Biology subjects

Cambiazo, V.

Publications and source records attributed to Cambiazo, V..

5 recordsLinked to original sources

bioRxiv2025

The rhizosphere of Pappostipa frigida as a hotspot of active bacterial communities in the Andean steppe of the Atacama Desert

BackgroundThe rhizosphere is a resource-rich microenvironment where plants, soil nutrients, and microorganisms interact. In arid and semi-arid regions, this tripartite relationship must withstand long periods of drought followed by brief periods of rainfall. In the present study, we employed a combination of RNA/DNA metabarcoding and shotgun metagenomic sequencing to provide insights into the functional capabilities and activity levels of the bacterial communities present in the bulk soil and rhizosphere samples of Pappostipa frigida, a grass species endemic to the Andean steppe of the Atacama Desert. ResultsThe active bacterial community in the rhizosphere of P. frigida exhibited greater diversity and a higher Shannon index than the total bacterial community. In terms of beta diversity, the structures of the total and active communities differed markedly between the BS and the RZ. Furthermore, active bacteria in the RZ showed a stronger correlation with total bacterial populations than those in the BS. This finding is consistent with the low proportion of ASVs derived from RNA extractions detected in the BS. Notably, 64% of these putative inactive bacterial populations were identified as active RZ members and 73% grew in culture media, suggesting they were likely dormant. The bacterial communities of the BS exhibited higher abundances of sporulation genes. In contrast, active bacterial communities in the RZ consistently contained higher abundances of genes associated with halotolerance, siderophore synthesis, and resuscitation-promoting factors. ConclusionsThe results emphasize the importance of the conditions created by plants in recruiting bacterial populations from the soil and provide insights into how the rhizosphere of arid native plants influences the activity and functional traits of soil microorganisms in their natural habitat. Additionally, this study advances our understanding of the mechanisms employed by soil microorganisms to cope with desiccation in natural environments, establishing P. frigida as a model in plant science for studying grass traits and responses to extreme environments.

microbiology↗

bioRxiv2025

Mobile-CRISPRi as a tool for genetic manipulation in the intracellular pathogen Piscirickettsia salmonis

Piscirickettsia salmonis is the causative agent of Salmonid Rickettsial Septicemia (SRS), the main bacterial disease affecting the salmon industry in Chile. In this work, we implemented a Mobile-CRISPRi system to generate gene silencing using a catalytically inactive dCas9 protein and an IPTG-inducible single-guide RNA (sgRNA). We demonstrate the efficacy of the CRISPRi system in P. salmonis by silencing an exogenous gene encoding green fluorescent protein (sfGFP), and the endogenous homolog of the fur gene, whose gene product regulates intracellular iron homeostasis in bacteria. The inducible expression of dcas9 and the sfGFP-directed sgRNA caused a 98.7% decrease in fluorescence in the knockdown strain. This silencing system was effective in seven P. salmonis strains from both genogroups. Furthermore, the same system was used to construct fur knockdown strains. A 50-fold decrease in fur expression level was determined in these strains, when the expression of the fur gRNA was induced with IPTG. By RNA-seq we detected a significant increase in the expression of genes encoding the Fe+2 and Fe+3 acquisition systems and iron mobilization in the fur1 knockdown, after IPTG induction. All the genes with over two-fold increased expression in the RNA-seq presented the Fur box consensus sequence in their regulatory region. The successful implementation of the Mobile-CRISPRi system in P. salmonis paves the way for systematic analysis of gene function in this pathogen We anticipate that these analyses will be very valuable in identifying genes involved in the mechanisms of pathogenesis of P. salmonis. ImportanceSalmon Rickettsial Septicemia (SRS) is an infectious disease caused by the marine bacterium Piscirickettsia salmonis. This Gamma-proteobacteria is a fastidious and facultative intracellular pathogen that has a nearly worldwide distribution, particularly impacting Chilean salmonid aquaculture. Its fastidious nature has made it hard to grow in labs, hindering research into its virulence and treatment, especially because of the lack of molecular techniques to study gene function. We show here the successful implementation of the Mobile-CRISPRi system for gene silencing. Significantly, we have adapted this technique for use with the marine pathogen P. salmonis, inserting exogenous genes into the bacteriums chromosome to ensure their constitutive and inducible expression, and silencing both exogenous and endogenous gene expression. The Mobile-CRISPRi system was also used to study the iron regulator Fur, confirming Furs relevance to the iron metabolism in the pathogen.

microbiology↗

bioRxiv2024

Modeling the emergent metabolic potential of soil microbiomes in Atacama landscapes

