The microbial dark matter and "wanted list" in worldwide wastewater treatment plants

Diversity, influential factor, and communication network construction of quorum sensing bacteria in global wastewater treatment plants

Quorum sensing (QS) is widespread in the microbial world and mediates microbial relationships in communities. However, the existing knowledge is far from a full description of the complex communication-based microbial interactions in engineered ecosystems, i.e., wastewater treatment plants (WWTPs). Herein, we conducted a systematic analysis of the diversity and influential factors of the QS-related microflora through the collection of global 1186 activated sludge microbiome samples. We found that the richness of bacteria associated with the universal bacterial secondary messenger presented the highest in QS system, whereas the bacteria related to the degradation of N-Acyl-homoserine lactones occupied the main position in the quorum quenching system. The community turnover of QS microflora was found more likely to be dominated by the deterministic process, such as the dissolved oxygen and resource availability (the ratio of organic matter to microorganisms). Meanwhile, these QS microflora in turn have a profound impact on the functions of WWTPs, especially multilingual intelligencers involving various language systems, such as Nitrospira. By connecting the signal molecule synthesis and acceptance bacteria, we constructed a QS communication network, which can be a robust tool for initial investigation of signaling molecule-mediated microbial interactions. The above results were further integrated into an online access website, named Quorum Sensing Communication Network in Activated Sludge (QSCNAS) (http://www.qscnas.cn/), which allowed users to browse and capture possible QS-based interactions of target bacterium. This work contributes to the understanding of bacterial communication in WWTPs and provides a platform to help in developing potential regulation strategies.

Earth's most needed uncultivated aquatic prokaryotes

Aquatic ecosystems house a significant fraction of Earth's biosphere, yet most prokaryotes inhabiting these environments remain uncultivated. While recently developed genome-resolved metagenomics and single-cell genomics techniques have underscored the immense genetic breadth and metabolic potential residing in uncultivated Bacteria and Archaea, cultivation of these microorganisms is required to study their physiology via genetic systems, confirm predicted biochemical pathways, exploit biotechnological potential, and accurately appraise nutrient turnover. Over the past two decades, the limitations of culture-independent investigations highlighted the importance of cultivation in bridging this vast knowledge gap. Here, we collected more than 80 highly sought-after uncultivated lineages of aquatic Bacteria and Archaea with global ecological impact. In addition to fulfilling critical roles in global carbon, nitrogen, and sulfur cycling, many of these organisms are thought to partake in key symbiotic relationships. This review highlights the vital contributions of uncultured microbes in aquatic ecosystems, from lakes and groundwater to the surfaces and depths of the oceans and will guide current and future initiatives tasked with cultivating our planet's most elusive, yet highly consequential aquatic microflora.

High-throughput single-cell sequencing of activated sludge microbiome

Wastewater treatment plants (WWTPs) represent one of biotechnology's largest and most critical applications, playing a pivotal role in environmental protection and public health. In WWTPs, activated sludge (AS) plays a major role in removing contaminants and pathogens from wastewater. While metagenomics has advanced our understanding of microbial communities, it still faces challenges in revealing the genomic heterogeneity of cells, uncovering the microbial dark matter, and establishing precise links between genetic elements and their host cells as a bulk method. These issues could be largely resolved by single-cell sequencing, which can offer unprecedented resolution to show the unique genetic information. Here we show the high-throughput single-cell sequencing to the AS microbiome. The single-amplified genomes (SAGs) of 15,110 individual cells were clustered into 2,454 SAG bins. We find that 27.5% of the genomes in the AS microbial community represent potential novel species, highlighting the presence of microbial dark matter. Furthermore, we identified 1,137 antibiotic resistance genes (ARGs), 10,450 plasmid fragments, and 1,343 phage contigs, with shared plasmid and phage groups broadly distributed among hosts, indicating a high frequency of horizontal gene transfer (HGT) within the AS microbiome. Complementary analysis using 1,529 metagenome-assembled genomes from the AS samples allowed for the taxonomic classification of 98 SAG bins, which were previously unclassified. Our study establishes the feasibility of single-cell sequencing in characterizing the AS microbiome, providing novel insights into its ecological dynamics, and deepening our understanding of HGT processes, particularly those involving ARGs. Additionally, this valuable tool could monitor the distribution, spread, and pathogenic hosts of ARGs both within AS environments and between AS and other environments, which will ultimately contribute to developing a health risk evaluation system for diverse environments within a One Health framework.

