Staphylococcus aureus forms biofilms consisting of cells embedded in a matrix made of proteins, polysaccharides, lipids, and extracellular DNA (eDNA). Biofilm-associated infections are difficult to ...treat and can promote antibiotic resistance, resulting in negative healthcare outcomes. eDNA within the matrix contributes to the stability, growth, and immune-evasive properties of S. aureus biofilms. eDNA is released by autolysis, which is mediated by murein hydrolases that access the cell wall via membrane pores formed by holin-like proteins. The eDNA content of S. aureus biofilms varies among individual strains and is influenced by environmental conditions, including the presence of antibiotics. eDNA plays an important role in biofilm development and structure by acting as an electrostatic net that facilitates protein-cell and cell-cell interactions. Because of eDNA’s structural importance in biofilms and its ubiquitous presence among S. aureus isolates, it is a potential target for therapeutics. Treatment of biofilms with DNase can eradicate or drastically reduce them in size. Additionally, antibodies that target DNABII proteins, which bind to and stabilize eDNA, can also disperse biofilms. This review discusses the recent literature on the release, structure, and function of eDNA in S. aureus biofilms, in addition to a discussion of potential avenues for targeting eDNA for biofilm eradication.
The aim of this study was to assess the chemical composition, antioxidant, antimicrobial and antibiofilm activity of the
essential oil. Changes in the biofilm profile of
and
were studied using ...MALDI-TOF MS Biotyper on glass and wooden surfaces. The molecular differences of biofilms in different days were observed as well. The major volatile compounds of the coriander essential oil in the present study were
-linalool 66.07%. Coriander essential oil radical scavenging activity was 51.05% of inhibition. Coriander essential oil expressed the strongest antibacterial activity against
followed by
and
The strongest antibiofilm activity of the coriander essential oil was found against S.
A clearly differentiated branch was obtained for early growth variants of
in case of planktonic cells and all experimental groups and time span can be reported for the grouping pattern of
preferentially when comparing to the media matrix, but without clear differences among variants. The results indicate that coriander was effective against the tested
in the vapor phase after 14 days with MID
367.19 and MID
445.92 µL/L of air.
Aeromonas veronii is an important aquatic zoonotic pathogen in humans and animals. In recent years, extracellular proteins from bacteria have been found to be the major pathogenic factors for aquatic ...animals. The aim of this study was to systematically analyze the extracellular proteins of nine sources of A. veronii and the effects of hisJ on virulence. We screened only the common proteins from nine different sources of A. veronii by liquid chromatography−tandem mass spectrometry and identified the gene hisJ. We then constructed ΔhisJ (deleted) and C‐hisJ (complemented) variants of A. veronii TH0426 to assess the biological function of hisJ. While the ΔhisJ strain did not show altered growth (P > 0.05), we observed that it had reduced colony formation and biofilm formation and reduced adhesion to and invasion of epithelioma papulosum cyprini cells by 2.0‐, 1.9‐, and 10.8‐fold, respectively. Additionally, infection experiments on zebrafish and mouse infection experiments showed that the virulence of the ΔhisJ strain was decreased by 865‐fold (P < 0.001) compared with the wild‐type strain; virulence of the complemented C‐hisJ strain was reduced only 2.8‐fold. Furthermore, in the context of hisJ deletion, flagella of A. veronii TH0426 were easily detached and the expression of virulence genes was downregulated. A persistence test (of bacterial colonies in crucian carp) showed that the number of bacteria in the immune organs of the ΔhisJ‐infected group was lower than that in the wild‐type–infected group. Overall, these results show that hisJ affects flagellar shedding, virulence, biofilm formation, adhesion, and invasion of A. veronii TH0426, and that hisJ is closely associated with virulence and plays a crucial role in its pathogenicity of A. veronii TH0426.
Using extracellular products of Aeromonas veronii TH0426 strain closely associated with its virulence factors and pathogenicity, we determined, from nine A. veronii strains isolated from different sources, that the common protein‐coding gene hisJ is associated with pathogenesis. To clarify the function of hisJ, we constructed ∆hisJ (hisJ deleted) and C‐hisJ (hisJ complemented) strains and performed preliminary analyses of their effects on pathogenicity. Our study provides a theoretical basis for elucidating the pathogenesis of A. veronii TH0426.
