Biology subjects

Bertilsson, S.

Publications and source records attributed to Bertilsson, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Culture-free single-cell transcriptomics shows short term functional and associative stability in non-model microeukaryotes under shading stress

Microeukaryotes are abundant, diverse, and morphologically and functionally complex. They represent one of the largest groups of primary producers and are involved in major ecosystem functions such as nutrient transformations and maintenance of food webs. Although ~74,000 species of microeukaryotes are estimated to exist, very few are available in culture and only ~3000 are represented by reference genomes and transcriptomes. This limited representation significantly hinders the study of microeukaryotes in their natural environments. Single-cell transcriptomics with sequencing of full-length transcripts has potential to bypass this limitation. In this study, we employ Smart-seq3xpress for taxonomic identification and functional characterization of non-model mixotrophic freshwater microeukaryotes in a culture-free and reference-free manner, while also enabling inferences to be made for their prokaryotic associations. Computational analyses revealed 22 distinct microeukaryote taxa upon sequencing of 1520 randomly sampled cells, with assemblies of 12 good quality de novo partial transcriptomes, followed by functional annotation using sequence and structure homology. Gene expression analysis of the transcriptome for the most abundant microeukaryote in the sample, Rhodomonas, revealed a transcriptomic dip a few hours after experimental shading, followed by a gradual recovery in the next few days. Compared to samples in illuminated conditions, there was widespread downregulation of photosynthesis-, lysosome-, and carbon metabolism-related pathways in the shade, but the prevailing associations with prokaryotic lineages was unaffected by the light conditions. The different microeukaryotes, all present in the same environmental sample, featured distinct prokaryotic associates that were consistent across illumination conditions. This reference-free and culture-free study of 22 different microeukaryotic taxa sets the stage for high-throughput single cell transcriptomics to study microeukaryotic diversity in complex natural ecosystems, for their population-level taxonomic identity, sub-population-level transcriptomic profiles and metabolic states, and individual-level prokaryotic associations.

microbiology↗

bioRxiv2025

From temperate to polar waters: Transition to non-cyanobacterial diazotrophy upon entering the Atlantic gateway of the Arctic Ocean

Nitrogen fixation, the microbial reduction of dinitrogen to ammonia, is increasingly recognized to occur in the Arctic Ocean. However, knowledge about the composition, biogeography, abundance, and ecology of nitrogen-fixing organisms (diazotrophs) is poor. This ultimately hinders prediction of ecosystem productivity fueled by nitrogen fixation in this rapidly changing and predominantly nitrogen-limited ocean. We assessed the composition and abundance of total and active diazotrophs in sub-surface water (8 m; amplicon sequencing and quantification of the marker gene nifH) over [~]3,400 km from the mouth of the brackish Baltic Sea to the sea ice edge in the Arctic Ocean. Upon entering nutrient-rich waters in the Atlantic gateway to the Arctic, we discovered an abrupt transition from autotrophic to heterotrophic diazotrophic activity. Our findings suggest that diazotrophy is functionally distinct in the Arctic Ocean compared to adjacent temperate-boreal waters - a difference likely driven by inorganic nutrients, salinity, and temperature. We identify three key non-cyanobacterial diazotroph groups in the Arctic Ocean with Arctic-specific (Rhodocyclales and Oceanospirillales) or more widespread (unknown Gammaproteobacterium) distribution patterns and report their nifH gene transcription levels (up to 103 nifH transcripts L-1). In contrast, actively transcribing diazotrophs in the warmer and more nutrient-poor Norwegian Sea with coastal-influenced water were dominated by sublineages of Candidatus Atelocyanobacterium thalassa (UCYN-A1, UCYN-A2, UCYN-A4; up to 104 nifH transcripts L-1). With ongoing atlantification of the Arctic pushing oceanic provinces and biogeographical ranges poleward, we predict a future displacement of the transition from autotrophic to heterotrophic diazotrophic activity with likely significant changes in nitrogen fixation.

ecology↗

bioRxiv2024

Cross-feeding options define eco-evolutionary dynamics of deep oligotrophic groundwater microbiome

