Blagoveschensk, Blagoveshchensk, Russian Federation
VAC 14.03.2000 Медико-биологические науки
UDK 61 Медицина. Охрана здоровья
GRNTI 76.03 Медико-биологические дисциплины
OKSO 30.07.01 Фундаментальная медицина
BBK 52 Общая патология. Мед. вирусология, микробиология, паразитология. Фармакология, фармац. и токсиколог.
TBK 5708 Гигиена и санитария. Эпидемиология. Медицинская экология
BISAC MED052000 Microbiology
A brief outline of the evolution of microscopic fungi, structure, chemical composition and role in nature. Attention is paid to adhesins of the cell surface of fungi that determine their colonization and the development of infectious pathology
microscopic fungi, evolution, adhesion, colonization, infectious pathology
Introduction. Fungi represent one of the most numerous and phylogenetically heterogeneous group of unicellular and multicellular aerophilic organisms with heterotrophic nutrition. Being eukaryotes, they combine some features of both plants (have a cell stack) and animals (have a true nucleus). But the shape, structure, life cycles, and features of the chemical composition of mycelial cells and their metabolic products differ significantly from them. Fungi are common in the atmosphere, terrestrial ecosystems and water bodies. At the same time, they perform the most important functions ─ participate in the biogeochemical circulation of substances and differentiation of chemical elements, decompose and mineralize the organic substrate to simple inorganic compounds. Fungi appeared on our planet about 1 billion years ago (in the Proterozoic eon) [4, 6, 8]. During this period, bacteria and algae have already reached their greatest development, the amount of oxygen in the atmosphere has increased to 1%, the climate and the duration of the day have changed [2, 9], different types of reproduction, biomineralization and predation have appeared [5, 10, 11]. In the process of evolution, fungi acquired filamentous mycelium, apical growth, the ability to release hydrolytic enzymes into the environment for the breakdown and assimilation of biogenic and abiogenic substances, adapt to various stressors, etc. Together with plants (430 million years ago), mushrooms emerged from land to land. After that, mycelial and yeast fungi became saprophytes, others - symbionts (human and animal microbiomes), and third parasites (some representatives of the genera Penicillium, Aspergillus, Mucor, Candida, etc.).
The biological structure of fungi is not simple. Only the thickness of their cell membrane is determined by 9-10 fibrillar layers unequal with available electron density [1]. In mycelial fungi, its inner layer consists of chitin and glycans, and the outer matrix consists of a layer of glycoproteins and glucans. and in yeast - from glycoproteins and mannans. Specific receptors (adhesins) are located in certain places on the surface of the cell wall. They ensure the survival, division, isolation of certain enzymes, etc. Most importantly, they initiate the colonization of microorganisms. It is with colonization that most infectious diseases begin.
Among fungi, mainly yeast-like species, species with high and low adhesion were discovered. In model experiments, C. albicans showed higher adhesion than C. tropicalis, while C. kruseu did not have this property. Currently, about 500 species of fungi, due to adhesion, attach to target cells (including blood proteins and muscle fibers) of people suffering from cancer, diabetes mellitus, diseases of the lungs and gastrointestinal tract or taking antibiotics, steroid drugs, etc. Although among there are no extremely dangerous species of fungi; according to the Russian classification, there are pathogens of deep mycoses, conditionally pathogenic (accessible) mycoses caused by a decrease in human immunity and superficial mycoses (dermatophytes) [7]. They cause cryptococcosis, coccilliosis, histoplasmosis, blastomycosis and penicillosis. But candidiasis and aspergillosis are more common. The fungus Candida albicans affects the mucous membranes and skin, fungus Aspergillum affects the internal organs, mucous membranes and skin. The adhesion of fungi is a surface phenomenon, a complex and multifactorial process, which is genetically programmed and is the main sign of the existence of fungi, at the same time is their initial cause of pathogenicity. Объект исследования
Purpose of the study. Visualize the adhesion of mycelium, individual cells and conidia of Penicillium canescens fungi to the surface of mineral substrates when they are cultured in the presence of technogenic objects.
Methodology. In Erlenmeyer flasks with a volume of 250 ml of liquid medium (nitrogen source NaNO3, initial pH 7.0), the 14-day-old conidia of Penicillium canescens were inoculated with a loop. An alkali-washed gold plate of the highest standard was placed in one flask, and sterile samples from the tailings of the processing plant were placed in another. Six days later, the mycelium grown in the flasks was applied onto grids with formar substrate. All preparations were dried, sprayed with carbon in a vacuum unit and viewed on a JEOL jsm-35 C scanning electron microscope (SEM) (Japan). The preparation of mycelium for study in a TESLA BS 500 transmission electron microscope was carried out in the traditional way. Ultrathin sections of the mycelium were performed on an LKB-OWA ultra-microtome.
Results and discussion. As can be seen from fig. 1, the appearance and shape of the strain of
P. caanescens remained virtually unchanged. However, the cell wall and internal structures were intensely “stained” with ions of various metals that were contained in technogenic samples. This convincingly proves the adhesion of branched mycelium to organomineral particles of any size and density. Consequently, nutrients are absorbed by mycelium and distributed in its cells along this chain. Previously, adhesion was called physical or chemical adsorption, which is not true, since adhesion is a more complex diverse phenomenon, which still does not have a unified theory of “binding” mechanisms. heterogeneous materials in close contact.
1 2 3
4 5 6
Fig. 1. Electron microscopy of the fungus Penicillium canescens:
1 - growth of the fungus in the presence of a sample from the Sophia mine concentrate
concentrator (x 1000); 2 - fixation of particles on a cell (x 7000);
3 - particles of colloidal gold on the surface of the myceliumof (x 16000);
4 - cross section of hyphae with many particles on the surface, in the center of the cell nucleus (x 17000); 5 - damage and detachment of the surface layer and septum seeding (x 7000);
6 - adhesion of gold particles with conidia (x 17000).
Thus, according to recent data, fungi as eukaryotes appeared on Earth about a billion years ago. They acquired branched mycelium, apical growth, haploid organization of nuclei and a complex life cycle. Being an integral component of terrestrial and aquatic ecosystems, fungi perform a wide range of biospheric functions, primarily as destructors of organic matter. Their adhesion to biogenic and abiogenic substrates determines the release of digestive exoenzymes and the absorption of nutrients over the entire surface of the mycelium, and is also a pathogenicity factor.
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