Fingerprinting Species and Strains of<i>Bacilli</i>Spores by Distinctive Coat Surface Morphology

Wang, Rong; Krishnamurthy, Soumya; Jeong, Jaesun; Driks, Adam; Mehta, Manav; Gingras, Bruce A.

doi:10.1021/la701788d

Cited by 13 publications

(11 citation statements)

References 37 publications

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“…We restricted our model to two dimensions, both because the wrinkle morphology is that of long ridges along the spore, and in order to focus on a minimal model. Typical parameter values in our model are as follows: spore radius R coat , and thickness, h, of the coat to be approximately 300 and 40 nm, respectively [2,21,22] (see the electronic supplementary material, table S1), the measured elastic modulus of the B. subtilis coat E approximately 13.6 GPa using an atomic force microscope [23] (AFM), and the energy of adhesion between the coat and the cortex, J, approximately 10 J m…”

Section: Resultsmentioning

confidence: 99%

Physical basis for the adaptive flexibility of Bacillus spore coats

Şahin

Yong

Driks

et al. 2012

J. R. Soc. Interface.

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Bacillus spores are highly resistant dormant cells formed in response to starvation. The spore is surrounded by a structurally complex protein shell, the coat, which protects the genetic material. In spite of its dormancy, once nutrient is available (or an appropriate physical stimulus is provided) the spore is able to resume metabolic activity and return to vegetative growth, a process requiring the coat to be shed. Spores dynamically expand and contract in response to humidity, demanding that the coat be flexible. Despite the coat's critical biological functions, essentially nothing is known about the design principles that allow the coat to be tough but also flexible and, when metabolic activity resumes, to be efficiently shed. Here, we investigated the hypothesis that these apparently incompatible characteristics derive from an adaptive mechanical response of the coat. We generated a mechanical model predicting the emergence and dynamics of the folding patterns uniformly seen in Bacillus spore coats. According to this model, spores carefully harness mechanical instabilities to fold into a wrinkled pattern during sporulation. Owing to the inherent nonlinearity in their formation, these wrinkles persist during dormancy and allow the spore to accommodate changes in volume without compromising structural and biochemical integrity. This characteristic of the spore and its coat may inspire design of adaptive materials.

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Section: Resultsmentioning

confidence: 99%

Physical basis for the adaptive flexibility of Bacillus spore coats

Şahin

Yong

Driks

et al. 2012

J. R. Soc. Interface.

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“…showed that the surface of Bacillus thuringiensis is covered with crystalline hexagonal honeycomb structures; the surface of Bacillus cereus spores is covered with small randomly oriented domains. The AFM studies of Chada et al (51), Giorno et al (52), and Wang et al (53) revealed that the Bacillus spore surface is covered with nanometer-sized circular bumps. The surface of Bacillus subtilis and Bacillus anthracis spores is populated by ridge structures largely oriented with the long axis of the spore.…”

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confidence: 99%

Nanomechanical Characterization of Bacillus anthracis Spores by Atomic Force Microscopy

Burggraf

Xing

2016

Appl Environ Microbiol

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The study of structures and properties of bacterial spores is important to understanding spore formation and biological responses to environmental stresses. While significant progress has been made over the years in elucidating the multilayer architecture of spores, the mechanical properties of the spore interior are not known. Here, we present a thermal atomic force microscopy (AFM) study of the nanomechanical properties of internal structures of Bacillus anthracis spores. We developed a nanosurgical sectioning method in which a stiff diamond AFM tip was used to cut an individual spore, exposing its internal structure, and a soft AFM tip was used to image and characterize the spore interior on the nanometer scale. We observed that the elastic modulus and adhesion force, including their thermal responses at elevated temperatures, varied significantly in different regions of the spore section. Our AFM images indicated that the peptidoglycan (PG) cortex of Bacillus anthracis spores consisted of rod-like nanometer-sized structures that are oriented in the direction perpendicular to the spore surface. Our findings may shed light on the spore architecture and properties. IMPORTANCEA nanosurgical AFM method was developed that can be used to probe the structure and properties of the spore interior. The previously unknown ultrastructure of the PG cortex of Bacillus anthracis spores was observed to consist of nanometer-sized rodlike structures that are oriented in the direction perpendicular to the spore surface. The variations in the nanomechanical properties of the spore section were largely correlated with its chemical composition. Different components of the spore materials showed different thermal responses at elevated temperatures. Structures and material properties of bacterial spores play an important role in protecting them against a variety of environmental stresses, such as toxic chemicals (1), radiation (2, 3), and heat (3-5). The current knowledge of spore structures has been obtained largely using transmission electron microscopy (TEM) methods in various forms (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). A mature spore usually shows a concentric multilayer structure, consisting of the core, inner membrane, germ cell wall, cortex, outer membrane, and coat assembly. For Bacillus anthracis spores, there is an exosporium layer that loosely encases the spore. The spore core, which contains mostly DNA, RNA, enzymes, and dipicolinic acid (DPA), is in a dehydrated and metabolically dormant state (21-25). The ability of bacterial spores to survive for long durations, sometimes in harsh environments, has been attributed to the immobilization of essential DNA, RNA, and enzymes by small, acid-soluble spore proteins (SASP) (28-30). It was suggested that the DPA can be intercalated with spore DNA and RNA through covalent bonds, forming a gel-like polymer matrix (26,27). It is worth mentioning that the DPA structure in the spore core is not well understood. The germ cell wall (e.g., inner cortex) and ...

