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Mild spore inactivation can be challenging in industry because of the remarkable resistance of bacterial spores. High pressure (HP) can trigger spore germination, which reduces the spore's resistance, and thereby allows mild spore inactivation. However, spore germination is heterogenous. Some slowly germinating or non-germinating spores called superdormant spores remain resistant and can survive. Therefore, superdormant spores need to be characterized to understand the causes of their germination deficiency. Bacillus subtilis spores were pressurized for 50 s – 6 min at a very high pressure (vHP) level of 550 MPa and 60 °C in buffer to trigger germination. For a rapid quantification of the remaining ungerminated superdormant spores, flow cytometry (FCM) analysis was validated using single cell sorting and growth analysis. FCM based on propidium iodide (PI) and SYTO16 can be used for 550 MPa-superdormant spores after short vHP treatments of ≤1 min and post-HP incubation at 37 °C or 60 °C. The need for a post-HP incubation is particular for vHP treatments. The incubation was successful to separate FCM signals from superdormant and germinated spores, thus allowing superdormant spore quantification. The SYTO16 and PI fluorescence levels did not necessarily indicate superdormancy or apparent viability. This highlights the general need for FCM validation for different HP treatment conditions. The ∼7 % of ungerminated, i.e., superdormant, spores were isolated after a vHP treatment (550 MPa, 60 °C, 43–52 s). This allowed the characterization of vHP superdormant spores for the first time. The superdormant spores had a similar dipicolinic acid content as spores of the initial dormant population. Descendants of superdormant spores had a normal vHP germination capacity. The causes of vHP superdormancy were thus unlikely linked to the dipicolinic acid content or a permanent genetic change. Isolated superdormant spores germinated better in a second vHP treatment compared to the initial spore population. This has not been observed for other germination stimuli so far. In addition, the germination capacity of the initial spore population was time-dependent. A vHP germination deficiency can therefore be lost over time and seems to be caused by transient factors. Permanent cellular properties played a minor role as causes of superdormancy under chosen HP treatment conditions. The study gained new fundamental insights in vHP superdormancy which are of applied interest. Understanding superdormancy helps to efficiently develop a strategy to avoid superdormant spores and hence to inactivate all spores. The development of a mild HP spore germination-inactivation process aims at better preserving the food quality. • Bacterial spores superdormant (SD) to very high pressure (vHP) were characterized. • Flow cytometry is usable for SD spores after ≤1 min at vHP and post-HP incubation. • The vHP (550 MPa, 60 °C) SD spores had a normal dipicolinic acid content. • Superdormancy (resistance to vHP) was lost over time and not genetically inherited. • Superdormancy to vHP was unlikely caused by permanent cellular properties. [ABSTRACT FROM AUTHOR]

The study explored the effects of electric field strength, temperature, and frequency on the inactivation of Clostridium sporogenes PA3679 spores (a surrogate of Clostridium botulinum) within buffer. The experiments were conducted at three different field strengths (30, 40, and 50 V/cm), temperatures (110, 120, and 130 °C), and frequencies (60, 1000, and 5000 Hz). Ohmic heating resulted in significantly greater reduction of C. sporogenes compared to conventional heating. Electric field strength significantly influenced spore inactivation. It was found that lower frequencies led to quicker rates of inactivation. Given that high field strengths have dual benefits of increasing both heating and spore kill rate, the possibility exists to process foods to sterility without a hold. This is expected to result in improved product quality, reduced process times and increased efficiency. • Ohmic heating results in higher bacterial spore inactivation than conventional heating. • This study also confirms the existence of non-thermal effects of ohmic heating. • Higher field strength offered significantly higher inactivation of spores. • 60Hz and 5000 Hz offered highest and lowest inactivation of Clostridium sporogenes. [ABSTRACT FROM AUTHOR]

Pulsed electric field (PEF) treatment, an alternative to thermal processing in the food industry, is insufficient to inactivate bacterial spores. Although spores that have been treated in this manner remain alive, specific understanding of their physiological properties is limited. The purpose of this study is to describe the morphology, viability, and germination behavior of Bacillus atrophaeus spores treated with PEF. Our findings indicate that nonlethal PEF treatment results in spore deformation, dipicolinic acid (DPA) leakage, and a shorter and more uniform germination lag time (Tlag), but that there is no change in release duration (ΔTrelease), germination ratio, or viability. Based on our findings, we conclude that an intact morphologic state and DPA content are not prerequisites for germination and full viability and that, in contrast to nutrient-induced germination in which initially slowly released DPA triggers subsequent germination events, leaked DPA during PEF treatment does not. Spores that have been subjected to this procedure remain dormant and preserve their full germinability. We found that PEF-treated spores respond to germinants more quickly and with less heterogeneity, possibly because the tiny cracks formed on the spore surface facilitate the germinants’ access to the germination receptors situated on the spore’s inner membrane. The consensus view that nonlethal PEF has less impact on spores that are still capable of forming CFUs under proper conditions is one-sided. This research advances our understanding of how spores behave following nonlethal PEF treatment and gives information on the topics of nosocomial sterilization, food safety, and public health. [ABSTRACT FROM AUTHOR]

