Acetogenesis: Reality in the Laboratory, Uncertainty Elsewhere

This chapter focuses on recent work in our research group that further extends our awareness of the diverse metabolic potentials of acetogens and, consequently, broadens our uncertainty in making accurate predictions of the role acetogens actually play at the ecosystem level (i.e., “elsewhere” per the title of this chapter). Without debating what ecosystems are, acetogens are difficult to study in their natural habitat. This difficulty stems largely from the fact that the main product we think they make (i.e., acetate) is not easily assessed (a gaseous product minimizes this complication) and likely turns over rapidly in vivo. Likewise, many of the substrates they may consume are also problematic to assess. In addition, approaches such as the [3H]thymidine incorporation method to assess the productivity of acetogens may greatly underestimate their magnitude (Winding, 1992; Wellsbury et al., 1993). Thus, although enrichment and physiological studies have been somewhat elegant in recent years relative to defining acetogenic potentials in the laboratory, comparatively little is known about what they really do “elsewhere” (as emphasized in Chapter 7). Clearly, native ecosystems such as forests have little in common with test-tube cultures. In the present chapter and those that follow in Part IV these realities and uncertainties are addressed.