Detection and partial characterization of extracellular inducers of persistence in Staphylococcus epidermidis and Staphylococcus aureus

Single-cell Raman spectroscopy identifies Escherichia coli persisters and reveals their enhanced metabolic activities

Microbial persisters are the featured tiny sub-population of microorganisms that are highly tolerant to multiple antimicrobials. Currently, studies on persisters remain a considerable challenge owing to technical limitations. Here, we explored the application of single-cell Raman spectroscopy (SCRS) in the investigation of persisters. Escherichia coli (ATCC 25922) cells were treated with a lethal dosage of ampicillin (100 μg/mL, 32 × MIC, 4 h) for the formation of persisters. The biochemical characters of E. coli and its persisters were assessed by SCRS, and their metabolic activities were labeled and measured with D₂O-based single-cell Raman spectroscopy (D₂O-Ramanometry). Notable differences in the intensity of Raman bands related to major cellular components and metabolites were observed between E. coli and its ampicillin-treated persisters. Based on their distinct Raman spectra, E. coli and its persister cells were classified into different projective zones through the principal component analysis and t-distributed stochastic neighbor embedding. According to the D₂O absorption rate, E. coli persisters exhibited higher metabolic activities than those of untreated E. coli. Importantly, after the termination of ampicillin exposure, these persister cells showed a temporal pattern of D₂O intake that was distinct from non-persister cells. To our knowledge, this is the first report on identifying E. coli persisters and assessing their metabolic activities through the integrated SCRS and D₂O-Ramanometry approach. These novel findings enhance our understanding of the phenotypes and functionalities of microbial persister cells. Further investigations could be extended to other pathogens by disclosing microbial pathogenicity mechanisms for developing novel therapeutic strategies and approaches.

A Study on the Bio-responses of a Freshwater Snail (Biomphalaria alexandrina) to Fungal-derived Compounds

BACKGROUND

Biomphalaria alexandrina snails, as transitional hosts of schistosomiasis, plays an essential part in the spread of the illness. Control of these snails by the substance molluscicides antagonistically influences the oceanic climate, causing poisonous and cancer-causing consequences for non-target life forms.

OBJECTIVE

Looking for new naturally safe substances that can treat schistosomiasis disease with minimal side effects on the environment and plants, fish wealth and do not affect vital human functions.

METHODS

Fifty fungal species were used to evaluate their activity against Biomphalaria alexandrina. Study the effect of the fungal extract on vital functions of Biomphalaria alexandrina and fish wealth. Purification of active substances and identification of their chemical structures.

RESULTS

Cladosporium nigrellum and Penicillium aurantiogresium metabolites were effective against B. alexandrina snails, and the effects of promising fungal extracts sublethal concentrations (IC₁₀ & IC₂₅) on the levels of steroid sex hormones, liver enzymes, total protein, lipids, albumin and glucose were determined. Chemical analyses of this filtrate separated a compound effective against snails; it was identified. Protein electrophoresis showed that fungal filtrate affects the protein pattern of snails' haemolymph. Little or no mortality of Daphnia pulex individuals was observed after their exposure to sublethal concentrations of each treatment.

CONCLUSION

Certain compounds from fungal cultures could be safely used for biological control of Biomphalaria alexandrina snails.