Farha Arakkaveettil Kabeer

Biofilms formed by Escherichia coli are composed of amyloid curli and cellulose and have been shown to be linked to pathogenicity, antibiotic resistance, and chronic infections. Guanabenz acetate (GABE), an antihypertensive drug, was identified as a potential strategic repurposing drug due to its biofilm inhibitory properties following an extensive antimicrobial screening assay of 2,202 Food and Drug Administration-approved non-antibiotic agents. The results of this study provide insights into the effectiveness of GABE as a therapeutic alternative against E. coli biofilm-associated infectious diseases. IMPORTANCE: Biofilm-associated bacterial infections are one of the major problems in medical settings. There are currently limited biofilm inhibitors available for clinical use. Guanabenz acetate, a drug used to treat high blood pressure, was found to be an effective anti-biofilm agent against Escherichia coli . Our results show that this drug can inhibit the production of cellulose and curli amyloid protein, which are the two main components of E. coli biofilms. Our findings highlight the possibility of repurposing a drug to prevent E. coli biofilm formation.

Salmonella enterica is an important foodborne pathogen that causes gastroenteritis and systemic infection in humans and livestock. Salmonella biofilms consist of two major components—amyloid curli and cellulose—which contribute to the prolonged persistence of Salmonella inside the host. Effective agents for inhibiting the formation of biofilms are urgently needed. We investigated the antibiofilm effect of Raspberry Ketone (RK) and its mechanism of action against Salmonella Typhimurium 14028 using the Congo red agar method, Calcofluor staining, crystal violet method, pellicle assay, and the TMT-labeled quantitative proteomic approach. RK suppressed the formation of different types of Salmonella biofilms, including pellicle formation, even at low concentrations (200 µg/mL). Furthermore, at higher concentrations (2 mg/mL), RK exhibited bacteriostatic effects. RK repressed cellulose deposition in Salmonella biofilm through an unknown mechanism. Swimming and swarming motility analyses demonstrated reduced motility in RK-treated S. typhimurium. Proteomics analysis revealed that pathways involved in amyloid curli production, bacterial invasion, flagellar motility, arginine biosynthesis, and carbohydrate metabolism, were targeted by RK to facilitate biofilm inhibition. Consistent with the proteomics data, the expressions of csgB and csgD genes were strongly down-regulated in RK-treated S. typhimurium. These findings clearly demonstrated the Salmonella biofilm inhibition capability of RK, justifying its further study for its efficacy assessment in clinical and industrial settings.

A marine bacterial isolate, Bacillus vietnamensis sp. MSB17 from the sediments collected from the continental slope of the eastern Arabian Sea exhibited good Malachite Green (MG) decolorization ability in mineral medium supplemented with glucose and yeast extract under static conditions. The complete decolorization of dye (50 mg/L) was attained within 4 h of incubation. The activities of enzymes such as tyrosinase (0.62 IU/ml), laccase (12.02 U/ml), and manganese peroxidase (6.23 U/ml) were observed during dye degradation. UV-VIS, FT-IR, and GC-MS analysis of dye samples extracted with ethyl acetate confirmed the biodegradation of MG into methanone, [4-(dimethylamino) phenyl] phenyl- and 2, 6-bis (1, 1-dimethylethyl) phenol. The metabolites obtained from B. vietnamensis sp. MSB17 mediated MG degradation did not exhibit any microbial toxicity and phytotoxicity. The present study indicated the efficiency of Bacillus vietnamensis sp. MSB17 to effectively degrade MG, revealing its potential to be further utilized for bioremediation purposes.

Marine fungi, one of the major decomposers of marine environment, is found to produce potential enzymes and novel biomolecules. The present study explored bioprospecting potentials such as antimicrobial, anticancer and enzymatic activities of marine sediment-derived fungi isolated from continental slope of Eastern Arabian Sea. Morphology and ITS sequencing identified the fungus as Penicillium sp. ArCSPf. The fungal strain exhibited amylase, gelatinase, phytase, lipase and pectinase activity. The active fraction obtained from the ethyl acetate extract column fractionation (F2) of fungus showed antibacterial activity against both methicillin-resistant Staphylococcus aureus (MRSA) and Bacillus cereus. Minimum inhibitory concentrations of F2 were 125 μg/mL for MRSA and 62.5 μg/mL for B. cereus. The active fraction showed a significant anticancer activity (IC₅₀ = 22.79 µg/mL) against MCF-7 breast cancer cells. The secondary metabolite (Z)-Octadec-9-enamide (oleamide, m/z 282.27 (M + H⁺)] was identified in the LC-MS/MS analysis of active fraction F2 in positive ionisation mode. To the best of our knowledge, this is the first report on exploring the bioprospecting potential of a sediment-derived fungus from continental slope of eastern Arabian Sea for the production of therapeutically active compounds.