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Special Issue "Bacterial Spores"

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Molecular Microbiology".

Deadline for manuscript submissions: 30 June 2021.

Special Issue Editors

Prof. Dr. Ezio Ricca
Website
Guest Editor
Università degli Studi di Napoli Federico II, Naples, Italy
Interests: bacterial spores; spore structure; Bacillus; probiotics; spore-display
Prof. Dr. Simon M. Cutting
Website
Co-Guest Editor
Royal Holloway University of London
Interests: Bacillus; spore formers; Clostridium difficile; vaccines; probiotics
Prof. Dr. Imrich Barak
Website
Co-Guest Editor
Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, Slovakia
Interests: bacterial sporulation; spore coat; bacterial cell division; programmed cell death

Special Issue Information

Dear Colleagues,

This Special Issue will follow the 9th European Spores Conference, which will be held in Naples, Italy, on 15–17 April 2020 (www.sporesconference.org). Selected topics from those presented at the conference will be the core of this Special Issue on “Bacterial Spores”, focused on basic and applied research on spore-forming bacteria, mainly belonging to the Bacillus and Clostridium genera.

For many years, spore formers have been considered to be model systems to study gene expression, microbial differentiation, and formation of complex subcellular structures. Besides remaining powerful models, spore formers have recently received growing attention because of the possible use of spores as probiotics, mucosal delivery systems, and live nanobiotechnological tools with multiple potential applications. In addition, spore formers of some species, including C. difficile and B. cereus, are involved in a number of diseases and have been linked to foodborne outbreaks.

Based on these considerations, this Special Issue will gather papers from a number of leading scientists in the field, which is a very active area of basic microbiology research with a strong impact on applied sciences, ranging from health to food safety to bioremediation.

Prof. Dr. Ezio Ricca
Prof. Dr. Simon M. Cutting
Prof. Dr. Imrich Barak
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Molecular Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. There is an Article Processing Charge (APC) for publication in this open access journal. For details about the APC please see here. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • bacterial spores
  • spore structure
  • spore formers
  • Bacillus
  • Clostridium
  • probiotics

Published Papers (5 papers)

