Biology subjects

Guazzaroni, M.-E.

Publications and source records attributed to Guazzaroni, M.-E..

13 recordsLinked to original sources

bioRxiv2025

Discovery and Functional Characterization of Salinity-Responsive Promoters in Pseudomonas putida KT2440

Microbial bioprocesses are associated with environmental advantages, but their freshwater demand remains a challenge. Seawater is abundant and a sustainable alternative; however, high salinity often limits microbial growth and survival. This study aimed to identify biological parts involved in microbial salt stress responses for applications in microbial engineering. Regulatory regions adjacent to genes related to salinity and other industrially relevant conditions in Pseudomonas putida KT2440 were cloned into a reporter plasmid for functional evaluation. We identified and characterized the promoters of PP_1833 and PP_4707 as salt-inducible in KT2440, showing fluorescence levels 1.9- and 2.8-fold greater than a standard strong constitutive promoter (Pj100) under 3.5% NaCl (w/v), respectively, while no activity was detected in Escherichia coli DH10B. These results provide a basis for developing salt-responsive regulatory circuits in P. putida KT2440. For table of contents only O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=69 SRC="FIGDIR/small/687801v1_ufig1.gif" ALT="Figure 1"> View larger version (11K): org.highwire.dtl.DTLVardef@1b5214org.highwire.dtl.DTLVardef@1a9bde0org.highwire.dtl.DTLVardef@f0d071org.highwire.dtl.DTLVardef@4c0bd_HPS_FORMAT_FIGEXP M_FIG C_FIG

synthetic biology↗

bioRxiv2025

Differences in GenBank and RefSeq annotations may affect genomics data interpretation for Pseudomonas putida KT2440

Annotations of genomic features are cornerstone data that support routine workflows in conventional omics analyses in Pseudomonas putida KT2440 and other organisms. The GenBank and the RefSeq versions of the annotated KT2440 genome are two popular resources widely cited in the literature; yet, they originate from distinct prediction pipelines and possess potentially different biological information that is often overlooked. In this study, we systematically compared the features present in these resources and found that approximately 16% of the total of KT2440 ORFs show differences in their predicted genomic positions across GenBank and RefSeq, despite sharing equivalent locus tag codes. Furthermore, we show that these discrepancies can affect the results of high-throughput analyses by processing a collection of RNAseq expression datasets utilizing both annotations. Our findings provide a comprehensive overview of the current state of available resources for genomics research in P. putida KT2440 and highlight a rarely addressed yet widespread potential pitfall in the literature on this organism, with possible implications for other prokaryotes. ImportanceGenome annotation databases often rely on different statistical models for their function predictions and inherently carry biases propagated into studies using them. This work provides a quantitative assessment of two popular annotation resources for the model bacterium P. putida KT2440 and their influence on data interpretation. As large-scale omics datasets are commonly used to inform experimental decisions, our results aim to promote awareness of the caveats associated with these computational resources and foster reproducibility and transparency in P. putida research.

bioinformatics↗

bioRxiv2024

Alternate routes to acetate tolerance lead to varied isoprenol production from mixed carbon sources in Pseudomonas putida

Lignocellulose is a renewable resource for the production of a diverse array of platform chemicals, including the biofuel isoprenol. While this carbon stream provides a rich source of sugars, other organic compounds, such as acetate, can be used by microbial hosts. Here we examined growth and isoprenol production in a Pseudomonas putida strain pre-tolerized ("PT") background where its native isoprenol catabolism pathway is deleted, using glucose and acetate as carbon source. We found that PT displays impaired growth in minimal medium containing acetate, and often fails to grow in glucose-acetate medium. Using a mutant recovery-based approach, we generated tolerized strains that overcame these limitations, achieving fast growth and isoprenol production in the mixed carbon feed. Changes in the glucose and acetate assimilation routes, including an upregulation in PP_0154 (SpcC, succinyl-CoA:acetate CoA-transferase) and differential expression of the gluconate assimilation pathways, were key for higher isoprenol titers in the tolerized strains, while a different set of mechanisms were likely enabling tolerance phenotypes in media containing acetate. Among these, a coproporphyrinogen-III oxidase (HemN) was upregulated across all tolerized strains, and in one isolate required for acetate tolerance. Utilizing a defined glucose and acetate mixture ratio reflective of lignocellulosic feedstocks for isoprenol production in P. putida allowed us to obtain insights into the dynamics and challenges unique to dual carbon source utilization that are obscured when studied separately. Together, this enabled development of a P. putida bioconversion chassis able to use a more complex carbon stream to produce isoprenol. ImportanceAcetate is a relatively abundant component of many lignocellulosic carbon streams and has the potential of being used together with sugars, especially in microbes with versatile catabolism such as P. putida. However, the use of mixed carbon streams necessitates additional optimization. Further, the use of P. putida for the production of the biofuel target, isoprenol, requires the use of engineered strains that have additional growth and production constraints when cultivated in acetate and glucose mixtures. In this study we generate acetate tolerant P. putida strains that overcome these challenges and examine their ability to produce isoprenol. We show that acetate tolerance and isoprenol production, though independent phenotypes can both be optimized in a given P. putida strain. Using proteomics and whole genome sequencing we examine the molecular basis of both phenotypes and show that tolerance to acetate can occur via alternate routes and result in different impacts on isoprenol production.

