Trace Metal Imaging of Sulfate-Reducing Bacteria and Methanogenic Archaea at Single-Cell Resolution by Synchrotron X-Ray Fluorescence Imaging

<p>Metal cofactors are required for many enzymes in anaerobic microbial respiration. This study examined iron, cobalt, nickel, copper, and zinc in cellular and abiotic phases at the single-cell scale for a sulfate-reducing bacterium (<i>Desulfococcus multivorans</i>) and a methanogenic archaeon (<i>Methanosarcina acetivorans</i>) using synchrotron X-ray fluorescence microscopy. Relative abundances of cellular metals were also measured by inductively coupled plasma mass spectrometry. For both species, zinc and iron were consistently the most abundant cellular metals. <i>M. acetivorans</i> contained higher nickel and cobalt content than <i>D. multivorans</i>, likely due to elevated metal requirements for methylotrophic methanogenesis. Cocultures contained spheroid zinc sulfides and cobalt/copper sulfides.</p>