The 'microgenderome' provides a paradigm shift that highlights the role of sex 
differences in the host-microbiota interaction relevant for autoimmune and 
neuro-immune conditions. Analysis of cross-sectional self-report and faecal 
microbial data from 274 patients with Myalgic Encephalomyelitis/Chronic Fatigue 
Syndrome (ME/CFS) suggests that commensal gut microorganisms may play both 
protective and deleterious roles in symptom expression. Results revealed 
significant sex-specific interactions between Firmicutes (Clostridium, 
Streptococcus, Lactobacillus and Enterococcus) and ME/CFS symptoms (including 
neurological, immune and mood symptoms), regardless of compositional similarity 
in microbial levels across the sexes. Extending animal studies, we provide 
support for the microgenderome in a human clinical population. Applied and 
mechanistic research needs to consider sex-interactions when examining the 
composition and function of human microbiota.