Little is known about the bacteria that degrade cellulose. Symbiotic bacteria in Xylophaga may play a role in the degradation of sunken wood; while bacteria such as Alphaproteobacteria, Flavobacteria, Actinobacteria, Clostridia, and Bacteroidetes have been detected in wood submerged over a year.
How long was the wood submerged in water in the study that discovered the types of bacteria in it?
{'text': 'over a year', 'answer_start': 284}