Passalid Gut Forest (IMAGE) DOE/Lawrence Berkeley National Laboratory Caption A close-up look at the passalid beetle's compartmentalized gut, and the distribution of metabolic processes and microbial composition by compartment. In the midgut (MG), plant polymers are changed into simpler components, which are then fermented in the anterior hindgut (AHG), where nitrogen is fixed and methane and hydrogen produced. Transformation of plant biomass (or polymers again) continues in the posterior hindgut (PHG), up to the release of frass rich in nutrients and metabolites such as acetate, ethanol, and benzoate. Credit Javier Ceja-Navarro/Berkeley Lab Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.