Biology subjects

Palomo, A.

Publications and source records attributed to Palomo, A..

5 recordsLinked to original sources

bioRxiv2020

Sewage-Borne Pathogens and Indigenous Denitrifiers are Active and Key Multi-Antibiotic Resistant Players in Wastewater Treatment Plants

The global rise and spread of antibiotic resistance greatly challenge the treatment of bacterial infections. Wastewater treatment plants (WWTPs) harbor and discharge antibiotic resistance genes (ARGs) as environmental contaminants. However, the knowledge gap on the host identity, activity and functionality of ARGs limits transmission and health risk assessment of WWTPs resistome. Hereby, a genome-centric quantitative metatranscriptomic approach was exploited to realize high-resolution qualitative and quantitative analyses of bacterial hosts of ARGs (i.e., multi-resistance, pathogenicity, activity and niches) throughout 12 urban WWTPs. We found that [~]45% of 248 recovered genomes expressed ARGs against multiple classes of antibiotics, among which bacitracin and aminoglycoside resistance genes in Proteobacteria was the most prevalent scenario. Both potential pathogens and indigenous denitrifying bacteria were transcriptionally active hosts of ARGs. The almost unchanged relative expression levels of ARGs in the most resistant populations (66.9%) and the surviving ARG hosts including globally emerging pathogens (e.g., Aliarcobacter cryaerophilus) in treated WWTP effluent prioritizes future examination on the health risks related with resistance propagation and human exposure in the receiving environment.

microbiology↗

bioRxiv2020

Evolutionary ecology of natural comammox Nitrospira populations

Microbes commonly exists in diverse and complex communities where species interact, and their genomic repertoires evolve over time. Our understanding of species interactions and evolution has increased in the last decades, but most studies of evolutionary dynamics are based on single species in isolation or in experimental systems composed of few interacting species. Here, we use the microbial ecosystem found in groundwater-fed sand filters as a model to avoid this limitation. In these open systems, diverse microbial communities experience relatively stable conditions, and the coupling between chemical and biological processes is generally well defined. Metagenomic analysis of 12 sand filters revealed systematic co-occurrence of at least five comammox Nitrospira species, likely promoted by low ammonium concentrations. These Nitrospira species showed intra-population sequence diversity, although possible clonal expansion was detected in few abundant local comammox populations. They showed low homologous recombination and strong purifying selection, the latter process being especially strong in genes essential in energy metabolism. Positive selection was detected on genes related to resistance to foreign DNA and phages. We found that, compared to other habitats, groundwater-fed sand filters impose strong purifying selection and low recombination on comammox Nitrospira populations. These results suggest that evolutionary processes are more affected by habitat type than by species identity. Together, this study improves our understanding of species interactions and evolution in complex microbial communities, and sheds light on the environmental dependency of evolutionary processes.

microbiology↗

bioRxiv2020

Temperature modulates stress response in anammox reactors

Autotrophic nitrogen removal by anaerobic ammonium oxidizing (anammox) bacteria is an energy-efficient nitrogen removal process in wastewater treatment. However, full-scale deployment under mainstream conditions remains challenging for practitioners due to the high stress susceptibility of anammox bacteria towards fluctuations in dissolved oxygen and temperature. Here, we investigated the response of microbial biofilms with verified anammox activity to oxygen shocks under favorable and cold temperature regimes. Genome-centric metagenomics and metatranscriptomics were used to investigate the stress response on various biological levels. We show that temperature regime and strength of oxygen perturbations induced divergent responses from the process level down to the transcriptional profile of individual taxa. Temperature induced distinct transcriptional states in compositionally identical communities and transient pulses of dissolved oxygen resulted in the upregulation of stress-response only under favorable temperatures. Anammox species and other key biofilm taxa display different transcriptional responses to the induced stress regimes.

microbiology↗

bioRxiv2019

Genomic profiling of Nitrospira species reveals ecological success of comammox Nitrospira

