AbstractImpregnation of spruce and other conifers is very difficult due to aspiration of pits in tracheids. In this experiment, freshly cut and instantly debarked Norway spruce logs were pre-treated with the bacterium Bacillus subtilis at their ponding for 1, 3, 6 and 9 weeks under laboratory conditions at 30 °C or under outdoor conditions during the summer at 5 to 35 °C. Significant increases of the permeability and the impregnability of spruce sapwood were observed already after 3 weeks of its ponding due to bacterial attack and opening of pits in tracheids. Applied bio-treatments did not have a significant influence on selected mechanical properties of spruce wood. This method could be effectively used for poles and other round products from spruce or other conifers before their impregnation with preservatives or modification substances. However, its use for squared spruce timbers is not convenient because tracheids in the bacterially treated heartwood zone remained unchanged.