ML map of the quartet representing Bacillus subtilis, the deep branching bacteria T. maritima and A. aeolicus, and the salt-loving archaeon Halobacterium sp.. The majority of the orthologous datasets support the grouping of the Halobacterium with Bacillus subtilis. The topology that corresponds to the 16S rRNA topology (lower left vertex) is supported by the least number of orthologous datasets. The result stayed qualitatively the same when B. subtilis was replacedwith the cyanobacterium Synechocystis sp. (see results for quartet #11 in Table 3). For details on the figure notations see legend for Figure 4. A. Probabilities calculated according to Strimmer and von Haeseler . B. Probabilities calculated with the MrBayes program .