Method evaluation for viruses in activated sludge: Concentration, sequencing, and identification

Activated sludge (AS) in wastewater treatment plants is one of the largest artificial microbial ecosystems on earth and it makes enormous contributions to human societies. Viruses are an important component in AS with a high abundance. However, their communities and functionalities have not been as widely explored as those of other microorganisms, such as bacteria. This gap is mainly due to technical challenges in effective viral concentration, extraction, and sequencing. In this study, we compared four kinds of concentration methods, two sequencing approaches, and four identification bioinformatic tools to evaluate the whole analysis workflow for viruses in AS. Results showed flocculation, filtration, and resuspension (FFR) could get the longest DNA lengths and ultracentrifugation obtained the highest DNA yields for viruses in AS. Based on the results of present study, FFR and tangential flow filtration with the membrane pore size of 100 kDa were most recommended to concentrate viruses in AS samples with huge volumes. Besides, different concentration methods could get different viral catalogs and thus multiple methods should be combined to get the whole picture of viruses in the system. In addition, geNomad was the most recommended identification tool for viruses in the present study and the long-read sequencing could improve the assembly statistics of viruses when compared with the short-read sequencing. For the 8192 viral operational taxonomic units in this study, 95.1 % of them were phages and belonged to the same lineage at the order level of Caudovirales. Virulent phages dominated the AS system and Pseudomonadota were the main host. Taken together, this study provides new insights into methods selection for virus research of AS.

Exploring Microbial Dark Matter for the Discovery of Novel Natural Products: Characteristics, Abundance Challenges and Methods

The objective of this review is to investigate microbial dark matter (MDM) with a focus on its potential for discovering novel natural products (NPs). This first part will examine the characteristics and abundance of these previously unexplored microbial communities, as well as the challenges faced in identifying and harnessing their unique biochemical properties and novel methods in this field. MDMs are thought to hold great potential for the discovery of novel NPs, which could have significant applications in medicine, agriculture, and industry. In recent years, there has been a growing interest in exploring MDM to unlock its potential. In fact, developments in genome-sequencing technologies and sophisticated phylogenetic procedures and metagenomic techniques have contributed to drastically make important changes in our sights on the diversity of microbial life, including the very outline of the tree of life. This has led to the development of novel technologies and methodologies for studying these elusive microorganisms, such as single-cell genomics, metagenomics, and culturomics. These approaches enable researchers to isolate and analyze individual microbial cells, as well as entire communities, providing insights into their genetic and metabolic potential. By delving into the MDM, scientists hope to uncover new compounds and biotechnological advancements that could have far-reaching impacts on various fields.

Rhodobacteraceae are Prevalent and Ecologically Crucial Bacterial Members in Marine Biofloc Aquaculture

Bioflocs are microbial aggregates primarily composed of heterotrophic bacteria that play essential ecological roles in maintaining animal health, gut microbiota, and water quality in biofloc aquaculture systems. Despite the global adoption of biofloc aquaculture for shrimp and fish cultivation, our understanding of biofloc microbiota-particularly the dominant bacterial members and their ecological functions-remains limited. In this study, we employed integrated metataxonomic and metagenomic approaches to demonstrate that the family Rhodobacteraceae of Alphaproteobacteria consistently dominates the biofloc microbiota and plays essential ecological roles. We first analyzed a comprehensive metataxonomic dataset consisting of 200 16S rRNA gene amplicons collected across three Asian countries: South Korea, China, and Vietnam. Taxonomic investigation identified Rhodobacteraceae as the dominant and consistent bacterial members across the datasets. The predominance of this taxon was further validated through metagenomics approaches, including read taxonomy and read recruitment analyses. To explore the ecological roles of Rhodobacteraceae, we applied genome-centric metagenomics, reconstructing 45 metagenome-assembled genomes. Functional annotation of these genomes revealed that dominant Rhodobacteraceae genera, such as Marivita, Ruegeria, Dinoroseobacter, and Aliiroseovarius, are involved in vital ecological processes, including complex carbohydrate degradation, aerobic denitrification, assimilatory nitrate reduction, ammonium assimilation, and sulfur oxidation. Overall, our study reveals that the common practice of carbohydrate addition in biofloc aquaculture systems fosters the growth of specific heterotrophic bacterial communities, particularly Rhodobacteraceae. These bacteria contribute to maintaining water quality by removing toxic nitrogen and sulfur compounds and enhance animal health by colonizing gut microbiota and exerting probiotic effects.