Nitrification was long thought to consist in the stepwise oxidation of ammonia to nitrite and of nitrite to nitrate by ammonia oxidizing and nitrite oxidizing microorganisms, respectively. Recently, single microorganisms capable of complete ammonia to nitrate oxidation (comammox) were identified in the Nitrospira genus. This genus, previously considered to only contain canonical nitrite oxidizers is diverse and has a broad environmental distribution. Yet, a global insight into the abundance, niche preference, and genomic diversity of Nitrospira is missing. Here, we established the largest Nitrospira genome database to date, revealing 68 putative species, most without cultivated representatives. We performed a global survey through read recruitment of metagenomic data from various environments against this database that identified that environmental filtering structures species distribution, without large scale biogeographical signal. The ecological success of comammox Nitrospira is evident as they outnumber and are more diverse than canonical Nitrospira in communities from all environments but wastewater treatment plants. We detect a phylogenetic signal in Nitrospira species habitat preference, that is strongest for canonical Nitrospira species. Comammox Nitrospira eco-evolutionary history is more complex with subclades achieving rapid niche divergence via horizontal transfer of genes, including that encoding the hydroxylamine oxidoreductase, one of the key enzymes involved in nitrification.

microbiology↗

bioRxiv2017

Comparative Genomics Sheds Light On Niche Differentiation And The Evolutionary History Of Comammox Nitrospira

The description of comammox Nitrospira spp., performing complete ammonium-to-nitrate oxidation, and their co-occurrence with canonical betaproteobacterial ammonium oxidizing bacteria ({beta}-AOB) in the environment, call into question the metabolic potential of comammox Nitrospira and the evolutionary history of their ammonium oxidation pathway. We report four new comammox Nitrospira genomes, constituting two novel species, and the first comparative genomic analysis on comammox Nitrospira.\n\nComammox Nitrospira has lost the potential to use external nitrite as energy and nitrogen source: compared to strictly nitrite oxidizing Nitrospira; they lack genes for assimilative nitrite reduction and reverse electron transport from nitrite. By contrast, compared to other Nitrospira, their ammonium oxidizer physiology is exemplified by genes for ammonium and urea transporters and copper homeostasis and the lack of cyanate hydratase genes. Two comammox clades are different in their ammonium uptake systems. Contrary to {beta}-AOB, comammox Nitrospira genomes have single copies of the two central ammonium oxidation pathway genes, lack genes involved in nitric oxide reduction, and encode genes that would allow efficient growth at low oxygen concentrations. Hence, comammox Nitrospira seems attuned to oligotrophy and hypoxia compared to {beta}-AOB.\n\n{beta}-AOBs are the clear origin of the ammonium oxidation pathway in comammox Nitrospira: reconciliation analysis indicates two separate early amoA gene transfer events from {beta}-AOB to an ancestor of comammox Nitrospira, followed by clade specific losses. For haoA, one early transfer from {beta}-AOB to comammox Nitrospira is predicted - followed by intra-clade transfers. We postulate that the absence of comammox genes in most Nitrospira genomes is the result of subsequent loss.\n\nSignificanceThe recent discovery of comammox bacteria - members of the Nitrospira genus able to fully oxidize ammonia to nitrate - upset the long-held conviction that nitrification is a two-step process. It also opened key questions on the ecological and evolutionary relations of these bacteria with other nitrifying prokaryotes. Here, we report the first comparative genomic analysis of comammox Nitrospira and related nitrifiers. Ammonium oxidation genes in comammox Nitrospira had a surprisingly complex evolution, originating from ancient transfer from the phylogenetically distantly related ammonia-oxidizing betaproteobacteria, followed by within-lineage transfers and losses. The resulting comammox genomes are uniquely adapted to ammonia oxidation in nutrient-limited and low-oxygen environments and appear to have lost the genetic potential to grow by nitrite oxidation alone.

microbiology↗