Increased Production of Pathogenic, Airborne Fungal Spores upon Exposure of a Soil Mycobiota to Chlorinated Aromatic Hydrocarbon Pollutants.

Organic pollutants are omnipresent and can penetrate all environmental niches. We evaluated the hypothesis that short-term (acute) exposure to aromatic hydrocarbon pollutants could increase the potential for fungal virulence. Specifically, we analyzed whether pentachlorophenol and triclosan pollution results in the production of airborne fungal spores with greater virulence than those derived from an unpolluted (Control) condition. Each pollutant altered the composition of the community of airborne spores compared to the control, favoring an increase in strains with in vivo infection capacity (the wax moth Galleria mellonella was used as an infection model). Fungi subsisting inside larvae at 72 h postinjection with airborne spore inocula collected in polluted and unpolluted conditions exhibited comparable diversity (mainly within Aspergillus fumigatus). Several virulent Aspergillus strains were isolated from larvae infected with the airborne spores produced in a polluted environment. Meanwhile, strains isolated from larvae injected with spores from the control, including one A. fumigatus strain, showed no virulence. Potential pathogenicity increased when two Aspergillus virulent strains were assembled, suggesting the existence of synergisms that impact pathogenicity. None of the observed taxonomic or functional traits could separate the virulent from the avirulent strains. Our study emphasizes pollution stress as a possible driver of phenotypic adaptations that increase Aspergillus pathogenicity, as well as the need to better understand the interplay between pollution and fungal virulence. IMPORTANCE Fungi colonizing soil and organic pollutants often meet. The consequences of this encounter constitute an outstanding question. We scrutinized the potential for virulence of airborne fungal spores produced under unpolluted and polluted scenarios. The airborne spores showed increased diversity of strains with higher infection capacity in Galleria mellonella whenever pollution is present. Inside the larvae injected with either airborne spore community, the surviving fungi demonstrated a similar diversity, mainly within Aspergillus fumigatus. However, the isolated Aspergillus strains greatly differ since virulence was only observed for those associated with a polluted environment. The interplay between pollution and fungal virulence still hides many unresolved questions, but the encounter is costly: pollution stress promotes phenotypic adaptations that may increase Aspergillus pathogenicity.

In-Silico Analysis Highlights the Existence in Members of Burkholderia cepacia Complex of a New Class of Adhesins Possessing Collagen-like Domains.

Burkholderia cenocepacia is a multi-drug-resistant lung pathogen. This species synthesizes various virulence factors, among which cell-surface components (adhesins) are critical for establishing the contact with host cells. This work in the first part focuses on the current knowledge about the adhesion molecules described in this species. In the second part, through in silico approaches, we perform a comprehensive analysis of a group of unique bacterial proteins possessing collagen-like domains (CLDs) that are strikingly overrepresented in the Burkholderia species, representing a new putative class of adhesins. We identified 75 CLD-containing proteins in Burkholderia cepacia complex (Bcc) members (Bcc-CLPs). The phylogenetic analysis of Bcc-CLPs revealed the evolution of the core domain denominated "Bacterial collagen-like, middle region". Our analysis remarkably shows that these proteins are formed by extensive sets of compositionally biased residues located within intrinsically disordered regions (IDR). Here, we discuss how IDR functions may increase their efficiency as adhesion factors. Finally, we provided an analysis of a set of five homologs identified in B. cenocepacia J2315. Thus, we propose the existence in Bcc of a new type of adhesion factors distinct from the described collagen-like proteins (CLPs) found in Gram-positive bacteria.

Continuous Production of Dietetic Structured Lipids Using Crude Acidic Olive Pomace Oils.

