Proteolytic bacterial dominance in a full-scale municipal solid waste anaerobic reactor assessed by 454 pyrosequencing technology

Biomethanization entails a good means to reduce the organic fraction (OF) derived from municipal solid wastes (MSW). The bacterial diversity of a full scale MSW anaerobic reactor located in Madrid (Spain) was investigated using high-throughput 454 pyrosequencing. Even though the proteolytic bacteria prevailed throughout all of the process, community shifts were observed from the start-up to the steady-state conditions, with an increasing biodiversity displayed over time. The Bacteroidetes and the Firmicutes were the majority phyla: 55.1 and 40.2% (start-up) and 18.7 and 78.7 (steady-state) of the total reads. The system's lack of evenness remains noteworthy as the sequences affiliated to the proteolytic non-saccharolytic Proteiniphylum, Gallicola and Fastidiosipila genera, together with the saccharolytic Saccharofermentans, were predominant on the system and this predominance appears to correlate with the presence of a high ammonium concentration. The 454 pyrosequencing revealed a great diversity of rare organisms which seemingly do not sustain any metabolic roles in the course of the OF-MSW degradation. However, this scarce and unique microbiota can confer great resilience to the system as a buffer against nutritional and environmental changing conditions, thus opening the door to increase the current knowledge about the bacterial community dynamics taking place during MSW treatment processes. •Bacterial community of a full-scale MSW reactor was elucidated by pyrosequencing.•Population shifts took place within of the MSW reactor.•Proteiniphilum, Gallicola and Saccharofermentans composition shifts were detected.•Fermentative proteolytic bacteria were predominant over the saccharolytic microbes.•High ammonium concentrations inhibited the saccharolytic bacteria.