1
|
Liu ZL, Chen X. Water-Content-Dependent Morphologies and Mechanical Properties of Bacillus subtilis Spores' Cortex Peptidoglycan. ACS Biomater Sci Eng 2022; 8:5094-5100. [PMID: 36442506 DOI: 10.1021/acsbiomaterials.2c01209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Peptidoglycan (PG), bacterial spores' major structural component in their cortex layers, was recently found to regulate the spore's water content and deform in response to relative humidity (RH) changes. Here, we report that the cortex PG dominates the Bacillus subtilis spores' water-content-dependent morphological and mechanical properties. When exposed to an environment having RH varied between 10% and 90%, the spores and their cortex PG reversibly expand and contract by 30.7% and 43.2% in volume, which indicates that the cortex PG contributes to 67.3% of a spore's volume change. The spores' and cortex PG's significant volumetric changes also lead to changes in their Young's moduli from 5.7 and 9.0 GPa at 10% RH to 0.62 and 1.2 GPa at 90% RH, respectively. Interestingly, these significant changes in the spores' and cortex PG's morphological and mechanical properties are only caused by a minute amount of the cortex PG's water exchange that occupies 28.0% of the cortex PG's volume. The cortex PG's capability in sensing and responding to environmental RH and effectively changing its structures and properties could provide insight into spores' high desiccation resistance and dormancy mechanisms.
Collapse
Affiliation(s)
- Zhi-Lun Liu
- Advanced Science Research Center (ASRC), The City University of New York, 85 St. Nicholas Terrace, New York, New York10031, United States.,Department of Chemical Engineering, The City College of New York, 275 Convent Ave., New York, New York10031, United States
| | - Xi Chen
- Advanced Science Research Center (ASRC), The City University of New York, 85 St. Nicholas Terrace, New York, New York10031, United States.,Department of Chemical Engineering, The City College of New York, 275 Convent Ave., New York, New York10031, United States.,Ph.D. Program in Physics, The Graduate Center of the City University of New York, 365 Fifth Ave., New York, New York10016, United States.,Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, 365 Fifth Ave., New York, New York10016, United States
| |
Collapse
|
2
|
Swanson J, Navarrette A, Hazelton C, Richmann M, Stanley F. Biomass and salt-dependent effects of Bacillus spores on radionuclide migration from the Waste Isolation Pilot Plant. CHEMOSPHERE 2021; 280:130680. [PMID: 34162079 DOI: 10.1016/j.chemosphere.2021.130680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/19/2021] [Accepted: 04/20/2021] [Indexed: 06/13/2023]
Abstract
Spores of a Bacillus sp., isolated from radioactive waste, were tested for their ability to influence the fate and transport of neodymium (Nd3+) under high salt conditions expected at the Waste Isolation Pilot Plant (WIPP) nuclear waste repository. Spores were suspended in neodymium-spiked saline solutions up to 4 M NaCl, and concentrations of Nd and the complexing agent dipicolinic acid (DPA), a component of spores, were monitored along with optical densities and spore numbers. Results support neodymium bioassociation that is dependent upon biomass, with more apparent adsorption occurring at higher spore concentrations. However, probable spore lysis in 2 and 4 M NaCl solutions and possible germination at 0.15 M NaCl appear to drive the release of DPA and subsequent return of Nd to solution. The implications of this work for the WIPP will depend on actual biomass levels and the ionic strength of the repository brines.
Collapse
Affiliation(s)
- Juliet Swanson
- Los Alamos National Laboratory-Carlsbad Operations, 1400 University Drive, Carlsbad, NM, 88220, USA.
| | - Adrianne Navarrette
- Los Alamos National Laboratory-Carlsbad Operations, 1400 University Drive, Carlsbad, NM, 88220, USA
| | - Cindi Hazelton
- Los Alamos National Laboratory-Carlsbad Operations, 1400 University Drive, Carlsbad, NM, 88220, USA
| | - Michael Richmann
- Los Alamos National Laboratory-Carlsbad Operations, 1400 University Drive, Carlsbad, NM, 88220, USA
| | - Floyd Stanley
- Los Alamos National Laboratory-Carlsbad Operations, 1400 University Drive, Carlsbad, NM, 88220, USA
| |
Collapse
|
3
|
Power AL, Barber DG, Groenhof SRM, Wagley S, Liu P, Parker DA, Love J. The Application of Imaging Flow Cytometry for Characterisation and Quantification of Bacterial Phenotypes. Front Cell Infect Microbiol 2021; 11:716592. [PMID: 34368019 PMCID: PMC8335544 DOI: 10.3389/fcimb.2021.716592] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 07/08/2021] [Indexed: 12/25/2022] Open
Abstract
Bacteria modify their morphology in response to various factors including growth stage, nutrient availability, predation, motility and long-term survival strategies. Morphological changes may also be associated with specific physiological phenotypes such as the formation of dormant or persister cells in a “viable but non-culturable” (VBNC) state which frequently display different shapes and size compared to their active counterparts. Such dormancy phenotypes can display various degrees of tolerance to antibiotics and therefore a detailed understanding of these phenotypes is crucial for combatting chronic infections and associated diseases. Cell shape and size are therefore more than simple phenotypic characteristics; they are important physiological properties for understanding bacterial life-strategies and pathologies. However, quantitative studies on the changes to cell morphologies during bacterial growth, persister cell formation and the VBNC state are few and severely constrained by current limitations in the most used investigative techniques of flow cytometry (FC) and light or electron microscopy. In this study, we applied high-throughput Imaging Flow Cytometry (IFC) to characterise and quantify, at single-cell level and over time, the phenotypic heterogeneity and morphological changes in cultured populations of four bacterial species, Bacillus subtilis, Lactiplantibacillus plantarum, Pediococcus acidilactici and Escherichia coli. Morphologies in relation to growth stage and stress responses, cell integrity and metabolic activity were analysed. Additionally, we were able to identify and morphologically classify dormant cell phenotypes such as VBNC cells and monitor the resuscitation of persister cells in Escherichia coli following antibiotic treatment. We therefore demonstrate that IFC, with its high-throughput data collection and image capture capabilities, provides a platform by which a detailed understanding of changes in bacterial phenotypes and their physiological implications may be accurately monitored and quantified, leading to a better understanding of the role of phenotypic heterogeneity in the dynamic microbiome.
