Inner-mitochondrial membrane protein PfMPV17 is linked to P. falciparum in vitro resistance to the indoloquinolizidine alkaloid alstonine

Background There are an estimated 260 million malaria cases and ∼600 000 deaths annually. Challenges to malaria eradication include the lack of highly effective and broadly applicable vaccines and parasite drug resistance. This is driving the need for new tools, including novel drugs and drug targets. The indoloquinolizidine alkaloid alstonine was previously shown to have in vitro activity against Plasmodium falciparum malaria parasites and a slow-action activity that is different from other slow-action antiplasmodial compounds such as clindamycin. Objectives To investigate the action of the antiplasmodial compound alstonine by validating a putative resistance mutation and determining whether the activity of alstonine is linked to the mitochondrial electron transport chain. Materials and methods In vitro evolution of resistance was used to generate alstonine-resistant P. falciparum, followed by whole-genome sequencing and CRISPR/Cas9 gene editing of wildtype parasites to validate a putative resistance-associated mutation. Links to mitochondrial function were assessed using oxygen consumption rate measurements and activity of alstonine in P. falciparum expressing the yeast dihydroorotate dehydrogenase. Results P. falciparum parasites were selected with ∼20-fold reduced sensitivity to alstonine compared to wild-type parasites. Whole-genome sequencing of alstonine-resistant P. falciparum sub-clones identified several mutations including a copy number variation and point mutation (A318P) in a gene encoding a putative inner-mitochondrial membrane protein (PfMPV17). Introduction of the A318P mutation into the PfMPV17 gene in wild-type P. falciparum yielded parasites with reduced alstonine sensitivity. While a direct link between alstonine action and mitochondrial respiratory function was not found, a transgenic P. falciparum line resistant to the cytochrome bc1 inhibitor atovaquone and pyrimidine synthesis inhibitor DSM265 had reduced sensitivity to alstonine. Conclusions These data demonstrate that PfMPV17 is linked to alstonine resistance and suggest that alstonine action is linked to the mitochondria and/or pyrimidine biosynthesis pathways.</p

Inhibition of Steptococcus mutans biofilm formation by extracts of Tenacibaculum sp. 20J, a bacterium with wide-spectrum quorum quenching activity

Background: Previous studies have suggested the quorum sensing signal AI-2 as a potential target to prevent the biofilm formation by Streptococcus mutans, a pathogen involved in tooth decay. Objective: To obtain inhibition of biofilm formation by S. mutans by extracts obtained from the marine bacterium Tenacibaculum sp. 20J interfering with the AI-2 quorum sensing system. Design: The AI-2 inhibitory activity was tested with the biosensors Vibrio harveyi BB170 and JMH597. S. mutans ATCC25175 biofilm formation was monitored using impedance real-time measurements with the xCELLigence system®, confocal laser microscopy, and the crystal violet quantification method. Results: The addition of the cell extract from Tenacibaculum sp. 20J reduced biofilm formation in S. mutans ATCC25175 by 40–50% compared to the control without significantly affecting growth. A decrease of almost 40% was also observed in S. oralis DSM20627 and S. dentisani 7747 biofilms. Conclusions: The ability of Tenacibaculum sp. 20J to interfere with AI-2 and inhibit biofilm formation in S. mutans was demonstrated. The results indicate that the inhibition of quorum sensing processes may constitute a suitable strategy for inhibiting dental plaque formation, although additional experiments using mixed biofilm models would be required

Bioconjugated Quantum Dots in Rapid Detection of Water Microbial Load: An Emerging Technology

International audienceDrinking water contaminated with pathogenic living forms is a major concern for human health in developing countries because it can lead to acute and sometimes life-threatening gastrointestinal diseases. There is thus a need to detect potentially harmful pathogens and identify them in the presence of several other nonpathogenic microbes, particularly in the urban water systems to prevent infection and disease