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
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.
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.
Despite its low abundance, phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) is a key modulator of membrane-associated signaling events in eukaryotic cells. Temporal and spatial regulation of ...PI(4,5)P2 concentration can achieve localized increases in the levels of this lipid, which are crucial for the activation or recruitment of peripheral proteins to the plasma membrane. The recent observation of the dramatic impact of physiological divalent cation concentrations on PI(4,5)P2 clustering, suggests that protein anchoring to the plasma membrane through PI(4,5)P2 is likely not defined solely by a simple (monomeric PI(4,5)P2)/(protein bound PI(4,5)P2) equilibrium, but instead depends on complex protein interactions with PI(4,5)P2 clusters. The insertion of PI(4,5)P2-binding proteins within these clusters can putatively modulate protein–protein interactions in the membrane, but the relevance of such effects is largely unknown. In this work, we characterized the impact of Ca2+ on the organization and protein–protein interactions of PI(4,5)P2-binding proteins. We show that, in giant unilamellar vesicles presenting PI(4,5)P2, the membrane diffusion properties of pleckstrin homology (PH) domains tagged with a yellow fluorescent protein (YFP) are affected by the presence of Ca2+, suggesting direct interactions between the protein and PI(4,5)P2 clusters. Importantly, PH-YFP is found to dimerize in the membrane in the absence of Ca2+. This oligomerization is inhibited in the presence of physiological concentrations of the divalent cation. These results confirm that cation-dependent PI(4,5)P2 clustering promotes interactions between PI(4,5)P2-binding proteins and has the potential to dramatically influence the organization and downstream interactions of PI(4,5)P2-binding proteins in the plasma membrane.
, one of the most common pathogens found in hospital-acquired infections, is often resistant to multiple antibiotics. In fact, multidrug-resistant (MDR)
producing KPC or OXA-48-like carbapenemases ...are recognized as a serious global health threat. In this sense, we evaluated the virulence of
KPC(+) or OXA-48(+) aiming at potential antimicrobial therapeutics.
carbapenemase (KPC) and the expanded-spectrum oxacillinase OXA-48 isolates were obtained from patients treated in medical care units in Lisbon, Portugal. The virulence potential of the
clinical isolates was tested using the
model. For that,
larvae were inoculated using patients KPC(+) and OXA-48(+) isolates. Using this in vivo model, the KPC(+)
isolates showed to be, on average, more virulent than OXA-48(+). Virulence was found attenuated when a low bacterial inoculum (one magnitude lower) was tested. In addition, we also report the use of a synthetic polycationic oligomer (L-OEI-h) as a potential antimicrobial agent to fight infectious diseases caused by MDR bacteria. L-OEI-h has a broad-spectrum antibacterial activity and exerts a significantly bactericidal activity within the first 5-30 min treatment, causing lysis of the cytoplasmic membrane. Importantly, the polycationic oligomer showed low toxicity against in vitro models and no visible cytotoxicity (measured by survival and health index) was noted on the in vivo model
, thus L-OEI-h is foreseen as a promising polymer therapeutic for the treatment of MDR
infections.
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
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.
Persistence and virulence of
infections are multifactorial phenomena, whose understanding is crucial to design more suitable therapeutic strategies. In this study, the putative multidrug transporter ...CgDtr1, encoded by ORF
, is identified as a determinant of
virulence in the infection model
.
deletion is shown to decrease the ability to kill
larvae by decreasing
ability to proliferate in
hemolymph, and to tolerate the action of hemocytes. The possible role of CgDtr1 in the resistance to several stress factors that underlie death induced by phagocytosis was assessed.
was found to confer resistance to oxidative and acetic acid stress. Consistently, CgDtr1 was found to be a plasma membrane acetic acid exporter, relieving the stress induced upon
cells within hemocytes, and thus enabling increased proliferation and virulence against
larvae.
