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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.
Aetiology and Laboratory Diagnosis
Published in Raimo E Suhonen, Rodney P R Dawber, David H Ellis, Fungal Infections of the Skin, Hair and Nails, 2020
Raimo E Suhonen, Rodney P R Dawber, David H Ellis
Cultures of these species are usually sterile with no conidia present. Chlamydoconidia or other hyphal structures may be present but are non-diagnostic. In practice sporulation may need stimulation, e.g. to decide between non-sporing strains of M. canis or T. rubrum. Common species in this group include M. audouinii, T. verrucosum and T. violaceum. Less common ones are T. concentricum, T. schoenleinii, T. soudanense and M. ferrugineum.
Therapy with Oncolytic Clostridium novyi-NT: From Mice to Men
Published in Ananda M. Chakrabarty, Arsénio M. Fialho, Microbial Infections and Cancer Therapy, 2019
The C. novyi-NT spore is approximately 1–1.5 μm in diameter, with a multilayered spore coat to ensure its resilience in a potentially hostile environment. Ultrastructural studies suggest that formation of the spore coat layers follows a self-assembly process similar to crystallization, which could be influenced by pH, salt concentrations, and impurities in the sporulation culture [85]. Thus, the protocol for spore manufacture should be standardized to minimize variation in the quality of spores. Mature C. novyi-NT spores contain mRNA enriched in those encoding proteins for biosynthesis and degradation of the spores [86]. The mRNA molecules are quite stable despite incubation of the spores at 37° C for 14 days followed by storage at 4° C for a year. The mRNA stored in spores could allow rapid synthesis of proteins that are required in the initial stage of germination. The spore-specific mRNA also includes those predicted to code for proteins with redox activity, such as glutathione peroxidase, NADPH thioredoxin reductase, and glutaredoxin. Interestingly, the genes for these proteins are organized into a single operon. Furthermore, glutathione peroxidases have been implicated as major scavengers for hydrogen peroxide and several organic hydroperoxides in other organisms [86–88]. Thus, it is tempting to speculate that the pre-existing mRNA would allow rapid reconstitution of a redox chain during germination to ensure the reduced microenvironment necessary for the survival of a nascent oxygen-sensitive vegetative bacterium.
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.
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).
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.