Collapse
Affiliation(s)
- Ann L Power
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Daniel G Barber
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Sophie R M Groenhof
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Sariqa Wagley
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Ping Liu
- Shell International Exploration & Production Inc., Westhollow Technology Center, Houston, TX, United States
| | - David A Parker
- Shell International Exploration & Production Inc., Westhollow Technology Center, Houston, TX, United States
| | - John Love
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| |
Collapse
|
4
|
Intracellular membranes of bacterial endospores are reservoirs for spore core membrane expansion during spore germination. Sci Rep 2018; 8:11388. [PMID: 30061638 PMCID: PMC6065386 DOI: 10.1038/s41598-018-29879-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 07/16/2018] [Indexed: 11/08/2022] Open
Abstract
Bacterial endospores are formed by certain bacteria, such as Bacillus subtilis or the pathogenic Bacillus anthracis and Clostridioides difficile, to allow survival in environmental conditions which are lethal to vegetative bacteria. The spores possess a particular architecture and molecular inventory which endow them with a remarkable resistance against desiccation, heat and radiation. Another remarkable spore feature is their rapid return to vegetative growth during spore germination and outgrowth. The underlying processes of this latter physiological and morphological transformation involve a number of different events, some of which are mechanistically not entirely understood. One of these events is the expansion of the central spore core, which contains the DNA, RNA and most spore enzymes. To date, it has been unclear how the ~1.3- to 1.6-fold expansion of the core membrane surface area that accompanies core expansion takes place, since this occurs in the absence of significant if any ATP synthesis. In the current work, we demonstrate the presence of intracellular membrane structures in spores located just below the core membrane. During spore germination these internal core membranes disappear when the core size increases, suggesting that they are integrated into the core membrane to allow core expansion. These intracellular membranes are most probably present as more or less compressed vesicles or tubules within the dormant spore core. Investigations of spores from different species suggest that these intracellular membrane structures below the core membrane are a general feature of endospore forming bacteria.
Collapse
|
5
|
Xu Zhou K, Wisnivesky F, Wilson D, Christie G. Effects of culture conditions on the size, morphology and wet density of spores ofBacillus cereus569 andBacillus megateriumQM B1551. Lett Appl Microbiol 2017; 65:50-56. [DOI: 10.1111/lam.12745] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 04/04/2017] [Accepted: 04/06/2017] [Indexed: 11/27/2022]
Affiliation(s)
- K. Xu Zhou
- Department of Chemical Engineering and Biotechnology; University of Cambridge; Cambridge UK
| | - F. Wisnivesky
- Department of Materials Science and Metallurgy; University of Cambridge; Cambridge UK
| | - D.I. Wilson
- Department of Chemical Engineering and Biotechnology; University of Cambridge; Cambridge UK
| | - G. Christie
- Department of Chemical Engineering and Biotechnology; University of Cambridge; Cambridge UK
| |
Collapse
|
6
|
Van Der Hofstadt M, Fabregas R, Millan-Solsona R, Juarez A, Fumagalli L, Gomila G. Internal Hydration Properties of Single Bacterial Endospores Probed by Electrostatic Force Microscopy. ACS NANO 2016; 10:11327-11336. [PMID: 28024372 DOI: 10.1021/acsnano.6b06578] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We show that the internal hydration properties of single Bacillus cereus endospores in air under different relative humidity (RH) conditions can be determined through the measurement of its electric permittivity by means of quantitative electrostatic force microscopy (EFM). We show that an increase in the RH from 0% to 80% induces a large increase in the equivalent homogeneous relative electric permittivity of the bacterial endospores, from ∼4 up to ∼17, accompanied only by a small increase in the endospore height, of just a few nanometers. These results correlate the increase of the moisture content of the endospore with the corresponding increase of environmental RH. Three-dimensional finite element numerical calculations, which include the internal structure of the endospores, indicate that the moisture is mainly accumulated in the external layers of the endospore, hence preserving the core of the endospore at low hydration levels. This mechanism is different from what we observe for vegetative bacterial cells of the same species, in which the cell wall at high humid atmospheric conditions is not able to preserve the cytoplasmic region at low hydration levels. These results show the potential of quantitative EFM under environmental humidity control to study the hygroscopic properties of small-scale biological (and nonbiological) entities and to determine its internal hydration state. A better understanding of nanohygroscopic properties can be of relevance in the study of essential biological processes and in the design of bionanotechnological applications.