microbiology↗

bioRxiv2024

Characterization of a marine bacteria through a novel metabologenomics approach

Exploiting microbial natural products is a key pursuit of the bioactive compound discovery field. Recent advances in modern analytical techniques have increased the volume of microbial genomes and their encoded biosynthetic products measured by mass spectrometry-based metabolomics. However, connecting multi-omics data to uncover metabolic processes of interest is still challenging. This results in a large portion of genes and metabolites remaining unannotated. Further exacerbating the annotation challenge, databases and tools for annotation and omics integration are scattered, requiring complex computations to annotate and integrate omics datasets. Here we performed a two-way integrative analysis combining genomics and metabolomics data to describe a new approach to characterize the marine bacterial isolate BRA006 and to explore its biosynthetic gene cluster (BGC) content as well as the bioactive compounds detected by metabolomics. We described BRA006 genomic content and structure by comparing Illumina and Oxford Nanopore MinION sequencing approaches. Digital DNA:DNA hybridization (dDDH) taxonomically assigned BRA006 as a potential new species of the Micromonospora genus. Starting from LC-ESI(+)-HRMS/MS data, and mapping the annotated enzymes and metabolites belonging to the same pathways, our integrative analysis allowed us to correlate the compound Brevianamide F to a new BGC, previously assigned to other function.

biochemistry↗

bioRxiv2022

Metagenomic insights for antimicrobial resistance surveillance in soils with different land uses in Brazil

Anthropization in terrestrial environments commonly leads to land use transformation, changing soil properties and their microbial communities. This, combined with the exacerbated use of antibiotics in human and animal health promotes the expansion of the soil resistome. Considering the urgent need for surveillance of antimicrobial resistance (AMR), we aimed to evaluate how different land practices (urban, farming and forest) can affect the soil resistome and the dynamics of their bacterial communities. We collected eight soil samples from different locations in the countryside of Sao Paulo (Brazil), assessed the community profiles based on 16S rRNA sequencing and analyzed the soil metagenomes based on shotgun sequencing. Our results highlight differences in the communities structure and their dynamics which were correlated with land practices. Additionally, differences were observed in the abundance and diversity of antibiotic resistance genes (ARGs) and virulence factors (VFs) across studied soils, where a higher presence and homogeneity of vanRO, mtrA and rbpA genes were detected in livestock soils. We observed that Staphylococcus and Bacillus are positively correlated with each other and are markers for agricultural communities. Moreover, the abundance and diversity of ARGs and VFs observed in farming soils raises concerns regarding the potential spread of these genes in the environment. Together, our findings reinforce the importance and urgency of AMR surveillance in the environment, especially in soils undergoing deep land use transformations due to anthropic activity.

microbiology↗

bioRxiv2022

A termination-aware vector design improves heterologous gene expression in Pseudomonas putida

Transcriptional terminators are key players in the flow of genetic information, but are often overlooked in circuit design. In this work, we used the Standard European Vector Architecture (SEVA) as a scaffold to investigate the effects of different terminators in the output of a reporter construct expressed in two bacterial species and found that replacing the conventional T1 and T0 transcriptional terminators of the SEVA vector format with a set of broad-host metagenomic terminators resulted in a significant improvement in the signal of a fluorescent device in Pseudomonas putida KT2440. Interestingly, this new vector design displayed the same performance as pSEVA231 in Escherichia coli DH10B. Our results support the notion that transcriptional terminators may affect the interconnected mesh of biological processes taking place in gene expression, leading to a host-dependent output that should be heeded for optimal circuit expression in different microbial hosts.

synthetic biology↗

bioRxiv2022

Mining novel cis-regulatory elements from the emergent host Rhodosporidium toruloides using transcriptomic data

