 E. coli can live on a wide variety of substrates and uses mixed @-@ acid fermentation in anaerobic conditions , producing lactate , succinate , ethanol , acetate , and carbon dioxide . Since many pathways in mixed @-@ acid fermentation produce hydrogen gas , these pathways require the levels of hydrogen to be low , as is the case when E. coli lives together with hydrogen @-@ consuming organisms , such as methanogens or sulphate @-@ reducing bacteria . 
