FIG 8.

Thiamine metabolism in B. thailandensis E264. The illustration depicts thiamine metabolism in E264. Thiazole synthetic pathways are highlighted in green. Synthesis of the pyrimidine moiety and the CytX transporter for HMP uptake are represented in blue. The proteins that combine the moieties to make TMP and TPP are depicted in red. Extracellular thiaminase I, ThiA, is depicted as orange octagons acting on both thiamine and pyrithiamine. The “X” on thiamine represents the side chains thiamine, TMP, or TPP. The “R” on the HMP molecule represents the diversity of organic nucleophiles attached to it. Unclear or unknown pathways are represented as dashed lines. In our model, thiamine disulfide is abiotically converted to thiamine (represented by gray lines), which ThiA can act on. In the model, dibenzoyl thiamine loses the benzoyl group attached at the sulfur abiotically; the compound is then acted on by ThiA. It is unclear how the second benzoyl group is removed. We suspect the HMP-R is imported through an unknown transporter (white oval with a “?”), and processed intracellularly by an unknown enzyme (white triangle with a “?”) to HMP. THZ is likely imported by an unknown transporter (white oval with a “?”). For THZ molecules containing phosphates, they are likely removed extracellularly, and the THZ is then imported.