Punica granatum sarcotesta lectin (PgTeL) impairs growth, structure, viability, aggregation, and biofilm formation ability of Staphylococcus aureus clinical isolates

Purification, Characterization, and Assessment of Antimicrobial Activity and Toxicity of Portulaca elatior Leaf Lectin (PeLL)

Lectins are carbohydrate-binding proteins with several bioactivities, including antimicrobial properties. Portulaca elatior is a species found at Brazilian Caatinga and data on the biochemical composition of this plant are scarce. The present work describes the purification of P. elatior leaf lectin (PeLL) as well as the assessment of its antimicrobial activity and toxicity. PeLL, isolated by chromatography on a chitin column, had native liquid charge and subunit composition evaluated by electrophoresis. Hemagglutinating activity (HA) of PeLL was determined in the presence of carbohydrates or divalent cations, as well as after heating and incubation at different pH values. Changes in the lectin conformation were monitored by evaluating intrinsic tryptophan fluorescence and using the extrinsic probe bis-ANS. Antimicrobial activity was evaluated against Pectobacterium strains and Candida species. The minimal inhibitory (MIC), bactericidal (MBC), and fungicidal (MFC) concentrations were determined. Finally, PeLL was evaluated for in vitro hemolytic activity in human erythrocytes and in vivo acute toxicity in mice (5 and 10 mg/kg b.w. per os). PeLL (pI 5.4; 20 kDa) had its HA was inhibited by mannose, galactose, Ca²⁺, Mg²⁺, and Mn²⁺. PeLL HA was resistant to heating at 100 °C, although conformational changes were detected. PeLL was more active in the acidic pH range, in which no conformational changes were observed. The lectin presented MIC and MBC of 0.185 and 0.74 μg/mL for all Pectobacterium strains, respectively; MIC of 1.48 μg/mL for C. albicans, C. tropicalis, and C. krusei; MIC and MFC of 0.74 and 2.96 μg/mL for C. parapsilosis. No hemolytic activity or signs of acute toxicity were observed in the mice. In conclusion, a new, low-toxic, and thermostable lectin was isolated from P. elatior leaves, being the first plant compound to show antibacterial activity against Pectobacterium.

Control Measurements of Escherichia coli Biofilm: A Review

Escherichia coli (E. coli) is a common pathogen that causes diarrhea in humans and animals. In particular, E. coli can easily form biofilm on the surface of living or non-living carriers, which can lead to the cross-contamination of food. This review mainly summarizes the formation process of E. coli biofilm, the prevalence of biofilm in the food industry, and inhibition methods of E. coli biofilm, including chemical and physical methods, and inhibition by bioactive extracts from plants and animals. This review aims to provide a basis for the prevention and control of E. coli biofilm in the food industry.

A review on the antimicrobial properties of lectins

Lectins are biologically versatile biomolecules with remarkable antimicrobial effects, notably against bacteria, fungi and protozoa, in addition to modulating host immunity. For this, the lectins bind to carbohydrates on the surface of the pathogen, which can cause damage to the cell wall and prevent the attachment of microorganisms to host cells. Thus, this study intends to review the biological activities of lectins, with an emphasis on antimicrobial activity. Lectins of plant stood out for its antimicrobial effects, demonstrating that they act against a variety of strains, where in vitro were able to inhibit their development and affect their morphology. In vivo, they modulated host immunity, signaling and activating defense cells. Some of these lectins were capable to modulate the action of antibiotics, indicating their potential to minimize the antibiotic resistance. The results suggest that lectins have antimicrobial activity with potential to be used in drug development.

Antibacterial and antitumor activities of a lectin-rich preparation from Microgramma vacciniifolia rhizome

The rhizome of Microgramma vacciniifolia contains a lectin (carbohydrate-binding protein) called MvRL. Studies demonstrated that a MvRL-rich fraction did not show in vivo genotoxicity and acute toxicity in mice. This study aimed to evaluate the MvRL-rich fraction from M. vacciniifolia rhizome for antibacterial activity in vitro and in vivo as well as antitumor effect in vivo using the Ehrlich carcinoma model in mice. The fraction showed antibacterial activity against Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus with minimal inhibitory concentrations ranging from 31.2 to 125.0 ​μg/mL and minimal bactericidal concentrations from 62.5 to 200 ​μg/mL. The fraction was also effective in vivo against infection caused by these bacteria on Tenebrio molitor larvae considering the parameters evaluated. In regard to the antitumor activity, the treatments of Ehrlich carcinoma-bearing mice with the fraction at 100 and 200 ​mg/kg per os resulted in 62.58% and 75.43% of tumor inhibition, respectively. In conclusion, the MvRL-rich fraction showed in vivo antibacterial and antitumor activities and thus can be considered as an alternative of natural origin for the development of candidates for therapy.

