Unveiling hidden bacterial players: A closer look at the succession characteristics and co-occurrence patterns of abundant, intermediate and rare bacteria in biological soil crusts

Abstract

The bacterial communities of biological soil crusts (BSCs) often comprise abundant, intermediate and rare taxa that form complex ecosystems through interspecies interactions and play essential roles in regulating the process of vegetative restoration. However, the community structure of nonabundant bacteria and the interactions among these abundance categories are still largely unknown. In light of this, we used Illumina MiSeq sequencing to investigate the succession characteristics and co-occurrence patterns of abundant bacteria (ABs), intermediate bacteria (IBs) and rare bacteria (RBs) in the three developmental stages of BSCs (cyanobacteria-, lichen- and moss-dominated crusts) on the southeastern edge of the Tengger Desert. The results showed that the changes in the Chao richness and taxonomic composition of ABs, IBs and RBs were significantly different during BSC succession. The results of the co-occurrence network analysis revealed that most of the observed associations were between RBs (more than 80 %), positive correlations were predominant (more than 77 %), and the vast majority of the keystone taxa in the BSC bacterial networks were RBs (only one belonged to IBs). Moreover, the driving effects of environmental variables on ABs, IBs and RBs were not exactly the same, and their diversity was a key driver of the co-occurrence network properties of the BSCs. These findings are crucial for understanding the establishment and maintenance of BSC bacterial diversity and provide a new perspective for utilizing microbial resources and/or regulating environmental factors to achieve the sustainable development of desert ecosystems.