Observation of Cytotoxicity of Phosphonium Derivatives Is Explained: Metabolism Inhibition and Adhesion Alteration.

The search for new antibiotics, substances that kill prokaryotic cells and do not kill eukaryotic cells, is an urgent need for modern medicine. Among the most promising are derivatives of triphenylphosphonium, which can protect the infected organs of mammals and heal damaged cells as mitochondria-targeted antioxidants. In addition to the antioxidant action, triphenylphosphonium derivatives exhibit antibacterial activity. It has recently been reported that triphenylphosphonium derivatives cause either cytotoxic effects or inhibition of cellular metabolism at submicromolar concentrations. In this work, we analyzed the MTT data using microscopy and compared them with data on changes in the luminescence of bacteria. We have shown that, at submicromolar concentrations, only metabolism is inhibited, while an increase in alkyltriphenylphosphonium (CnTPP) concentration leads to adhesion alteration. Thus, our data on eukaryotic and prokaryotic cells confirm a decrease in the metabolic activity of cells by CnTPPs but do not confirm a cytocidal effect of TPPs at submicromolar concentrations. This allows us to consider CnTPP as a non-toxic antibacterial drug at low concentrations and a relatively safe vector for delivering other antibacterial substances into bacterial cells.

Constructing of Bacillus subtilis-Based Lux-Biosensors with the Use of Stress-Inducible Promoters.

Here, we present a new lux-biosensor based on Bacillus subtilis for detecting of DNA-tropic and oxidative stress-causing agents. Hybrid plasmids pNK-DinC, pNK-AlkA, and pNK-MrgA have been constructed, in which the Photorhabdus luminescens reporter genes luxABCDE are transcribed from the stress-inducible promoters of B. subtilis: the SOS promoter PdinC, the methylation-specific response promoter PalkA, and the oxidative stress promoter PmrgA. The luminescence of B. subtilis-based biosensors specifically increases in response to the appearance in the environment of such common toxicants as mitomycin C, methyl methanesulfonate, and H2O2. Comparison with Escherichia coli-based lux-biosensors, where the promoters PdinI, PalkA, and Pdps were used, showed generally similar characteristics. However, for B. subtilis PdinC, a higher response amplitude was observed, and for B. subtilis PalkA, on the contrary, both the amplitude and the range of detectable toxicant concentrations were decreased. B. subtilis PdinC and B. subtilis PmrgA showed increased sensitivity to the genotoxic effects of the 2,2'-bis(bicyclo [2.2.1] heptane) compound, which is a promising propellant, compared to E. coli-based lux-biosensors. The obtained biosensors are applicable for detection of toxicants introduced into soil. Such bacillary biosensors can be used to study the differences in the mechanisms of toxicity against Gram-positive and Gram-negative bacteria.