Iñigo Lasa

Public University of Navarre | UPNA · Navarrabiomed

Staphylococcus aureus is among the leading causes of hospital-acquired infections. Critical to S. aureus biology and pathogenesis are the cell wall-anchored glycopolymers wall teichoic acids (WTA). Approximately one-third of S. aureus isolates decorates WTA with a mixture of α1,4- and β1,4- N -acetylglucosamine (GlcNAc), which requires the dedicate...

Sonicating explanted prosthetic implants to physically remove biofilms is a recognized method for improving the microbiological diagnosis of prosthetic joint infection (PJI); however, chemical and enzymatic treatments have been investigated as alternative biofilm removal methods. We compared the biofilm dislodging efficacy of sonication followed by...

Dormant prophages protect lysogenic cells by expressing diverse immune systems, which must avoid targeting their cognate prophages upon activation. Here we report that multiple Staphylococcus aureus prophages encode Tha (tail-activated, HEPN (higher eukaryotes and prokaryotes nucleotide-binding) domain-containing anti-phage system), a defence syste...

Bacteria synchronise the expression of genes with related functions by organizing genes into operons so that they are cotranscribed together in a single polycistronic messenger RNA. However, some cellular processes may benefit if the simultaneous production of the operon proteins coincides with the inhibition of the expression of an antagonist gene...

The overuse of antibiotics in humans and livestock has driven the emergence and spread of antimicrobial resistance and has therefore prompted research on the discovery of novel antibiotics. Complestatin (Cm) and corbomycin (Cb) are glycopeptide antibiotics with an unprecedented mechanism of action that is active even against methicillin-resistant a...

Staphylococcus aureus is a leading cause of prosthetic joint infections (PJI). Surface adhesins play an important role in the primary attachment to plasma proteins that coat the surface of prosthetic devices after implantation. Previous efforts to identify a genetic component of the bacterium that confers an enhanced capacity to cause PJI have focu...

Non-contiguous operon stands for operons that contain a gene(s) transcribed in the opposite direction, resulting in a transcript that is antisense in its full length to the operon transcript. Initial evidence suggest that this transcriptional organization provides a mechanism to coordinate gene expression by two mechanisms: transcriptional interfer...

Contribution of genetic variations in the regulatory region of surface adhesin encoding genes to colonization of prosthetic implants by Staphylococcus aureus

Biofilm engineering has emerged as a controllable way to fabricate living structures with programmable functionalities. The amyloidogenic proteins comprising the biofilms can be engineered to create self-assembling extracellular functionalized surfaces. In this regard, facultative amyloids, which play a dual role in biofilm formation by acting as a...

This study addresses the presence and frequency of particular genetic variants and virulence factors found in staphylococcal bacteria causing periprosthetic joint infection (PJI) of the hip and knee to ascertain their clinical relevance as predictors of treatment failure. We characterized the genetic virulence traits of a large collection of clinic...

In bacteria, adaptation to changes in the environment is mainly controlled through two-component signal transduction systems (TCSs). Most bacteria contain dozens of TCSs, each of them responsible for sensing a different range of signals and controlling the expression of a repertoire of target genes (regulon). Frequently, TCS control key physiologic...

Staphylococcus aureus is a leading cause of prosthetic joint infections (PJI) characterized by bacterial biofilm formation and recalcitrance to immune-mediated clearance and antibiotics. The molecular events behind PJI infection are yet to be unraveled. In this sense, identification of polymorphisms in bacterial genomes may help to establish associ...

Bacterial genomes are pervasively transcribed, generating a wide variety of antisense RNAs (asRNAs). Many of them originate from transcriptional read-through events (TREs) during the transcription termination process. Previous transcriptome analyses revealed that the lexA gene from Staphylococcus aureus, which encodes the main SOS response regulato...

Two-component systems (TCSs) are a prominent sensory system in bacteria. A prototypical TCS comprises a membrane-bound sensor histidine kinase (HK) responsible for sensing the signal and a cytoplasmic response regulator (RR) that controls target gene expression. Signal binding activates a phosphotransfer cascade from the HK to the RR. As a result,...

Background Periprosthetic joint infections (PJI) are challenging complications following arthroplasty. Staphylococci are a frequent cause of PJI and known biofilm producers. Biofilm formation decreases antimicrobial susceptibility, thereby challenging favourable treatment outcomes. The aims of this study were to characterize the biofilm abilities a...

