Clostridium
Dongyou Liu in Handbook of Foodborne Diseases, 2018
Sporulation is crucial for pathogenesis of these pathogens clostridia since toxin expression is sporulation specific. Nutrient derivation and other environmental factors have been implicated as the trigger that starts the process of sporulation of clostridia.34 During normal vegetative growth, cells divide symmetrically by binary fission, and the cells exhibit the typical rod-shaped morphology while consuming glucose and producing organic acids. When acid concentrations increase and the pH of the medium drops, the environment becomes increasingly toxic to the cells. Then, the cells initiate the survival mechanism: sporulation.35,36 Sporulation, which results in a highly resistant spore, is a long-term survival mechanism allowing the cells to survive until a more suitable environment is established. Spores are considered important for the transmission of Clostridium food poisoning, as they likely facilitate survival in temperature-abused foods.
The Azolia-Anabaena Symbiosis
Peter M. Gresshoff in Molecular Biology of Symbiotic Nitrogen Fixation, 2018
Azolla reproduces both asexually and sexually. Sexual reproduction of Azolla is a most complex and improbable process that presents many fascinating challenges to developmental biologists. The fern is the sporophyte generation. The male and female gametophytes are small, different from the other, and arise in microspores and megaspores, respectively. The two kinds of spore develop in micro- and megasporangia, borne in micro- and megasporocarps. Sporulation is sporadic in nature. Ferns of some species sporulate at regular intervals, while others very rarely, if ever, produce spores. The factors controlling the induction of sporulation are not understood; however, in Azolla filiculoides it is associated with mat formation11 and occurs in summer months in temperate regions.12
Fungal Allergens
Richard F. Lockey, Dennis K. Ledford in Allergens and Allergen Immunotherapy, 2014
Fungi are usually heterotrophic, which means they cannot fix carbon because they lack chlorophyll [2]. The various modes of fungal reproduction include fragmentation, fission, budding, and spore production, and most produce both sexual and asexual spores. Fungal spores can be thick-walled, dry, pigmented, hydrophobic or colorless, and slimy [2]. Fungal cell walls are composed of chitin (acetyl glucosamine polymer) but also may contain mannans, glucans, and cellulose [2]. The fungal cell membrane is composed of ergosterol; DNA content is very low whereas RNA in the form of ribosomal RNA may comprise up to 10% of the dry weight of a fungus [2]. Glycogen is the main storage carbohydrate of fungi that allows them to metabolize glucose by aerobic respiration into CO2 and water or by fermentation into CO2 and alcohol or lactic acid [2]. Fungi produce many unique protease enzymes that are important for the degradation of resistant materials like cellulose and polyethylene [2].
Flagellum and toxin phase variation impacts intestinal colonization and disease development in a mouse model of Clostridioides difficile infection
Published in Gut Microbes, 2022
Dominika Trzilova, Mercedes A. H. Warren, Nicole C. Gadda, Caitlin L. Williams, Rita Tamayo
Sporulation was assayed as described previously.66 Briefly, C. difficile strains were grown overnight in BHIS medium supplemented with 0.1% taurocholic acid (TA) and 0.2% fructose to prevent spore accumulation. Cultures were diluted 1:30 in BHIS-0.1% TA-0.2% fructose and upon reaching OD600 0.5, 250 µL of culture was applied to 70:30 agar.64 An ethanol resistance sporulation assay was performed at this point to confirm the absence of spores at the initiation of the assay. After 24 hours of growth at 37°C, cells were suspended in BHIS to an OD600 1.0, and an ethanol resistance assay was performed. To eliminate all vegetative cells, 0.5 mL of culture was mixed with 0.5 mL of 57% ethanol to achieve a final concentration of 28.5% ethanol, vortexed and incubated for 15 minutes. To enumerate spores, serial dilutions were made in PBS-0.1% TA and plated on BHIS-0.1% TA agar. To enumerate vegetative cells, serial dilutions of the BHIS cell suspension were plated on BHIS agar. Sporulation efficiency was calculated as the total number of spores divided by the total number of viable cells (spores plus vegetative).
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.
A case of mistaken identity: Saksenaea vasiformis of the orbit
Published in Orbit, 2021
Allison J. Chen, Lilangi S. Ediriwickrema, Rohan Verma, Vera Vavinskaya, Solomon Shaftel, Adam S. Deconde, Bobby S. Korn, Don O. Kikkawa, Catherine Y. Liu
This is a rare case of chronic, invasive rhino-orbital Saksenaea vasiformis infection. To the authors' knowledge, there are two prior cases reported in a 21-month-old child in sub-Saharan Africa and in an 11-year-old child in Missouri, both of whom were immunocompetent, presented in a subacute fashion, and received systemic, but not intra-orbital, antifungal treatment.5,6 On pathology, it is difficult and sometimes not possible to distinguish this diagnosis from Mucor as both produce broad irregularly branching hyphae with rare or no septations. Furthermore, growth on media requires extended time and use of nutrient-depleted media such as tap water agar to induce sporulation.7Saksenaea typically infects skin and soft tissue in immunocompetent hosts and is generally susceptible to systemic AmB and posaconazole treatment.8 The patient presented to our hospital with the presumed diagnosis of Mucor. Given the high associated mortality rate, the patient was initially treated accordingly. Her stable appearance and immunocompetence, however, raised suspicion for an alternate diagnosis.
Related Knowledge Centers
- Endospore
- Multicellular Organism
- Ploidy
- Sexual Reproduction
- Meiosis
- Biological Dispersal
- Biological Life Cycle
- Mitosis
- Zygote
- Alternation of Generations