Arbitrary expression levels as introduced in Nicolas et al. (2012) were used. The number corresponds to logarithmical presentation of the experimentally determined expression. To select this set of proteins, we used two conditions: First, the average expression level under 104 conditions should be above 13. Second, the gene should be highly expressed under all conditions. Exceptions were allowed for low expression during sporulation. Proteins were regarded unknown if no function had be identified prior to a large scale in vivointeraction study (O’Reilly et al., 2023). The list is also accessible online (http://www.subtiwiki.uni-goettingen.de/v4/category?id=SW.6.1).