Crude olive pomace oil (OPO) is a by-product of olive oil extraction. In this study, low-calorie structured triacylglycerols (TAGs) were produced by acidolysis of crude OPO with medium-chain fatty acids (caprylic, C8:0; capric, C10:0) or interesterification with their ethyl ester forms (C8EE, C10EE). These new TAGs present long-chain fatty acids (L) at position sn-2 and medium-chain fatty acids (M) at positions sn-1,3 (MLM). Crude OPO exhibited a high acidity (12.05-28.75% free fatty acids), and high contents of chlorophylls and oxidation products. Reactions were carried out continuously in a packed-bed bioreactor for 70 h, using sn-1,3 regioselective commercial immobilized lipases (Thermomyces lanuginosus lipase, Lipozyme TL IM; and Rhizomucor miehei lipase, Lipozyme RM IM), in solvent-free media at 40 °C. Lipozyme RM IM presented a higher affinity for C10:0 and C10EE. Lipozyme TL IM preferred C10:0 over C8:0 but C8EE over C10EE. Both biocatalysts showed a high activity and operational stability and were not affected by OPO acidity. The New TAG yields ranged 30-60 and the specific productivity ranged 0.96-1.87 g NewTAG/h.g biocatalyst. Lipozyme RM IM cost is more than seven-fold the Lipozyme TL IM cost. Therefore, using Lipozyme TL IM and crude acidic OPO in a continuous bioreactor will contribute to process sustainability for structured lipid production by lowering the cost of the biocatalyst and avoiding oil refining.

Core-shell polycationic polyurea pharmadendrimers: new-generation of sustainable broad-spectrum antibiotics and antifungals.

The efficacy of conventional antimicrobials is falling to critical levels and raising alarming concerns around the globe. In this scenery, engineered nanoparticles emerged as a solid strategy to fight growing deadly infections. Here, we show the in vitro and in vivo performance of pharmadendrimers, a novel class of engineered polyurea dendrimers that are synthetic mimics of antibacterial peptides, against a collection of both Gram-positive and Gram-negative bacteria and fungi. These nanobiomaterials are stable solids prepared by low-cost and green processes, display a dense positively charged core-shell, and are biocompatible and hemocompatible drugs. Mechanistic data, corroborated by coarse-grained molecular dynamics simulations, points towards a fast-killing mechanism via membrane disruption, triggered by electrostatic interactions. Altogether this study provides strong evidence and support for the future use of polyurea pharmadendrimers in antibacterial and antifungal nanotherapeutics.

Insights into the Antimicrobial Activities and Metabolomes of Aquimarina (Flavobacteriaceae, Bacteroidetes) Species from the Rare Marine Biosphere.

Two novel natural products, the polyketide cuniculene and the peptide antibiotic aquimarin, were recently discovered from the marine bacterial genus Aquimarina. However, the diversity of the secondary metabolite biosynthetic gene clusters (SM-BGCs) in Aquimarina genomes indicates a far greater biosynthetic potential. In this study, nine representative Aquimarina strains were tested for antimicrobial activity against diverse human-pathogenic and marine microorganisms and subjected to metabolomic and genomic profiling. We found an inhibitory activity of most Aquimarina strains against Candida glabrata and marine Vibrio and Alphaproteobacteria species. Aquimarina sp. Aq135 and Aquimarina muelleri crude extracts showed particularly promising antimicrobial activities, amongst others against methicillin-resistant Staphylococcus aureus. The metabolomic and functional genomic profiles of Aquimarina spp. followed similar patterns and were shaped by phylogeny. SM-BGC and metabolomics networks suggest the presence of novel polyketides and peptides, including cyclic depsipeptide-related compounds. Moreover, exploration of the 'Sponge Microbiome Project' dataset revealed that Aquimarina spp. possess low-abundance distributions worldwide across multiple marine biotopes. Our study emphasizes the relevance of this member of the microbial rare biosphere as a promising source of novel natural products. We predict that future metabologenomics studies of Aquimarina species will expand the spectrum of known secondary metabolites and bioactivities from marine ecosystems.

RNase R, a New Virulence Determinant of Streptococcus pneumoniae.

Pneumococcal infections have increasingly high mortality rates despite the availability of vaccines and antibiotics. Therefore, the identification of new virulence determinants and the understanding of the molecular mechanisms behind pathogenesis have become of paramount importance in the search of new targets for drug development. The exoribonuclease RNase R has been involved in virulence in a growing number of pathogens. In this work, we used Galleria mellonella as an infection model to demonstrate that the presence of RNase R increases the pneumococcus virulence. Larvae infected with the RNase R mutant show an increased expression level of antimicrobial peptides. Furthermore, they have a lower bacterial load in the hemolymph in the later stages of infection, leading to a higher survival rate of the larvae. Interestingly, pneumococci expressing RNase R show a sudden drop in bacterial numbers immediately after infection, resembling the eclipse phase observed after intravenous inoculation in mice. Concomitantly, we observed a lower number of mutant bacteria inside larval hemocytes and a higher susceptibility to oxidative stress when compared to the wild type. Together, our results indicate that RNase R is involved in the ability of pneumococci to evade the host immune response, probably by interfering with internalization and/or replication inside the larval hemocytes.

