Complete genome sequences of T5-related Escherichia coli bacteriophages DT57C and DT571/2 isolated from horse feces.

This research involved sequencing the complete genomes of two bacteriophages related to T5, named DT57C and DT571/2, which were found in horse feces. The bacteriophages share 96% sequence identity at the nucleotide level, making them representatives of a new species within the T5likevirus genus. Differences were found in the phages’ ltfA gene due to recent recombination, which could explain why they have different host ranges. Comparison to their closest known relative, coliphage T5, showed strong similarity in terms of genome organization and the sequences of most proteins, while also highlighting different genes and tail fiber organization indicating they are a distinct species.

Complete Genome Sequencing

• Researchers sequenced the full genomes of two bacteriophages (viruses that infect bacteria), named DT57C and DT571/2, which were found within the feces of a horse.
• The two viruses were found to share a high nucleotide sequence identity of 96%, meaning they are highly similar at the genetic level. As result, they are considered to represent a new species within the T5likevirus genus, which comprises T5-like bacteriophages.

Genetic Variation and Host-Range Differences

• There were observed differences in the ltfA gene of the two bacteriophages, which is known to have resulted from a recent recombination event – a form of genetic reorganization.
• This genetic variation could help to explain why the two viruses have different host ranges – the range of organisms that a virus can infect.
• The researchers suggest that this finding illustrates the importance of modular mechanisms in the short-term evolution or adaptation of T5-like phage genomes within intestinal ecosystems.

Comparisons to Coliphage T5

• The researchers compared the genomes of DT57C and DT571/2 to those of coliphage T5, the closest known relative of the two bacteriophages.
• They found a high level of overall synteny, meaning the genes were arranged in the same order on the chromosomes, and high conservation of the sequences of the majority of proteins, as well as other proteins with identified functions.
• However, they also noted numerous alterations and replacements of non-structural protein genes, mostly those with unknown functions, as well as substantial differences in the organization of tail fiber locus – the genomic region responsible for producing the structures that the viruses use to attach to their host bacteria.
• These differences confirm that DT57C and DT571/2 form a distinct group at the species level, separate from bacteriophage T5.