Genome-centric metagenomics provides insights into the core microbial community and functional profiles of biofloc aquaculture

Bioflocs are microbial aggregates that play a pivotal role in shaping animal health, gut microbiota, and water quality in biofloc technology (BFT)-based aquaculture systems. Despite the worldwide application of BFT in aquaculture industries, our comprehension of the community composition and functional potential of the floc-associated microbiota (FAB community; ≥3 µm size fractions) remains rudimentary. Here, we utilized genome-centric metagenomic approach to investigate the FAB community in shrimp aquaculture systems, resulting in the reconstruction of 520 metagenome-assembled genomes (MAGs) spanning both bacterial and archaeal domains. Taxonomic analysis identified Pseudomonadota and Bacteroidota as core community members, with approximately 93% of recovered MAGs unclassified at the species level, indicating a large uncharacterized phylogenetic diversity hidden in the FAB community. Functional annotation of these MAGs unveiled their complex carbohydrate-degrading potential and involvement in carbon, nitrogen, and sulfur metabolisms. Specifically, genomic evidence supported ammonium assimilation, autotrophic nitrification, denitrification, dissimilatory nitrate reduction to ammonia, thiosulfate oxidation, and sulfide oxidation pathways, suggesting the FAB community's versatility for both aerobic and anaerobic metabolisms. Conversely, genes associated with heterotrophic nitrification, anaerobic ammonium oxidation, assimilatory nitrate reduction, and sulfate reduction were undetected. Members of Rhodobacteraceae emerged as the most abundant and metabolically versatile taxa in this intriguing community. Our MAGs compendium is expected to expand the available genome collection from such underexplored aquaculture environments. By elucidating the microbial community structure and metabolic capabilities, this study provides valuable insights into the key biogeochemical processes occurring in biofloc aquacultures and the major microbial contributors driving these processes.

IMPORTANCE

Biofloc technology has emerged as a sustainable aquaculture approach, utilizing microbial aggregates (bioflocs) to improve water quality and animal health. However, the specific microbial taxa within this intriguing community responsible for these benefits are largely unknown. Compounding this challenge, many bacterial taxa resist laboratory cultivation, hindering taxonomic and genomic analyses. To address these gaps, we employed metagenomic binning approach to recover over 500 microbial genomes from floc-associated microbiota of biofloc aquaculture systems operating in South Korea and China. Through taxonomic and genomic analyses, we deciphered the functional gene content of diverse microbial taxa, shedding light on their potential roles in key biogeochemical processes like nitrogen and sulfur metabolisms. Notably, our findings underscore the taxa-specific contributions of microbes in aquaculture environments, particularly in complex carbon degradation and the removal of toxic substances like ammonia, nitrate, and sulfide.

Synthetic Biology of Natural Products Engineering: Recent Advances Across the Discover-Design-Build-Test-Learn Cycle

Advances in genome engineering and associated technologies have reinvigorated natural products research. Here we highlight the latest developments in the field across the discover-design-build-test-learn cycle of bioengineering, from recent progress in computational tools for AI-supported genome mining, enzyme and pathway engineering, and compound identification to novel host systems and new techniques for improving production levels, and place these trends in the context of responsible research and innovation, emphasizing the importance of anticipatory analysis at the early stages of process development.

Global WWTP Microbiome-based Integrative Information Platform: From experience to intelligence

Domestic and industrial wastewater treatment plants (WWTPs) are facing formidable challenges in effectively eliminating emerging pollutants and conventional nutrients. In microbiome engineering, two approaches have been developed: a top-down method focusing on domesticating seed microbiomes into engineered ones, and a bottom-up strategy that synthesizes engineered microbiomes from microbial isolates. However, these approaches face substantial hurdles that limit their real-world applicability in wastewater treatment engineering. Addressing this gap, we propose the creation of a Global WWTP Microbiome-based Integrative Information Platform, inspired by the untapped microbiome and engineering data from WWTPs and advancements in artificial intelligence (AI). This open platform integrates microbiome and engineering information globally and utilizes AI-driven tools for identifying seed microbiomes for new plants, providing technical upgrades for existing facilities, and deploying microbiomes for accidental pollution remediation. Beyond its practical applications, this platform has significant scientific and social value, supporting multidisciplinary research, documenting microbial evolution, advancing Wastewater-Based Epidemiology, and enhancing global resource sharing. Overall, the platform is expected to enhance WWTPs' performance in pollution control, safeguarding a harmonious and healthy future for human society and the natural environment.