Third generation cephalosporin-resistant Klebsiella pneumoniae thriving in patients and in wastewater: what do they have in common?

BACKGROUND: Klebsiella pneumoniae are ubiquitous bacteria and recognized multidrug-resistant opportunistic pathogens that can be released into the environment, mainly through sewage, where they can survive even after wastewater treatment. A major question is if once released into wastewater, the selection of lineages missing clinically-relevant traits may occur. Wastewater (n = 25) and clinical (n = 34) 3rd generation cephalosporin-resistant K. pneumoniae isolates were compared based on phenotypic, genotypic and genomic analyses. RESULTS: Clinical and wastewater isolates were indistinguishable based on phenotypic and genotypic characterization. The analysis of whole genome sequences of 22 isolates showed that antibiotic and metal resistance or virulence genes, were associated with mobile genetic elements, mostly transposons, insertion sequences or integrative and conjugative elements. These features were variable among isolates, according to the respective genetic lineage rather than the origin. CONCLUSIONS: It is suggested that once acquired, clinically relevant features of K. pneumoniae may be preserved in wastewater, even after treatment. This evidence highlights the high capacity of K. pneumoniae for spreading through wastewater, enhancing the risks of transmission back to humans.

Marine Sponge and Octocoral-Associated Bacteria Show Versatile Secondary Metabolite Biosynthesis Potential and Antimicrobial Activities against Human Pathogens.

Marine microbiomes are prolific sources of bioactive natural products of potential pharmaceutical value. This study inspected two culture collections comprising 919 host-associated marine bacteria belonging to 55 genera and several thus-far unclassified lineages to identify isolates with potentially rich secondary metabolism and antimicrobial activities. Seventy representative isolates had their genomes mined for secondary metabolite biosynthetic gene clusters (SM-BGCs) and were screened for antimicrobial activities against four pathogenic bacteria and five pathogenic Candida strains. In total, 466 SM-BGCs were identified, with antimicrobial peptide- and polyketide synthase-related SM-BGCs being frequently detected. Only 38 SM-BGCs had similarities greater than 70% to SM-BGCs encoding known compounds, highlighting the potential biosynthetic novelty encoded by these genomes. Cross-streak assays showed that 33 of the 70 genome-sequenced isolates were active against at least one Candida species, while 44 isolates showed activity against at least one bacterial pathogen. Taxon-specific differences in antimicrobial activity among isolates suggested distinct molecules involved in antagonism against bacterial versus Candida pathogens. The here reported culture collections and genome-sequenced isolates constitute a valuable resource of understudied marine bacteria displaying antimicrobial activities and potential for the biosynthesis of novel secondary metabolites, holding promise for a future sustainable production of marine drug leads.

The Azurin-Derived Peptide CT-p19LC Exhibits Membrane-Active Properties and Induces Cancer Cell Death.

Peptides have been thoroughly studied as new therapeutic strategies for cancer treatment. In this work, we explored in vitro the anticancer potential of three novel peptides derived from the C-terminal of azurin, an anticancer bacterial protein produced by Pseudomonas aeruginosa. CT-p26, CT-p19 and CT-p19LC peptides were previously obtained through an in silico peptide design optimization process, CT-p19LC being the most promising as it presented higher hydrophobicity and solubility, positive total charge and, most importantly, greater propensity for anticancer activity. Therefore, in this study, through proliferation and apoptosis assays, CT-p19LC was tested in four cancer cell lines-A549, MCF-7, HeLa and HT-29-and in two non-cancer cell lines-16HBE14o- and MCF10A. Its membrane-targeting activity was further evaluated with zeta potential measurements and membrane order was assessed with the Laurdan probe. The results obtained demonstrated that CT-p19LC decreases cell viability through induction of cell death and binds to the plasma membrane of cancer cells, but not to non-cancer cells, making them less rigid. Overall, this study reveals that CT-p19LC is an auspicious selective anticancer peptide able to react with cancer cell membranes and cause effective action.

From the first touch to biofilm establishment by the human pathogen Candida glabrata: a genome-wide to nanoscale view.