Deep groundwaters populated by diverse and active microbes are among the most energy and nutrient-limited ecosystems. Characteristics of this ecosystem including nutrient and dispersal limitations, low cell densities, and episodic growth strategy interactively underpin the so far elusive eco-evolutionary dynamics of its microbiome. Here we applied a modular metabolic analyses on genome-resolved reconstructed community of disconnected deep groundwaters in the Fennoscandian Shield. In the community of deeper groundwaters despite their highly oligotrophic nature, lineages with larger genomes maintained larger populations which we hypothesize to be connected with their limited cross-feeding options. Thus providing an extension on the streamlining theory emphasizing the importance of ecological interactions in genome evolution which is further supported by the observed decrease in abundance of lineages with known metabolic dependencies, such as Patescibacteria and DPANN, with depth. The modular metabolic analyses showed that remarkably common niches based on same cross-feeding interactions are also available in different groundwaters, in addition to common niches for primary production. While these shared niches are critical for community assembly in this ecosystem, in different boreholes different lineages populated them. Our results provided new insights into the role of metabolic cross-feeding in genome evolution and community assembly of deep groundwater microbiome.

microbiology↗

bioRxiv2024

The ecology of potentially pathogenic Vibrio spp. in a seagrass meadow ecosystem

Seagrass meadow ecosystems offer several valuable ecosystem services in coastal regions around the world. Recent studies have suggested that one such important service is reduction of pathogenic bacteria and specifically Vibrio spp. in adjacent waters. The specific mechanisms of pathogen reduction remain unclear, although increased sedimentation has been suggested as one likely process for pathogens to be quenched from the water column. Whether Vibrio spp. persist in the sediment or in other compartments of the seagrass meadow is currently not known, but it has been shown that marine surface biofilms can function as reservoirs of pathogenic vibrios. This general feature may also apply to seagrass and sediment surfaces. In this study, we investigated the relative abundance and community ecology of Vibrio spp. bacteria in Baltic Sea seagrass meadows using both culturing and culture-independent methods. While we did not detect a significant reduction of Vibrio spp., the highest relative abundances of Vibrio spp. were observed in the water column above unvegetated sites as compared to seagrass meadows. We also detected high relative abundances of Vibrio spp. on seagrass roots, supporting previous observations that marine surfaces are selectively colonized by Vibrio spp., implying that these habitats are important for the persistence and possibly release of Vibrio spp. into the water column. Our results emphasize the need to understand the interactions of pathogenic bacteria with coastal habitats, including interactions with host organisms such as seagrasses that provide biofilm microenvironments, in order to understand how diseases associated with these organisms develop.

ecology↗

bioRxiv2024

Non-sulfate-based hydrogen sulfide production in engineered systems

Unwanted microbiological production of hydrogen sulfide (H2S) is a major challenge in engineered systems, such as sewage treatment plants, landfills, and aquaculture systems. While sulfur-rich amino acids and other substrates for non-sulfate-based H2S production are commonly present, the ability and potential of different microorganisms to perform sulfate-free H2S production has not yet been resolved. Here, we reveal the identity, activity, and genomic characteristics of bacteria that degrade cysteine to produce H2S in anaerobic enrichment bioreactors seeded with material from aquaculture systems. We compared them with canonical sulfate reducing bacteria and found that both sulfur sources led to microbial H2S production, yet with the process being more rapid with cysteine than with sulfate. 16S rRNA amplicon sequencing and metagenomic analysis showed four bacterial families, Dethiosulfatibacteraceae, Fusobacteriaceae, Vibrionaceae, and Desulfovibrionaceae to be centrally involved in non-sulfate H2S production. Metagenome/metatranscriptome assembled genomes uncovered the main cysteine-degradation pathway mediated by cysteine desulfidase cyuA and revealed that some bacteria potentially also use cysteine as a carbon source in sulfate-based H2S production.

microbiology↗

bioRxiv2024

A matter of salt: global assessment of the effect of salt ionic composition as a driver of aquatic bacterial diversity