Effects of different assembly strategies on gene annotation in activated sludge

Activated sludge comprises diverse bacteria, fungi, and other microorganisms, featuring a rich repertoire of genes involved in antibiotic resistance, pollutant degradation, and elemental cycling. In this regard, hybrid assembly technology can revolutionize metagenomics by detecting greater gene diversity in environmental samples. Nonetheless, the optimal utilization and comparability of genomic information between hybrid assembly and short- or long-read technology remain unclear. To address this gap, we compared the performance of the hybrid assembly, short- and long-read technologies, abundance and diversity of annotated genes, and taxonomic diversity by analysing 46, 161, and 45 activated sludge metagenomic datasets, respectively. The results revealed that hybrid assembly technology exhibited the best performance, generating the most contiguous and longest contigs but with a lower proportion of high-quality metagenome-assembled genomes than short-read technology. Compared with short- or long-read technologies, hybrid assembly technology can detect a greater diversity of microbiota and antibiotic resistance genes, as well as a wider range of potential hosts. However, this approach may yield lower gene abundance and pathogen detection. Our study revealed the specific advantages and disadvantages of hybrid assembly and short- and long-read applications in wastewater treatment plants, and our approach could serve as a blueprint to be extended to terrestrial environments.

Metagenomic insights into the toxicity of carbamazepine to functional microorganisms in sludge anaerobic digestion

Contaminants of emerging concern (CECs) contained in sludge, such as carbamazepine, may be toxic to microorganisms and affect the biogenesis of methane during anaerobic digestion. In this study, different scales of anaerobic digesters were constructed to investigate the inhibitory effect of carbamazepine. Results showed that carbamazepine reduced methane production by 11.3 % and 62.1 % at concentrations of 0.4 and 2 mg/g TS, respectively. Carbamazepine hindered the dissolution of organic matter and the degradation of protein. Carbamazepine inhibited some fermentative bacteria, especially uncultured Aminicenantales, whose abundance decreased by 9.5-93.4 % under carbamazepine stress. It is worth noting that most prior studies investigated the effects of CECs only based on well-known microorganisms, ignoring the metabolisms of uncultured microorganisms. Genome-predicted metabolic potential suggested that 54 uncultured metagenome-assembled genomes (MAGs) associated with acidogenesis or acetogenesis. Therein, uncultured Aminicenantales related MAGs were proved to be acetogenic fermenters, their significant reduction may be an important reason for the decrease of methane production under carbamazepine stress. The toxicity of carbamazepine to microorganisms was mainly related to the overproduction of reactive oxygen species. This study elucidates the inhibition mechanism of carbamazepine and emphasizes the indispensable role of uncultured microorganisms in anaerobic digestion.

Effects of operational parameters on bacterial communities in Hong Kong and global wastewater treatment plants

Wastewater treatment plants (WWTPs) are indispensable biotechnology facilities for modern cities and play an essential role in modern urban infrastructure by employing microorganisms to remove pollutants in wastewater, thus protecting public health and the environment. This study conducted a 13-month bacterial community survey of six full-scale WWTPs in Hong Kong with samples of influent, activated sludge (AS), and effluent to explore their synchronism and asynchronism of bacterial community. Besides, we compared AS results of six Hong Kong WWTPs with data from 1,186 AS amplicon data in 269 global WWTPs and a 9-year metagenomic sequencing survey of a Hong Kong WWTP. Our results showed the compositions of bacterial communities varied and the bacterial community structure of AS had obvious differences across Hong Kong WWTPs. The co-occurrence analysis identified 40 pairs of relationships that existed among Hong Kong WWTPs to show solid associations between two species and stochastic processes took large proportions for the bacterial community assembly of six WWTPs. The abundance and distribution of the functional bacteria in worldwide and Hong Kong WWTPs were examined and compared, and we found that ammonia-oxidizing bacteria had more diversity than nitrite-oxidizing bacteria. Besides, Hong Kong WWTPs could make great contributions to the genome mining of microbial dark matter in the global "wanted list." Operational parameters had important effects on OTUs' abundance, such as the temperature to the genera of Tetrasphaera, Gordonia and Nitrospira. All these results obtained from this study can deepen our understanding of the microbial ecology in WWTPs and provide foundations for further studies.