Candida glabrata is an opportunistic pathogen that adheres to human epithelial mucosa and forms biofilm to cause persistent infections. In this work, Single-cell Force Spectroscopy (SCFS) was used to glimpse at the adhesive properties of C. glabrata as it interacts with clinically relevant surfaces, the first step towards biofilm formation. Following a genetic screening, RNA-sequencing revealed that half of the entire transcriptome of C. glabrata is remodeled upon biofilm formation, around 40% of which under the control of the transcription factors CgEfg1 and CgTec1. Using SCFS, it was possible to observe that CgEfg1, but not CgTec1, is necessary for the initial interaction of C. glabrata cells with both abiotic surfaces and epithelial cells, while both transcription factors orchestrate biofilm maturation. Overall, this study characterizes the network of transcription factors controlling massive transcriptional remodelling occurring from the initial cell-surface interaction to mature biofilm formation.

p28-functionalized PLGA nanoparticles loaded with gefitinib reduce tumor burden and metastases formation on lung cancer.

Lung cancer is still the main cause of cancer-related deaths worldwide. Its treatment generally includes surgical resection, immunotherapy, radiotherapy, and chemo-targeted therapies such as the application of tyrosine kinase inhibitors. Gefitinib (GEF) is one of them, but its poor solubility in gastric fluids weakens its bioavailability and therapeutic activity. In addition, like all other chemotherapy treatments, GEF administration can cause damage to healthy tissues. Therefore, the development of novel GEF delivery systems to increase its bioavailability and distribution in tumor site is highly demanded. Herein, an innovative strategy for GEF delivery, by functionalizing PLGA nanoparticles with p28 (p28-NPs), a cell-penetrating peptide derived from the bacterial protein azurin, was developed. Our data indicated that p28 potentiates the selective interaction of these nanosystems with A549 lung cancer cells (active targeting). Further p28-NPs delivering GEF (p28-NPs-GEF) were able to selectively reduce the metabolic activity of A549 cells, while no impact was observed in non-tumor cells (16HBE14o-). In vivo studies using A549 subcutaneous xenograft showed that p28-NPs-GEF reduced A549 primary tumor burden and lung metastases formation. Overall, the design of a p28-functionalized delivery nanosystem to effectively penetrate the membranes of cancer cells while deliver GEF could provide a new strategy to improve lung cancer therapy.

Burkholderia cenocepacia BCAM2418-induced antibody inhibits bacterial adhesion, confers protection to infection and enables identification of host glycans as adhesin targets.

Trimeric Autotransporter Adhesins (TAA) found in Gram-negative bacteria play a key role in virulence. This is the case of Burkholderia cepacia complex (Bcc), a group of related bacteria able to cause infections in patients with cystic fibrosis. These bacteria use TAAs, among other virulence factors, to bind to host protein receptors and their carbohydrate ligands. Blocking such contacts is an attractive approach to inhibit Bcc infections. In this study, using an antibody produced against the TAA BCAM2418 from the epidemic strain Burkholderia cenocepacia K56-2, we were able to uncover its roles as an adhesin and the type of host glycan structures that serve as recognition targets. The neutralisation of BCAM2418 was found to cause a reduction in the adhesion of the bacteria to bronchial cells and mucins. Moreover, in vivo studies have shown that the anti-BCAM2418 antibody exerted an inhibitory effect during infection in Galleria mellonella. Finally, inferred by glycan arrays, we were able to predict for the first time, host glycan epitopes for a TAA. We show that BCAM2418 favoured binding to 3'sialyl-3-fucosyllactose, histo-blood group A, α-(1,2)-linked Fuc-containing structures, Lewis structures and GM1 gangliosides. In addition, the glycan microarrays demonstrated similar specificities of Burkholderia species for their most intensely binding carbohydrates.

Burkholderia cenocepacia transcriptome during the early contacts with giant plasma membrane vesicles derived from live bronchial epithelial cells.