Xylem-limited bacterial pathogens cause some of the most destructive plant diseases. Though imposed measures to control these pathogens are generally ineffective, even among susceptible taxa, some ...hosts can limit bacterial loads and symptom expression. Mechanisms by which this resistance is achieved are poorly understood. In particular, it is still unknown how differences in vascular structure may influence biofilm growth and spread within a host. To address this, we developed a novel theoretical framework to describe biofilm behaviour within xylem vessels, adopting a polymer-based modelling approach. We then parameterised the model to investigate the relevance of xylem vessel diameters on Xylella fastidiosa resistance among olive cultivars. The functionality of all vessels was severely reduced under infection, with hydraulic flow reductions of 2–3 orders of magnitude. However, results suggest wider vessels act as biofilm incubators; allowing biofilms to develop over a long time while still transporting them through the vasculature. By contrast, thinner vessels become blocked much earlier, limiting biofilm spread. Using experimental data on vessel diameter distributions, we were able to determine that a mechanism of resistance in the olive cultivar Leccino is a relatively low abundance of the widest vessels, limiting X. fastidiosa spread.
Small molecular organic acids (SMOAs) in root exudates are critical for plant–microbe interaction, especially under environmental stresses. However, the dominant organic acids driving the process and ...promoting the colonization are unclear. Here, using a target metabolomics, 20 main SMOAs of rice root exudates were identified and analyzed in control and 10 mg/L thiamethoxam-treated groups. The composition of these SMOAs differed significantly between the two treatments. Among which, malic acid, citric acid, succinic acid, and proline induced a chemotactic response, swimming ability, and biofilm formation of Enterobacter cloacae TMX-6 in a dose-dependent manner. The maximal chemotactic response of TMX-6 was induced by proline at 10 mg/L, and a strong chemotactic response was even observed at 0.01 mg/L. The recruitment assay confirmed that the addition of these four compounds promoted the colonization of TMX-6. The results provide insight for directional regulation of plant–microbe interactions for beneficial outcomes.
Filamentous phage impact biofilm development, stress tolerance, virulence, biofilm dispersal, and colony variants. Previously, we identified 137
PA14 mutants with more than threefold enhanced and 88 ...mutants with more than 10-fold reduced biofilm formation by screening 5850 transposon mutants (
: e1000483, 2009). Here, we characterized the function of one of these 225 mutations,
(PA14_58350), in regard to biofilm formation. DppA1 is a substrate-binding protein (SBP) involved in peptide utilization via the DppBCDF ABC transporter system. We show that compared to the wild-type strain, inactivating
led to 68-fold less biofilm formation in a static model and abolished biofilm formation in flow cells. Moreover, the
mutant had a delay in swarming and produced 20-fold less small-colony variants, and both biofilm formation and swarming were complemented by producing DppA1. A whole-transcriptome analysis showed that only 10 bacteriophage Pf5 genes were significantly induced in the biofilm cells of the
mutant compared to the wild-type strain, and inactivation of
resulted in a 600-fold increase in Pf5 excision and a million-fold increase in phage production. As expected, inactivating Pf5 genes PA0720 and PA0723 increased biofilm formation substantially. Inactivation of DppA1 also reduced growth (due to cell lysis). Hence, DppA1 increases biofilm formation by repressing Pf5 prophage.
The opportunistic human pathogen Pseudomonas aeruginosa causes chronic infections that involve multicellular aggregates called biofilms. Biofilm formation is modulated by the host environment and the ...presence of cues and/or signals, likely affecting the pool of the bacterial second messenger cyclic diguanylate monophosphate (c-di-GMP). The manganese ion Mn
is a divalent metal cation that is essential for pathogenic bacterial survival and replication during the infection in a host organism. In this study, we investigated how Mn
alters P. aeruginosa biofilm formation via the regulation of c-di-GMP levels. Exposure to Mn
was found to temporally enhance attachment but impair subsequent biofilm development, apparent by reduced biofilm biomass accumulation and lack of microcolony formation due to the induction of dispersion. Moreover, exposure to Mn
coincided with reduced production of the exopolysaccharides Psl and Pel, decreased transcriptional abundance of
and
, and decreased levels of c-di-GMP. To determine whether the effect of Mn
was linked to the activation of phosphodiesterases (PDEs), we screened several PDE mutants for Mn
-dependent phenotypes (attachment and polysaccharide production) as well as PDE activity. The screen revealed that the PDE RbdA is activated by Mn
and is responsible for Mn
-dependent attachment, inhibition of Psl production, and dispersion. Taken together, our findings suggest Mn
is an environmental inhibitor of P. aeruginosa biofilm development that acts through the PDE RbdA to modulate c-di-GMP levels, thereby impeding polysaccharide production and biofilm formation but enhancing dispersion.