IMPORTANCE

Wastewater treatment plants (WWTPs) are an indispensable component of modern cities, as they can remove pollutants in wastewater to prevent anthropogenic activities. Activated sludge (AS) is a fundamental wastewater treatment process and it harbors a highly complex microbial community that forms the main components and contains functional groups. Unveiling "who is there" is a long-term goal of the research on AS microbiology. High-throughput sequencing provides insights into the inventory diversity of microbial communities to an unprecedented level of detail. At present, the analysis of communities in WWTPs usually comes from a specific WWTP and lacks comparisons and verification among different WWTPs. The wide-scale and long-term sampling project and research in this study could help us evaluate the AS community more accurately to find the similarities and different results for different WWTPs in Hong Kong and other regions of the world.

Proton Pump Inhibitor Use and Complications of Cirrhosis Are Linked With Distinct Gut Microbial Bacteriophage and Eukaryotic Viral-Like Particle Signatures in Cirrhosis

INTRODUCTION

Proton pump inhibitors (PPIs) modulate the progression of cirrhosis to hepatic encephalopathy (HE) and can affect the bacterial microbiome. However, the impact of PPI on the virome in cirrhosis using viral-like particle (VLP) analysis is unclear.

METHODS

We determined the VLP in the stool microbiome in patients with cirrhosis cross-sectionally (ascites, HE, and PPI use analyzed) who were followed up for 6-month hospitalizations and through 2 clinical trials of PPI withdrawal and initiation.

RESULTS

In a cross-sectional study, PPI users had greater ascites prevalence and 6-month hospitalizations, but VLP α diversity was similar. Among phages, PPI users had lower Autographviridae and higher Streptococcus phages and Herelleviridae than nonusers, whereas opposite trends were seen in ascites and HE. Trends of eukaryotic viruses (higher Adenoviridae and lower Virgaviridae/Smacoviridae) were similar for PPI, HE, and ascites. Twenty-one percent were hospitalized, mostly due to HE. α Diversity was similar in the hospitalized/nonhospitalized/not groups. Higher Gokushovirinae and lower crAssphages were related to hospitalizations such as HE-related cross-sectional VLP changes. As part of the clinical trial, PPIs were added and withdrawn in 2 different decompensated groups over 14 days. No changes in α diversity were observed. Withdrawal reduced crAssphages, and initiation reduced Gokushovirinae and Bacteroides phages.

DISCUSSION

In cirrhosis, PPI use has a gut microbial VLP phage signature that is different from that in HE and ascites, and VLP changes are linked with hospitalizations over 6 months, independent of clinical biomarkers. Eukaryotic viral patterns were consistent across PPI use, HE, and ascites, indicating a relationship with the progression of cirrhosis. PPIs alone showed modest VLP changes with withdrawal or initiation. Distinct phage and eukaryotic viral patterns are associated with the use of PPIs in cirrhosis.

GDPF: a data resource for the distribution of prokaryotic protein families across the global biosphere

Microorganisms encode most of the functions of life on Earth. However, conventional research has primarily focused on specific environments such as humans, soil and oceans, leaving the distribution of functional families throughout the global biosphere poorly comprehended. Here, we present the database of the global distribution of prokaryotic protein families (GDPF, http://bioinfo.qd.sdu.edu.cn/GDPF/), a data resource on the distribution of functional families across the global biosphere. GDPF provides global distribution information for 36 334 protein families, 19 734 superfamilies and 12 089 KEGG (Kyoto Encyclopedia of Genes and Genomes) orthologs from multiple source databases, covering typical environments such as soil, oceans, animals, plants and sediments. Users can browse, search and download the distribution data of each entry in 10 000 global microbial communities, as well as conduct comparative analysis of distribution disparities among multiple entries across various environments. The GDPF data resource contributes to uncovering the geographical distribution patterns, key influencing factors and macroecological principles of microbial functions at a global level, thereby promoting research in Earth ecology and human health.