Collapse
Affiliation(s)
- Marc Van Der Hofstadt
- Institut de Bioenginyeria de Catalunya (IBEC) , c/Baldiri i Reixac 11-15, Barcelona 08028, Spain
- Departament d'Enginyeries: Electrònica, Universitat de Barcelona , C/Martí i Franqués 1, Barcelona 08028, Spain
| | - Rene Fabregas
- Institut de Bioenginyeria de Catalunya (IBEC) , c/Baldiri i Reixac 11-15, Barcelona 08028, Spain
- Departament d'Enginyeries: Electrònica, Universitat de Barcelona , C/Martí i Franqués 1, Barcelona 08028, Spain
| | - Ruben Millan-Solsona
- Institut de Bioenginyeria de Catalunya (IBEC) , c/Baldiri i Reixac 11-15, Barcelona 08028, Spain
| | - Antonio Juarez
- Institut de Bioenginyeria de Catalunya (IBEC) , c/Baldiri i Reixac 11-15, Barcelona 08028, Spain
- Departament de Microbiologia, Universitat de Barcelona , Av. Diagonal 643, Barcelona 08028, Spain
| | - Laura Fumagalli
- School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
| | - Gabriel Gomila
- Institut de Bioenginyeria de Catalunya (IBEC) , c/Baldiri i Reixac 11-15, Barcelona 08028, Spain
- Departament d'Enginyeries: Electrònica, Universitat de Barcelona , C/Martí i Franqués 1, Barcelona 08028, Spain
| |
Collapse
|
7
|
Omardien S, Brul S, Zaat SAJ. Antimicrobial Activity of Cationic Antimicrobial Peptides against Gram-Positives: Current Progress Made in Understanding the Mode of Action and the Response of Bacteria. Front Cell Dev Biol 2016; 4:111. [PMID: 27790614 PMCID: PMC5063857 DOI: 10.3389/fcell.2016.00111] [Citation(s) in RCA: 112] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Accepted: 09/21/2016] [Indexed: 01/11/2023] Open
Abstract
Antimicrobial peptides (AMPs) have been proposed as a novel class of antimicrobials that could aid the fight against antibiotic resistant bacteria. The mode of action of AMPs as acting on the bacterial cytoplasmic membrane has often been presented as an enigma and there are doubts whether the membrane is the sole target of AMPs. Progress has been made in clarifying the possible targets of these peptides, which is reported in this review with as focus gram-positive vegetative cells and spores. Numerical estimates are discussed to evaluate the possibility that targets, other than the membrane, could play a role in susceptibility to AMPs. Concerns about possible resistance that bacteria might develop to AMPs are addressed. Proteomics, transcriptomics, and other molecular techniques are reviewed in the context of explaining the response of bacteria to the presence of AMPs and to predict what resistance strategies might be. Emergent mechanisms are cell envelope stress responses as well as enzymes able to degrade and/or specifically bind (and thus inactivate) AMPs. Further studies are needed to address the broadness of the AMP resistance and stress responses observed.
Collapse
Affiliation(s)
- Soraya Omardien
- Department of Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam Amsterdam, Netherlands
| | - Stanley Brul
- Department of Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam Amsterdam, Netherlands
| | - Sebastian A J Zaat
- Department of Medical Microbiology, Center for Infection and Immunity Amsterdam, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
| |
Collapse
|
8
|
Intracellular pH Response to Weak Acid Stress in Individual Vegetative Bacillus subtilis Cells. Appl Environ Microbiol 2016; 82:6463-6471. [PMID: 27565617 DOI: 10.1128/aem.02063-16] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 08/21/2016] [Indexed: 11/20/2022] Open
Abstract
Intracellular pH (pHi) critically affects bacterial cell physiology. Hence, a variety of food preservation strategies are aimed at perturbing pHi homeostasis. Unfortunately, accurate pHi quantification with existing methods is suboptimal, since measurements are averages across populations of cells, not taking into account interindividual heterogeneity. Yet, physiological heterogeneity in isogenic populations is well known to be responsible for differences in growth and division kinetics of cells in response to external stressors. To assess in this context the behavior of intracellular acidity, we have developed a robust method to quantify pHi at single-cell levels in Bacillus subtilis Bacilli spoil food, cause disease, and are well known for their ability to form highly stress-resistant spores. Using an improved version of the genetically encoded ratiometric pHluorin (IpHluorin), we have quantified pHi in individual B. subtilis cells, cultured at an external pH of 6.4, in the absence or presence of weak acid stresses. In the presence of 3 mM potassium sorbate, a decrease in pHi and an increase in the generation time of growing cells were observed. Similar effects were observed when cells were stressed with 25 mM potassium acetate. Time-resolved analysis of individual bacteria in growing colonies shows that after a transient pH decrease, long-term pH evolution is highly cell dependent. The heterogeneity at the single-cell level shows the existence of subpopulations that might be more resistant and contribute to population survival. Our approach contributes to an understanding of pHi regulation in individual bacteria and may help scrutinizing effects of existing and novel food preservation strategies. IMPORTANCE This study shows how the physiological response to commonly used weak organic acid food preservatives, such as sorbic and acetic acids, can be measured at the single-cell level. These data are key to coupling often-observed single-cell heterogeneous growth behavior upon the addition of weak organic acid food preservatives. Generally, these data are gathered in the form of plate counting of samples incubated with the acids. Here, we visualize the underlying heterogeneity in cellular pH homeostasis, opening up avenues for mechanistic analyses of the heterogeneity in the weak acid stress response. Thus, microbial risk assessment can become more robust, widening the scope of use of these well-known weak organic acid food preservatives.
