Anoxic subseafloor crustal fluids from sediment-covered ocean crust in the flank of the Juan de Fuca Ridge (JdFR) were collected and used to isolate anaerobic chemosynthetic microorganisms fueled by rock-derived energy sources within the oceanic crust. Here, we present results of Thermaerobacter sp. strain 36, which represents the first confirmed isolate obtained directly from the subseafloor crustal aquifer at JdFR. Strain 36 grows as a thermophilic primary producer through the microbial oxidation of H2 coupled either to As(V) or Fe(III) reduction. Under these conditions, laboratory growth is slow and reaches low cell densities. Cells are pleiomorphic, meaning that they change from small cocci to short rods and elongated filaments during growth. Phylogenetic analysis of the 16s rRNA gene sequence shows that the closest relative of strain 36 is Thermaerobacter marianensis, a bacterium isolated from sediments of the Challenger Deep at the Mariana Trench. Whole genome analyses are currently underway to better understand the relationship between strain 36 and T. marianensis and their role in deep marine crustal environments. We hypothesize that both organisms represent a species capable of long-distance dispersal as spores.