Tomography of bacteria–mineral associations within the deep-sea hydrothermal vent shrimp Rimicaris exoculata

Rimicaris exoculata flourishes around deep-sea hydrothermal vent environments along the Mid-Atlantic Ridge (MAR). Epibiotic bacteria and minerals found within the branchial chamber of the shrimp are of interest in the search for the metabolic energy pathways sustaining shrimp swarms at the Rainbow vent site (MAR). Here we examine the three-dimensional (3D) relationships between epibionts and their associated minerals. The morphology and chemical composition of the minerals were analysed by Energy Filtering Transmission Electron Microscopy (EFTEM) and the 3D organisation was determined by Transmission Electron Tomography (TET). The minerals are preferentially associated with small, rod-shaped bacteria. The iron oxide deposits exhibit three main associations with the bacterial exterior: (1) close, (2) zoned/layered and (3) distant. Iron is the most prevalent element, with a close association with the bacteria, and co-occurs with oxygen. 3D reconstructions reveal a discontinuous network of deposits around the bacteria, showing the intricate nature of these iron oxides.