Soil microbiomes harbor complex communities and exhibit important ecological roles resulting from biochemical transformations and microbial interactions. Difficulties in characterizing the mechanisms and consequences of such interactions together with the multidimensionality of niches hinder our understanding of these ecosystems. The Atacama Desert is an extreme environment that includes unique combinations of stressful abiotic factors affecting microbial life. In particular, the Talabre Lejia transect has been proposed as a unique natural laboratory for understanding adaptation mechanisms. We propose a systems biology-based computational framework for the reconstruction and simulation of community-wide and genome-resolved metabolic models, in order to provide an overview of the metabolic potential as a proxy of how microbial communities are prepared to respond to the environment. Through a multifaceted approach that includes taxonomic and functional profiling of microbiomes, simulation of the metabolic potential, and multivariate analyses, we were able to identify key species and functions from six contrasting soil samples across the Talabre Lejia transect. We highlight the functional redundancy of whole metagenomes, which act as a gene reservoir from which site-specific functions emerge at the species level. We also link the physicochemistry from the puna and the lagoon samples to specific metabolic machineries that could be associated with their adaptation to the unique environmental conditions found there. We further provide an abstraction of community composition and structure for each site that allows to describe them as sensitive or resilient to environmental shifts through putative cooperation events. Our results show that the study of community-wide and genome-resolved metabolic potential, together with targeted modeling, may help to elucidate the role of producible metabolites in the adaptation of microbial communities. Our framework was designed to handle non-model microorganisms, making it suitable for any (meta)genomic dataset that includes nucleotide sequence data and high-quality environmental metadata for different samples.

systems biology↗

bioRxiv2024

Life on the edge: microbial diversity, resistome, and virulome in soils from the Union Glacier cold desert

The high-latitude regions of Antarctica remain among the most remote, extreme, and least explored areas on Earth. Despite the highly restrictive conditions, microbial life has been found in these environments, although with limited information on their genetic properties and functional capabilities. Moreover, the accelerated melting of the Antarctic permafrost, the increasing exposure of soils, and the growing human transit pose the question of whether these environments could be a source of microbes or genes that could emerge and cause global health problems. In this line, although a high bacterial diversity and autochthonous multidrug-resistant bacteria have been found in soils of the Antarctic Peninsula, we still lack information regarding the resistome of areas closer to the South Pole. Moreover, no previous studies have evaluated the pathogenic potential of microbes inhabiting Antarctic soils. In this work, we combined metagenomic and culture-dependent approaches to investigate the microbial diversity, resistome, virulome, and mobile genetic elements (MGEs) in soils from Union Glacier, a high-latitude cold desert in West Antarctica. Despite the low organic matter content, diverse bacterial lineages were found, predominating Actinomycetota and Pseudomonadota, with limited archaeal and fungal taxa. We recovered more than 80 species-level representative genomes (SRGs) of predominant bacterial taxa and the archaeon Nitrosocosmicus sp. Diverse putative resistance and virulence genes were predicted among the SRGs, metagenomic reads, and contigs. Furthermore, we characterized bacterial isolates resistant to up to 24 clinical antibiotics, mainly Pseudomonas, Arthrobacter, Plantibacter, and Flavobacterium. Moreover, some isolates produced putative virulence factors, including siderophores, pyocyanins, and exoenzymes with hemolytic, lecithinase, protease, and DNAse activity. This evidence uncovers a largely unexplored resistome and virulome hosted by deep Antarcticas soil microbial communities and the presence of bacteria with pathogenic potential, highlighting the relevance of One Health approaches for environmental surveillance in the white continent. HIGHLIGHTS-Union Glacier soils host a microbial community dominated by bacteria, mainly from the phylum Actinomycetota. -Archaea from the Nitrosocosmicus genus (family Nitrosphaeraceae) were ubiquitously detected. -Although extreme and remote, these soils host multidrug-resistant and potentially pathogenic bacteria. Some were cultured and tested in vitro. -Metagenomes and species-level representative genomes revealed diverse putative resistance and virulence genes. -Part of the putative antimicrobial resistance genes and virulence factors could be associated with mobile elements in bacterial genomes.

microbiology↗

bioRxiv2018

Whole genome sequence of Mapuche-Huilliche Native Americans

BackgroundWhole human genome sequencing initiatives provide a compendium of genetic variants that help us understand population history and the basis of genetic diseases. Current data mostly focuses on Old World populations and information on the genomic structure of Native Americans, especially those from the Southern Cone is scant.\n\nResultsHere we present a high-quality complete genome sequence of 11 Mapuche-Huilliche individuals (HUI) from Southern Chile (85% genomic and 98% exonic coverage at > 30X), with 96-97% high confidence calls. We found approximately 3.1x106 single nucleotide variants (SNVs) per individual and identified 403,383 (6.9%) of novel SNVs that are not included in current sequencing databases. Analyses of large-scale genomic events detected 680 copy number variants (CNVs) and 4,514 structural variants (SVs), including 398 and 1,910 novel events, respectively. Global ancestry composition of HUI genomes revealed that the cohort represents a marginally admixed population from the Southern Cone, whose genetic component is derived from early Native American ancestors. In addition, we found that HUI genomes display highly divergent and novel variants with potential functional impact that converge in ontological categories essential in cell metabolic processes.\n\nConclusionsMapuche-Huilliche genomes contain a unique set of small- and large-scale genomic variants in functionally linked genes, which may contribute to susceptibility for the development of common complex diseases or traits in admixed Latinos and Native American populations. Our data represents an ancestral reference panel for population-based studies in Native and admixed Latin American populations.

genomics↗