While the strong general effects of salinity on microbial diversity are well-known and described for marine and freshwater habitats, the impact of the specific composition of major inorganic ions remains largely unexplored. In this study, we assess how microbial community structure in inland saline aquatic habitats is influenced by ionic composition as compared to salinity, spatial factors, and other environmental parameters. We collected and analysed 16S rRNA gene V4 and V3-V4 amplicon datasets from freshwater to hypersaline aquatic environments worldwide (in total 375 samples from 130 lakes). With an emphasis on saline inland waters characterised by highly variable ionic composition, we demonstrated that the ionic composition of the major ions explained more variability in community composition than bulk salinity and that the geographic location of the sampling sites had only an ambiguous effect. We also identified the taxa contributing the most to the observed dissimilarity between communities from sites with different ionic composition and found mostly lineages known to be characteristic for a given habitat type, such as Actinobacteria acI in freshwater, Halomonadaceae in saline, or Nitriliruptorales in soda and soda-saline habitats. Many of these habitat type-specific indicator lineages were monophyletic, underpinning ionic composition as a crucial eco-evolutionary driver of aquatic microbial diversity.

microbiology↗

bioRxiv2024

The need for high-resolution gut microbiome characterization to design efficient strategies for sustainable aquaculture production

Microbiome-directed dietary interventions such as microbiota-directed fibers (MDFs) have a proven track record in eliciting responses in beneficial gut microbes and are increasingly being promoted as an effective strategy to improve animal production systems. Here we used initial metataxonomic data on fish gut microbiomes as well as a wealth of a priori mammalian microbiome knowledge on -MOS and {beta}-mannan-derived MDFs to study effects of such feed supplements in Atlantic salmon (Salmo salar) and their hitherto poorly characterized gut microbiomes. Our multi-omic analysis revealed that the investigated MDFs (two -mannans and an acetylated {beta}-galactoglucomannan), at a dose of 0.2%, had negligible effects on both host gene expression, and gut microbiome structure and function under studied conditions. While a subsequent trial using a higher (4%) dietary inclusion of {beta}-mannan significantly shifted the gut microbiome composition, there were still no biologically relevant effects on salmon metabolism and physiology. Only a single Burkholderia-Caballeronia-Paraburkholderia (BCP) population demonstrated consistent and significant abundance shifts across both feeding trials, although with no evidence of {beta}-mannan utilization capabilities or changes in gene transcripts for producing metabolites beneficial to the host. In light of these findings, we revisited our omics data to predict and outline novel and potentially beneficial endogenous lactic acid bacteria that should be targeted with future, conceivably more suitable, MDF strategies for salmon. IMPORTANCEThis study focuses on the potential of MDFs to improve aquaculture production. Despite preliminary 16S rRNA amplicon data suggested that populations in the salmon gut microbiome could utilize structurally complex mannans, our findings indicates that endogenous microbes could not metabolize it, nor the host responds to its dietary inclusion, at least not under the trial conditions investigated in this study. We highlight that high-resolution and host-specific microbiome characterization can greatly improve trial design and selection of candidate MDFs for future nutritional interventions. Understanding the intricate interplay between host and its gut microbiome is paramount in studies seeking to leverage endogenous microbial communities to benefit the host. While each new condition, whether it is a disease onset or a nutritional stressor, has the potential to profoundly reshape the microbial diversity, composition and outputs, the functional microbiome information gained under healthy conditions represent a pivotal step towards designing more effective trials involving microbiome-reprogramming feed additives. Overall, we envisage that these results will lead to improved focus on coupling fundamental microbiome characterization to the design of next-generation feeds for salmon aquaculture.

microbiology↗

bioRxiv2023

The Salmon Microbial Genome Atlas enables novel insights into bacteria-host interactions via functional mapping

The essential role of the gut microbiota for host health and nutrition is well established for many terrestrial animals, while its importance for fish and particularly Atlantic salmon is unclear. Here, we present the Salmon Microbial Genome Atlas (SMGA) originating from wild and farmed fish both in freshwater and seawater, and consisting of 211 high-quality bacterial genomes, recovered by cultivation (n=131) and gut metagenomics (n=80). Bacterial genomes were taxonomically assigned into 14 different orders, including 28 distinctive genera and 31 potentially novel species. Benchmarking the SMGA, we functionally characterized key populations in the salmon gut that were detected in vivo. This included the ability to degrade diet-derived fibers and release vitamins and other exo-metabolites with known beneficial effects, which were validated by in vitro cultivation and untargeted metabolomics. Together, the SMGA enables high resolution functional insight into salmon gut microbiota with relevance for salmon nutrition and health.

microbiology↗

bioRxiv2023

De novo assembled single-cell transcriptomes from aquatic phytoflagellates reveal a metabolically distinct cell population

