Abstract
BackgroundIt is of critical importance to understand how anammox consortia respond to disturbance events and fluctuations in the wastewater treatment reactors. Although the responses of anammox consortia to operational parameters (e.g., temperature, dissolved oxygen, nutrient concentrations) have frequently been reported in previous studies, less is known about their responses and resilience when they suffer from nutrient interruption.ResultsHere, we investigated the anammox community states and transcriptional patterns before and after a short-term nutrient starvation (3 days) to determine how anammox consortia respond to and recover from such stress. The results demonstrated that the remarkable changes in transcriptional patterns, rather than the community compositions were associated with the nutritional stress. The divergent expression of genes involved in anammox reactions, especially the hydrazine synthase complex (HZS), and nutrient transportation might function as part of a starvation response mechanism in anammox bacteria. In addition, effective energy conservation and substrate supply strategies (ATP accumulation, upregulated amino acid biosynthesis, and enhanced protein degradation) and synergistic interactions between anammox bacteria and heterotrophs might benefit their survival during starvation and the ensuing recovery of the anammox process. Compared with abundant heterotrophs in the anammox system, the overall transcription pattern of the core autotrophic producers (i.e., anammox bacteria) was highly resilient and quickly returned to its pre-starvation state, further contributing to the prompt recovery when the feeding was resumed.ConclusionsThese findings provide important insights into nutritional stress-induced changes in transcriptional activities in the anammox consortia and would be beneficial for the understanding of the capacity of anammox consortia in response to stress and process stability in the engineered ecosystems.7cebb1f-VYhKkDnFTSZAj9Video
Highlights
It is of critical importance to understand how anammox consortia respond to disturbance events and fluctuations in the wastewater treatment reactors
Microbial community dynamics and transcriptomic expression A total of 88 bacterial metagenome-assembled genomes (MAGs) were retrieved from the metagenome
Active response of anammox bacteria to nutrient starvation The expression pattern showed that AMX1 maintained a high transcriptional level at S2, which was consistent with the energetic transcriptional responses of some key genes involved in the anammox process
Summary
It is of critical importance to understand how anammox consortia respond to disturbance events and fluctuations in the wastewater treatment reactors. The anaerobic ammonium oxidation (anammox) process is one of the most energy-efficient biotechnologies for nitrogen removal and has been widely implemented in wastewater treatment plants [1]. This process is mediated by a deeply branching group of chemolithoautotrophic bacteria affiliated with the phylum of Planctomycetes that are capable of oxidizing. Numerous studies have elucidated the effects of operational factors (e.g., temperature and dissolved oxygen (DO)) on anammox performance and the microbial community based on 16S rRNA gene or metagenomic analysis [19,20,21,22]. Few studies have revealed the effect of starvation caused by short-term nutrient deprivation (e.g., caused by system failures) on the anammox system, especially using multi-omics strategies
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