Genomics of Rhodococcus for Biofuels Figure 2. Phylogenetic analysis of type 1a and type 1b fatty acids synthases. a) A phylogenetic tree that shows FAS type 1a is found in Actinobacteria, Stramenopiles, and Fungi. b) A phylogenetic tree of MAS-family type 1b proteins. This gene family is expanded in the genera Mycobacterium, Frankia, and Streptomyces but present in single copy in Rhodococcus belonging to branch containing the PKS12 from M. tuberculosis NP_216564 that also contains similar protein domain architecture. doi:10.1371/journal.pgen.1002219.g002 twelve functional domains and common domain architecture as PKS12 (Figure 1d), suggesting a related role in branched-lipid biosynthesis that was shown in M. tuberculosis to be production of C30–34 length methyl-branched phospholipids containing a 4,8,12,16, 20-pentamethylpentacosyl lipid subunit [36]. Only one MAS-family type 1b gene is encoded in R. opacus PD630 and related R. opacus B4, and R. jostii RHA1 genomes; whereas in the genera Mycobacterium, Frankia, and Streptomyces expansion of this gene-family has occurred (Figure 2b). In Mycobacterium the MAS- family synthases generate methyl-branched lipids adding to the diversity observed in their cell wall lipids that have been shown to be key in persistence, pathogenicity, and immune recognition [37,38,39]. By contrast, Streptomyces also contain several MAS- family proteins but do not encode for the FAS type 1a protein PLoS Genetics | www.plosgenetics.org 5 September 2011 | Volume 7 | Issue 9 | e1002219