Single-cell transcriptomics is a vital tool for unraveling metabolism and tissue diversity in model organisms. Its potential for elucidating the ecological roles of microeukaryotes, especially non-model ones, remains largely unexplored. This study employed the Smart-seq2 protocol on Ochromonas triangulata, a microeukaryote lacking a reference genome, showcasing how transcriptional states align with growth phases. Unexpectedly, a third transcriptional state was identified, across both growth phases. Metabolic mapping revealed a down-regulation trend in pathways associated with ribosome functioning, CO2 fixation, and carbohydrate catabolism from fast to slow growth to the third transcriptional state. Using carry-over rRNA reads, taxonomic identity of Ochromonas triangulata was re-confirmed and distinct bacterial communities associated with transcriptional states were identified. This study underscores single-cell transcriptomics as a powerful tool for characterizing metabolic states in microeukaryotes without a reference genome, offering insights into unknown physiological states and individual-level interactions with different bacterial taxa. This approach holds broad applicability for uncovering ecological roles, surpassing alternative methods like metagenomics or metatranscriptomics.

microbiology↗

bioRxiv2023

Geographic population structure and distinct population dynamics of globally abundant freshwater bacteria

Geographic separation is a principal factor for structuring populations of macroorganisms, with important consequences for evolution, by means of processes such as allopatric speciation. For free-living prokaryotes, implications of geographic separation on their evolution are more unclear. The limited phylogenetic resolution of commonly used markers such as 16S rRNA gene sequences have since long impeded prokaryotic population genetics. However, the vast amount of metagenome sequencing data generated during the last decades from various habitats around the world, now provides an excellent opportunity for such investigations. Here we exploited publicly available and new freshwater metagenomes in combination with genomes of abundant freshwater bacteria to study the impact of geographic separation on population structure. We focused on species that were detected across broad geographic ranges at high enough sequence coverage for meaningful population genomic analyses, i.e. members of the predominant freshwater taxa acI, LD12, Polynucleobacter and Ca. Methylopumilus. Population differentiation increased significantly with spatial distance in all species, but notable dispersal barriers (e.g. oceanic) were not apparent. Yet, the different species showed contrasting rates of geographic divergence and strikingly different population dynamics in time series within individual lakes. While certain populations hardly diverged over several years, others displayed high divergence after merely a few months, similar in scale to populations separated by thousands of kilometers. We speculate that populations with higher strain diversity evolve more monotonously, while low strain diversity enables more drastic clonal expansion of genotypes which will be reflected in strong but transient differentiation between temporally or spatially adjacent populations.

evolutionary biology↗

bioRxiv2022

Large-scale phylogenomics of aquatic bacteria reveal molecular mechanisms for adaptation to salinity

The crossing of environmental barriers poses major adaptive challenges. Rareness of freshwater-marine transitions separates the bacterial communities, but how these are related to brackish counterparts remains elusive, as are molecular adaptations facilitating cross-biome transitions. Here, we conduct large-scale phylogenomic analysis of freshwater, brackish, and marine quality-filtered metagenome-assembled genomes (11,276 MAGs). Average nucleotide identity analyses showed that bacterial species rarely existed in multiple biomes. Distinct brackish basins co-hosted numerous species despite differences in salinity and geographic distance, the latter having stronger intra-species population structuring effects. We further identified the most recent cross-biome transitions, which were rare, ancient, and most commonly directed towards the brackish biome. Transitions were accompanied by changes in isoelectric point distribution and amino acid composition of inferred proteomes, as well as convergent gains or losses of specific gene functions. Therefore, adaptive challenges entailing proteome reorganization and specific changes in gene content result in species-level separation between aquatic biomes.

microbiology↗

bioRxiv2022

A metagenomic view on fungal diversity in freshwater lakes

Fungi are essential components in a wide range of ecosystems and while major efforts have been spent on disentangling the diversity and functional roles of fungi in terrestrial environments, our knowledge about aquatic fungi is lagging. To address this knowledge gap, we explored metagenomes from 25 lakes from the arctic and boreal zone and one tropical reservoir with the aim of describing the community structure of fungi and fungi-like organisms (Oomycota). A second objective was to identify possible environmental factors influencing the composition of the fungal communities. Our results show that the main fungal phyla and orders are the same across all the lakes despite the differences in geographic location and prevailing climate. Still, there was differential distribution of more highly resolved taxa across the lakes that accordingly featured distinct communities, possibly caused by differential availability of carbon substrates in the lakes. A more detailed classification of sequences related to the pathogenic Oomycota genus Phytophthora clearly demonstrated that while technologies now exist for sequencing entire microbial communities in great detail, we are still severely limited by insufficient coverage of eukaryotic sequences and genomes in public databases.

