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Amatoxin
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
A. phalloides can reproduce both sexually through mitosis and sexually through fertilization, meiosis, and hyphal fusion. In asexual reproduction, spores (dispersed by basidiospores, which are generated by basidia on the gills) develop through mitosis into hyphae, mycelium, and then mature fruiting bodies without involving spores of opposite mating types. In sexual reproduction, after the fruiting body matures, the basidia (singular basidium) undergo karyogamy (fusion of two nuclei or fertilization) to create zygote (with one nucleus, or diploid cell). The newly fertilized zygote undergoes meiosis (or germination) to generate basidium that contains basidiospores (with haploid number of chromosomes), which, once dispersed, are called the primary mycelium. As the haploid basidiospores keep increasing through mitosis, the basidiospores from opposite mating types meet at one point and undergo hyphal fusion (plasmogamy), during which the cytoplasms of the two mating types of basidiospores fuse together into the secondary mycelium (with two separated nuclei, “dikaryon”) and then into a new fruiting body through mitosis.
Pneumocystis carinii
Published in Peter D. Walzer, Robert M. Genta, Parasitic Infections in the Compromised Host, 2020
Peter D. Walzer, C. Kurtis Kim, Melanie T. Cushion
The life-cycle studies conducted in our laboratory have focused on rat P. carinii obtained from infected lung homogenates or grown in tissue culture (103). Human P. carinii from bronchoalveolar lavage specimens has also been used. Most of these studies have used a combination of light microscopic and staining techniques to perform detailed examination of P. carinii stages in unfixed specimens. These procedures were chosen to avoid alterations induced by harsh reagents used in the fixation and embedding process. All developmental stages identified using these procedures were verified by examination of impression smears stained with Diff Quik, a variant of the Giemsa stain. From these data, we have proposed a life cycle for P. carinii that includes both an asexual and a sexual phase of development (Fig. 2). The predominant form of the organism in culture is the trophic form, which frequently occurs in large clusters together with other developmental stages. These forms appear to replicate by binary fission in the lung, and this replicatoon probably occurs in vitro as well. Initiation of the sexual cycle in other protozoans usually begins with gametic fusion and karyogamy (nuclear fusion). Since microgametic or macrogametic forms of P. carinii have not been identified, it may be possible that some forms identified as trophic stages function as isogametes (Fig. 2A, B) (105). Once nuclear fusion takes place, the diploid zygote is formed and is considered an early precyst (80). Subsequent meiosis and mitosis occur within the cyst wall, and the organism differentiates from the precyst to the mature cyst form. We have identified various cystic stages, based on the morphological changes of the intracystic bodies, ranging from ellipsoidal forms to very elongated thin forms (Fig. 2J-N). Presumably the crescent-shaped forms represent empty excysted cysts, although the actual process of excystment has not been adequately documented.
Enhanced production of tanshinone IIA in endophytic fungi Emericella foeniculicola by genome shuffling
Published in Pharmaceutical Biology, 2018
Pengyu Zhang, Yiting Lee, Xiying Wei, Jinlan Wu, Qingmei Liu, Shanning Wan
Genome shuffling is dependent upon the recursive fusion of protoplasts to carry out recombination. This recursive strategy permits the quick obtainment of phenotypes of interest. The high frequency of protoplast formation and regeneration is the basis of the efficient genome shuffling. When the protoplasts were mixed with PEG solution, they stuck together and then formed paired protoplasts. Later, the plasma membranes in the contact area of protoplasts were dissolved, and the protoplasmic contents were fused. The fusion of two or more cell membranes and the resultant formation of a heterokaryon were observed through a high-power microscope. Subsequently, the nuclei of some paired protoplasts were fused together (karyogamy). Ultimately, the fused protoplasts were turned into single, large, round or oval-shaped structures, respectively (data not shown).