Identification of a class of protein ADP-ribosylating sirtuins in microbial pathogens by Rack, J, Morra, R, Barkauskaite, E, Kraehenbuehl, R, Ariza, A, Qu, Y, Ortmayer, M, Leidecker, O, Cameron, D, Matic, I, Peleg, A, Leys, D, Traven, A, Ahel, I