phage

Histones also might protect archaea against invaders, such as phages or transposable elements, which would find it harder to integrate into the genome when it’s wrapped around the proteins.

So Zhao and colleagues in China chose a phage called SH-Ab 15497 that infects Acinetobacter bacteria, and confirmed that its DNA alphabet also has Z in place of A, his team reports.

Periodically, Marlière searched genetic databases for other phages that have PurZ and might contain the elusive picky polymerase.

Why phages would bother with the unconventional DNA was still unknown.

By 2050, 10 million people are projected to die each year from antibiotic-resistant infections, and phages could be our last hope.