Methicillin-resistant Staphylococcus aureus infections are a global health problem. New control strategies, including fifth-generation cephalosporins such as ceftaroline, have been developed, however rare sporadic resistance has been reported. Our study aimed to determine whether disruption of two-component environmental signal systems detectably l...

Non-contiguous operons are transcription units consisting of groups of genes that are transcribed together despite being separated by a gene(s) that is transcribed in the opposite direction. In this transcription architecture, the transcript produced in the opposite direction is antisense to the transcript of the operon and a mechanism of mutual ex...

The Staphylococcal Bap proteins sense environmental signals (such as pH, [Ca2+ ]) to build amyloid scaffold biofilm matrices via unknown mechanisms. We here report the crystal structure of the aggregation-prone region of Staphylococcus aureus Bap which adopts a dumbbell-shaped fold. The middle module (MM) connecting the N-terminal and C-terminal lo...

Plasmids have largely contributed to the spread of antimicrobial resistance genes among Staphylococcus strains. Knowledge about the fitness cost that plasmids confer on clinical staphylococcal isolates and the coevolutionary dynamics that drive plasmid maintenance is still scarce. In this study, we aimed to analyze the initial fitness cost of plasm...

One of the major components of the staphylococcal biofilm is surface proteins that assemble as scaffold components of the biofilm matrix. Among the different surface proteins able to contribute to biofilm formation, this review is dedicated to the Biofilm Associated Protein (Bap). Bap is part of the accessory genome of Staphylococcus aureus but ort...

Several dinucleotide cyclases, including cyclic GMP-AMP synthase, and their involvement in STING-mediated immunity have been extensively studied. In this study, we tested five bacterial diguanylate cyclases from the Gram-negative bacterium Salmonella Enteritidis, identifying AdrA as the most potent inducer of a STING-mediated IFN response. AdrA wil...

Abstract Salmonellosis is the second most common food-borne zoonosis in the European Union, with pigs being a major reservoir of this pathogen. Salmonella control in pig production requires multiple measures amongst which vaccination may be used to reduce subclinical carriage and shedding of prevalent serovars, such as Salmonella enterica serovar T...

Functional amyloids are considered as common building block structures of the biofilm matrix in different bacteria. In previous work, we have shown that the staphylococcal surface protein Bap, a member of the Biofilm-Associated Proteins (BAP) family, is processed and the fragments containing the N-terminal region become aggregation-prone and self-a...

The opportunistic pathogen Staphylococcus aureus is responsible for causing infections related to indwelling medical devices, where this pathogen is able to attach and form biofilms. The intrinsic properties given by the self-produced extracellular biofilm matrix confer high resistance to antibiotics, triggering infections difficult to treat. There...

Bacterial biofilms provide high cell density and a superior adaptation and protection from stress conditions compared to planktonic cultures, making them a very promising approach for bioremediation. Several Rhodococcus strains can desulfurize dibenzothiophene (DBT), a major sulphur pollutant in fuels, reducing air pollution from fuel combustion. D...

Infections caused by Staphylococcus aureus pose a serious and sometimes fatal health issue. With the aim of exploring a novel therapeutic approach, we chose GraXRS, a Two-Component System (TCS) that determines bacterial resilience against host innate immune barriers, as an alternative target to disarm S. aureus. Following a drug repurposing methodo...

Bacteria are able to sense environmental conditions and respond accordingly. Their sensorial system relies on pairs of sensory and regulatory proteins, known as two-component systems (TCSs). The majority of bacteria contain dozens of TCSs, each of them responsible for sensing and responding to a different range of signals. Traditionally, the functi...

Objective As a consequence of the health crisis arising from the SARS-CoV-2 coronavirus pandemic, ozone treatments are being applied as disinfectant in emergency vehicles, without objective evidence on its efficacy. Here we evaluate the efficacy of ozone treatment over bacterial strains and virus-like particles. Method A preparation of a lentivira...

Commons Attribution License (CC BY 4.0). Phage-inducible chromosomal islands (PICIs) are a widespread family of mobile genetic elements, which have an important role in bacterial pathogenesis. These elements mobilize among bacterial species at extremely high frequencies, representing an attractive tool for the delivery of synthetic genes. However,...

