The relationship between the dimensions of a microbe and the accumulation of that microbe in porous. inorganic structures has been determined. That relationship is dependent upon the cell dimensions, the mode of reproduction, and the pore diameter of the material. In order to achieve high accumulation of microbes that reproduce by fission. at least 70% of the pores of an inorganic carrier should have pore diameters in the range of one times the smallest major dimension through five times the largest major dimension of the cell. To achieve the highest accumulation of microbes that reproduce by budding, at least 70% of the pores should have pore diameters in the range of one times the smallest dimension of the cell and less than four times the largest cell dimension. These relationships were established by varying the physical parameters of the carriers a s well a s their chemical composition.

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SUMMARYThe introduction of sodium acetate-2-14C into a bovine rumen resulted in the in vivo labelling of the rumen gases and volatile fatty acids. The relative isotope concentration in substrate and products indicated that a maximum of 5.6 % of the methane and 11% of the carbon dioxide in rumen gas might have been derived from the methyl carbon of acetate when the substrate was added to the rumen 18 hr. after the animal had been fed a normal ration, A maximum of 3-53 % of the methane and 4.2 % of the carbon dioxide might have been derived from the methyl carbon of sodium acetate-2-14C when this substrate was introduced into the rumen immediately after the animal had been fed. The addition of sodium acetate-l-14C to the rumen 18 hr. after feeding indicated that 2 yo of the methane and 10 yo of the carbon dioxide was derived from the carboxyl carbon of the substrate. Most of the derived radioactivity of the volatile acids of the rumen was found in the butyric acid fraction, although smaller amounts appeared in propionic acid and the volatile fatty acids with a chain length of greater than 4 carbons.

SummaryThe relationship between the dimensions of a spore and the accumulation of that microbe in a porous, inorganic structure has been determined. In order to achieve high accumulation of mycelial growth. at least 70% of the pores of an inorganic carrier should have pore diameters in the range of one times the smallest dimension of the fungal spore but less than about I6 times the largest dimension of that spore. This relationship was established by varying the physical parameters of the carriers as well as their chemical composition.

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