Electroporation is a phenomenon occurring due to exposure of cells to Pulsed Electric Fields (PEF) which leads to increase of membrane permeability. Electroporation is used in medicine, biotechnology, and food processing. Recently, as an alternative to electroporation by PEF, Pulsed ElectroMagnetic Fields (PEMF) application causing similar biological effects was suggested. Since induced electric field in PEMF however is 2–3 magnitudes lower than in PEF electroporation, the membrane permeabilization mechanism remains hypothetical. We have designed pilot experiments where Saccharomyces cerevisiae and Candida lusitaniae cells were subjected to single 100–250 μs electrical pulse of 800 V with and without concomitant delivery of magnetic pulse (3, 6 and 9 T). As expected, after the PEF pulses only the number of Propidium Iodide (PI) fluorescent cells has increased, indicative of membrane permeabilization. We further show that single sub-millisecond magnetic field pulse did not cause detectable poration of yeast. Concomitant exposure of cells to pulsed electric (PEF) and magnetic field (PMF) however resulted in the increased number PI fluorescent cells and reduced viability. Our results show increased membrane permeability by PEF when combined with magnetic field pulse, which can explain electroporation at considerably lower electric field strengths induced by PEMF compared to classical electroporation.

A number of thermophilic bacteria capable of utilizing naphthalene as a sole source of carbon were isolated from a high-temperature oilfield in Lithuania. These isolates were able to utilize several other aromatic compounds, such as anthracene, benzene, phenol, benzene-1, 3-diol, protocatechuic acid as well. Thermophilic isolate G27 ascribed to Geobacillus genus was found to have a high aromatic compound degrading capacity. Spectrophotometric determination of enzyme activities in cell-free extracts revealed that the last aromatic ring fission enzyme in naphthalene biotransformation by Geobacillus sp. G27 was inducible via protocatechuate 3, 4-dioxygenase; no protocatechuate 4, 5-dioxygenase, protocatechuate 2, 3-dioxygenase activities were detected. Intermediates such as o-phthalic and protocatechuic acids detected in culture supernatant confirmed that the metabolism of naphthalene by Geobacillus sp. G27 can proceed through protocatechuic acid via ortho-cleavage pathway and thus differs from the pathways known for mesophilic bacteria.

A spacecraft is a confined system that is inhabited by a changing microbial consortium, mostly originating from life-supporting devices, equipment collected in pre-flight conditions, and crewmembers. Continuous monitoring of the spacecraft’s bioburden employing culture-based and molecular methods has shown the prevalence of various taxa, with human skin-associated microorganisms making a substantial contribution to the spacecraft microbiome. Microorganisms in spacecraft can prosper not only in planktonic growth mode but can also form more resilient biofilms that pose a higher risk to crewmembers’ health and the material integrity of the spacecraft’s equipment. Moreover, bacterial biofilms in space conditions are characterized by faster formation and acquisition of resistance to chemical and physical effects than under the same conditions on Earth, making most decontamination methods unsafe. There is currently no reported method available to combat biofilm formation in space effectively and safely. However, antibacterial photodynamic inactivation based on natural photosensitizers, which is reviewed in this work, seems to be a promising method.

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Abstract:The purpose of this study was purification and characterization of catechol 1,2-dioxygenase from Geobacillus sp. G27 strain, which degrades α-naphthol by the β-ketoadipate pathway. The catechol 1,2-dioxygenase (C1,2O) was purified using four steps of ammonium sulfate precipitation, DEAE-celullose, Sephadex G-150 and hydroxylapatite chromatographies. The enzyme was purified about 18-fold with a specific activity of 7.42 U mg of protein -1. The relative molecular mass of the native enzyme estimated on gel chromatography of Sephadex G-150 was 96 kDa. The pH and temperature optima for enzyme activity were 7 and 60 o C, respectively. A half-life of the catechol 1,2-dioxygenase at the optimum temperature was 40 min. The kinetic parameters of the Geobacillus sp. G27 strain catechol 1,2-dioxygenase were determined. The enzyme had apparent K m of 29 µM for catechol and the cleavage activities for methylcatechols were much less than for catechol and no activity with gentisate or protocatechuate was detected.