Sergio A Álvarez

• PhD in Biochemistry
• University of Chile

The type III secretion systems (T3SS) encoded in pathogenicity islands SPI-1 and SPI-2 are key virulence factors of Salmonella. These systems translocate proteins known as effectors into eukaryotic cells during infection. To characterize the functionality of T3SS effectors, gene fusions to the CyaA’ reporter of Bordetella pertussis are often used....

Inorganic polyphosphate (polyP) and its metabolic enzymes are important in several cellular processes related with virulence and antibiotic susceptibility. Accordingly, bacterial polyP synthesis has been proposed as a good target for designing novel antivirulence molecules as alternative to conventional antibiotics. In most pathogenic bacteria, pol...

The twin-arginine translocation (Tat) system is a specialized secretion pathway required for bacteria to export fully folded proteins through the cytoplasmic membrane. This system is crucial during Salmonella infection of animal hosts. In this study, we show that Salmonella enterica serovar Typhimurium (S. Typhimurium) requires the Tat system to su...

Acidithiobacillus ferrooxidans resists extremely high concentrations of copper. Strain ATCC 53993 is much more resistant to the metal compared with strain ATCC 23270, possibly due to the presence of a genomic island in the former one. The global response of strain ATCC 53993 to copper was analyzed using iTRAQ (isobaric tag for relative and absolute...

Lipid A is the bioactive component of lipopolysaccharide, and presents a dynamic structure that undergoes modifications in response to environmental signals. Many of these structural modifications influence Salmonella virulence. This is the case of lipid A hydroxylation, a modification catalyzed by the dioxygenase LpxO. Although it has been establi...

Recently, we reported the production of Cadmium sulfide (CdS) fluorescent semiconductor nanoparticles (quantum dots, QDs) by acidophilic bacteria of the Acidithiobacillus genus. Here, we report that the addition of inorganic phosphate to Acidithiobacillus thiooxidans ATCC 19703 cultures favors the biosynthesis of CdS QDs at acidic conditions (pH 3....

RSM experimental conditions. Two experimental conditions were used for RSM construction; MIC conditions and Biosynthesis conditions. The nine coded conditions used and the corresponding values of variables for the two experimental conditions are indicated. The biosynthesis of NPs was evaluated in supernatants of cell cultures exposed 24 h to the in...

HR-TEM and EDS analysis of CdS-QDs biosynthesized by A. thiooxidans ATCC 19703 at pH 3.5 in presence of two PO43- and Cd2+ concentrations used to construct the surface response of Figure 1C. QDs biosynthesized by A. thiooxidans ATCC 19703 after exposure to 85 mM PO43-/8.3 mM Cd2+ (A,B) and 50 mM PO43-/10 mM Cd2+ (C,D) were purified from culture sup...

The use of bacterial cells to produce fluorescent semiconductor nanoparticles (quantum dots, QDs) represents a green alternative with promising economic potential. In the present work, we report for the first time the biosynthesis of CdS QDs by acidophilic bacteria of the Acidithiobacillus genus. CdS QDs were obtained by exposing A. ferrooxidans, A...

The social amoeba Dictyostelium discoideum has proven to be a useful model for studying relevant aspects of the host-pathogen interaction. In this work, D. discoideum was used as a model to study the ability of Salmonella Typhimurium to survive in amoebae and to evaluate the contribution of selected genes in this process. To do this, we performed i...

Lipopolysaccharide (LPS) consists of three covalently linked domains: the lipid A, the core region and the O antigen (OAg), consisting of repeats of an oligosaccharide. S. Enteritidis produces a LPS with two OAg preferred chain lengths: a long (L)-OAg controlled by WzzSE and a very long (VL)-OAg controlled by WzzfepE. In this work, we show that OAg...

We report the draft genome sequence of Salmonella enterica serovar Typhi strain STH2370, isolated from a typhoid fever patient in Santiago, Chile. This clinical isolate has been used as the reference wild-type strain in numerous studies conducted in our laboratories during the last 15 years.

We report the draft genome sequence of Salmonella enterica serovar Typhi strain STH2370, isolated from a typhoid fever patient in Santiago, Chile. This clinical isolate has been used as the reference wild-type strain in numerous studies conducted in our laboratories during the last 15 years.

Salmonella enterica serotype Gallinarum is the causative agent of fowl typhoid, a disease characterized by high morbidity and mortality that causes major economic losses in poultry production. We have reported that S. Gallinarum harbors a type VI secretion system (T6SS) encoded in Salmonella pathogenicity island 19 (SPI-19) that is required for eff...

Shigella flexneri causes bacillary dysentery in humans. Essential to the establishment of the disease is the invasion of the colonic epithelial cells. Here we investigated the role of the lipopolysaccharide (LPS) O antigen in the ability of S. flexneri to adhere to and invade polarized Caco-2 cells. The S. flexneri 2a O antigen has two preferred ch...

Shigella flexneri causes bacillary dysentery in humans. Essential to the establishment of the disease is the invasion of the colonic epithelial cells. Here we investigated the role of the lipopolysaccharide (LPS) O antigen in the ability of S. flexneri to adhere to and invade polarized Caco-2 cells. The S. flexneri 2a O antigen has two preferred ch...

Shigella flexneri is endemic in most underdeveloped countries, causing diarrheal disease and dysentery among young children. In order to reach its target site, the colon, Shigella must overcome the acid environment of the stomach. Shigella is able to persist in this stressful environment and, because of this ability it can initiate infection follow...

The role of lipopolysaccharide (LPS) in entry of Salmonella Typhimurium into epithelial cells remains unclear. In this study, we tested the ability of a series of mutants with deletions in genes for the synthesis and assembly of the O antigen and the outer core of LPS to adhere to and invade HeLa, BHK, and IB3 epithelial cells lines. Mutants devoid...

The lipopolysaccharide O antigen of Shigella flexneri 2a has two preferred chain lengths, a short (S-OAg) composed of an average of 17 repeated units and a very long (VL-OAg) of about 90 repeated units. These chain length distributions are controlled by the chromosomally encoded WzzB and the plasmid-encoded Wzz(pHS-2) proteins, respectively. In thi...

The amount of lipopolysaccharide (LPS) O antigen (OAg) and its chain length distribution are important factors that protect bacteria from serum complement. Salmonella enterica serovar Typhi produces LPS with long chain length distribution (L-OAg) controlled by the wzz gene, whereas serovar Typhimurium produces LPS with two OAg chain lengths: an L-O...

Shigella flexneri 2a 2457T produces lipopolysaccharide (LPS) with two O-antigen (OAg) chain lengths: a short (S-OAg) controlled by WzzB and a very long (VL-OAg) determined by Wzz(pHS-2). This study demonstrates that the synthesis and length distribution of the S. flexneri OAg are under growth-phase-dependent regulation. Quantitative electrophoretic...

Salmonella enterica serovar Typhi causes typhoid fever in humans. Central to the pathogenicity of serovar Typhi is its capacity to invade intestinal epithelial cells. The role of lipopolysaccharide (LPS) in the invasion process of serovar Typhi is unclear. In this work, we constructed a series of mutants with defined deletions in genes for the synt...

For some bacteria and algae, it has been proposed that inorganic polyphosphates and transport of metal-phosphate complexes could participate in heavy metal tolerance. To test for this possibility in Acidithiobacillus ferrooxidans, a microorganism with a high level of resistance to heavy metals, the polyphosphate levels were determined when the bact...