This Virtual Issue is the first in our ‘Landmarks in Microbiology’ series. These collections will celebrate influential papers in the discipline published in the FEMS journals, as well as the exciting research that has grown from standing on the shoulders of these landmarks.

Our first collection focuses on anaerobic ammonium oxidation, or Anammox, a process first described in FEMS Microbiology Ecology in 1995. The papers that follow on from the original further explore this intriguing microbial metabolism, from reporting on environmental factors determining distribution and activity of anammox bacteria in minerotrophic fen soils, to deep-sea methane seep sediments in the Okhotsk Sea sustaining diverse and abundant anammox bacteria. These papers, spanning over two decades, show the wealth of knowledge we have come to understand, and start what we hope will be a fascinating series for our community.