The Firmicutes were represented mainly by the classes Clostridia (from 5% to 42% of total reads) and Bacilli (from 1% to 9% of total reads), whereas the other classes did not exceed 1% of total reads (Fig. 7). The most abundant Clostridia are known to produce a variety of extracellular enzymes capable of degrading large organic molecules, such as cellulose, lipids, and proteins. The same species of the genus Clostridium are important cellulose digesters (Schwarz, 2001).