Figure 1.

The lifestyle dataset consists of 58 bacteria. The 58 bacteria were classified in 4 broader lifestyle groups based on the location of the bacterium in its host: obligate intracellular INTRA, cell associated CA, extracellular EXTRA (16, 17 and 19 organisms, respectively) and the control group FL. We further grouped them in subcategories on the basis of the association type (mutualism M, commensalism C, parasitism P) and the transmission mode (vertical V, horizontal H). INTRA includes only obligate intracellular bacteria, whereas CA includes bacteria which are facultatively intracellular, live on the surface of the host cell or are extracellular with a described intracellular step. These two groups have bacteria with obligate associations with their host (the totality of the individuals of the first group and 76% of the second one). EXTRA presents only bacteria that are facultatively associated with their host and are also free-living. The group FL has been used as a control group for all the analyses performed and includes organisms that have none of the three types of associations used for the grouping in the HAMAP information on interactions [40]. For that reason we included in FL one representative of each taxonomic class present in the dataset depending on the availability in the Microscope platform [39]. Two Mycoplasma species were classified in the CA group as they live on the surface of the host cell, although in another study they have been grouped together with the INTRA because of their reduced genome and the invariant environment within the hosts [44]. The codes for the organisms are the ones from HAMAP [40].

Klein et al. BMC Genomics 2012 13:438   doi:10.1186/1471-2164-13-438
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