Elucidating the antibiofilm activity of Frangula emodin against Staphylococcus aureus biofilms

AIMS

Because the Staphylococcus aureus is one of the most well-known pathogens associated with medical devices and nosocomial infections, the aim of the study was to examine antibiofilm potential of emodin against it.

METHODS AND RESULTS

Antibacterial activity was examined through microdilution assay. Antibiofilm testing included crystal violet staining of biofilm biomass and morphology analysis by Atomic force microscopy (AFM). Furthermore, aerobic respiration was monitored using the Micro-Oxymax respirometer. For investigation of gene expression qRT-PCR was performed. Emodin demonstrated strong antibacterial activity and ability to inhibit biofilm formation of all tested strains. The effect on preformed biofilms was spotted in few strains. AFM revealed that emodin affects biofilm structure and roughness. Monitoring of respiration under emodin treatment in planktonic and biofilm form revealed that emodin influenced aerobic respiration. Moreover, qRT-PCR showed that emodin modulates expression of icaA, icaD, srrA and srrB genes, as well as RNAIII, and that this activity was strain-specific.

CONCLUSION

The results obtained in this study indicate the novel antibiofilm activity of emodin and its multiple pathways of action.

SIGNIFICANCE AND IMPACT OF STUDY

This is the first study that examined pathways through which emodin expressed its antibiofilm activity.

Toxicity investigation of CeO2 nanoparticles coated with glucose and exopolysaccharides levan and pullulan on the bacterium Vibrio fischeri and aquatic organisms Daphnia magna and Danio rerio

Cerium oxide nanoparticles (nCeO₂) have widespread applications, but they can be hazardous to the environment. Some reports indicate the toxic effect of nCeO₂ on tested animals, but literature data are mainly contradictory. Coating of nCeO₂ can improve their suspension stability and change their interaction with the environment, which can consequently decrease their toxic effects. Herein, the exopolysaccharides levan and pullulan, due to their high water solubility, biocompatibility, and ability to form film, were used to coat nCeO₂. Additionally, the monosaccharide glucose was used, since it is a common material for nanoparticle coating. This is the first study investigating the impact of carbohydrate-coated nCeO₂ in comparison to uncoated nCeO₂ using different model organisms. The aim of this study was to test the acute toxicity of carbohydrate-coated nCeO₂ on the bacterium Vibrio fischeri NRRL B-11177, the crustacean Daphnia magna, and zebrafish Danio rerio. The second aim was to investigate the effects of nCeO₂ on respiration in Daphnia magna which was performed for the first time. Finally, it was important to see the relation between Ce bioaccumulation in Daphnia magna and Danio rerio and other investigated parameters. Our results revealed that the coating decreased the toxicity of nCeO₂ on Vibrio fischeri. The coating of nCeO₂ did not affect the nanoparticles' accumulation/adsorption or mortality in Daphnia magna or Danio rerio. Monitoring of respiration in Daphnia magna revealed changes in CO₂ production after exposure to coated nCeO₂, while the crustacean's O₂ consumption was not affected by any of the coated nCeO₂. In summary, this study revealed that, at 200 mg L^-1, uncoated and carbohydrate-coated nCeO₂ are not toxic for the tested organisms, however, the CO₂ production in Daphnia magna is different when they are treated with coated and uncoated nCeO₂. The highest production was in glucose and levan-coated nCeO₂ according to their highest suspension stability. Daphnia magna (D. magna), Danio rerio (D. rerio), Vibrio fischeri (V. fischeri).

