Metals, microbes, and minerals: the biogeochemical side of life, vol. 21 of metal ions in life sciences (Guest Editors: Peter M. H. Kroneck and Martha E. Sosa Torres. Series Editors: Astrid Sigel, Eva Freisinger, Roland K. O. Sigel). Walter de Gruyter, Berlin, Germany, 2021, 341 + xlv pp. ISSN: 1559-0836; 1868-0402 (electronic). ISBN: 978-3-11-058890-3; 978-3-11-058977-1 (electronic PDF); 978-3-11-058893-4 (electronic EPUB). DOI: 10.1515/9783110588903. Walter de Gruyter, GmbH, Berlin, Germany, 2021