Representatives Of Microorganisms Research Articles

Procedure for rapid determination of bile-tolerant gram-negative bacteria in drugs

The European Pharmacopoeia is a single reference study for the quality control of drugs. The official standards published within it provide a legal and scientific basis for quality control in the processes of drugs development, production and marketing. However, the long experience and the multitude of studies have demonstrated that medicinal forms represent unstable dispersed systems and can undergo various manifest or non-manifest changes, leading to drug incompatibilities. Along with the physico-chemical transformations, microbiological transformations can occur with the contamination of the final product with pathogenic, conditionally pathogenic or even saprophytic germs, especially medicines that do not undergo final sterilization or are not aseptically prepared. Microbial contamination of the drug can be an indicator of the production conditions; it can cause the instability of the product through the microbial decomposition of auxiliary substances, the alteration or definitive cancellation of the therapeutic effect of the active substances, the appearance of metabolites with toxic properties, especially those fractions of endotoxins on the wall cell of gram-negative bacteria with the development of allergenic, pyrogenic substances and the induction of the danger of local orgeneral infections. An important role is attributed to the group of bile-tolerant gram-negative bacteria as representatives of microorganisms that are inadmissible in one g/ml for the absence test and for the quantitative test <10 NCP/g/ml (probable number of bacteria), inadmissible in non-sterile medicinal products, herbal medicinal products for oral use and extracts used in their preparation. Due to the diversity of medicinal forms in terms of content, method of application, and therapeutic action, these preparations fulfil the indispensable conditions for the growth of microorganisms, therefore a primary concern is to avoid microbial contamination from the technological phase to the administration phase in order to prevent complications associated with bacterial infections. The given study reveals the testing of the procedure for the rapid determination of inadmissible microorganisms in non-sterile medicinal products and herbal drugs for oral use and the extracts used in their preparation, especially microorganisms of the group Enterobacteriaceae spp.

Growth of an anaerobic sulfate-reducing bacterium sustained by oxygen respiratory energy conservation after O2 -driven experimental evolution.

Desulfovibrio species are representatives of microorganisms at the boundary between anaerobic and aerobic lifestyles, since they contain the enzymatic systems required for both sulfate and oxygen reduction. However, the latter has been shown to be solely a protective mechanism. By implementing the oxygen-driven experimental evolution of Desulfovibrio vulgaris Hildenborough, we have obtained strains that have evolved to grow with energy derived from oxidative phosphorylation linked to oxygen reduction. We show that a few mutations are sufficient for the emergence of this phenotype and reveal two routes of evolution primarily involving either inactivation or overexpression of the gene encoding heterodisulfide reductase. We propose that the oxygen respiration for energy conservation that sustains the growth of the O2 -evolved strains is associated with a rearrangement of metabolite fluxes, especially NAD+ /NADH, leading to an optimized O2 reduction. These evolved strains are the first sulfate-reducing bacteria that exhibit a demonstrated oxygen respiratory process that enables growth.

Preliminary investigations into the action of nitric oxide in the control of biodeterioration

Environmental control is the preferred and often the most appropriate response in the prevention of biodeterioration of cultural materials. For immoveable heritage or objects housed under conditions where temperature and humidity favour the processes of biodecay, however, chemical-based biocide treatments are often required. Unfortunately, the potential for treatment damage, and the significant adverse environmental and personal health implications of using chemical biocides are a major consideration in their use. Therefore investigation into, and development of, less invasive and less toxic treatment methodologies are sought (Young et al. 2008). The observed antimicrobial properties of the free radical molecule nitric oxide (NO•) have led to the application of nitric oxide donor compounds in the control of biofilm formation on medical implants, and as antifoulants in the marine biofouling and coating industries (Barraud et al. 2006; Nablo, Rothrock & Schoenfisch 2004). In researching alternative methods for the treatment of biodeterioration in conservation, preliminary investigations into the suitability of nitric oxide-based treatments were undertaken. The NO• used in this study originates from two sources: a direct source in the form of a nitric oxide releasing compound, the nitric oxide donor DETA/NO•; and an indirect source in which NO• is produced from the reduction of nitrate by nitrate reducing bacteria. Test populations for this study included Pseudomonas aeruginosa PAO1, a known nitrate reducer, and a mixed population representative of microorganisms from various samples of cultural material.

Double-doped TiO2 nanoparticles as an efficient visible-light-active photocatalyst and antibacterial agent under solar simulated light

Silver and nitrogen doped TiO2 nanoparticles (NPs) were synthesized via sol–gel method. The physicochemical properties of the achieved NPs were characterized by various methods including X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultra violet–visible absorption spectroscopy (UV–vis). Both visible-light photocatalytic activity and antimicrobial properties were successfully demonstrated for the degradation of Rhodamine B (Rh. B.), as a model dye, and inactivation of Escherichia coli (E. coli), as a representative of microorganisms. The concentration of the employed dopant was optimized and the results revealed that the silver and nitrogen doped TiO2 NPs extended the light absorption spectrum toward the visible region and significantly enhanced the photodegradation of model dye and inactivation of bacteria under visible-light irradiation while double-doped TiO2 NPs exhibited highest photocatalytic and antibacterial activity compared with single doping. The significant enhancement in the photocatalytic activity and antibacterial properties of the double doped TiO2 NPs, under visible-light irradiation, can be attributed to the generation of two different electronic states acting as electron traps in TiO2 and responsible for narrowing the band gap of TiO2 and shifting its optical response from UV to the visible-light region.

Microorganism Retention on Microfiltration Membranes

Several types of microfiltration membranes — polypropylene, cellulose diacetate (nominal pore size=0.2 μm) and polycarbonate (pore size=0.4 μm) — were tested for their microorganism retention ability. Suspensions of Pseudomonas diminuta and bovine red blood cells (RBC) were used for experimental purposes as representatives of microorganisms. Based on microscopy and microbiological evaluation it was demonstrated that individual cells of both types are able to cross a membranes that is generally rated as an aseptic one. A simple mathematical model is also proposed to describe the process by which the cells are transported across the membrane.