ABSTRACT
A number of parasitic and endosymbiotic protists and helminths have a fermentative metabolism, i.e. produce organic acids and alcohols from hexoses used as energy source, instead of completely oxidizing them to CO2 amd H2O. Several thrive in the absence of O2 and can be termed ‘anaerobic’. The degree of independence from O2 varies from species to species and some could be termed more properly ‘microaerophilic’. For convenience, however, only the term ‘anaerobic’ will be used here with full realization of its ambiguity.