ecology↗

bioRxiv2022

Genome-resolved analyses show an extensive diversification in key aerobic hydrocarbon-degrading enzymes across bacteria and archaea

Hydrocarbons (HCs) are organic compounds composed solely of carbon and hydrogen. They mainly accumulate in oil reservoirs, but aromatic HCs can also have other sources and are widely distributed in the biosphere. Our perception of pathways for biotic degradation of major HCs and genetic information of key enzymes in these bioconversion processes have mainly been based on cultured microbes and are biased by uneven taxonomic representation. Here we use Annotree to provide a gene-centric view of aerobic degradation of aliphatic and aromatic HCs in a total of 23446 genomes from 123 bacterial and 14 archaeal phyla. Apart from the widespread genetic potential for HC degradation in Proteobacteria, Actinobacteriota, Bacteroidota, and Firmicutes, genomes from an additional 18 bacterial and 3 archaeal phyla also hosted key HC degrading enzymes. Among these, such degradation potential has not been previously reported for representatives in the phyla UBA8248, Tectomicrobia, SAR324, and Eremiobacterota. While genomes containing full pathways for complete degradation of HCs were only detected in Proteobacteria and Actinobacteriota, other lineages capable of mediating such key steps could partner with representatives with truncated HC degradation pathways and collaboratively drive the process. Phylogeny reconstruction shows that the reservoir of key aerobic hydrocarbon-degrading enzymes in Bacteria and Archaea undergoes extensive diversification via gene duplication and horizontal gene transfer. This diversification could potentially enable microbes to rapidly adapt to novel and manufactured HCs that reach the environment.

microbiology↗

bioRxiv2022

Exploring intra-species diversity through non-redundant pangenome assemblies

At the genome level, microorganisms are highly adaptable both in terms of allele and gene composition. Such heritable traits emerge in response to different environmental niches and can have a profound influence on microbial community dynamics. As a consequence of this, any individual genome or clonal population will contain merely a fraction of the total genetic diversity of any operationally defined "species", with the collective from that group presenting the broader genomic diversity known as the pangenome. Pangenomes are valuable concepts for studying evolution and adaptation in microorganisms, as they partition genomes into core regions (present in all the genomes, and responsible for housekeeping and species-level niche adaptation) and accessory regions (present only in some genomes, and responsible for ecotype divergence). Here we present SuperPang, an algorithm capable of producing pangenome assemblies from a set of input genomes of varying quality, including metagenome-assembled genomes or MAGs. SuperPang runs in linear time and its results are complete, non-redundant, preserve gene ordering and contain both coding and non-coding regions. Our approach provides a modular view of the pangenome, identifying operons and genomic islands, and allowing to track their prevalence in different populations. We illustrate our approach by analyzing the intra-species diversity of Polynucleobacter, a clade of ubiquitous freshwater microorganisms characterized by their streamlined genomes and their ecological versatility. We show how SuperPang facilitates the simultaneous analysis of allelic and gene content variation under different environmental pressures, allowing us to study the drivers of microbial diversification at unprecedented resolution.

bioinformatics↗

bioRxiv2022

Taxonomic and functional diversity of aquatic heterotrophs is sustained by dissolved organic matter chemodiversity

Dissolved organic matter (DOM) is ubiquitous in aquatic ecosystems and fundamental for planetary processes and ecosystem functioning. While the link between microbial community composition and heterotrophic utilization of DOM has been recognized, the full diversity of organic compounds, their bioavailability, degradability and specific influences on the diversity and function of heterotrophs are still not clear. Here we experimentally investigate heterotrophic bacteria in thirty-three freshwater model communities. We identified 34 different heterotrophs growing in ambient lake DOM with taxonomic affiliations matching abundant freshwater bacterioplankton. We further describe 25 different heterotrophs growing in the phycosphere of M. Aeruginosa and 6 heterotrophs growing on the DOM produced by M. Aeruginosa with taxonomic affiliation in accord to phycosphere heterotrophs. In our experiment we observed that heterotrophs that live in the phycosphere remove more dissolved organic carbon than abundant freshwater heterotrophs. Moreover, phycosphere heterotrophs have bigger genomes than abundant lake bacteria. Altogether of the 4224 chemical features that were resolved by LC-MS, only 1229 were seen in all three treatments. None of the common/shared compounds were removed across all the model communities, suggesting contrasting niches of the studied taxa. Altogether our study highlights how each model community, with its unique taxonomic assemblages and organotroph functioning is upkept by the chemodiversity of DOM.