•

The rhizome of Microgramma vacciniifolia contains a lectin called MvRL.

•

MvRL-rich fraction showed antibacterial activity.

•

The fraction was also effective in vivo against bacterial infection.

•

MvRL-rich fraction causedn 62.58–75.43% inhibition of Erlich carcinoma.

Quantum dots conjugated to lectins from Schinus terebinthifolia leaves (SteLL) and Punica granatum sarcotesta (PgTeL) as potential fluorescent nanotools for investigating Cryptococcus neoformans

This study reports the development of conjugates based on quantum dots (QD)s and lectins from Schinus terebinthifolia leaves (SteLL) and Punica granatum sarcotesta (PgTeL). Cryptococcus neoformans cells were chosen to evaluate the efficiency of the conjugates. Lectins were conjugated to QDs via adsorption, and the optical parameters (emission and absorption) were monitored. Lectin stability in the conjugates towards denaturing agents was investigated via fluorometry. The conjugation was evaluated using fluorescence microplate (FMA) and hemagglutination (HA) assays. The labeling of the C. neoformans cell surface was quantified using flow cytometry and observed via fluorescence microscopy. The QDs-SteLL and QDs-PgTeL conjugates, obtained at pH 7.0 and 8.0, respectively, showed the maintenance of colloidal and optical properties. FMA confirmed the conjugation, and the HA assay indicated that the lectin carbohydrate-binding ability was preserved after conjugation. SteLL and PgTeL showed stability towards high urea concentrations and heating. Conjugates labeled over 90% of C. neoformans cells as observed via flow cytometry and confirmed through fluorescence microscopy. C. neoformans labeling by conjugates was inhibited by glycoproteins, suggesting specific interactions through the lectin carbohydrate-binding site. Thus, an effective protocol for the conjugation of SteLL or PgTeL with QDs was proposed, yielding new nanoprobes useful for glycobiological studies.

Antibacterial effects of the lectin from pomegranate sarcotesta (PgTeL) against Listeria monocytogenes

AIMS

To investigate the effects of the lectin from Punica granatum sarcotesta (PgTeL) on growth, viability, cell structure, biofilm formation and chitinase activity of Listeria monocytogenes. In addition, the effect of PgTeL on the adhesion and invasion of human cells (HeLa) was determined.

METHODS AND RESULTS

PgTeL showed bacteriostatic and bactericidal effects on the strains L. monocytogenes N53-1 and EGD-e, causing morphometric alterations, cell aggregation, strong deformation and cell disruption. PgTeL inhibited biofilm formation by EGD-e and N53-1 and also interfered with the adhesion and invasion processes of EGD-e and N53-1 in HeLa cells. Finally, the chitinase activity of L. monocytogenes EGD-e was reduced in the presence of PgTeL, which can be involved in the inhibition of adhesion process.

CONCLUSION

PgTeL is an antibacterial agent against L. monocytogenes, inhibiting growth and promoting cell death, as well as impairing biofilm formation and bacterial adhesion and invasion into human cells.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results stimulate future investigations on the potential of PgTeL for protection of contamination in food products.

Mycobacterium Von Willebrand factor protein MSMEG_3641 is involved in biofilm formation and intracellular survival

Aim: Mycobacterium tuberculosis in vitro biofilm is associated with the virulence and persistence capability. Our aim is to delineate factors involved in biofilms development. Materials & methods: We performed transposon mutants screen and found that mutation of MSMEG_3641, a homolog of M. tuberculosis Rv1836c, can change M. smegmatis colony morphology and biofilm. Results: MSMEG_3641 contains a vWA domain that is highly conserved among Mycobacteria. The phenotypes of MSMEG_3641 mutants include disrupted biofilm, weakened migration ability and changed colony morphology. All phenotypes might be contributed to the enhanced cell wall permeability and declined cell aggregation ability. Conclusion: To our knowledge, this is the first report concerning the mycobacteria Von Willebrand factor domain function, especially in colony morphology and biofilm development.