Collapse
|
9
|
Friedline AW, Zachariah MM, Johnson K, Thomas KJ, Middaugh AN, Garimella R, Powell DR, Vaishampayan PA, Rice CV. Water behavior in bacterial spores by deuterium NMR spectroscopy. J Phys Chem B 2014; 118:8945-55. [PMID: 24950158 PMCID: PMC4216197 DOI: 10.1021/jp5025119] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Dormant bacterial spores are able
to survive long periods of time
without nutrients, withstand harsh environmental conditions, and germinate
into metabolically active bacteria when conditions are favorable.
Numerous factors influence this hardiness, including the spore structure
and the presence of compounds to protect DNA from damage. It is known
that the water content of the spore core plays a role in resistance
to degradation, but the exact state of water inside the core is a
subject of discussion. Two main theories present themselves: either
the water in the spore core is mostly immobile and the core and its
components are in a glassy state, or the core is a gel with mobile
water around components which themselves have limited mobility. Using
deuterium solid-state NMR experiments, we examine the nature of the
water in the spore core. Our data show the presence of unbound water,
bound water, and deuterated biomolecules that also contain labile
deuterons. Deuterium–hydrogen exchange experiments show that
most of these deuterons are inaccessible by external water. We believe
that these unreachable deuterons are in a chemical bonding state that
prevents exchange. Variable-temperature NMR results suggest that the
spore core is more rigid than would be expected for a gel-like state.
However, our rigid core interpretation may only apply to dried spores
whereas a gel core may exist in aqueous suspension. Nonetheless, the
gel core, if present, is inaccessible to external water.
Collapse
Affiliation(s)
- Anthony W Friedline
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma , 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Kaieda S, Setlow B, Setlow P, Halle B. Mobility of core water in Bacillus subtilis spores by 2H NMR. Biophys J 2014; 105:2016-23. [PMID: 24209846 DOI: 10.1016/j.bpj.2013.09.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Revised: 09/17/2013] [Accepted: 09/19/2013] [Indexed: 11/19/2022] Open
Abstract
Bacterial spores in a metabolically dormant state can survive long periods without nutrients under extreme environmental conditions. The molecular basis of spore dormancy is not well understood, but the distribution and physical state of water within the spore is thought to play an important role. Two scenarios have been proposed for the spore's core region, containing the DNA and most enzymes. In the gel scenario, the core is a structured macromolecular framework permeated by mobile water. In the glass scenario, the entire core, including the water, is an amorphous solid and the quenched molecular diffusion accounts for the spore's dormancy and thermal stability. Here, we use (2)H magnetic relaxation dispersion to selectively monitor water mobility in the core of Bacillus subtilis spores in the presence and absence of core Mn(2+) ions. We also report and analyze the solid-state (2)H NMR spectrum from these spores. Our NMR data clearly support the gel scenario with highly mobile core water (~25 ps average rotational correlation time). Furthermore, we find that the large depot of manganese in the core is nearly anhydrous, with merely 1.7% on average of the maximum sixfold water coordination.
Collapse
Affiliation(s)
- Shuji Kaieda
- Department of Biophysical Chemistry, Lund University, Lund, Sweden
| | | | | | | |
Collapse
|
11
|
Inactivation of chemical and heat-resistant spores of Bacillus and Geobacillus by nitrogen cold atmospheric plasma evokes distinct changes in morphology and integrity of spores. Food Microbiol 2014; 45:26-33. [PMID: 25481059 DOI: 10.1016/j.fm.2014.03.018] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 03/03/2014] [Accepted: 03/06/2014] [Indexed: 11/21/2022]
Abstract
Bacterial spores are resistant to severe conditions and form a challenge to eradicate from food or food packaging material. Cold atmospheric plasma (CAP) treatment is receiving more attention as potential sterilization method at relatively mild conditions but the exact mechanism of inactivation is still not fully understood. In this study, the biocidal effect by nitrogen CAP was determined for chemical (hypochlorite and hydrogen peroxide), physical (UV) and heat-resistant spores. The three different sporeformers used are Bacillus cereus a food-borne pathogen, and Bacillus atrophaeus and Geobacillus stearothermophilus that are used as biological indicators for validation of chemical sterilization and thermal processes, respectively. The different spores showed variation in their degree of inactivation by applied heat, hypochlorite, hydrogen peroxide, and UV treatments, whereas similar inactivation results were obtained with the different spores treated with nitrogen CAP. G. stearothermophilus spores displayed high resistance to heat, hypochlorite, hydrogen peroxide, while for UV treatment B. atrophaeus spores are most tolerant. Scanning electron microscopy analysis revealed distinct morphological changes for nitrogen CAP-treated B. cereus spores including etching effects and the appearance of rough spore surfaces, whereas morphology of spores treated with heat or disinfectants showed no such changes. Moreover, microscopy analysis revealed CAP-exposed B. cereus spores to turn phase grey conceivably because of water influx indicating damage of the spores, a phenomenon that was not observed for non-treated spores. In addition, data are supplied that exclude UV radiation as determinant of antimicrobial activity of nitrogen CAP. Overall, this study shows that nitrogen CAP treatment has a biocidal effect on selected Bacillus and Geobacillus spores associated with alterations in spore surface morphology and loss of spore integrity.