Metabolic implications for predatory and parasitic bacterial lineages in activated sludge wastewater treatment systems

Deciphering unclear microbial interactions is key to improving biological wastewater treatment processes. Microbial predation and parasitism in wastewater treatment ecosystems are unexplored survival strategies that have long been known and have recently attracted attention because these interspecies interactions may contribute to the reduction of excess sludge. Here, microbial community profiling of 600 activated sludge samples taken from six industrial and one municipal wastewater treatment processes (WWTPs) was conducted. To identify the shared lineages in the WWTPs, the shared microbial constituents were defined as the family level taxa that had ≥ 0.1% average relative abundance and detected in all processes. The microbial community analysis assigned 106 families as the shared microbial constituents in the WWTPs. Correlation analysis showed that 98 of the 106 shared families were significantly correlated with total carbon (TC) and/or total nitrogen (TN) concentrations, suggesting that they may contribute to wastewater remediation. Most possible predatory or parasitic bacteria belonging to the phyla Bdellovibrionota, Myxococcota, and Candidatus Patescibacteria were found to be the shared families and negatively correlated with TC/TN; thus, they were frequently present in the WWTPs and could be involved in the removal of carbon/nitrogen derived from cell components. Shotgun metagenome-resolved metabolic reconstructions indicated that gene homologs associated with predation or parasitism are conserved in the Bdellovibrionota, Myxococcota, and Ca. Patescibacteria genomes (e.g., host interaction (hit) locus, Tad-like secretion complexes, and type IV pilus assembly proteins). This study provides insights into the complex microbial interactions potentially linked to the reduction of excess sludge biomass in these processes.

Microbial Secondary Metabolites via Fermentation Approaches for Dietary Supplementation Formulations

Food supplementation formulations refer to products that are designed to provide additional nutrients to the diet. Vitamins, dietary fibers, minerals and other functional compounds (such as antioxidants) are concentrated in dietary supplements. Specific amounts of dietary compounds are given to the body through food supplements, and these include as well so-called non-essential compounds such as secondary plant bioactive components or microbial natural products in addition to nutrients in the narrower sense. A significant social challenge represents how to moderately use the natural resources in light of the growing world population. In terms of economic production of (especially natural) bioactive molecules, ways of white biotechnology production with various microorganisms have recently been intensively explored. In the current review other relevant dietary supplements and natural substances (e.g., vitamins, amino acids, antioxidants) used in production of dietary supplements formulations and their microbial natural production via fermentative biotechnological approaches are briefly reviewed. Biotechnology plays a crucial role in optimizing fermentation conditions to maximize the yield and quality of the target compounds. Advantages of microbial production include the ability to use renewable feedstocks, high production yields, and the potential for cost-effective large-scale production. Additionally, it can be more environmentally friendly compared to chemical synthesis, as it reduces the reliance on petrochemicals and minimizes waste generation. Educating consumers about the benefits, safety, and production methods of microbial products in general is crucial. Providing clear and accurate information about the science behind microbial production can help address any concerns or misconceptions consumers may have.

Mechanisms of persistence and impact of ordinary heterotrophic organisms in aerobic granular sludge

The stability of granules, contaminant removal and microbial structure of an aerobic granular sludge (AGS) process were investigated with a focus on ordinary heterotrophic organisms (OHOs). Long-term stable granules and high removals of COD (97 %), NH₄⁺ (98 %), P (85 %) and total N (77 %) were achieved. Sequencing analyses identified 6.6 % of phosphorus-accumulating organisms in the sludge, concordant with the observed bio-P removal capacity. However, OHOs were the most abundant bacteria in the sludge (70-93 %) without resulting in unstable aggregates. Under current dogmas of microbial competition in activated sludge, it seemed contradictory that OHOs could persist in the long term in the AGS where COD was depleted beginning in the anaerobic phase. Microbial analyses showed that OHOs could survive in granules by micropredation, proteolysis, fermentation and EPS consumption. Heterotrophic-nitrification/ aerobic-denitrification was an active pathway in the AGS. These findings contribute to a better understanding of microbial competition in AGS and its stability.