Life history strategies are shaped by multiple traits that determine species adaption, growth and survival. A classic life history framework for microbes is proposed as the copiotroph–oligotroph continuum. Copiotrophs exhibit relatively fast growth in resource rich environments, whereas oligotrophs are more efficient in exploiting resource scarce environments at the expense of reproduction. As a result, these two strategies represent a fundamental trade-off between reproductive investment and resource use efficiency. Despite the fact that copiotrophs and oligotrophs differ in functional capacity and genomic attributes, how this variation in microbial life history strategies among species impacts the relationship between community structure and functional attributes remains undetermined.
Here, we applied a trait-based approach to investigate the soil microbial communities of vegetation patches and adjacent bare soils in 4 sites in the Sonoran Desert (AZ, USA). Soil microbial community structure and functional attributes were characterized by 16S rRNA gene amplicon sequencing and shotgun metagenomics, respectively. Genomic traits were inferred from metagenomic data to shed light on microbial life history strategies.
Results/Conclusions
Microbial communities in vegetated soils had a higher predicted maximum grow rate and more 16S rRNA gene copies than those in bare soils. These genomic trait differences suggest that microbial life history strategy in desert soils follows the copiotroph-oligotroph continuum: vegetated soils tended to harbor fast-growing copiotrophs, whereas bare soils were dominated by slow-growing oligotrophs. Microbes in bare soils were more functionally redundant, with their lower magnitudes of functional shifts in response to taxonomic shifts. Furthermore, more unannotated genes were found in bare soils. Unannotated bare soil genes presumably originated from both unclassified oligotrophs and classified oligotrophs with insufficient genomic information. In vegetation patches, however, those unannotated genes were most likely derived from unclassified copiotrophs. Collectively, these results suggest that life-history strategies of microbial communities affect functional stability and have implications for the discovery of novel functions in arid ecosystems.