Bacteria use two-component systems (TCSs) to sense and respond to their environments. Free-living bacteria usually contain dozens of TCSs, each of them responsible for sensing and responding to a different range of signals. Differences in the content of two-component systems are related with the capacity of the bacteria to colonize different niches...

In the last decade, the implementation of high‐throughput methods for RNA profiling has uncovered that a large part of the bacterial genome is transcribed well beyond the boundaries of known genes. Therefore, the transcriptional space of a gene very often invades the space of a neighbouring gene, creating large regions of overlapping transcription....

Due to its multifaceted lifestyle, Staphylococcus aureus needs a complex regulatory network to connect environmental signals with cellular physiology. One particular transcription factor, named σ B (SigB), is involved in the general stress response and the expression of virulence factors. For many years, great confusion has existed about the role o...

Pathogenic bacteria must rapidly adapt to ever-changing environmental signals resulting in metabolism remodeling. The carbon catabolite repression, mediated by the catabolite control protein A (CcpA), is used to express genes involved in utilization and metabolism of the preferred carbon source. Here, we have identified RsaI as a CcpA-repressed sma...

Significance In bacteria, functionally related genes are often cotranscribed in a single mRNA molecule under the same upstream promoter, forming a polycistronic operon unit. With this strategy, bacteria guarantee that production of all proteins related to a specific cellular process is simultaneously switched on or off. Here, we report the identifi...

Amyloid fibrils formed by a variety of peptides are biological markers of different human diseases, such as Alzheimer’s disease, Parkinson’s disease, and type II diabetes, and are structural constituents of bacterial biofilms. Novel fluorescent probes offering improved sensitivity or specificity toward that diversity of amyloid fibrils or providing...

Despite the number of examples that correlate interspecies interactions in polymicrobial infections with variations in pathogenicity and antibiotic susceptibility of individual organisms, antibiotic therapies are selected to target the most relevant pathogen, with no consideration of the consequences that the presence of other bacterial species may...

Two-component systems (TCS) are modular signal transduction pathways that allow cells to adapt to prevailing environmental conditions by modifying cellular physiology. Staphylococcus aureus has 16 TCSs to adapt to the diverse microenvironments encountered during its life cycle, including host tissues and implanted medical devices. S. aureus is part...

Pathogenic bacteria must rapidly adapt to ever-changing environmental signals or nutrient availability resulting in metabolism remodeling. The carbon catabolite repression represents a global regulatory system, allowing the bacteria to express genes involved in carbon utilization and metabolization of the preferred carbon source. In Staphylococcus...

Bacteria use two-component systems (TCSs) to sense and respond to environmental changes. The core genome of the major human pathogen Staphylococcus aureus encodes 16 TCSs, one of which (WalRK) is essential. Here we show that S. aureus can be deprived of its complete sensorial TCS network and still survive under growth arrest conditions similarly to...

RNA-binding proteins (RBPs) are essential to fine-tune gene expression. RBPs containing the cold-shock domain are RNA chaperones that have been extensively studied. However, the RNA targets and specific functions for many of them remain elusive. Here, combining comparative proteomics and RBP-immunoprecipitation-microarray profiling, we have determi...

Many bacteria build biofilm matrices using a conserved exopolysaccharide named PGA or PNAG (poly-β-1,6-N-acetyl-D-glucosamine). Interestingly, while E. coli and other members of the family Enterobacteriaceae encode the pgaABCD operon responsible for PGA synthesis, Salmonella lacks it. The evolutionary force driving this difference remains to be det...

Strains and plasmids used in this study. (PDF)

Analysis of PGA synthesis dependence on c-di-GMP. Quantification of PGA exopolysaccharide production by dot blot. Serial dilutions (1/10) of the samples were spotted onto nitrocellulose membranes and PGA production was detected with specific anti PIA/PNAG antibodies. UD; undiluted sample. (A) Dot blot analysis of the PGA accumulated by S. Enteritid...

Oligonucleotides used in this study. (PDF)

Strains WT PphoP::adrA and ΔbcsA PphoP::adrA PcL::pga produce cellulose and PGA, respectively, in a phoP dependent fashion. A cellulose based biofilm is produced by WT PphoP::adrA after overnight growth in low-Mg2+ liquid medium (top panel). An aggregate of ΔbcsA PphoP::adrA PcL::pga bacteria can be observed at the bottom of the tube as Mg2+ concen...