Collapse
|
12
|
Kong L, Setlow P, Li YQ. Direct analysis of water content and movement in single dormant bacterial spores using confocal Raman microspectroscopy and Raman imaging. Anal Chem 2013; 85:7094-101. [PMID: 23815288 DOI: 10.1021/ac400516p] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Heavy water (D2O) has a distinct molecular vibration spectrum, and this has been used to analyze the water content, distribution, and movement in single dormant Bacillus cereus spores using confocal Raman microspectroscopy and Raman imaging. These methods have been used to measure the kinetics of D2O release from spores suspended in H2O, the spatial distribution of D2O in spores, and the kinetics of D2O release from spores during dehydration in air at room temperature. The results obtained were as follows. (1) The Raman spectrum of single D2O-loaded dormant spores suggests that D2O in spores is in a relatively weak hydrogen-bonded mode, compared to the strong hydrogen-bonded mode in pure D2O. (2) The D2O content of individual spores in a population was somewhat heterogeneous. (3) The spatial distribution of D2O in single dormant spores is uneven, and is less dense in the central core region. Raman images of different molecular components indicate that the water distribution is somewhat different from those of proteins and Ca-dipicolinic acid. (4) Exchange of spore D2O with external H2O took place in less than 1 s. (5) However, release of spore D2O during air dehydration at room temperature was slow and heterogeneous and took 2-3 h for complete D2O release.
Collapse
Affiliation(s)
- Lingbo Kong
- Department of Physics, East Carolina University, Greenville, North Carolina 27858-4353, United States
| | | | | |
Collapse
|
13
|
van Beilen JWA, Brul S. Compartment-specific pH monitoring in Bacillus subtilis using fluorescent sensor proteins: a tool to analyze the antibacterial effect of weak organic acids. Front Microbiol 2013; 4:157. [PMID: 23785365 PMCID: PMC3685010 DOI: 10.3389/fmicb.2013.00157] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 05/30/2013] [Indexed: 11/25/2022] Open
Abstract
The internal pH (pHi) of a living cell is one of its most important physiological parameters. To monitor the pH inside Bacillus subtilis during various stages of its life cycle, we constructed an improved version (IpHluorin) of the ratiometric, pH-sensitive fluorescent protein pHluorin by extending it at the 5′ end with the first 24 bp of comGA. The new version, which showed an approximate 40% increase in fluorescence intensity, was expressed from developmental phase-specific, native promoters of B. subtilis that are specifically active during vegetative growth on glucose (PptsG) or during sporulation (PspoIIA, PspoIIID, and PsspE). Our results show strong, compartment-specific expression of IpHluorin that allowed accurate pHi measurements of live cultures during exponential growth, early and late sporulation, spore germination, and during subsequent spore outgrowth. Dormant spores were characterized by an pHi of 6.0 ± 0.3. Upon full germination the pHi rose dependent on the medium to 7.0–7.4. The presence of sorbic acid in the germination medium inhibited a rise in the intracellular pH of germinating spores and inhibited germination. Such effects were absent when acetic was added at identical concentrations.
Collapse
Affiliation(s)
- Johan W A van Beilen
- Department of Molecular Microbial Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam Amsterdam, Netherlands
| | | |
Collapse
|
14
|
Kong L, Setlow P, Li YQ. Analysis of the Raman spectra of Ca2+-dipicolinic acid alone and in the bacterial spore core in both aqueous and dehydrated environments. Analyst 2012; 137:3683-9. [DOI: 10.1039/c2an35468c] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
15
|
Segev E, Smith Y, Ben-Yehuda S. RNA dynamics in aging bacterial spores. Cell 2011; 148:139-49. [PMID: 22209493 DOI: 10.1016/j.cell.2011.11.059] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 09/13/2011] [Accepted: 11/30/2011] [Indexed: 12/21/2022]
Abstract
Upon starvation, the bacterium Bacillus subtilis enters the process of sporulation, lasting several hours and culminating in formation of a spore, the most resilient cell type known. We show that a few days following sporulation, the RNA profile of spores is highly dynamic. In aging spores incubated at high temperatures, RNA content is globally decreased by degradation over several days. This degradation might be a strategy utilized by the spore to facilitate its dormancy. However, spores kept at low temperature exhibit a different RNA profile with evidence supporting transcription. Further, we demonstrate that germination is affected by spore age, incubation temperature, and RNA state, implying that spores can acquire dissimilar characteristics at a time they are considered dormant. We propose that, in contrast to current thinking, entering dormancy lasts a few days, during which spores are affected by the environment and undergo corresponding molecular changes influencing their emergence from quiescence.
