Fig. 4

Cell Wall Differences in H37Ra and H37Rv. a State of knowledge following publication of H37RaJH. At this time it was known that the SNP in the DNA-binding site of phoP abrogated synthesis of sulfolipids (yellow) and acyltrehaloses (purple and red) of the mycomembrane outer leaflet, while two SNPs in pks12, both of which were refuted in our assembly, were thought to cause the observed lack of phthiocerol dimycocerosates (blue) in H37Ra. b Current state of knowledge. Advances were made in understanding the inner leaflet. A single nucleotide, frameshift deletion in the now annotated hadC gene was shown by Slama and colleagues [33] to alter the mycolic acid profile in three distinct ways: i. Lower proportion of oxygenated mycolic acids (K-MA and Me-MA; green and blue carbon skeletons, respectively) to α-MAs (orange carbon skeleton). There are seven Me-MAs depicted in H37Rv compared to three in H37Ra, reflecting the proportions reported by Slama and colleagues [33]. ii. Extra degree of unsaturation (red circles) in H37Ra mycolic acids due to truncation of the HadC protein in H37Ra. iii. Shorter chain lengths of mycolic acids in H37Ra. Note that Me-MAs have larger loops in H37Rv than in H37Ra, and that the height of the α-MAs is shorter in H37Ra than H37Rv. Carbon chain lengths are based on results reported by Slama and colleagues. The folding geometry of the mycolic acids is depicted in panel B, as described by Groenewald and colleagues [56], and inspired by the illustration style of Minnikin and colleagues [57]