Might play a role in defense against invading genetic elements, using short DNA sequences as guides to bind complementary target strands, resulting in slicing of the target nucleic acid (By similarity). Binds nucleic acids with decreasing affinity in the following order; ssDNA, ssRNA, dsDNA, RNA-DNA, RNA-RNA (PubMed:15800629). Association of the 5' seed region of the guide strand (nucleotides 2-7) with AfPiwi increases affinity for the corresponding target strand; the greatest increase in affinity is for guide DNA with target RNA (PubMed:19187762). Other ligands are provided by nucleic acid (PubMed:15800628, PubMed:15800629, PubMed:19187762). This is missing the N-terminal and PAZ domains compared to other prokaryotic argonaute proteins. Belongs to the argonaute family. Short pAgo subfamily. Despite its similarity to eukaryotic argonaute proteins this protein is probably not involved in RNA-mediated gene silencing (RNAi), as that process is not known to exist in prokaryotes.