Diel-scale temporal dynamics recorded for bacterial groups in Namib Desert soil

Gunnigle, E.
Frossard, A.
Guerrero, L.
Seely, M.
Cowan, D.A.
Ramond, J.-B.
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Nature Publishing Group
Microbes in hot desert soil partake in core ecosystem processes e.g., biogeochemical cycling of carbon. Nevertheless, there is still a fundamental lack of insights regarding short-term (i.e., over a 24-hour [diel] cycle) microbial responses to highly fluctuating microenvironmental parameters like temperature and humidity. To address this, we employed T-RFLP fingerprinting and 454 pyrosequencing of 16S rRNA-derived cDNA to characterize potentially active bacteria in Namib Desert soil over multiple diel cycles. Strikingly, we found that significant shifts in active bacterial groups could occur over a single 24-hour period. For instance, members of the predominant Actinobacteria phyla exhibited a significant reduction in relative activity from morning to night, whereas many Proteobacterial groups displayed an opposite trend. Contrary to our leading hypothesis, environmental parameters could only account for 10.5% of the recorded total variation. Potential biotic associations shown through co-occurrence networks indicated that non-random inter- and intra-phyla associations were 'time-of-day-dependent' which may constitute a key feature of this system. Notably, many cyanobacterial groups were positioned outside and/or between highly interconnected bacterial associations (modules); possibly acting as inter-module 'hubs' orchestrating interactions between important functional consortia. Overall, these results provide empirical evidence that bacterial communities in hot desert soils exhibit complex and diel-dependent inter-community associations.
Microbes, biogeochemical cycling, microenvironmental parameters, Namib Desert, Actinobacteria phyla
Gunnigle, E. et al. 2017. Diel-scale temporal dynamics recorded for bacterial groups in Namib Desert soil. SCIENTIFIC REPORTS 7, Article number 40189.