16S rRNA Gene and Transcript Profiling: an Application on Full-scale Anaerobic Reactors of Wastewater Sludges

Sludge anaerobic digestion is a wastewater treatment plant crucial point for the impact mitigation on environment. Such process reduces the disposable sludge volume and pollution potential, generating biogas. Despite its crucial role, sludge digestion microbiology is not clearly understood. In this work, the characterization of the microbiota into digesters fed by primary and secondary sludge was performed. Two sampling sessions were conducted and more than 120 samples were extracted and analyzed by PCR-DGGE. Cluster analysis on DGGE profiles suggested the presence of diverse communities associated with different sludge characteristics (ANOVA, p<0.01) and Shannon’s diversity index showed higher evenness into the secondary-one. Moreover, the comparison of community structure based on DNA and bacterial rRNA genes highlighted the presence of unexpressed bacterial genome, leading to a potential functionality overestimation using a DNA-based approach (Shannon index mean -16%, t-test p<0.05). This approach has proven to be suitable for a first useful assessment of microbial community dynamics during the anaerobic digestion process.