Microbial Community Response to Seasonal Temperature Variation in a Small-Scale Anaerobic Digester

The <i>Bacterial</i> and <i>Archaeal</i> communities in a 1.14 m³ ambient temperature anaerobic digester treating dairy cow manure were investigated using terminal restriction fragment length polymorphisms (T-RFLP) and direct sequencing of the cloned polymerase chain reaction (PCR) products. Results indicate shifts in the structure of the both the <i>Archaeal</i> and <i>Bacterial</i> communities coincided with digester re-inoculation as well as temperature and loading rate changes. Following re-inoculation of the sour digester, the predominant <i>Archaea</i> shifted from <i>Methanobrevibacter</i> to <i>Methanosarcina,</i> which was the most abundant <i>Archaea</i> in the inoculum. <i>Methonosarcina</i> was replaced by <i>Methanosaeta</i> after the resumption of digester loading in the summer of 2010. <i>Methanosaeta</i> began to decline in abundance as the digester temperature cooled in the fall of 2010 while <i>Methanobrevibacter</i> increased in abundance. The microbial community rate of change was variable during the study period, with the most rapid changes occurring after re-inoculation.