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“…on August 28, 2018 by guest http://aem.asm.org/ and these coat layers have been shown to be significantly flexible and to swell or shrink depending on the degree of spore hydration (39,41). The sixth new conclusion is that during wet-heat treatment SYTO 16 starts to enter the spore core and bind with spore's nucleic acids at a time that is earlier than T lag but close to the time T d of initiation of protein denaturation.…”

Section: Vol 77 2011 Dynamics Of Spore Wet-heat Inactivation 4767mentioning

confidence: 99%

Monitoring the Wet-Heat Inactivation Dynamics of Single Spores of Bacillus Species by Using Raman Tweezers, Differential Interference Contrast Microscopy, and Nucleic Acid Dye Fluorescence Microscopy

Zhang

Kong

Wang

et al. 2011

Appl Environ Microbiol

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Dynamic processes during wet-heat treatment of individual spores of Bacillus cereus, Bacillus megaterium, andBacillus subtilis at 80 to 90°C were investigated using dual-trap Raman spectroscopy, differential interference contrast (DIC) microscopy, and nucleic acid stain (SYTO 16) fluorescence microscopy. During spore wet-heat treatment, while the spores' 1:1 chelate of Ca 2؉ with dipicolinic acid (CaDPA) was released rapidly at a highly variable time T lag , the levels of spore nucleic acids remained nearly unchanged, and the T lag times for individual spores from the same preparation were increased somewhat as spore levels of CaDPA increased. The brightness of the spores' DIC image decreased by ϳ50% in parallel with CaDPA release, and there was no spore cortex hydrolysis observed. The lateral diameters of the spores' DIC image and SYTO 16 fluorescence image also decreased in parallel with CaDPA release. The SYTO 16 fluorescence intensity began to increase during wet-heat treatment at a time before T lag and reached maximum at a time slightly later than T release . However, the fluorescence intensities of wet-heat-inactivated spores were ϳ15-fold lower than those of nutrient-germinated spores, and this low SYTO 16 fluorescence intensity may be due in part to the low permeability of the dormant spores' inner membranes to SYTO 16 and in part to nucleic acid denaturation during the wet-heat treatment.Spores of Bacillus species are formed under starvation conditions and are metabolically dormant and extremely resistant to a variety of physical and chemical agents, including heat, radiation, and many chemical disinfectants (35). Since spores of many of these species can cause food spoilage and foodborne diseases (37), efforts to eliminate spores from foods are routinely made. High-temperature treatment of hydrated spores is very effective in spore killing and is the most common method used by the food industry for spore inactivation, even though hydrated dormant spores invariably resist much higher temperatures than do the growing cells of the same strain (40). Factors that contribute to spore wet-heat resistance include (i) the spore core's low water content (11,20,34), (ii) the core's high level of pyridine-2,6-dicarboxylic acid (dipicolinic acid [DPA]) plus its chelated divalent cations, predominantly Ca 2ϩ

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Fingerprinting Species and Strains ofBacilliSpores by Distinctive Coat Surface Morphology

Cited by 13 publications

References 37 publications

Physical basis for the adaptive flexibility of Bacillus spore coats

Physical basis for the adaptive flexibility of Bacillus spore coats

Nanomechanical Characterization of Bacillus anthracis Spores by Atomic Force Microscopy

Monitoring the Wet-Heat Inactivation Dynamics of Single Spores of Bacillus Species by Using Raman Tweezers, Differential Interference Contrast Microscopy, and Nucleic Acid Dye Fluorescence Microscopy

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