT571/2 (KM979355.1);DT57C (KM979354.1); FFH1 (KJ190157.1); AKFV33 (HQ665011.1); and APCEc03(KR422353.1)], conducted primarily with the programs BlastP and BlastX; ClustalOmega; Easyfig 2.1; ARAGORN and tRNAscan, revealeda collinear organization of their genes, with identities over 80% throughouttheir sequences, with phages CEV2 and FFH1 being most closely related, exceptin two regions: the ?LTF? and the ?tRNAs? regions located, respectively, at80-85- and 28-37-kb of their genomes. The LFT protein of CEV2 presented a 71%identity with that of phages FFH1 and APCEc03. The tRNA genes in these phagesranged from 9 to 23. CEV2 encodes 22 tRNAs, although Gly- and Tyr-tRNAisoaccepting species were not detected. On the other hand, T5 encodes 23 tRNAsand lacks tRNAs genes for glycine (Gly) and tryptophan (Trp). Thegreater diversity observed among the LFT proteins of these phages indicatestheir ability to adapt to different scenarios, in particular to the differenttypes of specific receptors located in the LPS of their host cells. In turn,the presence of a variable number and specific tRNAs may contribute to theoverall rate of protein synthesis during phage infection.