The demand for robust microbial cell factories that can produce valuable biomaterials while being resistant to stresses imposed by current bioprocesses is rapidly growing. R. toruloides is an emerging host that presents desirable features for bioproduction, since it can grow in a wide range of substrates and tolerate a variety of toxic compounds. In order to explore R. toruloides suitability for application as a cell factory in biorefineries, we sought to understand the transcriptional responses of this yeast when growing under experimental settings that simulated those used in biofuels-related industries. Thus, we performed RNA sequencing of the oleaginous, carotenogenic yeast in different contexts. The first ones were stress-related: two conditions of high temperature (37 {degrees}C and 42 {degrees}C) and two ethanol concentrations (2% and 4%), while the other was using the inexpensive and abundant sugarcane juice as substrate. Using transcriptomic data, differential expression and functional analysis were implemented to select differentially expressed genes and enriched pathways from each set-up. A reproducible bioinformatics workflow was developed for mining new regulatory elements. We then predicted, for the first time in this yeast, binding motifs for several transcription factors, including HAC1, ARG80, RPN4, ADR1, and DAL81. Most of the putative transcription factors uncovered here were involved in stress responses and found in the yeast genome. Our method for motif discovery provides a new realm of possibilities in the study of gene regulatory networks, not only for the emerging host R. toruloides, but for other organisms of biotechnological importance.

bioinformatics↗

bioRxiv2021

Nanopore sequencing provides rapid and reliable insight into microbial profiles of Intensive Care Units

Fast and accurate identification of pathogens is an essential task in healthcare settings. Next generation sequencing platforms such as Illumina have greatly expanded the capacity with which different organisms can be detected in hospital samples, and third-generation nanopore-driven sequencing devices such as Oxford Nanopores minION have recently emerged as ideal sequencing platforms for routine healthcare surveillance due to their long-read capacity and high portability. Despite its great potential, protocols and analysis pipelines for nanopore sequencing are still being extensively validated. In this work, we assess the ability of nanopore sequencing to provide reliable community profiles based on 16S rRNA sequencing in comparison to traditional Illumina platforms using samples collected from Intensive Care Units from a hospital in Brazil. While our results point that lower throughputs may be a shortcoming of the method in more complex samples, we show that the use of single-use Flongle flowcells in nanopore sequencing runs can provide insightful information on the community composition in healthcare settings.

microbiology↗

bioRxiv2019

Microbial communities profiling in intensive care units expose limitations in current sanitary standards

Hospital-associated infections (HAIs) are the leading cause of morbidity and mortality in intensive care units (ICUs) and neonatal intensive care units (NICUs). Organisms causing these infections are often present on surfaces around the patient. Given that microbiotas may vary across different ICUs, the HAI-related microbial signatures within these units remain underexplored. In this study, we use deep-sequencing analyses to explore and compare the structure of bacterial communities at inanimate surfaces of the ICU and NICU wards of The Medical School Clinics Hospital (Brazil). The data revealed that NICU presents higher biodiversity than ICU and surfaces closest to the patient showed a peculiar microbiota, distinguishing one unit from the other. Several facultative anaerobes or obligate anaerobes HAI-related genera were classified as biomarkers for the NICU, whereas Pseudomonas was the main biomarker for ICU. Correlation analyses revealed a distinct pattern of microbe-microbe interactions for each unit, including bacteria able to form multi-genera biofilms. Furthermore, we evaluated the effect of concurrent cleaning over the ICU bacterial community. The results showed that, although some bacterial populations decreased after cleaning, various HAI-related genera were quite stable to sanitization, suggesting being well-adapted to the ICU environment. Overall, these results enabled identification of discrete ICU and NICU reservoirs of potentially pathogenic bacteria and provided evidence for the presence of a set of biomarkers that distinguish these units. Moreover, the study exposed the inconsistencies of the routine cleaning to minimize HAI-related genera contamination.\n\nIMPORTANCEDue to the high impact of HAIs, there is an urgent need for the development of robust policies on microbial surveillance to help guide procedures, improving infection control. To the best of our knowledge, this is the first comprehensive study, using a high-throughput approach, focused on comparing the microbiota peculiarities of the ICU and NICU in one of the largest public hospitals in Brazil. The work highlighted bacteria associated with nosocomial infections, identifying the most potent reservoirs of contamination, and evaluated the microbiota changes related to the cleaning procedure. Therefore, this study contributes to increase the knowledge about (N)ICUs microbiomes and may help to reduce health-care-associated infections, especially in developing countries.

microbiology↗

bioRxiv2018

Expanding the toolbox of broad host-range transcriptional terminators for Proteobacteria through metagenomics

