Abstract
Granules enriched with anammox bacteria are essential in enhancing the treatment of ammonia-rich wastewater, but little is known about how anammox bacteria grow and multiply inside granules. Here, we combined metatranscriptomics, quantitative PCR and 16S rRNA gene sequencing to study the changes in community composition, metabolic gene content and gene expression in a granular anammox reactor with the objective of understanding the molecular mechanism of anammox growth and multiplication that led to formation of large granules. Size distribution analysis revealed the spatial distribution of granules in which large granules having higher abundance of anammox bacteria (genus Brocadia) dominated the bottom biomass. Metatranscriptomics analysis detected all the essential transcripts for anammox metabolism. During the later stage of reactor operation, higher expression of ammonia and nitrite transport proteins and key metabolic enzymes mainly in the bottom large granules facilitated anammox bacteria activity. The high activity resulted in higher growth and multiplication of anammox bacteria and expanded the size of the granules. This conceptual model for large granule formation proposed here may assist in the future design of anammox processes for mainstream wastewater treatment.
Highlights
From microbial communities, can shed light on microbial activities and their regulation
Estimation of total bacteria, anammox, ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) by quantitative PCR (qPCR) showed a gradual increase in the anammox copy number from 9.7 log copies mL−1 to 13 log copies mL−1 over a period of time (Supplementary Figure S3A)
A similar trend was observed by 16S rRNA gene sequences in which the relative abundance of anammox bacterial genus Candidatus Brocardia increased over time with the exception of the Day 52 samples (Fig. 1)
Summary
From microbial communities, can shed light on microbial activities and their regulation. Recent advances in mRNA enrichment from environmental samples[13] and the reliability of commercially available kits for rRNA subtraction[10] have facilitated the use of this technique to track low-frequency changes in gene expression of bacterial communities associated with complex microbial communities such as those involved in the granular anammox process. We employed rRNA-subtracted metatranscriptomics to track changes in gene expression of bacterial communities involved in the granular anammox process over space and time in a lab-scale sequencing batch reactor (SBR). The main objectives of this study were to: (i) define the microbial community structure of anammox communities using qPCR and 16S rRNA gene sequencing; (ii) reconstitute the enzymatic machinery for key pathways in the anammox process; and (iii) measure their expression dynamics over space and time using metatranscriptomics. We hypothesized the molecular mechanism of anammox growth and multiplication that led to the formation of large granules
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
