Diversity and metabolic energy in bacteria

Abstract

Why are some groups of bacteria more diverse than others? We hypothesize that the metabolic energy available to a bacterial functional group (a biogeochemical group or 'guild') has a role in such a group's taxonomic diversity. We tested this hypothesis by looking at the metacommunity diversity of functional groups in multiple biomes. We observed a positive correlation between estimates of a functional group's diversity and their metabolic energy yield. Moreover, the slope of that relationship was similar in all biomes. These findings could imply the existence of a universal mechanism controlling the diversity of all functional groups in all biomes in the same way. We consider a variety of possible explanations from the classical (environmental variation) to the 'non-Darwinian' (a drift barrier effect). Unfortunately, these explanations are not mutually exclusive, and a deeper understanding of the ultimate cause(s) of bacterial diversity will require us to determine if and how the key parameters in population genetics (effective population size, mutation rate, and selective gradients) vary between functional groups and with environmental conditions: this is a difficult task.

Keywords: bacteria; diversity; energy; metabolic.

Figure 1.

The relationship between the estimated metacommunity diversity and the energetic yield in wastewater treatment plants in the United Kingdom. P-value of slope = 0.0004, R² = 0.443.

Figure 2.

The relationship between the estimated metacommunity diversity in all biomes and the energetic yield. The overall slope is significant (slope = 0.73, P slope < 0.001; adjusted R² = 40%). Values for individual biomes are given in Table 2.

Figure 3.

The relationship between the meta-community diversity of functional groups in the EBI-Tara dataset thought to have simple substrates and: (A) energetic yield (not significant) (B) catabolic energy a (P = 0.02, R² = 79%).