As the field of synthetic biology moves towards the utilization of novel bacterial chassis, there is a growing need for biological parts with enhanced performance in a wide number of hosts. Is not unusual that biological parts (such as promoters and terminators), initially characterized in the model bacteria Escherichia coli, do not perform well when implemented in alternative hosts, such as Pseudomonas, therefore limiting the construction of synthetic circuits in industrially relevant bacteria. In order to address this limitation, we present here the mining of transcriptional terminators through functional metagenomics to identify novel parts with broad host-range activity. Using a GFP-based terminator trap strategy and a broad host-range plasmid, we identified 20 clones with potential terminator activity in Pseudomonas putida. Further characterization allowed the identification of 4 unique sequences between 58 bp and 181 bp long that efficiently terminates transcription in P. putida, E. coli, Burkholderia phymatum and two Pseudomonas strains isolated from Antarctica. Therefore, this work presents a new set of biological parts useful for the engineering of synthetic circuits in Proteobacteria.

synthetic biology↗

bioRxiv2018

Reverse engineering of an aspirin-responsive regulator in bacteria

Bacterial transcriptional factors (TFs) and their target promoters are key devices for engineering of complex circuits in many biotechnological applications. Yet, there is a dearth of well characterized inducer-responsive TFs that could be used in the context of an animal or human host. In this work we have deciphered the inducer recognition mechanism of two AraC/XylS regulators from Pseudomonas putida (BenR and XylS) for creating a novel expression system responsive to acetyl salicylate (i.e. Aspirin). Using protein homology modeling and molecular docking with the cognate inducer benzoate and a suite of chemical analogues, we identified the conserved binding pocket of these two proteins. Using site directed mutagenesis, we identified a single amino acid position required for efficient inducer recognition and transcriptional activation. While modification of this position in BenR abolishes protein activity, its modification in XylS increases the response to several aromatic compounds, including acetyl salicylic acid to levels close to those achieved by the canonical inducer. Moreover, by constructing chimeric proteins with swapped N-terminal domains, we created novel regulators with mixed promoter and inducer recognition profiles. As a result, a collection of engineered TFs was generated with enhanced response to a well characterized and largely innocuous molecule with a potential for eliciting heterologous expression of bacterial genes in animal carriers.

synthetic biology↗

bioRxiv2017

Assessing and characterising the repertoire of constitutive promoter elements in soil metagenomic libraries in Escherichia coli

Although functional metagenomics has been widely employed for the discovery of genes relevant to biotechnology and biomedicine, its potential for assessing the diversity of transcriptional regulatory elements of microbial communities has remained poorly explored. Here, we have developed a novel framework for prospecting, characterising and estimating the accessibility of promoter sequences in metagenomic libraries by combining a bi-directional reporter vector, high-throughput fluorescence assays and predictive computational methods. Using the expression profiling of fluorescent clones from two independent libraries from soil samples, we directly analysed the regulatory dynamics of novel promoter elements, addressing the relationship between the \"metaconstitutome\" of a bacterial community and its environmental context. Through the construction and screening of plasmid-based metagenomic libraries followed by in silico analyses, we were able to provide both (i) a consensus exogenous promoter elements recognizable by Escherichia coli and (ii) an estimation of the accessible promoter sequences in a metagenomic library, which was close to 1% of the whole set of available promoters. The results presented here should provide new directions for the exploration through functional metagenomics of novel regulatory sequences in bacteria, which could expand the Synthetic Biology toolbox for novel biotechnological and biomedical applications.

microbiology↗

bioRxiv2017

Big trouble with little inserts: boundaries in metagenomic screenings using lacZα based vectors

The vast biochemical repertoire found in microbial communities from a wide-range of environments allows screening and isolation of novel enzymes with improved catalytic features. In this sense, metagenomics approaches have been of high relevance for providing enzymes used in diverse industrial applications. For instance, glycosyl hydrolases, which catalyze the hydrolysis of carbohydrates to sugars, are essential for bioethanol production from renewable resources. In the current study, we have focused on the prospection of protease and glycosyl hydrolase activities from microbial communities inhabiting a soil sample by using the lacZ-based plasmid pSEVA232 in the generation of a screenable metagenomic library. For this, we used a functional screen based on skimmed milk agar and a pH indicator dye as previously reported in literature. Although we effectively identified nine positive clones in the screenings, subsequent experiments revealed that this phenotype was not because of the hydrolytic activity encoded in the metagenomic fragments, but rather due to the insertion of small metagenomic DNA fragments in frame within the coding region of the lacZ alpha gene present in the original vector. We concluded that the current method has a higher tendency for false positive recovery of clones, when used in combination with a lacZ-based vector. Finally, we discuss the molecular explanation for positive phenotype recovering and highlight the importance of reporting boundaries in metagenomic screenings methodologies.

molecular biology↗