Bee-collected pollen (BCP) is a well-known functional food. Honey bees process the collected pollen and store it in the hive, inside the comb cells. The processed pollen is called bee- bread or ambrosia and it is the main source of proteins, lipids, vitamins, macro-and micro-elements in honey bee nutrition. During storage, beebread undergoes solid state fermentation which preserves it and increases the bioavailability of nutrients. Research on beebread has been rather limited until now. In recent years, there is an increasing interest regarding the antimicrobial properties of BCP and beebread, due to emerging antimicrobial resistance by pathogens. Both BCP and beebread exhibit antimicrobial properties against diverse pathogens, like bacteria and fungi. As is the case with other bee products, lack of antimicrobial resistance might be attributed to the synergy of more than one antimicrobial compounds within BCP and beebread. Furthermore, BCP and bee bread exert targeted activity against pathogens and affect the host microbiome in a prebiotic manner. This review aims to present up to date research findings regarding these aspects as well as to discuss current challenges and future perspectives in the field.

https://www.mdpi.com/2079-6382/9/11/811/pdf

Antimicrobial Activity of Bee-Collected Pollen and Beebread: State of the Art and Future Perspectives.

Green chemistry was used to synthesize copper nanoparticles (CuNPs), using an aqueous extract of Rosa ‘Andeli’ double delight fresh petals (RAFE) or Gardenia jasminoides Ellis fresh leaves (GJLE), as stabilizing agents. The effect of the RAFE and GJLE on the CuNPs morphology, size, polydispersity, density of dislocations (δ), and their antibacterial activity against S. aureus and E. coli was determined. The green synthesized CuNPs have a spherical morphology, with an FCC (face-centered cubic) structure and a d‐spacing of 0.2089 nm. The size, dispersity, density of dislocations, and microstrain are found to be dependent, on the type of the aqueous extract employed as stabilizing agents. The CuNPs synthesized with RAFE (CuNPs/RAFE) have a mode size of 11.7 nm and higher polydispersity than the synthesized with GJLE (CuNPs/GJLE), which results in 3 nm size and monodispersed. The CuNPs/RAFE showed higher antibacterial activity against both bacteria, with a 0% survival percentage at 100 µg/mL (S. aureus), and 10% of survival percentage at 125 µg/mL (E. coli). 

Green synthesis of copper nanoparticles using different plant extracts and their antibacterial activity.

Porphyrin and phthalocyanine photosensitizers designed for targeted photodynamic therapy of colorectal cancer.

The thick mucus within the airways of individuals with cystic fibrosis (CF) promotes frequent respiratory infections that are often polymicrobial. Pseudomonas aeruginosa and Staphylococcus aureus are two of the most prevalent pathogens that cause CF pulmonary infections, and both are among the most common etiologic agents of chronic wound infections. Furthermore, the ability of P. aeruginosa and S. aureus to form biofilms promotes the establishment of chronic infections that are often difficult to eradicate using antimicrobial agents. In this study, we found that multiple LasR-regulated exoproducts of P. aeruginosa, including 2-heptyl-4-hydroxyquinoline N-oxide (HQNO), siderophores, phenazines, and rhamnolipids, likely contribute to the ability of P. aeruginosa PA14 to shift S. aureus Newman norfloxacin susceptibility profiles. Here, we observe that exposure to P. aeruginosa exoproducts leads to an increase in intracellular norfloxacin accumulation by S. aureus. We previously showed that P. aeruginosa supernatant dissipates the S. aureus membrane potential, and furthermore, depletion of the S. aureus proton motive force recapitulates the effect of the P. aeruginosa PA14 supernatant on shifting norfloxacin sensitivity profiles of biofilm-grown S. aureus Newman. From these results, we hypothesize that exposure to P. aeruginosa PA14 exoproducts leads to increased uptake of the drug and/or an impaired ability of S. aureus Newman to efflux norfloxacin. Surprisingly, the effect observed here of P. aeruginosa PA14 exoproducts on S. aureus Newman susceptibility to norfloxacin seemed to be specific to these strains and this antibiotic. Our results illustrate that microbially derived products can alter the ability of antimicrobial agents to kill bacterial biofilms. IMPORTANCEPseudomonas aeruginosa and Staphylococcus aureus are frequently coisolated from multiple infection sites, including the lungs of individuals with cystic fibrosis (CF) and nonhealing diabetic foot ulcers. Coinfection with P. aeruginosa and S. aureus has been shown to produce worse outcomes compared to infection with either organism alone. Furthermore, the ability of these pathogens to form biofilms enables them to cause persistent infection and withstand antimicrobial therapy. In this study, we found that P. aeruginosa-secreted products dramatically increase the ability of the antibiotic norfloxacin to kill S. aureus biofilms. Understanding how interspecies interactions alter the antibiotic susceptibility of bacterial biofilms may inform treatment decisions and inspire the development of new therapeutic strategies.

Pseudomonas aeruginosa PA14 Enhances the Efficacy of Norfloxacin against Staphylococcus aureus Newman Biofilms.

The antimycobacterial activity of cinnamaldehyde has already been proven for laboratory strains and for clinical isolates. What is more, cinnamaldehyde was shown to threaten the mycobacterial plasma membrane integrity and to activate the stress response system. Following promising applications of metabolomics in drug discovery and development we aimed to explore the mycobacteria response to cinnamaldehyde within cinnamon essential oil treatment by untargeted liquid chromatography–mass spectrometry. The use of predictive metabolite pathway analysis and description of produced lipids enabled the evaluation of the stress symptoms shown by bacteria. This study suggests that bacteria exposed to cinnamaldehyde could reorganize their outer membrane as a physical barrier against stress factors. They probably lowered cell wall permeability and inner membrane fluidity, and possibly redirected carbon flow to store energy in triacylglycerols. Being a reactive compound, cinnamaldehyde may also contribute to disturbances in bacteria redox homeostasis and detoxification mechanisms.

https://www.mdpi.com/2218-273X/10/3/357/pdf

Untargetted Metabolomic Exploration of the Mycobacterium tuberculosis Stress Response to Cinnamon Essential Oil

The effect of methanol, ethanol, acetone, N,N-dimethylformamide (DMF), dimethyl sulfoxide and Nujol on the growth of Escherichia coli DH5α, Bacillus subtilis and Saccharomyces cerevisiae D273 was investigated. All of the tested cultures appeared susceptible to the organic media they were treated with, which evinced in apparent hindering of cell development. The observed diverse solvent tolerance, except from their different biochemical activity, may also be related to the changes in cell membrane fluidity induced by the solvent species. Parallel electron paramagnetic resonance investigations using egg yolk lecithin model liposomes revealed that the fluidity of the phospholipid system in cell membranes may either be considerably decreased (Nujol, DMF, ethanol) or increased (acetone), thus rendering difficult the intracellular nutrient supply. Hence, even the chemically neutral Nujol produced a distinct cell-growth inhibitory effect. These results are fairly consistent with the outcome of the survival tests, particularly for the bacteria strains.

/pdf/the-effect-of-organic-solvents-on-selected-microorganisms-15n05wgbw2.pdf

Katarzyna Barchiewicz

Papers

The effect of organic solvents on selected microorganisms and model liposome membrane