Collapse
Affiliation(s)
- Einat Segev
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada (IMRIC), The Hebrew University-Hadassah Medical School, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | | | | |
Collapse
|
16
|
Spatially resolved characterization of water and ion incorporation in Bacillus spores. Appl Environ Microbiol 2010; 76:3275-82. [PMID: 20348293 DOI: 10.1128/aem.02485-09] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We present the first direct visualization and quantification of water and ion uptake into the core of individual dormant Bacillus thuringiensis subsp. israelensis (B. thuringiensis subsp. israelensis) endospores. Isotopic and elemental gradients in the B. thuringiensis subsp. israelensis spores show the permeation and incorporation of deuterium in deuterated water (D(2)O) and solvated ions throughout individual spores, including the spore core. Under hydrated conditions, incorporation into a spore occurs on a time scale of minutes, with subsequent uptake of the permeating species continuing over a period of days. The distribution of available adsorption sites is shown to vary with the permeating species. Adsorption sites for Li(+), Cs(+), and Cl(-) are more abundant within the spore outer structures (exosporium, coat, and cortex) relative to the core, while F(-) adsorption sites are more abundant in the core. The results presented here demonstrate that elemental abundance and distribution in dormant spores are influenced by the ambient environment. As such, this study highlights the importance of understanding how microbial elemental and isotopic signatures can be altered postproduction, including during sample preparation for analysis, and therefore, this study is immediately relevant to the use of elemental and isotopic markers in environmental microbiology and microbial forensics.
Collapse
|
17
|
Cronin U, Wilkinson M. The potential of flow cytometry in the study of Bacillus cereus. J Appl Microbiol 2010; 108:1-16. [DOI: 10.1111/j.1365-2672.2009.04370.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
|
18
|
Abstract
The bacterial spore, the hardiest known life form, can survive in a metabolically dormant state for many years and can withstand high temperatures, radiation, and toxic chemicals. The molecular basis of spore dormancy and resistance is not understood, but the physical state of water in the different spore compartments is thought to play a key role. To characterize this water in situ, we recorded the water (2)H and (17)O spin relaxation rates in D(2)O-exchanged Bacillus subtilis spores over a wide frequency range. The data indicate high water mobility throughout the spore, comparable with binary protein-water systems at similar hydration levels. Even in the dense core, the average water rotational correlation time is only 50 ps. Spore dormancy therefore cannot be explained by glass-like quenching of molecular diffusion but may be linked to dehydration-induced conformational changes in key enzymes. The data demonstrate that most spore proteins are rotationally immobilized, which may contribute to heat resistance by preventing heat-denatured proteins from aggregating irreversibly. We also find that the water permeability of the inner membrane is at least 2 orders of magnitude lower than for model membranes, consistent with the reported high degree of lipid immobilization in this membrane and with its proposed role in spore resistance to chemicals that damage DNA. The quantitative results reported here on water mobility and transport provide important clues about the mechanism of spore dormancy and resistance, with relevance to food preservation, disease prevention, and astrobiology.
Collapse
|
19
|
Carrera M, Zandomeni RO, Fitzgibbon J, Sagripanti JL. Difference between the spore sizes of Bacillus anthracis and other Bacillus species. J Appl Microbiol 2007; 102:303-12. [PMID: 17241334 DOI: 10.1111/j.1365-2672.2006.03111.x] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIMS To determine the size distribution of the spores of Bacillus anthracis, and compare its size with other Bacillus species grown and sporulated under similar conditions. METHODS AND RESULTS Spores from several Bacillus species, including seven strains of B. anthracis and six close neighbours, were prepared and studied using identical media, protocols and instruments. Here, we report the spore length and diameter distributions, as determined by transmission electron microscopy (TEM). We calculated the aspect ratio and volume of each spore. All the studied strains of B. anthracis had similar diameter (mean range between 0.81 +/- 0.08 microm and 0.86 +/- 0.08 microm). The mean lengths of the spores from different B. anthracis strains fell into two significantly different groups: one with mean spore lengths 1.26 +/- 0.13 microm or shorter, and another group of strains with mean spore lengths between 1.49 and 1.67 microm. The strains of B. anthracis that were significantly shorter also sporulated with higher yield at relatively lower temperature. The grouping of B. anthracis strains by size and sporulation temperature did not correlate with their respective virulence. CONCLUSIONS The spores of Bacillus subtilis and Bacillus atrophaeus (previously named Bacillus globigii), two commonly used simulants of B. anthracis, were considerably smaller in length, diameter and volume than all the B. anthracis spores studied. Although rarely used as simulants, the spores of Bacillus cereus and Bacillus thuringiensis had dimensions similar to those of B. anthracis. SIGNIFICANCE AND IMPACT OF THE STUDY Spores of nonvirulent Bacillus species are often used as simulants in the development and testing of countermeasures for biodefence against B. anthracis. The data presented here should help in the selection of simulants that better resemble the properties of B. anthracis, and thus, more accurately represent the performance of collectors, detectors and other countermeasures against this threat agent.
Collapse
Affiliation(s)
- M Carrera
- Research and Technology Directorate, Edgewood Chemical Biological Center, US Army, MD, USA
| | | | | | | |
Collapse
|
20
|
Huang SS, Chen D, Pelczar PL, Vepachedu VR, Setlow P, Li YQ. Levels of Ca2+-dipicolinic acid in individual bacillus spores determined using microfluidic Raman tweezers. J Bacteriol 2007; 189:4681-7. [PMID: 17468248 PMCID: PMC1913426 DOI: 10.1128/jb.00282-07] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pyridine-2,6-dicarboxylic acid (dipicolinic acid [DPA]) in a 1:1 chelate with calcium ion (Ca-DPA) comprises 5 to 15% of the dry weight of spores of Bacillus species. Ca-DPA is important in spore resistance to many environmental stresses and in spore stability, and Ca-DPA levels in spore populations can vary with spore species/strains, as well as with sporulation conditions. We have measured levels of Ca-DPA in large numbers of individual spores in populations of a variety of Bacillus species and strains by using microfluidic Raman tweezers, in which a single spore is trapped in a focused laser beam and its Ca-DPA is quantitated from the intensity of the Ca-DPA-specific band at 1,017 cm(-1) in Raman spectroscopy. Conclusions from these measurements include the following: (i) Ca-DPA concentrations in the spore core are >800 mM, well above Ca-DPA solubility; (ii) SpoVA proteins may be involved in Ca-DPA uptake in sporulation; and (iii) Ca-DPA levels differ significantly among individual spores in a population, but much of this variation could be due to variations in the sizes of individual spores.
