While the opaque-transparent switch is reversible, the rough phenotype results from irreversible deletion of cell envelope glycopeptidolipid genes and is irreversible [24, 51]. TLC (Thin Layer Chromatography) analysis of the different morphotypes from strain 104 has been performed by Torelles [21]. They also analysed the sugar composition of the glycopeptidolipids (GPL) by gas chromatography–mass spectrometry (GC–MS) analysis. They found that the smooth opaque and smooth transparent colonies formed similar GPL and both expressed besides the nsGPL (ns: non-specific) the ssGPL (ss:serovar specific) of serovar 1. However, the ssGPL was absent Palbociclib in vitro in the rough morphotype, which had a strong band of the nsGPL. A band in the lipopeptid

region devoid of sugars was present in the smooth transparent morphotype and the rough morphotype but lacking in the smooth opaque morphotype. ALK inhibitor The sugar composition of all morphotypes showed the typical profiles related to ns and ssGPL of serovar 1,

only in the rough morphotype 6-deoxytalose and 3-O-methyl-6-deoxytalose were missing. The transparent colony variant grows better in macrophages and animals compared to the opaque variant. Moreover, white transparent colonies survived better in macrophages than red transparent colonies [19, 24, 50, 51, 56]. These differences in intracellular survival may be caused by variations in the cytokine response towards infection by different Tolmetin morphotypes. The smooth opaque morphotype has been shown to induce higher levels of secretion of IL-1α, IL-1β and TNF-α by human blood-derived monocytes compared to the smooth-transparent morphotype [57]. Variation in cytokine response upon infection with either smooth-opaque

or smooth-transparent M. avium was also reported upon infection of human microglia cultures [58]. The colony morphology of the WT and the mutants upon plating on Congo Red Agar is shown in Figure  3. The WT (Figure  3 A) mainly formed smooth-domed-opaque (sdo) colonies along with smooth-transparent (st) colonies. Mutant MAV_2555 showed the same morphologies, but additionally smooth-flat-red (sfr) colonies were visible (Figure  3 B). Relatively few smooth-transparent and rough colonies occurred in mutant MAV_1888 (Figure  3 C), MAV_4334 (Figure  3 D) and MAV_5106 (Figure  3 E). Mutant MAV_4334 (Figure  3 D) showed a higher variation with respect to the intensity of red color of smooth-domed-opaque colonies. Mutant MAV_1778 showed a very high degree of variability displaying red-rough (rr) and smooth-flat-red colonies additionally to the smooth-domed-opaque, smooth-transparent and rough-white (rw) colonies (Figure  3 F). The colonies generated by mutant MAV_3128 (Figure  3 G) were in average larger in size and the smooth-opaque colonies appeared paler than in the WT. Also, the edges of these colonies were more irregular. Some red-rough colonies were also visible. The most multifaceted image was displayed by mutant MAV_3625.