Basic Microbiology
Philip A. Geis in Cosmetic Microbiology, 2020
Fungal cells are eukaryotic, containing membrane-bound intracellular organelles, but also possess cell walls. However, rather than peptidoglycan (bacterial) or cellulose (plants), the fungal cell wall is composed of glucans, mannans, glycoproteins, trehalose, and chitin (a strong and flexible polysaccharide). Single-celled microscopic fungi are referred to as “yeasts” and contain a single nucleus and ovoid morphology. Yeasts are commonly larger than bacteria and lack extracellular fibers like flagella or fimbriae. Multicellular fungal forms are called “molds” comprising long branching filaments called hyphae with many individual cells where the cytoplasm in the hyphae are contiguous with neighboring cells. The hyphae of molds generally form a tangled mass called a mycelium. “Dimorphic” fungi are those that can alternate between yeast and mold forms depending on environmental conditions. For example, Histoplasma capsulatum grows in the environment as a mold but upon infection of the lung grows exclusively as a yeast form (3).
Therapeutic Properties of Fermented Foods and Beverages
Megh R. Goyal, Preeti Birwal, Durgesh Nandini Chauhan in Herbs, Spices, and Medicinal Plants for Human Gastrointestinal Disorders, 2023
Bacillus group includes Bacillus licheniformis, B. pumilus and B. subtilis, etc. that carries out alkaline fermentation. This group causes hydrolysis of protein and forms amino acids, peptides and ammonia that can elevate the alkalinity of the substrate (especially protein rich foods, such as: legumes and soybean) as a result of which growth of spoilage causing microorganisms is inhibited.13 Yeast is involved in the fermentation by producing alcohol as the major product. Saccharomyces sp. and Schizo- saccharo myces sp. are the main species that bring about fermentation. S. boulderi and Sch. pombe are dominant yeasts involved in the fermentation of traditional fermented beverages.149 Different changes related to acid and flavor development, production of antimicrobial compounds that are related to change in texture and protein digestibility (Table 16.2) occur in the food products during fermentation.
Autologous Hematopoietic Stem Cell Transplantation for Crohn’s Disease
Richard K. Burt, Alberto M. Marmont in Stem Cell Therapy for Autoimmune Disease, 2019
Further support for intestinal flora as a cause of disease is the presence of anti-Saccharomyces cerevisiae antibody (ASCA) in patients with Crohn’s disease. Saccharomyces cerevisiae is Baker’s yeast. Yeast exert a strong adjuvant effect upon dendritic cells resulting in IL-12 production and priming of T cell responses, and are a commonly used assay for demonstrating intact Th1 delayed type hypersensitivity. ASCA may be used as a diagnostic marker to help differentiate Crohn’s disease from ulcerative colitis.28,29 Proliferation assays of peripheral blood lymphocytes incubated with Saccharomyces cerevisiae and pulsed with tritiated thymidine demonstrate a three fold increase in proliferative response from Crohn’s patients compared to normal controls, including healthy normal bakers.30 Pre and post transplant peripheral blood ASCA antibody, T cell proliferative responses, and T cell lines to intact Saccharomyces cerevisiae and/or extracts from Saccharomyces cerevisiae may be generated and analyzed to determine the role of gut flora in causing Crohn’s disease.
Toxicity of differently sized and charged silver nanoparticles to yeast Saccharomyces cerevisiae BY4741: a nano-biointeraction perspective
Published in Nanotoxicology, 2019
Kaja Kasemets, Sandra Käosaar, Heiki Vija, Umberto Fascio, Paride Mantecca
However, the majority of information on AgNPs as well as on other antimicrobial NPs (e.g. ZnO, CuO) concerns bacteria and relatively little is known on the interaction and toxic effects of NPs to an important group of unicellular microorganisms—yeasts and fungi. Like bacteria, yeasts and fungi (e.g. Candida sp) can also cause serious infections and become drug resistant and therefore there is an emerging need for new effective antifungals (Perfect 2016). AgNPs are considered promising for prevention or treatment of both, bacterial and fungal infections (Dakal et al. 2016). Although unicellular yeast and fungal cells structurally differ from bacterial cells, similar toxicity mechanism of AgNPs both to bacteria and yeasts/fungi have been proposed, e.g. inactivation of enzymes, disruption of cell membrane, interfering with electron transport system, and increasing ROS production (Kim et al. 2009; Saulou et al. 2010; Niazi et al. 2011; Hwang et al. 2012; Bayat et al. 2014; Galván Márquez et al. 2018). However, compared to bacteria, yeasts are generally less sensitive to AgNPs (Dorobantu et al. 2015; Suppi et al. 2015; Khatoon et al. 2017; Suvorov et al. 2017), most probably due to structural differences. Indeed, unlike bacteria, yeasts are eukaryotic organisms having e.g. nucleus, mitochondria, vesicular transport system, and vacuoles resembling the mammalian cell’s lysosomes. Importantly, yeasts have a rigid cell wall consisting of β-glucans, chitin and mannoproteins, and plasma membrane contains ergosterol (unlike mammalian cells having cholesterol).
Baker’s yeast induces apoptotic effects and histopathological changes on skin tumors in mice
Published in Cogent Medicine, 2018
Amany Elwakkad, Mamdooh Ghoneum, Mamdouh El-sawi, Saadia Ibrahim Mohamed, Amina A. Gamal el Din, Deyu Pan, Ghada Mahmoud Elqattan
Baker’s yeast is an essential component for the production of fermented foods like bread and beer. Our earlier studies showed that heat-killed baker’s yeast exerts anticancer activity against different types of cancer. This is based on the observation that cancer cells can engulf yeast, which ultimately shuts down and kills the cancer cell from within. This study aims to assess baker’s yeast as a novel natural product that can cause the death of skin cancer cells in animals. Several parameters were examined and show skin tumors stopped growing and regressed in mice treated with yeast compared to those untreated. Though several treatments for skin cancer exist, these are known to have severe side effects. We show the anticancer effects of yeast as a safe, non-toxic agent, which may suggest its possible use as treatment against skin cancer in humans.
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
Yeasts are largely used in industrial domains especially in food industry. However, cell wall of spent yeasts is often discarded after fermented broth collected or used in many applications such as yeast extract or nutraceutical food supplements (8, 9). Yeast cell walls are organized with approximately the same polysaccharides which mainly consist of mannoprotein, chitin, and (1→3)-β-D-glucan with (1→6)-β-D-glucan ramifications (10). Many studies have investigated the natural properties of yeast cell wall and suggested that their sugar composition, notably the β-glucan component, is mostly responsible for their strong anticancer, antineoplastic, and chemical properties in in vitro and in vivo models (11–13). Those properties depend on physicochemical nature of polysaccharides, such as molecular weight and sugars ratios, along with integrity of the polysaccharides network (e.g., triple-helix structure of glucan) which vary according to growth conditions, extraction methods, and yeast species (4, 14–16).