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Research

Open AccessArticle
Nasal Immunization with the C-Terminal Domain of Bcla3 Induced Specific IgG Production and Attenuated Disease Symptoms in Mice Infected with Clostridioides difficile Spores
Int. J. Mol. Sci. 2020, 21(18), 6696; https://doi.org/10.3390/ijms21186696 - 13 Sep 2020
Abstract
Clostridioides difficile is a Gram-positive, spore-forming bacterium that causes a severe intestinal infection. Spores of this pathogen enter in the human body through the oral route, interact with intestinal epithelial cells and persist in the gut. Once germinated, the vegetative cells colonize the [...] Read more.
Clostridioides difficile is a Gram-positive, spore-forming bacterium that causes a severe intestinal infection. Spores of this pathogen enter in the human body through the oral route, interact with intestinal epithelial cells and persist in the gut. Once germinated, the vegetative cells colonize the intestine and produce toxins that enhance an immune response that perpetuate the disease. Therefore, spores are major players of the infection and ideal targets for new therapies. In this context, spore surface proteins of C. difficile, are potential antigens for the development of vaccines targeting C. difficile spores. Here, we report that the C-terminal domain of the spore surface protein BclA3, BclA3CTD, was identified as an antigenic epitope, over-produced in Escherichia coli and tested as an immunogen in mice. To increase antigen stability and efficiency, BclA3CTD was also exposed on the surface of B. subtilis spores, a mucosal vaccine delivery system. In the experimental conditions used in this study, free BclA3CTD induced antibody production in mice and attenuated some C. difficile infection symptoms after a challenge with the pathogen, while the spore-displayed antigen resulted less effective. Although dose regimen and immunization routes need to be optimized, our results suggest BclA3CTD as a potentially effective antigen to develop a new vaccination strategy targeting C. difficile spores. Full article
(This article belongs to the Special Issue Bacterial Spores)
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Open AccessArticle
Visualization of Germination Proteins in Putative Bacillus cereus Germinosomes
Int. J. Mol. Sci. 2020, 21(15), 5198; https://doi.org/10.3390/ijms21155198 - 22 Jul 2020
Abstract
Bacillus cereus can survive in the form of spores for prolonged periods posing a serious problem for the manufacture of safe shelf-stable foods of optimal quality. Our study aims at increasing knowledge of B. cereus spores focusing primarily on germination mechanisms to develop [...] Read more.
Bacillus cereus can survive in the form of spores for prolonged periods posing a serious problem for the manufacture of safe shelf-stable foods of optimal quality. Our study aims at increasing knowledge of B. cereus spores focusing primarily on germination mechanisms to develop novel milder food preservation strategies. Major features of B. cereus spores are a core with the genetic material encased by multiple protective layers, an important one being the spores′ inner membrane (IM), the location of many important germination proteins. To study mechanisms involved in germination of B. cereus spores, we have examined the organization of germinant receptors (GRs) in spores′ IM. Previous studies have indicated that in spores of B.cereus ATCC 14579 the L-alanine responsive GR, GerR, plays a major role in the germination process. In our study, the location of the GerR GR subunit, GerRB, in spores was examined as a C-terminal SGFP2 fusion protein expressed under the control of the gerR operon′s promoter. Our results showed that: (i) the fluorescence maxima and integrated intensity in spores with plasmid-borne expression of GerRB-SGFP2 were significantly higher than in wild-type spores; (ii) western blot analysis confirmed the expression of the GerRB-SGFP2 fusion protein in spores; and (iii) fluorescence microscopy visualized GerRB-SGFP2 specific bright foci in ~30% of individual dormant spores if only GerRB-SGFP2 was expressed, but, noticeably, in ~85% of spores upon co-expression with GerRA and GerRC. Our data corroborates the notion that co-expression of GR subunits improves their stability. Finally, all spores displayed bright fluorescent foci upon expression of GerD-mScarlet-I under the control of the gerD promoter. We termed all fluorescent foci observed germinosomes, the term used for the IM foci of GRs in Bacillus subtilis spores. Our data are the first evidence for the existence of germinosomes in B. cereus spores. Full article
(This article belongs to the Special Issue Bacterial Spores)
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Open AccessArticle
Linking the Peptidoglycan Synthesis Protein Complex with Asymmetric Cell Division during Bacillus subtilis Sporulation
Int. J. Mol. Sci. 2020, 21(12), 4513; https://doi.org/10.3390/ijms21124513 - 25 Jun 2020
Cited by 1
Abstract
Peptidoglycan is generally considered one of the main determinants of cell shape in bacteria. In rod-shaped bacteria, cell elongation requires peptidoglycan synthesis to lengthen the cell wall. In addition, peptidoglycan is synthesized at the division septum during cell division. Sporulation of Bacillus subtilis [...] Read more.
Peptidoglycan is generally considered one of the main determinants of cell shape in bacteria. In rod-shaped bacteria, cell elongation requires peptidoglycan synthesis to lengthen the cell wall. In addition, peptidoglycan is synthesized at the division septum during cell division. Sporulation of Bacillus subtilis begins with an asymmetric cell division. Formation of the sporulation septum requires almost the same set of proteins as the vegetative septum; however, these two septa are significantly different. In addition to their differences in localization, the sporulation septum is thinner and it contains SpoIIE, a crucial sporulation specific protein. Here we show that peptidoglycan biosynthesis is linked to the cell division machinery during sporulation septum formation. We detected a direct interaction between SpoIIE and GpsB and found that both proteins co-localize during the early stages of asymmetric septum formation. We propose that SpoIIE is part of a multi-protein complex which includes GpsB, other division proteins and peptidoglycan synthesis proteins, and could provide a link between the peptidoglycan synthesis machinery and the complex morphological changes required for forespore formation during B. subtilis sporulation. Full article
(This article belongs to the Special Issue Bacterial Spores)
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Open AccessArticle
Artificial Sporulation Induction (ASI) by kinA Overexpression Affects the Proteomes and Properties of Bacillus subtilis Spores
Int. J. Mol. Sci. 2020, 21(12), 4315; https://doi.org/10.3390/ijms21124315 - 17 Jun 2020
Abstract
To facilitate more accurate spore proteomic analysis, the current study focuses on inducing homogeneous sporulation by overexpressing kinA and assesses the effect of synchronized sporulation initiation on spore resistance, structures, the germination behavior at single-spore level and the proteome. The results indicate that, [...] Read more.
To facilitate more accurate spore proteomic analysis, the current study focuses on inducing homogeneous sporulation by overexpressing kinA and assesses the effect of synchronized sporulation initiation on spore resistance, structures, the germination behavior at single-spore level and the proteome. The results indicate that, in our set up, the sporulation by overexpressing kinA can generate a spore yield of 70% within 8 h. The procedure increases spore wet heat resistance and thickness of the spore coat and cortex layers, whilst delaying the time to spore phase-darkening and burst after addition of germinant. The proteome analysis reveals that the upregulated proteins in the kinA induced spores, compared to spores without kinA induction, as well as the ‘wildtype’ spores, are mostly involved in spore formation. The downregulated proteins mostly belong to the categories of coping with stress, carbon and nitrogen metabolism, as well as the regulation of sporulation. Thus, while kinA overexpression enhances synchronicity in sporulation initiation, it also has profound effects on the central equilibrium of spore formation and spore germination, through modulation of the spore molecular composition and stress resistance physiology. Full article
(This article belongs to the Special Issue Bacterial Spores)
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Open AccessArticle
Induction of a Specific Humoral Immune Response by Nasal Delivery of Bcla2ctd of Clostridioides difficile
Int. J. Mol. Sci. 2020, 21(4), 1277; https://doi.org/10.3390/ijms21041277 - 14 Feb 2020
Cited by 1
Abstract
Clostridioides difficile, formerly known as Clostridium difficile, is a spore-forming bacterium considered as the most common cause of nosocomial infections in developed countries. The spore of C. difficile is involved in the transmission of the pathogen and in its first interaction [...] Read more.
Clostridioides difficile, formerly known as Clostridium difficile, is a spore-forming bacterium considered as the most common cause of nosocomial infections in developed countries. The spore of C. difficile is involved in the transmission of the pathogen and in its first interaction with the host; therefore, a therapeutic approach able to control C. difficile spores would improve the clearance of the infection. The C-terminal (CTD) end of BclA2, a spore surface protein of C. difficile responsible of the interaction with the host intestinal cells, was selected as a putative mucosal antigen. The BclA2 fragment, BclA2CTD, was purified and used to nasally immunize mice both as a free protein and after adsorption to the spore of Bacillus subtilis, a well-established mucosal delivery vehicle. While the adsorption to spores increased the in vitro stability of BclA2CTD, in vivo both free and spore-adsorbed BclA2CTD were able to induce a similar, specific humoral immune response in a murine model. Although in the experimental conditions utilized the immune response was not protective, the induction of specific IgG indicates that free or spore-bound BclA2CTD could act as a putative mucosal antigen targeting C. difficile spores. Full article
(This article belongs to the Special Issue Bacterial Spores)
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