New Thoughts on an Old Topic: Secrets of Bacterial Spore Resistance Slowly Being Revealed

Setlow, Peter; Christie, Graham

doi:10.1128/mmbr.00080-22

Cited by 32 publications

(16 citation statements)

References 187 publications

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“…This is attributed to their protective outer coat layers, the peptidoglycan (PG) layer of the spore cortex, reduced inner membrane permeability, high concentrations of dipicolinic acid with divalent cations, and specialized low-molecular-weight protective proteins. Such features are crucial for maintaining low core water content and safeguarding spore DNA [4–6].…”

Section: Introductionmentioning

confidence: 99%

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Visualization ofBacillus subtilisSpore Structure and Germination using Quick-Freeze Deep-Etch Electron Microscopy

Jalil,

Tahara,

Miyata

2024

Preprint

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Bacterial spores, known for their complex and resilient structures, have been the focus of visualization using various methodologies. In this study, we applied quick-freeze and replica electron microscopy techniques, allowing observation of Bacillus subtilis spores in high-contrast and three-dimensional detail. This method facilitated visualization of the spore structure with enhanced resolution and provided new insights into the spores and their germination processes. We identified and described five distinct structures: (i) hair-like structures on the spore surface, (ii) spike formation on the surface of lysozyme-treated spores, (iii) the fractured appearance of the outer spore cortex during germination, (iv) potential connections between small vesicles and the core membrane, and (v) the evolving surface structure of nascent vegetative cells during germination.

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Section: Introductionmentioning

confidence: 99%

“…A few sections resemble vegetative cell walls with glycan chains. The inner membrane that encloses the core plays an essential role in resistance and germination [6, 12]. The core itself contains a balanced mixture of Ca 2+ and d i p icolinic a cid (CaDPA), ribosomal proteins, and certain lytic enzymes [13, 14].…”

Section: Introductionmentioning

confidence: 99%

Visualization ofBacillus subtilisSpore Structure and Germination using Quick-Freeze Deep-Etch Electron Microscopy

Jalil,

Tahara,

Miyata

2024

Preprint

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“…Organisms can survive adverse conditions by reducing their metabolic activities ( 1 – 3 ). Bacteria such as Bacillus subtilis and other Firmicutes go so far as to produce metabolically dormant endospores (henceforth, spores) that are resistant to extreme environmental challenges including heat, starvation, desiccation, and antibiotics ( 4 , 5 ). Spores are produced through a developmental program that entails the cooperation between two cells of unequal size and developmental fate ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Catabolism of germinant amino acids is required to prevent premature spore germination in Bacillus subtilis

Kasu,

Reyes-Matte,

Bonive-Boscan

et al. 2024

mBio

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Spores of Bacillus subtilis germinate in response to specific germinant molecules that are recognized by receptors in the spore envelope. Germinants signal to the dormant spore that the environment can support vegetative growth, so many germinants, such as alanine and valine, are also essential metabolites. As such, they are also required to build the spore. Here we show that these germinants cause premature germination if they are still present at the latter stages of spore formation and beyond, but that B. subtilis metabolism is configured to prevent this: alanine and valine are catabolized and cleared from wild-type cultures even when alternative carbon and nitrogen sources are present. Alanine and valine accumulate in the spent media of mutants that are unable to catabolize these amino acids, and premature germination is pervasive. Premature germination does not occur if the germinant receptor that responds to alanine and valine is eliminated, or if wild-type strains that are able to catabolize and clear alanine and valine are also present in coculture. Our findings demonstrate that spore-forming bacteria must fine-tune the concentration of any metabolite that can also function as a germinant to a level that is high enough to allow for spore development to proceed, but not so high as to promote premature germination. These results indicate that germinant selection and metabolism are tightly linked, and suggest that germinant receptors evolve in tandem with the catabolic priorities of the spore-forming bacterium. IMPORTANCE Many bacterial species produce dormant cells called endospores, which are not killed by antibiotics or common disinfection practices. Endospores pose critical challenges in the food industry, where endospore contaminations cause food spoilage, and in hospitals, where infections by pathogenic endospore formers threaten the life of millions every year. Endospores lose their resistance properties and can be killed easily when they germinate and exit dormancy. We have discovered that the enzymes that break down the amino acids alanine and valine are critical for the production of stable endospores. If these enzymes are absent, endospores germinate as they are formed or shortly thereafter in response to alanine, which can initiate the germination of many different species' endospores, or to valine. By blocking the activity of alanine dehydrogenase, the enzyme that breaks down alanine and is not present in mammals, it may be possible to inactivate endospores by triggering premature and unproductive germination.

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“…Bacillus subtilis is the standard model for the study of spore development and structure [12]. The spore core is limited by a biomembrane with a thin outer layer of peptidoglycan (i.e., the primary cell wall) and contains the bacterial chromosome which is tightly packed with small acid-soluble proteins (Sasp) in a crystalline-like form to protect the DNA [13]. The core is surrounded by the cortex, the inner and the outer spore coats.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Sporulation in Bacillus cereus Biovar anthracis Which Contains an Insertion in the Gene for the Sporulation Factor σK

Gummelt,

Dupke,

Howaldt

et al. 2023

Pathogens

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Bacillus cereus biovar anthracis (Bcbva) is an untypical pathogen causing a fatal anthrax-like disease in a variety of wildlife species in African rainforest areas. In contrast to Bacillus anthracis and most species of the B. cereus group, all strains of the Bcbva cluster contain a 22 kb insertion in the sigK gene which encodes the essential late sporulation sigma factor σK. This insertion is excised during sporulation in a site-specific recombination process resulting in an intact sigK gene and a circular molecule. The sporulation kinetics of two strains each of Bcbva and B. anthracis were compared by the expression analysis of eight sporulation-associated genes, including sigK, using reverse transcriptase quantitative real-time PCR. In addition, morphological sporulation stages were analyzed and quantified by electron microscopy. Our results indicated that the necessary excision of the insertion in Bcbva neither delayed nor inhibited its sporulation. In two spontaneous mutants of Bcbva, the excision of the sigK insertion and sporulation were impeded due to mutations in the spo0A and spoVG regulator genes, respectively. The spo0A frameshift mutation was overcome by intragenic suppression in a revertant which was able to sporulate normally, despite an M171S amino acid exchange in the global regulator Spo0A. A screening of the NCBI database identified further strains of the B. cereus group which possess unrelated insertions in the sigK gene, and two strains containing almost identical insertions at the same gene position. Some of the sigK insertions encode putative prophages, whereas the Bcbva insertion encoded a type I restriction–modification system. The function of these insertions and if they are possibly essential for sporulation remains to be assessed.

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New Thoughts on an Old Topic: Secrets of Bacterial Spore Resistance Slowly Being Revealed

Abstract: The quest for bacterial survival is exemplified by spores formed by some Firmicutes members. They turn up everywhere one looks, and their ubiquity reflects adaptations to the stresses bacteria face.

Cited by 32 publications

References 187 publications

Visualization ofBacillus subtilisSpore Structure and Germination using Quick-Freeze Deep-Etch Electron Microscopy

Visualization ofBacillus subtilisSpore Structure and Germination using Quick-Freeze Deep-Etch Electron Microscopy

Catabolism of germinant amino acids is required to prevent premature spore germination in Bacillus subtilis

Analysis of Sporulation in Bacillus cereus Biovar anthracis Which Contains an Insertion in the Gene for the Sporulation Factor σK

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