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Basic Microbiology
Published in Philip A. Geis, Cosmetic Microbiology, 2020
Endospore—In a few genera, bacteria can internally generate this protective structure by a process termed “sporulation” usually induced by unfavorable conditions. The endospore is an environmentally resistant, metabolically inert structure which contains, at the least, the bacterial DNA, some proteins, calcium, and dipicolinic acid. Upon the return of favorable conditions, the endospore can reproduce the growing form of the bacteria by “vegetation” or outgrowth. Few genera contain spore-forming bacteria, most notably the Clostridium and Bacillus genera form spores.
Coccidioidomycosis
Published in Rebecca A. Cox, Immunology of the Fungal Diseases, 2020
The mold colony cultured from patients with coccidioidomycosis and the sporangia-like form observed in tissues represent the mycelial and spherule/endospore phases of C. immitis. In its saprobic form, the fungus exists in soil in the semi-arid regions of the Western Hemisphere, in an area extending from California to Argentina.8, 9 Endemic areas within the U.S. include parts of California, Arizona, Nevada, Utah, New Mexico, and Texas, which correspond to the Lower Sonoran Life Zone. The mycelia propagate by the formation of alternating enterothallic arthroconidia (previously designated arthrospores).10–12 These infectious arthroconidia (measuring 2 to 5 µm in length) are released by disintegration of the adjacent sterile cells and become airborne. Within host tissue, the arthroconidia transform into round cells that progressively enlarge with concomitant nuclear replication. These immature spherules undergo an internal segmentation process that leads to the formation of endospores. At maturity, the spherules (measuring up to 60 µm in diameter) rupture, releasing numerous endospores which then repeat the parasitic phase.11–13 This multiphasic, morphogenetic cycle (depicted in Figure 1) is unique among the pathogenic fungi and, by virtue of cell size and antigenic variance,14–18 presents a formidable challenge to the host’s immunologic armory.
Coccidioides
Published in Rossana de Aguiar Cordeiro, Pocket Guide to Mycological Diagnosis, 2019
During the filamentous phase of the biological cycle, Coccidioides spp. form hyaline hyphae that originate arthroconidia up to 7.5 μm in length, intercalated with cells devoid of cytoplasmic material (de Hoog et al., 2000). Arthroconidia are easily detachable from the vegetative mycelium and have cell wall remnants of the breaker cells at their ends, which facilitate their aerial dispersion. Upon being inhaled by a susceptible host, the arthroconidia undergo morphological changes, giving rise to yeast-like structures. In this parasitic phase, large, rounded, thick-walled structures called spherules appear, with a diameter varying from 20–200 μm. These structures increase in size and undergo successive cell divisions, and, upon reaching maturity approximately 72 hours later, release more than 800 endospores—small unicellular structures of 2–5 μm. Each endospore begins the development of a new spherule, resulting in exponential reproduction. Upon reaching the soil, the endospores grow into the filamentous form, thus guaranteeing continuity of the biological cycle (Cox & Magee, 2004).
Effect of bacterial toxin identified from the Bacillus subtilis against the Cnaphalocrocis medinalis Guenée (Lepidoptera: Crambidae)
Published in Toxin Reviews, 2023
Ramakrishnan Ramasubramanian, Sengodan Karthi, Sengottayan Senthil-Nathan, Haridoss Sivanesh, Narayanan Shyam Sundar, Vethamonickam Stanley-Raja, Govindaraju Ramkumar, Kanagaraj Muthu-Pandian Chanthini, Prabhakaran Vasantha-Srinivasan, Khaloud Mohammed Alarjani, Mohamed S Elshikh, Ahmed Abdel-Megeed, Patcharin Krutmuang
Entomopathogenic bacterial spores can be effective against insect pests and act as bacterial pesticides. Research continues to demonstrate the application of bacterial-based insecticides against a wide range of insect pests across many cropping systems (Usta 2013, Ruiu 2015). Almost all groups of microbes which include fungi, bacteria, yeast and viruses have members with the potential to produce toxins that can significantly suppress insect survival (Kumari et al. 2014, Chalivendra 2021). The genome B. subtilis encrypts ten chemoreceptors recognized as ligands, which are composed of carbon, amino acids, and oxygen (Hashem et al. 2019). Species of Bacillus generally make endospores to endure under environmental conditions. Spores permit long-term storage of biological control agents and can be delivered using a variety of formulations (Hashem et al. 2019). In general, strains of Bacillus have been shown to produce a natural blend of bio-active metabolites that are effective in controlling insect pests of plants and diseases caused by plant pathogens (Asaka and Shoda 1996, Ghribi et al. 2012). The present study reported on the detrimental effects of B. subtilis on larval stages of C. medinalis when ingested with treated rice leaves.
Visualizing germination of microbiota endospores in the mammalian gut
Published in Gut Microbes, 2022
Ningning Xu, Liyuan Lin, Yahui Du, Huibin Lin, Jia Song, Chaoyong Yang, Wei Wang
Many Gram-positive bacteria propagate by forming and spreading endospores. Recalcitrant to desiccation and most disinfectants, the production of endospores permits long-term survival of the microbes in hostile environments.1,2 Bacterial sporulation is initiated by an asymmetric cell division through the formation of a polar septum; after this prespore is engulfed by the mother cell, several durable proteinaceous layers are then assembled onto the forespore surface,3 which protect them from being lyzed by enzymes. The forespore then matures after its chromosome is saturated with small, acid-soluble proteins and cytoplasm partially dehydrated, enabling endospores’ resistance to UV radiation and heat. The mature endospores can then be released, and ubiquitously found in soil, water, air and almost all human surroundings.4–6 People can unintentionally inhale or ingest endospores, and their germination into vegetative bacteria in the respiratory or gastrointestinal tracts can profoundly affect our health.
Gut associated metabolites and their roles in Clostridioides difficile pathogenesis
Published in Gut Microbes, 2022
Andrea Martinez Aguirre, Joseph A. Sorg
Endospores are metabolically dormant forms of spore-forming bacteria produced in response to stress (e.g., nutrient limitation).9–11 For C. difficile, the spore form is essential for host-to-host transmission due to the strictly anaerobic nature of the vegetative form.12–14 Thus, in susceptible hosts, C. difficile spores must germinate into the active, vegetative form in order to multiply and cause disease. Germination by C. difficile spores is triggered upon recognition of certain bile acids and amino acids by germinant receptors.11,15,16