Microbial levan and pullulan as potential protective agents for reducing adverse effects of copper on Daphnia magna and Vibrio fischeri

Microbial polysaccharides, due to their unique physiochemical properties, have found application in the food industry, cosmetics, pharmacy and medicine. In the environment, microbes can use polysaccharides to alleviate the adverse effects of heavy metals in their close proximity. This adaptive property shows interesting potential for bioremediation. Herein, the effects of the exopolysaccharides (EPS) levan, produced by the bacterium Bacillus licheniformis NS032 and pullulan, produced by the fungus Aureobasidium pullulans CH-1 in the presence of copper (Cu²⁺) have been investigated for the first time on antioxidant enzyme activity, respiration and Cu²⁺ bioaccumulation of Daphnia magna as well as the bioluminescence of Vibrio fischeri. Both EPS decreased toxicity of Cu²⁺ in the acute test with D. magna. The activity of catalase (CAT) was significantly diminished after acute exposure to Cu²⁺ in comparison to treatments with Cu²⁺ and EPS, while in the prolonged acute exposure the CAT activity did not show statistically significant (P ≤ 0.05) differences between treatments with and without the EPS. According to ICP-MS results, during prolonged acute exposure of neonates, the bioaccumulation of Cu²⁺ in treatments without the EPS was 52.03 μg/g of biomass (wet), while in treatments with EPS, the bioaccumulation was lower by one order of magnitude. The respiration of neonates during acute exposure to Cu²⁺ with or without the EPS was monitored using the MicroOxymax respirometer, and the results show the EPS can positively effect the respiration. In the case of bacterial bioluminescence, the toxicity of Cu²⁺ decreased in treatments with EPS (30 min EC₁₀) from 3.54 mg/L to 140.61 mg/L (levan) and 45.00 mg/L (pullulan). This study demonstrates protective effect of EPS against Cu²⁺ toxicity on D. magna and V. fischeri, and opens the door for further investigation of potential application of levan and pullulan in bioremediation of heavy metals and mitigation of their adverse effects in the aquatic environment.

A comprehensive study of conditions of the biodegradation of a plastic additive 2,6-di-tert-butylphenol and proteomic changes in the degraderPseudomonas aeruginosasan ai

ThePseudomonas aeruginosasan ai strain was investigated for its capability to degrade the 2,6-di-tert-butylphenol (2,6-DTBP) plastic additive, a hazardous and toxic substance for aquatic life.

Cadmium specific proteomic responses of a highly resistantPseudomonas aeruginosasan ai

Pseudomonas aeruginosa san ai is a promising candidate for bioremediation of cadmium pollution, as it resists a high concentration of up to 7.2 mM of cadmium. Leaving biomass of P. aeruginosa san ai exposed to cadmium has a large biosorption potential, implying its capacity to extract heavy metal from contaminated medium. In the present study, we investigated tolerance and accumulation of cadmium on protein level by shotgun proteomics approach based on liquid chromatography and tandem mass spectrometry coupled with bioinformatics to identify proteins. Size exclusion chromatography was used for protein prefractionation to preserve native forms of metalloproteins and protein complexes. Using this approach a total of 60 proteins were observed as up-regulated in cadmium-amended culture. Almost a third of the total numbers of up-regulated were metalloproteins. Particularly interesting are denitrification proteins which are over expressed but not active, suggesting their protective role in conditions of heavy metal exposure. P. aeruginosa san ai developed a complex mechanism to adapt to cadmium, based on: extracellular biosorption, bioaccumulation, the formation of biofilm, controlled siderophore production, enhanced respiration and modified protein profile. An increased abundance of proteins involved in: cell energy metabolism, including denitrification proteins; amino acid metabolism; cell motility and posttranslational modifications, primarily based on thiol-disulfide exchange, were observed. Enhanced oxygen consumption of biomass in cadmium-amended culture versus control was found. Our results signify that P. aeruginosa san ai is naturally well equipped to overcome and survive high doses of cadmium and, as such, has a great potential for application in bioremediation of cadmium polluted sites.

When exposed to cadmium a highly resistant strain P. aeruginosa san ai responds by an increased metalloprotein expression (particularly denitrification proteins), an enhanced respiration, and a pronounced thiol-disulfide protein modifications.