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Photomodulation of Protonema Development
Published in R. N. Chopra, Satish C. Bhatla, Bryophyte Development: Physiology and Biochemistry, 2019
The further progress of spore germination is controlled by light. Greening of the spore content and bursting of the exosporium could be induced in Funaria hygrometrica by 3 h of irradiation with white light of low intensity.12 Bauer and Mohr15 demonstrated the involvement of phytochrome in this process. A red-light-induced stimulation of germination could be reversed by a subsequently applied far-red pulse of a few minutes. Apart from the red light stimulation, a lower but significant amount of germination was reported in the far-red control sample. Sophisticated studies by Schild16 and Cove et al.17 demonstrated a complicated involvement of phytochrome in moss spore germination, which is different from light induction in seeds. Krupa18 compared the influence of blue (425 nm) and red (654 nm) light on Funaria spore germination and found that the first light-dependent stage was induced by both spectral ranges. His study, however, revealed a significantly higher effectiveness of red light. Blue light, given after an inductive red irradiation, even caused a decrease in the germination ratio. All spectral regions affected early germination processes in the moss species Ceratodon purpureus, Dicranum scoparium, and F. hygrometrica, showing a lower significance of blue and far-red light for Funaría.19
Ramoplanin
Published in M. Lindsay Grayson, Sara E. Cosgrove, Suzanne M. Crowe, M. Lindsay Grayson, William Hope, James S. McCarthy, John Mills, Johan W. Mouton, David L. Paterson, Kucers’ The Use of Antibiotics, 2017
The mechanism of action of ramoplanin involves sequestration of peptidoglycan biosynthesis lipid intermediates, thus physically occluding these substrates from proper utilization by the late-stage peptidoglycan biosynthesis enzymes MurG and the transglycosylases (Cudic et al., 2002; McCafferty et al., 2002; Fang et al., 2006). This results in sequestering of lipid II, which causes inhibition of cell wall peptidoglycan biosynthesis and cell death. Additionally, ramoplanin was shown to bind to anion membranes of methicillin-susceptible S. aureus (ATCC 25923) and induced membrane depolarization at concentrations at or above the minimum bactericidal concentration (Cheng et al., 2014). Ramoplanin is structurally related to two cell wall–active lipodepsipeptide antibiotics, janiemycin and enduracidin, and is functionally related to members of the lantibiotic class of antimicrobial peptides (mersacidin, actagardin, nisin, and epidermin) and glycopeptide antibiotics (vancomycin and teicoplanin) (McCafferty et al., 2002). As a consequence of the unique mechanism of action of ramoplanin, cross-resistance with existing glycopeptides and beta-lactam antibiotics has not been observed. Ramoplanin has also been suggested to be active against spores of C. difficile. Using spores of C. difficile PCR ribotype 027, ramoplanin adhered to the exosporium, achieved a concentration equilibrium, and acted as an effective antimicrobial as it ambushed the germinating cell (Kraus et al., 2015).
Bacillus
Published in Dongyou Liu, Laboratory Models for Foodborne Infections, 2017
Jessica Minnaard, Ivanna S. Rolny, Pablo F. Pérez
Concerning models of professional phagocytic cells, studies with J774 macrophages demonstrate that the metalloprotease InhA1 (main component of the exosporium) is involved in the escape of Bacillus from macrophages.140 These findings are related to the ability of InhA1 to increase membrane permeability.140
Clostridioides difficile: innovations in target discovery and potential for therapeutic success
Published in Expert Opinion on Therapeutic Targets, 2021
Tanya M Monaghan, Anna M Seekatz, Benjamin H Mullish, Claudia C. E. R Moore-Gillon, Lisa F. Dawson, Ammar Ahmed, Dina Kao, Weng C Chan
Recent evidence suggests that binding by exosporium proteins to mucin glycoproteins is key to initial colonization, involving both binding and internalization of the spore to the intestinal epithelium. In vitro binding studies demonstrated that CotE, a peroxiredoxin-chitinase protein, mediated binding to the mucin glycoproteins, as well as the monomers GlcNAc and GalNAc [26]. Infection with strains lacking CotE also resulted in increased survival in a hamster model of disease. The collagen-like protein BclA1 have previously been demonstrated to aid binding to the epithelial layer [27]. A recent study extended this observation, demonstrating in vitro that BclA3 mediates binding and internalization of the spore via the host proteins fibronectin and vitronectin [28]. Mice infected with a BclA3 mutant strain demonstrated reduced recurrence rates, suggesting that spore adhesion could contribute to the persistence of spores in the gut during antibiotic treatment. Blocking exosporium protein binding may thus represent a therapeutic target to not only decrease initial colonization of C. difficile but also prevent recurrence. Indeed, preliminary studies suggest that BclA3 epitopes can induce anti-spore IgG antibodies in a mouse model of infection, highlighting new vaccine targets to inhibit C. difficile entry and persistence [29].
