Background Streptococcus agalactiae (Group B Streptococcus, GBS) is a leading cause of life-threatening neonatal meningitis and survivors often suffer permanent neurological damage. How this organism interacts with the meninges and subsequently with astrocytes that constitute the underlying cortical glia limitans superficialis is not known.Methodology/Principal FindingsIn this paper, we demonstrate dose-dependent adherence of GBS over time to human meningioma cells and fetal astrocytes in vitro, which was not influenced by expression of either β-haemolysin/cytolysin (β-h/c) toxin, different capsule serotypes or by absence of capsule (p>0.05). Internalization of GBS by both cell types was, however, a slow and an infrequent event (only 0.02–0.4% of associated bacteria were internalised by 9 h). Expression of β-h/c toxin did not play a role in invasion (p>0.05), whereas capsule expression lead to a reduction (p<0.05) in the numbers of intracellular bacteria recovered. GBS strains induced cytotoxicity as demonstrated by the measurement of lactate dehydrogenase (LDH) enzyme release by 9 h and by viable staining. Increasing levels of meningioma cell death correlated with bacterial growth and the phenotype of β-h/c toxin production, i.e. from weakly, to normo- to hyper-haemolytic. However, cytotoxicity was significantly greater (p<0.05) towards astrocytes, and infection with initial MOI≥0.003 induced 70–100% LDH release. By comparing wild-type (β-h/c+) and mutant (ΔcylE β-h/c−) strains and β-h/c toxin extracts and by using the surfactant dipalmitoylphosphatidylcholine in cytotoxicity inhibition experiments, β-h/c toxin was demonstrated as principally responsible for cell death.Conclusions/SignificanceThis study has described key events in the interactions of GBS with meningeal cells and astrocytes in vitro and a major virulence role for β-h/c toxin. Understanding the mechanisms involved will help to identify potential therapies for improving patient survival and for reducing the incidence and severity of neurological sequelae.
Potato peel wastes are generated in high quantities from potato processing industries. They are pollutants to the environment, and they release greenhouse gases into the atmosphere. The present study assessed the potentiality of hydrolyzing potato wastes by amylase-producing fungi to improve biogas generation from potato peels through the anaerobic digestion process. Different fungal isolates were screened for amylase production on potato wastes, and the highest amylase producer was selected for optimizing the efficacy of producing amylases in high quantities to efficiently allow the conversion of potato organic matter into fermentable sugars that are utilized for the anaerobic digestion process. The best amylase producers were those derived from Rhizopus stolonifer (32.61 ± 0.89 U/mL). The highest cumulative methane yield from hydrolyzed potato peel was 65.23 ± 3.9 mL CH4/g and the methane production rate was 0.39 mL CH4/h, whereas the highest biogas yield from unhydrolyzed potato wastes was 41.32 ± 2.15 mL CH4/g and the biogas production rate was 0.25 mL CH4/h. Furthermore, it was found that the two combined sequential stages of anaerobic digestion (biogas production) followed by biodiesel production (enzymatic esterification) were the most effective, recording 72.36 ± 1.85 mL CH4/g and 64.82% biodiesel of the total analytes. However, one-pot fermentation revealed that biogas yield was 22.83 ± 2.8 mL CH4/g and the biodiesel extracted was 23.67% of the total analytes. The insights of the current paper may increase the feasibility of potato peel-based biorefinery through the biological hydrolysis strategy of potato wastes using eco-friendly enzymes.
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