Identification and characterization of bioactive pigment carotenoids from shrimps and their biofilm inhibition

Characterization and antibiofilm activity of carotenoids derived from marine Bacillus infantis against Staphylococcus aureus and Pseudomonas aeruginosa

Antibiotic resistance and biofilm pose significant challenges in healthcare, impacting economic growth and human well-being. The quest must be conducted for plausible natural anti-biofilm agents. Liquid chromatography mass spectroscopy was used for identification of carotenoids. Thebiofilm inhibition and eradication activity were evaluated against P. aeruginosa and S. aureus using crystal violet, Congo Red agar, and Scanning electron microscopy (SEM). Along with apocarotenoids, di-O-demethylspirilloxanthin, dihydroxylycopene glucoside, 2,2'-dihydroxy astaxanthin, and all-trans-Rhodovibrin were detected. Carotenoids at a concentration of 200 µg/ml showed 89.42 ± 3.42%, and 44.72 ± 6.18% biofilm inhibition of S. aureus, and P. aeruginosa, respectively, and was able to eradicate 25.68 ± 1.87% preformed biofilm in S. aureus. SEM and Congo Red Agar confirmed that carotenoids inhibited bacterial growth, exopolysaccharide production and prevented biofilm formation. Our investigation indicated that carotenoids from B. infantis could be an effective inhibitor for biofilm formed by both organisms and also had good eradication activity against S. aureus.

Effect of culture conditions at lab-scale on metabolite composition and antibacterial and antibiofilm activities of Dunaliella tertiolecta

Dunaliella tertiolecta RCC6 was cultivated indoors in glass bubble column photobioreactors operated under batch and semi-continuous regimens and using two different conditions of light and temperature. Biomass was harvested by centrifugation, frozen, and then lyophilized. The soluble material was obtained by sequential extraction of the lyophilized biomass with solvents with a gradient of polarity (hexane, ethyl acetate, and methanol) and its metabolic composition was investigated through nuclear magnetic resonance (NMR) spectroscopy. The effect of light on chlorophyll biosynthesis was clearly shown through the relative intensities of the ¹ H NMR signals due to pheophytins. The highest signal intensity was observed for the biomasses obtained at lower light intensity, resulting in a lower light availability per cell. Under high temperature and light conditions, the ¹ H NMR spectra of the hexane extracts showed an incipient accumulation of triacylglycerols. In these conditions and under semi-continuous regimen, an enhancement of β-carotene and sterols production was observed. The antibacterial and antibiofilm activities of the extracts were also tested. Antibacterial activity was not detected, regardless of culture conditions. In contrast, the minimal biofilm inhibitory concentrations (MBICs) against Escherichia coli for the hexane extract obtained under semi-continuous regimen using high temperature and irradiance conditions was promising.

Deinococcus radiodurans Exopolysaccharide Inhibits Staphylococcus aureus Biofilm Formation

Deinococcus radiodurans is an extremely resistant bacterium against extracellular stress owing to on its unique physiological functions and the structure of its cellular constituents. Interestingly, it has been reported that the pattern of alteration in Deinococcus proportion on the skin is negatively correlated with skin inflammatory diseases, whereas the proportion of Staphylococcus aureus was increased in patients with chronic skin inflammatory diseases. However, the biological mechanisms of deinococcal interactions with other skin commensal bacteria have not been studied. In this study, we hypothesized that deinococcal cellular constituents play a pivotal role in preventing S. aureus colonization by inhibiting biofilm formation. To prove this, we first isolated cellular constituents, such as exopolysaccharide (DeinoPol), cell wall (DeinoWall), and cell membrane (DeinoMem), from D. radiodurans and investigated their inhibitory effects on S. aureus colonization and biofilm formation in vitro and in vivo. Among them, only DeinoPol exhibited an anti-biofilm effect without affecting bacterial growth and inhibiting staphylococcal colonization and inflammation in a mouse skin infection model. Moreover, the inhibitory effect was impaired in the Δdra0033 strain, a mutant that cannot produce DeinoPol. Remarkably, DeinoPol not only interfered with S. aureus biofilm formation at early and late stages but also disrupted a preexisting biofilm by inhibiting the production of poly-N-acetylglucosamine (PNAG), a key molecule required for S. aureus biofilm formation. Taken together, the present study suggests that DeinoPol is a key molecule in the negative regulation of S. aureus biofilm formation by D. radiodurans. Therefore, DeinoPol could be applied to prevent and/or treat infections or inflammatory diseases associated with S. aureus biofilms.