ABSTRACT
Another possible explanation for the crust origin may be the presence of micro-organisms such as bacteria which are in great abundance in marine sediments. Bacteria may either be transported through the water column or be active within the sediment. Turley et al. (1995), Ransom et al. (1997) and Bhaskar and Bhosle (2005) consider the formation of aggregates within the water column by the production of extra-cellular polymeric substances (EPS), which may be produced by bacteria. Parkes et al. (2000) suggest that bacterial numbers may exceed 109 cells per cubic centimetre of sediment within the top metre. Their presence within the clay matrix may hypothetically influence sediment mechanical properties such as permeability and shear strength through the production of EPS. These studies have considered the water-sediment interface whereas the interest of the current investigation is material from significantly greater depth. By undertaking comparative shear tests on sterile and bacterially-inoculated samples, Kuo and Bolton (2009a) showed that the presence of the bacterium Marinobacter aquaeolei only had a minor influence on shear strength.