ecology↗

bioRxiv2022

A consensus protocol for the recovery of mercury methylation genes from metagenomes

Mercury methylation genes (hgcAB) mediate the formation of the toxic methylmercury and have been identified from diverse environments, including freshwater and marine ecosystems, Arctic permafrost, forest and paddy soils, coal-ash amended sediments, chlor-alkali plants discharges and geothermal springs. Here we present the first attempt at a standardized protocol for the detection, identification and quantification of hgc genes from metagenomes. Our Hg-MATE (Hg-cycling Microorganisms in Aquatic and Terrestrial Ecosystems) database, a catalogue of hgc genes, provides the most accurate information to date on the taxonomic identity and functional/metabolic attributes of microorganisms responsible for Hg methylation in the environment. Furthermore, we introduce "marky-coco", a ready-to-use bioinformatic pipeline based on de novo single-metagenome assembly, for easy and accurate characterization of hgc genes from environmental samples. We compared the recovery of hgc genes from environmental metagenomes using the marky-coco pipeline with an approach based on co-assembly of multiple metagenomes. Our data show similar efficiency in both approaches for most environments except those with high diversity (i.e., paddy soils) for which a co-assembly approach was preferred. Finally, we discuss the definition of true hgc genes and methods to normalize hgc gene counts from metagenomes.

microbiology↗

bioRxiv2022

Abundance and expression of hgcAB genes and mercury availability jointly explain methylmercury formation in stratified brackish waters

Neurotoxic methylmercury (MeHg) is formed by microbial methylation of inorganic divalent Hg (HgII) and constitutes severe environmental and human health risks. The methylation is enabled by hgcA and hgcB genes, but it is not known if the associated molecular-level processes are rate-limiting or enable accurate prediction of MeHg formation in nature. In this study, we investigated the relationships between hgcA genes and MeHg across redox stratified water columns in the brackish Baltic Sea. We found that the abundance of hgcA genes and transcripts combined with the concentration of dissolved HgII-sulfide species were strong predictors of both HgII methylation rate and MeHg concentration, implying their roles as principal joint drivers of MeHg formation in these systems. In establishing relationships between hgcA genes and MeHg, we advance the fundamental understanding of mechanistic principles governing MeHg formation in nature and enable refined predictions of MeHg levels in coastal seas in response to the accelerating spread of oxygen deficient zones.

ecology↗

bioRxiv2022

Out of the blue: the independent activity of sulfur-oxidizers and diatoms mediate the sudden color shift of a tropical river

Rio Celeste ("Sky-Blue River") is a river located in the Tenorio National Park (Costa Rica) that has become an important hotspot for eco-tourism due to its striking sky-blue color. A previous study suggested that this color is not caused by dissolved chemical species, but by precipitation of lightscattering aluminosilicate particles at the mixing point of two colorless streams, the acidic Quebrada Agria and the neutral Rio Buenavista. We now present microbiological information on Rio Celeste and its two tributaries, as well as a more detailed characterization of the particles that occur at the mixing point. Our results overturn the previous belief that the light scattering particles are formed by the aggregation of smaller particles coming from Rio Buenavista, and rather point to chemical formation of hydroxyaluminosilicate colloids with Quebrada Agria as the main contributor to the phenomenon, with Rio Buenavista acting as a secondary source of silica to the reaction. We also show how the sky-blue color of Rio Celeste arises from the tight interaction between chemical and biological processes. Sulfur-oxidizing bacteria generate an acidic environment in Quebrada Agria, which in turn cause dissolution and mobilization of aluminum and other metals, while in Rio Buenavista the growth of diatoms transforms dissolved silicon into colloidal biogenic forms. The local interaction between these two well-known biological activities gives rise to the unique Rio Celeste phenomenon, in what constitutes a textbook example of emergent behavior in environmental microbiology.

microbiology↗