3.2.5. Actinobacteria

The Actinobacteria are the only major group of chemotrophic bacteria that show betaine biosynthesis from glycine. They form a distinct branch distantly related to *Chromatiales* and *Chloroherpeton* (Figure 1). In *Actinopolyspora halophila*, for example, a fused GMT/DMT gene is included in a gene cluster with MAT, MTHFR, and SAHase (Table 4).
