The pathogenic microbe came to be a widely acknowledged “scientific fact” by the end of the 19th century. Taking the transfer of bacteriological knowledge to Warsaw as an example, this article contributes to understanding the question of how knowledge of bacteria was stabilized outside of its original place of production. Conceiving bacteriological knowledge as a laboratory practice it describes the techniques of mobilizing the “laboratory network” this practice depended on. The case of the Polish medical student Odo Bujwid transporting Robert (...) Koch’s and Louis Pasteur’s laboratory networks to Warsaw will be analyzed. Bujwid used literary and visual inscriptions to make these laboratory networks immutably mobile in Bruno Latour’s sense. But he also had to transport three-dimensional objects central to the networks’ functioning back to Warsaw. Personal exchange was, furthermore, essential to their successful transportation to the Polish kingdom. Next to Bujwid’s efforts to transform the laboratory networks into immutable mobiles, the analysis will extend the focus to mutable mobiles as well and will thus show that the successful stabilization of bacteriological knowledge in Warsaw was due not only to the immutability of its laboratory network but to its flexibility and elasticity as well. (shrink)