Summary
Trimeric autotransporter adhesins (
TAAs
) are bacterial surface proteins that fulfil important functions in pathogenic
G
ram‐negative bacteria. Prominent examples of
TAAs
are found in
B
...urkholderia cepacia
complex, a group of bacterial species causing severe infections in patients with cystic fibrosis. While there is strong evidence that
Burkholderia cenocepacia
TAAs
mediate adhesion, aggregation and colonization of the respiratory epithelium, we still know very little about the molecular mechanisms behind these interactions. Here, we use single‐molecule atomic force microscopy to unravel the binding mechanism of
BCAM
0224, a prototype
TAA
from
B
. cenocepacia
K
56‐2. We show that the adhesin forms homophilic trans‐interactions engaged in bacterial aggregation, and that it behaves as a spring capable to withstand high forces. We also find that
BCAM
0224 binds collagen, a major extracellular component of host epithelia. Both homophilic and heterophilic interactions display low binding affinity, which could be important for epithelium colonization. We then demonstrate that
BCAM
0224 recognizes receptors on living pneumocytes, and leads to the formation of membrane tethers that may play a role in promoting adhesion. Collectively, our results show that
BCAM
0224 is a multifunctional adhesin endowed with remarkable binding properties, which may represent a general mechanism among
TAAs
for strengthening bacterial adhesion.
RICs are a family of bacterial proteins involved in the repair of iron centers containing proteins damaged by the antimicrobial reactive species liberated by the innate immune system of infected ...hosts. Staphylococcus aureus is a human pathogen with increasing antibiotic resistance that also contains a RIC-like protein. In this work, we show that the survival of S. aureus within macrophages decreases upon inactivation of ric, and that the viability was restored to levels similar to the wild-type strain by reintroduction of ric via in trans complementation. Importantly, in macrophages that do not produce reactive oxygen species, the lower survival of the ric mutant was no longer observed. In lung epithelial cells, the intracellular viability of the S. aureus ric mutant was also shown to be lower than that of the wild-type. The wax moth larvae Galleria mellonella infected with S. aureus ric mutant presented an approximately 2.5-times higher survival when compared to the wild-type strain. Moreover, significantly lower bacterial loads were determined in the larvae hemolymph infected with strains not expressing ric, and complementation assays confirmed that this behavior was related to RIC. Furthermore, expression of the S. aureus ric gene within the larvae increased along the course of infection with a ~20-fold increase after 8 h of infection. Altogether, the data show that RIC is important for the virulence of S. aureus.
Members of the trimeric autotransporter adhesin (TAA) family play a crucial role in adhesion of Gram-negative pathogens to host cells. Moreover, these proteins are multifunctional virulence factors ...involved in several other biological traits, including invasion into host cells and evasion of the host immune system. In cystic fibrosis epidemic Burkholderia cenocepacia strain J2315, we identified a unique TAA (BCAM0224)-encoding gene, previously described as being implicated in virulence. Here, we characterized this multifunctional protein, trying to establish its role in B. cenocepacia pathogenicity. We show that BCAM0224 occurs on the bacterial surface and adopts a trimeric conformation. Furthermore, we demonstrated that BCAM0224 is needed for earlier stages of biofilm formation and is required for swarming motility. In addition, BCAM0224 plays an important role in evasion of the human innate immune system, providing resistance against the bactericidal activity of serum via the complement classical pathway. Finally, BCAM0224 mediates bacterial adhesion to and invasion of cultured human bronchial epithelial cells. Together, these data reveal the high versatility of the BCAM0224 protein as a virulence factor in the pathogenic bacterium B. cenocepacia.
is a central transcriptional regulator of filamentation that is an important virulence factor of
. This study serves to assess
the applicability of the anti-
2'-
MethylRNA oligomer for inhibiting
...filamentation and to attenuate candidiasis, using the
model. For that, larvae infected with a lethal concentration of
cells were treated with a single dose and with a double dose of the anti-
2'
Me oligomer (at 40 and 100 nM). The anti-
2'OMe oligomer toxicity and effect on larvae survival was evaluated. No evidence of anti-
2'OMe oligomer toxicity was observed and the treatment with double dose of 2'OMe oligomer empowered larvae survival over 24 h (by 90%-100%) and prolonged its efficacy until 72 h of infection (by 30%). Undoubtedly, this work validates the
therapeutic potential of anti-
2'
Me oligomer for controlling
infections.
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