Anti-staphylococcal effects of Myracrodruon urundeuva lectins on nonresistant and multidrug resistant isolates

AIMS

To evaluate the anti-staphylococcal effects of lectins isolated from bark (MuBL), heartwood (MuHL) and leaves (MuLL) of Myracrodruon urundeuva.

METHODS AND RESULTS

The lectins were evaluated for: effects on growth, aggregation, haemolytic activity and biofilm-forming ability of Staphylococcus aureus clinical isolates nonresistant (8325-4) and multidrug resistant (LAC USA300); interference with the expression of virulence genes (hla, rnaIII and spa) of the Agr system of S. aureus; and synergistic effect with the antibiotics cefoxitin and cefotaxime. MuBL, MuHL and MuLL reduced growth (minimal inhibitory concentration (MIC): 12·5-50 µg ml^-1 ) and viability (minimal bactericidal concentration (MBC): 100 µg ml^-1 ) of 8325-4 and LAC USA300 cells. MuLL (at ½MIC and MIC) reduced LAC USA300 agglutination. The lectins did not interfere with haemolytic activity and expression of hla, rnaIII and spa genes. Only MuHL was able to reduce the biofilm production by 8325-4 (50-400 µg ml^-1 ) and LAC USA300 (400 µg ml^-1 ).

CONCLUSION

The M. urundeuva lectins showed antibacterial activity against nonresistant and resistant clinical isolates of S. aureus and synergistic effects with antibiotics in reducing growth and biofilm formation.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work reports bioactive molecules capable of acting as anti-staphylococcal agents, since there are increasing reports of multiresistant isolates of this bacterium.

Schinus terebinthifolia leaf lectin (SteLL) has anti-infective action and modulates the response of Staphylococcus aureus-infected macrophages

Staphylococcus aureus is recognized as an important pathogen causing a wide spectrum of diseases. Here we examined the antimicrobial effects of the lectin isolated from leaves of Schinus terebinthifolia Raddi (SteLL) against S. aureus using in vitro assays and an infection model based on Galleria mellonella larvae. The actions of SteLL on mice macrophages and S. aureus-infected macrophages were also evaluated. SteLL at 16 µg/mL (8 × MIC) increased cell mass and DNA content of S. aureus in relation to untreated bacteria, suggesting that SteLL impairs cell division. Unlike ciprofloxacin, SteLL did not induce the expression of recA, crucial for DNA repair through SOS response. The antimicrobial action of SteLL was partially inhibited by 50 mM N-acetylglucosamine. SteLL reduced staphyloxathin production and increased ciprofloxacin activity towards S. aureus. This lectin also improved the survival of G. mellonella larvae infected with S. aureus. Furthermore, SteLL induced the release of cytokines (IL-6, IL-10, IL-17A, and TNF-α), nitric oxide and superoxide anion by macrophagens. The lectin improved the bactericidal action of macrophages towards S. aureus; while the expression of IL-17A and IFN-γ was downregulated in infected macrophages. These evidences suggest SteLL as important lead molecule in the development of anti-infective agents against S. aureus.

Punica granatum sarcotesta lectin (PgTeL) has antibacterial activity and synergistic effects with antibiotics against β-lactamase-producing Escherichia coli

The sarcotesta of Punica granatum fruit contains an antimicrobial lectin called PgTeL. In this work, we evaluated the antibacterial activity of PgTeL against five drug-resistant Escherichia coli isolates able to produce β-lactamases. Minimum inhibitory (MIC) and bactericidal (MBC) concentrations were determined by broth dilution. Morphometric and viability analyses were performed by flow cytometry, and ultrastructural changes were evaluated by scanning electron microscopy. Potential synergistic effects of PgTeL with antibiotics and anti-biofilm effect were also evaluated. PgTeL showed antibacterial activity against all isolates with MIC and MBC values ranging from 12.5 to 50.0 μg/mL and from 25.0 to 100.0 μg/mL, respectively. For most isolates, PgTeL postponed the growth start by at least ten hours. At the MIC, the lectin caused alterations in size, shape and structure of bacterial cells. The combination PgTeL-ceftazidime showed a synergistic effect for all isolates. Synergy was also detected with ampicillin (one isolate), carbenicillin (one isolate), cefotaxime (one isolate), cephalexin (four isolates) and cefuroxime (three isolates). PgTeL exhibited anti-biofilm activity against all isolates, causing ≥50% inhibition of biofilms at or above 6.25 μg/mL. The antibacterial effect of PgTeL and its synergy with antibiotics indicate that this fruit-derived molecule may have potential for future treatment of multidrug-resistant infections.