Burkholderia cenocepacia is known for its capacity of adherence and interaction with the host, causing severe opportunistic lung infections in cystic fibrosis patients. In this work we produced Giant Plasma Membrane Vesicles (GPMVs) from a bronchial epithelial cell line and validated their use as a cell-like alternative to investigate the steps involved in the adhesion process of B. cenocepacia. RNA-sequencing was performed and the analysis of the B. cenocepacia K56-2 transcriptome after the first contacts with the surface of host cells allowed the recognition of genes implicated in bacterial adaptation and virulence-associated functions. The sensing of host membranes led to a transcriptional shift that caused a cascade of metabolic and physiological adaptations to the host specific environment. Many of the differentially expressed genes encode proteins related with central metabolic pathways, transport systems, cellular processes, and virulence traits. The understanding of the changes in gene expression that occur in the early steps of infection can uncover new proteins implicated in B. cenocepacia-host cell adhesion, against which new blocking agents could be designed to control the progression of the infectious process.

Role of CgTpo4 in Polyamine and Antimicrobial Peptide Resistance: Determining Virulence in Candida glabrata.

Candida glabrata is an emerging fungal pathogen whose success depends on its ability to resist antifungal drugs but also to thrive against host defenses. In this study, the predicted multidrug transporter CgTpo4 (encoded by ORF CAGL0L10912g) is described as a new determinant of virulence in C. glabrata, using the infection model Galleria mellonella. The CgTPO4 gene was found to be required for the C. glabrata ability to kill G. mellonella. The transporter encoded by this gene is also necessary for antimicrobial peptide (AMP) resistance, specifically against histatin-5. Interestingly, G. mellonella's AMP expression was found to be strongly activated in response to C. glabrata infection, suggesting AMPs are a key antifungal defense. CgTpo4 was also found to be a plasma membrane exporter of polyamines, especially spermidine, suggesting that CgTpo4 is able to export polyamines and AMPs, thus conferring resistance to both stress agents. Altogether, this study presents the polyamine exporter CgTpo4 as a determinant of C. glabrata virulence, which acts by protecting the yeast cells from the overexpression of AMPs, deployed as a host defense mechanism.

Designing P. aeruginosa synthetic phages with reduced genomes.

In the era where antibiotic resistance is considered one of the major worldwide concerns, bacteriophages have emerged as a promising therapeutic approach to deal with this problem. Genetically engineered bacteriophages can enable enhanced anti-bacterial functionalities, but require cloning additional genes into the phage genomes, which might be challenging due to the DNA encapsulation capacity of a phage. To tackle this issue, we designed and assembled for the first time synthetic phages with smaller genomes by knocking out up to 48% of the genes encoding hypothetical proteins from the genome of the newly isolated Pseudomonas aeruginosa phage vB_PaeP_PE3. The antibacterial efficacy of the wild-type and the synthetic phages was assessed in vitro as well as in vivo using a Galleria mellonella infection model. Overall, both in vitro and in vivo studies revealed that the knock-outs made in phage genome do not impair the antibacterial properties of the synthetic phages, indicating that this could be a good strategy to clear space from phage genomes in order to enable the introduction of other genes of interest that can potentiate the future treatment of P. aeruginosa infections.

Bacterial protein azurin and derived peptides as potential anti-SARS-CoV-2 agents: insights from molecular docking and molecular dynamics simulations.

The current pandemic SARS-CoV-2 has wreaked havoc in the world, and neither drugs nor vaccine is available for the treatment of this disease. Thus, there is an immediate need for novel therapeutics that can combat this deadly infection. In this study, we report the therapeutic assessment of azurin and its peptides: p18 and p28 against the viral structural S-protein and non-structural 3CLpro and PLpro proteins. Among the analyzed complexes, azurin docked relatively well with the S2 domain of S-protein compared to the other viral proteins. The derived peptide p18 bound to the active site domain of the PLpro protein; however, in other complexes, lesser interactions were recorded. The second azurin derived peptide p28, fared the best among the docked proteins. p28 interacted with all the three viral proteins and the host ACE-2 receptor by forming several electrostatic and hydrogen bonds with the S-protein, 3CLpro, and PLpro. MD simulations indicated that p28 exhibited a strong affinity to S-protein and ACE-2 receptor, indicating a possibility of p28 as a protein-protein interaction inhibitor. Our data suggest that the p28 has potential as an anti-SARS-CoV-2 agent and can be further exploited to establish its validity in the treatment of current and future SARS-CoV crisis.Communicated by Ramaswamy H. Sarma.

A new regulator in the crossroads of oxidative stress resistance and virulence in Candida glabrata: The transcription factor CgTog1.

