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The Fungi
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Infection is initiated by the inhalation of mycelial microconidia. These microco-nidia are phagocytosed and killed by both alveolar macrophages and PMNs, but if the inoculum is large and some escape killing phase transformation occurs with the production of large (5 to 20 μm in diameter), broad based budding yeast cells with a double refractile wall (Figure 18.3). The yeast cells are much more resistant to the effects of phagocytosis due to their large size, thick cell wall, and their ability to depress the generation of the peroxidase microbicidal system. The alpha-l,3,glucan of the cell wall has been associated with increased virulence though at this time how it does this is not known. It has been demonstrated experimentally, however, that mutants which have low levels of this carbohydrate are less virulent. A 120kD protein known as Wl-1 has recently been isolated from the yeast phase of Blastomyces. This protein functions as an adhesin by binding to the CD14 receptors on macrophages, thereby enhancing phagocytosis. It has been suggested that the abundant alpha-l,3,glucan of the more virulent clones masks this adhesin thereby allowing the yeasts to escape recognition by macrophages and disseminate more readily. Perhaps this is another example of the ability of a pathogen to alter its phenotype in response to environmental pressure.
Fungi and Water
Published in Chuong Pham-Huy, Bruno Pham Huy, Food and Lifestyle in Health and Disease, 2022
Chuong Pham-Huy, Bruno Pham Huy
Yeasts are primitive fungi. They are eukaryotic unicellular microorganisms that are classified, along with mushrooms and molds, as members of the kingdom Fungi (99–101). Evolution of yeasts is diverse; therefore, yeasts are classified into two separate phyla, Ascomycota or sac fungi and Basidiomycota or higher fungi (99, 100). They include about 1,500 identified species; among them, Saccharomyces cerevisiae and Candida albicans are the most well-known (101–102). Yeasts have existed for hundreds of millions of years. Yeast sizes vary from 3–4 μm to 40 μm in diameter (99–103). Yeasts are invisible to the naked eye. Their reproduction is asexual by budding (case of Saccharomyces) or by mitosis (case of Schizosaccharomyces). Yeast cells can also reproduce sexually. In sexual reproduction most yeasts form asci, which contain up to eight haploid ascospores (101).
Quality Control of Ayurvedic Medicines
Published in D. Suresh Kumar, Ayurveda in the New Millennium, 2020
V. Remya, Maggie Jo Alex, Alex Thomas
Several methods are used to monitor fermentation. Important among them is the counting of yeasts. After diluting the fermentation medium, the total number of yeast cells is counted under the microscope using a Malassez cell. The total cells enumerated in this way include both “dead” yeast and “live” yeast. The counting of “viable cells” is a better way to differentiate between the “dead” and “live” cells. When the diluted fermentation medium is placed in a solid nutritive medium, the viable yeast cells form a microscopic cluster. The number of viable yeast cells is enumerated by counting the colonies formed on this medium after nearly four days (Ribéreau-Gayon et al. 2006).
Research Progress in Bioinspired Drug Delivery Systems
Published in Expert Opinion on Drug Delivery, 2020
Qirong Tong, Na Qiu, Jianbo Ji, Lei Ye, Guangxi Zhai
Microbes can be used as mini cell factories to produce specific biopharmaceuticals, antibodies, and even vaccines. As a unicellular organism with a complete cell structure, yeast cells are considered a good choice for delivering drugs, proteins and genes. Elahe et al. successfully encapsulated cholecalciferol (vitamin D3) into Saccharomyces cerevisiae yeast cells-based yeast microcapsules (YS), presenting a high encapsulation efficiency (EE) of 76.10%, and sustained release of vitamin D3 (up to 35.75%) in simulated gastric fluid (SGF) medium (pH = 1.2), with a significant release (up to97.9%) in simulated intestinal fluid (SIF) medium (pH = 7.4), indicating good absorption in the small intestine [134]. There are three primary methods to incorporate particles into YS, including electrostatic interaction, layer-by-layer self-assembly, and surface derivatization, among which electrostatic interaction is the most common approach. Usually, positively charged particles can be efficiently encapsulated by yeast microcapsules while negatively charged particles need the assistance of positively charged particles for incorporation. Being a unicellular organism with a complete cell structure, yeast has a unique advantage over other BDDS. Further strategies based on ‘mini-factory’ need to be considered, including taking advantage of some possible and useful reactions in unicellular organisms including yeast in the design of BDDS.
Cancer Chemopreventive, Antiproliferative, and Superoxide Anion Scavenging Properties of Kluyveromyces marxianus and Saccharomyces cerevisiae var. boulardii Cell Wall Components
Published in Nutrition and Cancer, 2018
Olivier Fortin, Blanca Aguilar-Uscanga, Khanh Dang Vu, Stephane Salmieri, Monique Lacroix
Colorectal cancer (CRC) is the second leading cause of deaths due to cancer in males and the third in females (1). It is also the third most prevalent cancer in Canada (2). Since treatment for CRC can be expensive and invasive for patients, prevention methods still seem to be the most efficient approach. It has been shown that lifestyle plays an important role in the incidence of many cancers, and diet has been related to almost 70% of CRC incidence. Thus, consumption of diet containing agents with CRC preventive properties could reduce the risks of CRC incidence (3). The impact of CRC on the health of the population in Canada and USA triggered a demand of natural products with CRC preventive properties to prevent or reduce the development of this disease. Among natural agents, yeast cell wall components have been interesting due to their anticancer properties which can be utilized in nutrition, in pharmaceutical, and in medical applications (4–7).
Disseminated histoplasmosis: case report and review of the literature
Published in Acta Clinica Belgica, 2018
Séverine Evrard, Philippe Caprasse, Pierre Gavage, Myriam Vasbien, Jean Radermacher, Marie-Pierre Hayette, Rosalie Sacheli, Marjan Van Esbroeck, Lieselotte Cnops, Eric Firre, Laurent Médart, Filip Moerman, Jean-Marc Minon
It is not uncommon for the diagnosis to be made by chance from microscopic examination, especially in non-endemic areas. Microscopy is simple, rapid, and cheap but sensitivity is less than 50% [23]. It can be applied to a large variety of samples including bronchoalveolar lavage, tissue biopsies, peripheral blood, or bone marrow aspiration. Smears are usually stained with May-Grünwald Giemsa and a search for yeasts inside macrophages is carried out. Small yeast cells (2–4 μm in length) are usually ovoid with budding on a narrow base at the smaller end. The yeasts reproduce within monocytes or macrophages and, when released, often remain in clusters. In Giemsa-stained preparations, a pale blue ring (the fungus cell wall) surrounds the darker blue cytoplasm that retracts from the wall, often giving the false impression of a capsule; the chromatin stains dark violet and appears as a crescent-shaped mass within the cell (Figures 1 and 2). A halo or pseudocapsule also appears with H&E, but the organism stains well and evenly with Gomori methenamine silver (GMS) or PAS (Figure 3) [24]. GMS and PAS both stain well structures containing a high proportion of carbohydrates molecules, such as cell walls of fungi. The first one stains structures in black and the second one gives magenta color. They allow differentiation between fungi and protozoa (Leishmania spp.). Penicillium marneffei, another dimorphic fungus, is also stained by GMS and PAS but its yeast-like forms show a characteristic intracytoplasmic transverse septum [25–27]. In some cases of severe disseminated histoplasmosis, accompanied by shock and multiorgan failure, routine peripheral smears may reveal yeast forms within circulating neutrophils [5,13].