While diverse environmental conditions such as the availability of metal ions have been shown to affect biofilm development, little is known about the mechanism. Here, we demonstrate that Mn
affects Pseudomonas aeruginosa biofilm development by stimulating phosphodiesterase RbdA activity to reduce the signaling molecule c-di-GMP levels, thereby hindering polysaccharide production and biofilm formation but enhancing dispersion. Our findings demonstrate that Mn
acts as an environmental inhibitor of P. aeruginosa biofilms, further suggesting manganese to be a promising new antibiofilm factor.
Biofilm formation and capsule production are known microbial strategies used by bacterial pathogens to survive adverse conditions in the hospital environment. The relative importance of these ...strategies individually is unexplored. This project aims to compare the contributory roles of biofilm formation and capsule production in bacterial survival on hospital surfaces.
Representative strains of bacterial species often causing hospital-acquired infections were selected, including Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa. The importance of biofilm formation and capsule production on bacterial survival was evaluated by comparing capsule-positive wild-type and capsule-deficient mutant strains, and biofilm and planktonic growth modes respectively, against three adverse hospital conditions, including desiccation, benzalkonium chloride disinfection and ultraviolet (UV) radiation. Bacterial survival was quantitatively assessed using colony-forming unit (CFU) enumeration and the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay and qualitatively by scanning electron microscopy (SEM). Correlations between capsule production and biofilm formation were further investigated.
Biofilm formation contributed significantly to bacterial survival on hospital surface simulators, mediating high resistance to desiccation, benzalkonium chloride disinfection and UV radiation. The role of capsule production was minor and species-specific; encapsulated A. baumannii but not K. pneumoniae cells demonstrated slightly increased resistance to desiccation, and neither showed enhanced resistance to benzalkonium chloride. Interestingly, capsule production sensitized K. pneumoniae and A. baumannii to UV radiation. The loss of capsule in K. pneumoniae and A. baumannii enhanced biofilm formation, possibly by increasing cell surface hydrophobicity.
In summary, this study confirms the crucial role of biofilm formation in bacterial survival on hospital surfaces. Conversely, encapsulation plays a relatively minor role and may even negatively impact bacterial biofilm formation and hospital survival.
Diabetes mellitus is a chronic disease that is associated with increased morbidity and mortality. Unfortunately, foot ulcers and amputations due to diabetes are very common in developing countries. ...The purpose of this study was to characterize the clinical presentation of diabetic foot ulcer (DFU) infections, isolate the causative agent, and analyze the biofilm formation and distribution of biofilm-related genes among isolated Staphylococci.
The study included 100 diabetic patients suffering from DFUs attending Assiut University Hospital. Swabs were collected and antimicrobial susceptibility testing of the isolates was performed. Biofilm formation was tested phenotypically among staphylococcal isolates and the frequency of different biofilm genes was analyzed by PCR. Clinical presentations of diabetic foot ulcers were correlated with bacterial genetic characteristics. Spa types were determined using DNA Gear-a software.
Microbiological analysis showed that 94/100 of the DFUs were positive for bacterial growth. The majority of infections were polymicrobial (54%, n=54/100). Staphylococci were the most commonly detected organisms, of which
37.5% (n=24/64),
23.4% (n=15/64), S.
34.3% (n=22/64) and other CNS 4.7% (n=3/64). Interestingly, co-infection with more than one species of Staphylococci was observed in 17.1% (n=11/64) of samples. A high level of antibiotic resistance was observed, where 78.1% (n=50/64) of
were multidrug-resistant (MDR). Phenotypic detection showed that all isolated Staphylococci were biofilm-formers with different grades. Analysis of biofilm-forming genes among Staphylococci showed that the most predominant genes were icaD,
, and
. Isolates with a higher number of biofilm-related genes were associated with strong biofilm formation. Sequencing of the spa gene in
showed that our isolates represent a collection of 17 different spa types.
The majority of DFUs in our hospital are polymicrobial. Staphylococci other than
are major contributors to infected DFUs. MDR and biofilm formation are marked among isolates, which is paralleled by the presence of different categories of virulence-related genes. All severely infected wounds were associated with either strong or intermediate biofilm formers. The severity of DFU is directly related to the number of biofilm genes.
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