Fitness of ΔbcsA versus the wild type or ΔbcsA PcL::pga strains. The competitive fitness of ΔbcsA in co-culture with either the wild type or ΔbcsA PcL::pga was determined by combining the two strains in LB broth, incubating at 37°C and enumerating each strain over time. (EPS)

Gene neighborhood analysis for pgaA, as provided in the STRING database [36]. Results for Enterobacteriaceae genomes are fully displayed, while those from other groups are presented in a collapsed mode. (EPS)

Hydrophobicity analysis of macrocolony biofilms formed by WT PcL::adrA and ΔbcsA PcL::adrA pJET::pga. (A) The cellulose overproducing strain, WT PcL::adrA, the PGA overproducing strain, ΔbcsA PcL::adrA pJET::pga and the control strain, ΔbcsA PcL::adrA, were incubated on LB agar or LB agar Cb media for 48h at 28°C. A bent tip was used to visualize t...

Synthesis of PGA by a Salmonella strain that constitutively expresses the pgaABCD operon from the chromosome. Comparison of the PGA accumulated by WT PcL::pga and WT pJET::pga, expressing the pgaABCD operon from the chromosome or from a plasmid, respectively, after 24 hours of growth at 37°C in LB or LB Cb media. Serial dilutions (1/10) of the samp...

PGA is overproduced by E. coli MG1655 when the pgaABCD operon is expressed from a constitutive promoter. Dot blot analysis of the PGA accumulated by E. coli MG1655, a pgaC mutant and a derivative of E. coli MG1655 in which the pgaABCD operon was placed under the control of the constitutive promoter PcL, after 24 hours of growth at 37°C in LB media....

Phylogenetic trees of the analyzed proteins. First column indicates the protein name, and the second column is the phylogenetic tree in standard newick format. Labels indicate species names, as retrieved from NCBI, followed by an underscore separator and the gene identifier. (PDF)

Recent insights into bacterial biofilm matrix structures have induced a paradigm shift towards the recognition of amyloid fibers as common building block structures that confer stability to the exopolysaccharidic matrix. Herein, we describe the functional amyloid systems related with biofilm matrix formation in both gram-negative and gram-positive...

Salmonellosis is one of the most important bacterial zoonotic diseases transmitted through the consumption of contaminated food, with chicken and pig related products being key reservoirs of infection. Although numerous studies on animal vaccination have been performed in order to reduce Salmonella prevalence, there is still a need for an ideal vac...

Representative IFN-γ and TNF-α/CD4 staining for ΔXIII stimulated splenocytes. 28 days after immunization, splenocytes from control and ΔXIII immunized mice were plated and stimulated for 6 hours with medium, 106 or 107 cfu of heat-killed ΔXIII bacteria. Cells were surface stained with anti-CD4-FITC antibody and intracellularly stained with anti IFN...

Strains used in this study. (DOCX)

Biofilms are communities of bacteria that grow encased in an extracellular matrix that often contains proteins. The spatial organization and the molecular interactions between matrix scaffold proteins remain in most cases largely unknown. Here, we report that Bap protein of Staphylococcus aureus self-assembles into functional amyloid aggregates to...

Effect of pH and calcium addition on Bap aggregation and biofilm formation. Bacterial clumping (A) and biofilm formation (B) of S. aureus V329, Δbap and Δbap expressing Bap_B cultured in LB media acidified with 0.1 M HCl to a final pH 4.5, at 37°C, 200 rpm. C) Reversibility of bacterial aggregates formed by S. aureus V329 and Δbap expressing Bap_B...

Role of biofilm matrix molecules in Bap mediated aggregation and biofilm phenotype. For detachment experiments, biofilms formed by S. aureus V329 and 15981 strains grown in LB-glu for 24 h, were treated with 0,4 μg/ml dispersin B (DspB) (A) or 0,4 μg/ml DNase I (B) for 2 h at 37°C. The quantification of adhered biofilm was performed by the solubili...

A) Summary of sedimentation velocity and sedimentation equilibrium parameters of rBap_B at pH 7 and in the presence or absence of calcium confirms monomeric state of the protein in both conditions. B) Sedimentation equilibrium analysis of 2 mg/ml rBap_B in the presence or absence of CaCl2, and at different rpm. Dotted lines show global fits. Residu...