Candida glabrata is a prominent pathogenic yeast which exhibits a unique ability to survive the harsh environment of host immune cells. In this study, we describe the role of the transcription factor encoded by the gene CAGL0F09229g, here named CgTog1 after its Saccharomyces cerevisiae ortholog, as a new determinant of C. glabrata virulence. Interestingly, Tog1 is absent in the other clinically relevant Candida species (C. albicans, C. parapsilosis, C. tropicalis, C. auris), being exclusive to C. glabrata. CgTog1 was found to be required for oxidative stress resistance and for the modulation of reactive oxygen species inside C. glabrata cells. Also, CgTog1 was observed to be a nuclear protein, whose activity up-regulates the expression of 147 genes and represses 112 genes in C. glabrata cells exposed to H2O2, as revealed through RNA-seq-based transcriptomics analysis. Given the importance of oxidative stress response in the resistance to host immune cells, the effect of CgTOG1 expression in yeast survival upon phagocytosis by Galleria mellonella hemocytes was evaluated, leading to the identification of CgTog1 as a determinant of yeast survival upon phagocytosis. Interestingly, CgTog1 targets include many whose expression changes in C. glabrata cells after engulfment by macrophages, including those involved in reprogrammed carbon metabolism, glyoxylate cycle and fatty acid degradation. In summary, CgTog1 is a new and specific regulator of virulence in C. glabrata, contributing to oxidative stress resistance and survival upon phagocytosis by host immune cells.

Conditioned Medium From Azurin-Expressing Human Mesenchymal Stromal Cells Demonstrates Antitumor Activity Against Breast and Lung Cancer Cell Lines.

Recently, cell-based therapies have been explored as a strategy to enhance the specificity of anticancer therapeutic agents. In this perspective, human mesenchymal stromal cells (MSC) hold a promising future as cell delivery systems for anticancer proteins due to their unique biological features. In this study, we engineered human MSC to secrete a human codon-optimized version of azurin (hazu), a bacterial protein that has demonstrated anticancer activity toward different cancer models both in vitro and in vivo. To this end, microporation was used to deliver plasmid DNA encoding azurin into MSC derived from bone marrow (BM) and umbilical cord matrix (UCM), leading to expression and secretion of hazu to the conditioned medium (CM). Engineered hazu-MSC were shown to preserve tumor tropism toward breast (MCF-7) and lung (A549) cancer cell lines, comparable to non-modified MSC. Azurin was detected in the CM of transfected MSC and, upon treatment with hazu-MSC-CM, we observed a decrease in cancer cell proliferation, migration, and invasion, and an increase in cell death for both cancer cell lines. Moreover, expression of azurin caused no changes in MSC expression profile of cytokines relevant in the context of cancer progression, thus suggesting that the antitumoral effects induced by hazu-MSC secretome might be due to the presence of azurin independently. In conclusion, data shown herein indicate that MSC-produced azurin in a CM configuration elicits an anticancer effect.

Phenotypic characterization of trimeric autotransporter adhesin-defective bcaC mutant of Burkholderia cenocepacia: cross-talk towards the histidine kinase BCAM0218.

Burkholderia cenocepacia is a virulent species belonging to the Burkholderia cepacia complex (Bcc) and one of the most problematic agents of chronic lung infection in cystic fibrosis patients. B. cenocepacia possesses a large panel of virulence traits that include trimeric autotransporter adhesins (TAAs). Such proteins are obligate homotrimeric anchored in the outer membrane. They are players in the adhesion events that occur between bacteria and biotic/abiotic surfaces. In this study, we constructed two insertional-mutants for TAA bcaC and Histidine kinase (HK) BCAM0218 genes, which are clustered together within the B. cenocepacia K56-2 TAA cluster. The bcaC-mutant affects B. cenocepacia adhesion to extracellular matrix proteins and red blood cells hemagglutination. BcaC contributes to enhancing B. cenocepacia K56-2 adhesion to bronchial epithelial cells. The expression of bcaC seems to affect biofilm formation negatively. Due to a BCAM0218 disruption, the bcaC expression increases significantly, indicating that they are functionally linked. The overexpression of bcaC in the BCAM0218-mutant background rescues at least part of the BcaC functions. Altogether, these findings reveal the multifunctionality of BcaC as a novel B. cenocepacia K56-2 virulence factor and postulate the involvement of a sensor HK (BCAM0218) in the control of this TAA gene.