Collapse
Affiliation(s)
- Shu-shi Huang
- Department of Physics, East Carolina University, Greenville, NC 27858-4353, USA
| | | | | | | | | | | |
Collapse
|
21
|
Abstract
A number of mechanisms are responsible for the resistance of spores of Bacillus species to heat, radiation and chemicals and for spore killing by these agents. Spore resistance to wet heat is determined largely by the water content of spore core, which is much lower than that in the growing cell protoplast. A lower core water content generally gives more wet heat-resistant spores. The level and type of spore core mineral ions and the intrinsic stability of total spore proteins also play a role in spore wet heat resistance, and the saturation of spore DNA with alpha/beta-type small, acid-soluble spore proteins (SASP) protects DNA against wet heat damage. However, how wet heat kills spores is not clear, although it is not through DNA damage. The alpha/beta-type SASP are also important in spore resistance to dry heat, as is DNA repair in spore outgrowth, as Bacillus subtilis spores are killed by dry heat via DNA damage. Both UV and gamma-radiation also kill spores via DNA damage. The mechanism of spore resistance to gamma-radiation is not well understood, although the alpha/beta-type SASP are not involved. In contrast, spore UV resistance is due largely to an alteration in spore DNA photochemistry caused by the binding of alpha/beta-type SASP to the DNA, and to a lesser extent to the photosensitizing action of the spore core's large pool of dipicolinic acid. UV irradiation of spores at 254 nm does not generate the cyclobutane dimers (CPDs) and (6-4)-photoproducts (64PPs) formed between adjacent pyrimidines in growing cells, but rather a thymidyl-thymidine adduct termed spore photoproduct (SP). While SP is formed in spores with approximately the same quantum efficiency as that for generation of CPDs and 64PPs in growing cells, SP is repaired rapidly and efficiently in spore outgrowth by a number of repair systems, at least one of which is specific for SP. Some chemicals (e.g. nitrous acid, formaldehyde) again kill spores by DNA damage, while others, in particular oxidizing agents, appear to damage the spore's inner membrane so that this membrane ruptures upon spore germination and outgrowth. There are also other agents such as glutaraldehyde for which the mechanism of spore killing is unclear. Factors important in spore chemical resistance vary with the chemical, but include: (i) the spore coat proteins that likely react with and detoxify chemical agents; (ii) the relative impermeability of the spore's inner membrane that restricts access of exogenous chemicals to the spore core; (iii) the protection of spore DNA by its saturation with alpha/beta-type SASP; and (iv) DNA repair for agents that kill spores via DNA damage. Given the importance of the killing of spores of Bacillus species in the food and medical products industry, a deeper understanding of the mechanisms of spore resistance and killing may lead to improved methods for spore destruction.
Collapse
Affiliation(s)
- P Setlow
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, 06030-3305, USA.
| |
Collapse
|
22
|
Stecchini ML, Del Torre M, Venir E, Morettin A, Furlan P, Maltini E. Glassy state in Bacillus subtilis spores analyzed by differential scanning calorimetry. Int J Food Microbiol 2006; 106:286-90. [PMID: 16257078 DOI: 10.1016/j.ijfoodmicro.2005.06.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2004] [Revised: 04/01/2005] [Accepted: 06/30/2005] [Indexed: 10/25/2022]
Abstract
Thermal properties of dried spores of Bacillus subtilis, investigated by differential scanning calorimetry (DSC), were studied. A reversible heat capacity shift ascribable to glass-rubber transition was observed at 90-115 degrees C. The transition was found to be a pressure-inhibited volume-activated event. The decoated spores and the extracted peptidoglycan material exhibited glass transition, suggesting that the cortex could be involved in the event. Furthermore, the glass transition was evident when spores were treated with strong acid, and when the isogenic strain PS578 was scanned, indicating that core integrity and core components are not involved in the occurrence of the event. These results suggest that in the dried B. subtilis spores an amorphous biomaterial, possibly the cortex peptidoglycan, is present as a glass.
Collapse
Affiliation(s)
- Mara Lucia Stecchini
- Department of Food Science, University of Udine, Via Marangoni n. 97, 33100 Udine, Italy.
| | | | | | | | | | | |
Collapse
|
23
|
Cowan AE, Olivastro EM, Koppel DE, Loshon CA, Setlow B, Setlow P. Lipids in the inner membrane of dormant spores of Bacillus species are largely immobile. Proc Natl Acad Sci U S A 2004; 101:7733-8. [PMID: 15126669 PMCID: PMC419675 DOI: 10.1073/pnas.0306859101] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2003] [Accepted: 04/05/2004] [Indexed: 11/18/2022] Open
Abstract
Bacterial spores of various Bacillus species are impermeable or exhibit low permeability to many compounds that readily penetrate germinated spores, including methylamine. We now show that a lipid probe in the inner membrane of dormant spores of Bacillus megaterium and Bacillus subtilis is largely immobile, as measured by fluorescence redistribution after photobleaching, but becomes free to diffuse laterally upon spore germination. The lipid immobility in and the slow permeation of methylamine through the inner membrane of dormant spores may be due to a significant (1.3- to 1.6-fold) apparent reduction of the membrane surface area in the dormant spore relative to that in the germinated spore, but is not due to the dormant spore's high levels of dipicolinic acid and divalent cations.
