Fig. 4.

Pathways and enzymes associated with sour odor-producing compounds in the neck. a Number of enzymes (KOs) encoded by malodor-associated microbes in the neck region for “valine, leucine, and isoleucine biosynthesis/degradation” and “pyruvate metabolism” KEGG pathways. Numbers in the bars indicate the number of KOs where the relative abundance is significantly correlated with odor intensity. b–d Corresponding KEGG pathway diagrams, with pink boxes indicating significant positively correlated KOs in Staphylococcus species among children and gray boxes indicating enzymes that are present but do not have a significant correlation with odor intensity. Odor producing compounds and their precursors are marked with a star (*)