The Sporobiota of the Human Gut
Published in Gut Microbes, 2021
Muireann Egan, Eugene Dempsey, C. Anthony Ryan, R. Paul Ross, Catherine Stanton
As mentioned above, Bacillus subtilis is considered a model organism for endospore formation.24,25 Unlike the exospores and myxospores described above, endospores are formed within the mother cell which then lyses, releasing the spore.24 The ability to form an endospore depends on the presence of a core set of at least 60 to 100 genes which are specific to the endosporulating species of the Firmicutes phylum. Mutations in these genes can lead to a reduced or inability to sporulate.7,26,27 The master regulator of endosporulation is the spo0A gene, encoding a transcriptional regulator, which is absent in non-sporulating species and outside the Firmicutes phylum.26,28 The structure of the endospore is relatively conserved across species, consisting of a core compartment that contains a single copy of the genome, as well as enzymes, ribosomes and tRNAs. This is surrounded by the inner membrane and germ cell wall which are enveloped by two protective structures, namely the cortex peptidoglycan and the protein coat which are themselves separated by an outer membrane. In some species, usually those of Bacillus cereus sensu lacto, the protein coat is also surrounded by an exosporium (Figure 1).29 Fifteen to twenty-five percent of the dry weight of the spore consists of dipicolonic acid (DPA) which protects the spore DNA from external stressors. DPA is chelated to divalent cations, mostly Ca2+.3 A group of small, acid-soluble spore proteins (SASP) are also essential in spore resistance. These proteins are only found in the spore core, where they saturate the spore DNA, altering its structure and protecting it from heat, certain chemicals, and UV radiation.3
Vaccines against anthrax based on recombinant protective antigen: problems and solutions
Published in Expert Review of Vaccines, 2019
Olga A. Kondakova, Nikolai A. Nikitin, Ekaterina A. Evtushenko, Ekaterina M. Ryabchevskaya, Joseph G. Atabekov, Olga V. Karpova
Apart from recombinant full-size РА-based vaccines, recombinant vaccines based on PA domains are being developed. Flick-Smith et al. [119] designed a panel of recombinant proteins based on individual domains or their combinations, and estimated their immunogenicity and protective efficacy. Immunization of mice with recombinant proteins resulted in different degrees of protection. 100% protection was observed only in the case of immunization with proteins containing domain VI of PA. Abboud and Casadevall [53] demonstrated that immunization of mice with rPA containing all the four domains leads to significantly higher toxin-neutralizing antibody titres than immunization with recombinant proteins containing domain I or domain IV or domains II-IV. To further enhance the immune response, candidate vaccines based on chimeric proteins, including the N-terminal domain of LF and full-length rPA or its domains [120–123], domain IV of PA and the antigenic component of exosporium (Bacillus collagen-like protein of anthracis, BclA) [124], as well as conjugate and combined vaccines based on rPA83 or domain IV of PA and B. anthracis poly-D-γ-glutamic acid (PDGA) [125–128], were developed. Immunization of mice with a new chimeric vaccine, containing domain IV of the PA and BclA N-terminal domain, generated high titers of antibodies, which contributed to the spores phagocytic uptake, inhibited their germinating into vegetative cells and completely protected animals against both B. anthracis Ames spores and the toxin challenge [124]. Candidate vaccines based on PA and PDGA induced a different level of PA-specific and PDGA-specific antibodies titers and demonstrated protectiveness on variable animal models. Chimeric vaccines based on PA and LF in general show a protective efficacy comparable with PA83 [120–123]. However in one study toxin-neutrolizing antibodies titers induced by LF-PA hybrid were 3–7 times lower than that of PA83 [120]. Stability of such vaccines should be explored to assess their prospective use.