Collapse
Affiliation(s)
- Ann E Cowan
- Department of Molecular, Microbial, and Structural Biology and Center for Biomedical Imaging Technology, University of Connecticut Health Center, Farmington, CT 06032, USA
| | | | | | | | | | | |
Collapse
|
24
|
Abstract
Fluorescence recovery after photobleaching (FRAP) of green fluorescent protein (GFP) has been used to report on protein mobility in single spores. Proteins found in dormant Bacillus spores are not mobile; however, mobility is restored when germination occurs and the core rehydrates. Spores of a cwlD mutant, in which the cortex is resistant to hydrolysis, are able to complete the earliest stages of germination in response to a specific germinant stimulus; in these circumstances, the protein in the spore remains immobile. Therefore, the earliest stages of spore germination, including loss of resistance to extreme heat and the complete release of the spore component dipicolinic acid, are achieved without the restoration of protein mobility.
Collapse
Affiliation(s)
- Anne Moir
- Department of Molecular Biology & Biotechnology, University of Sheffield, S10 2TN, Sheffield, UK.
| |
Collapse
|
25
|
Cowan AE, Koppel DE, Setlow B, Setlow P. A soluble protein is immobile in dormant spores of Bacillus subtilis but is mobile in germinated spores: implications for spore dormancy. Proc Natl Acad Sci U S A 2003; 100:4209-14. [PMID: 12646705 PMCID: PMC404470 DOI: 10.1073/pnas.0636762100] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2002] [Indexed: 11/18/2022] Open
Abstract
Fluorescence redistribution after photobleaching has been used to show that a cytoplasmic GFP fusion is immobile in dormant spores of Bacillus subtilis but becomes freely mobile in germinated spores in which cytoplasmic water content has increased approximately 2-fold. The GFP immobility in dormant spores is not due to the high levels of dipicolinic acid in the spore cytoplasm, because GFP was also immobile in germinated cwlD spores that had excreted their dipicolinic acid but where cytoplasmic water content had only increased to a level similar to that in dormant spores of several other Bacillus species. The immobility of a normally mobile protein in dormant wild-type spores and germinated cwlD spores is consistent with the lack of metabolism and enzymatic activity in these spores and suggests that protein immobility, presumably due to low water content, is a major reason for the metabolic dormancy of spores of Bacillus species.
Collapse
Affiliation(s)
- Ann E Cowan
- Center for Biomedical Imaging Technology, University of Connecticut Health Center, Farmington, CT 06032, USA
| | | | | | | |
Collapse
|
26
|
Abstract
Differential scanning calorimetry (DSC) measurements of dormant bacterial spores is traditionally associated with an endothermic transition at around 50 degrees C. This endothermic transition was described as an indicator for two main physico-chemical states in spores. These were a glassy state in the dormant spore core as a model for spore dormancy and a heat-activated state that generally facilitates spore resuscitation. The idea of a glassy state in dormant spores is based on the observation that a similar transition as in dormant spores was observed in low moisture biopolymers that are in a glassy state. Thermal properties of spores of Bacillus subtilis and B. cereus in a dormant and germinated, resuscitated state and of an outer and an inner coatless spore mutant of B. subtilis were investigated. Biopolymers with low moisture (<15%) and high moisture (>30%) contents such as maize starch, pectin, RNA and DNA were further studied. Critical evaluation of results revealed that the low temperature transition in dormant spores has some similarities to those observed in glassy biopolymers, but also to those of fully hydrated proteins and therefore does not necessarily indicate a glassy low moisture state. Its origin can also be attributed to the outer spore coats and it occurred at a lower temperature and for a shorter duration to be of significance for thermal heat activation of spores.
Collapse
|
27
|
Leuschner RG, Lillford PJ. Investigation of bacterial spore structure by high resolution solid-state nuclear magnetic resonance spectroscopy and transmission electron microscopy. Int J Food Microbiol 2001; 63:35-50. [PMID: 11205952 DOI: 10.1016/s0168-1605(00)00396-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
High resolution solid-state nuclear magnetic resonance spectroscopy (NMR) in combination with transmission electron microscopy (TEM) of spores of Bacillus cereus, an outer coatless mutant B. subtilis 322, an inner coatless mutant B. subtilis 325 and of germinated spores of B. subtilis CMCC 604 were carried out. Structural differences in the coats, mainly protein of spores were reflected by NMR spectra which indicated also differences in molecular mobility of carbohydrates which was partially attributed to the cortex. Dipicolinic acid (DPA) of spores of B. cereus displayed a high degree of solid state order and may be crystalline. Heat activation was studied on spores of B. subtilis 357 lux + and revealed a structural change when analysed by TEM but this was not associated with increases in molecular mobility since no effects were measured by NMR.
Collapse
Affiliation(s)
- R G Leuschner
- Unilever Research Colworth, Sharnbrook, Bedford, UK.
| | | |
Collapse
|