THE EXPERIMENTAL SILICIFICATION OF BACILLUS SUBTILIS By

Silica, particularly the stable phase of silica, quartz is chemically and physically resistant to weathering. Microorganisms are commonly incorporated into silica deposits formed by silica precipitation from geothermal fluids that are over saturated with respect to silica. Silica deposits have provided the oldest evidence of life identified on Earth in the form of fossil microorganisms. The first signs of life found beyond Earth may occur as microfossils in silica deposits. Experiments were conducted on the gram positive bacterium Bacillus subtilis to test the effects of silica concentration, dissolved Fe, and dissolved Al upon silicification processes. Results from initial experiments demonstrated that Bacillus subtilis a common soil bacterium, persists in better condition in the presence of Fe and that silica interacts with cellular surfaces in the presence and absence of Fe. The initial experiments were conducted by combining a suspension of bacterial cells with stock solutions in a 1/1 ratio