Bacterial spores displaying heterologous proteins have been proposed as a safe and efficient method for delivery of antigens and enzymes to animal mucosal surfaces. Initial studies have been performed using Bacillus subtilis spores, but other spore forming organisms have also been considered. B. megaterium spores have been shown capable of displaying large amounts of a model heterologous protein ( Discosoma red fluorescent protein mRFP) that in part crossed the exosporium to localize in the space between the outer coat layer and the exosporium. Here, B. megaterium spores have been used to adsorb Bcp1 (bacterioferritin comigratory protein 1), a peroxiredoxin of the archaeon Sulfolobus solfataricus, known to have an antioxidant activity. The spores were highly efficient in adsorbing the heterologous enzyme which, once adsorbed, retained its activity. The adsorbed Bcp1 localized beneath the exosporium, filling the space between the outer coat and the exosporium. This unusual localization contributed to the stability of the enzyme-spore interaction and to the protection of the adsorbed enzyme in simulated intestinal or gastric conditions. [ABSTRACT FROM AUTHOR]

Since the 2001 anthrax attacks, researchers have focused on the development of a bacterial spore biomarker detector with rapid response time and high sensitivity and selectivity. Hence, a ratiometric fluorescent nanosensor based on lanthanide-functionalized attapulgite (Atta) was designed and prepared using dye-doped Atta as an internal reference. Atta, which is famous because of Maya Blue, is a hydrated magnesium aluminum silicate present in nature, with pronounced adsorption and a large specific surface area rich in silicon hydroxyl. The adsorption of dye molecules benefits the formation of an internal reference with orange fluorescence. Meanwhile, silicon hydroxyl would be available for terbium (Tb 3+ ) complex grafting, which favors the sensitization of the bacterial spore biomarker. With increasing dipicolinic acid (DPA) concentrations, energy transfer from DPA to Tb 3+ gradually enhanced, thereby resulting in strong and predominant green fluorescence. The ratiometric fluorescence intensity is highly sensitive. It has a limit of detection of 9.8 nM, which is much lower than the infectious dosage of Bacillus anthracis spores (60 μM) for humans. The rapid response time (10s), high selectivity, and reliable and practical performances in actual applications make this ratiometric fluorescent nanosensor useful in the detection of biomarkers for various bacterial spores. Moreover, the reported construction of visual ratiometric detection system follows the sustainable development idea of ‘‘from nature, for nature, into the nature’’ and promotes the use of naturally renewable resources to produce promising and eco-friendly functional materials for various applications. [ABSTRACT FROM AUTHOR]

Since bacterial spores, such as Bacillus anthracis spores, are extremely hazardous to human beings and animals, efforts have focused on the development of bacterial spore detector with rapid response and high selectivity and sensitivity. Therefore, we reported a facile one-step chelating-reagent-assisted hydrothermal synthesis of lanthanide-doped fluorapatite (FA) nanoprobes for detecting the biomarker of bacterial spores. In FA synthesis, ethylenediaminetetraacetic acid (EDTA) can serve not only as a shape controller and a stabilizer but also as a chelating reagent for lanthanide ions. After the fabrication, terbium (or europium) ions were not only embedded into lattice models of FA nanocrystals, but also chelated by EDTA on the surface of the FA nanocrystals, which can be available for detecting the biomarker (i.e., dipicolinic acid) of bacterial spores. The obtained FA: Ln–EDTA nanoprobes can provide reference fluorescence which play crucial roles in the calibration and correction of concentration. The fluorescence intensities of FA: Tb–EDTA or FA: Eu–EDTA from Tb 3+ or Eu 3+ emission were highly sensitive and increased gradually with increasing DPA concentrations. The limit of detection of FA: Tb–EDTA was 8.2 nM, which is lower than that of FA: Eu–EDTA (20.9 nM). It can be attributed to the fact that DPA can achieve a more effective energy transfer to Tb 3+ than to Eu 3+ . Additionally, the nanoprobes were successfully applied for the determination of DPA in fetal calf serum samples. Given their rapid response and high sensitivity and selectivity, these ratiometric fluorescent nanoprobes are promising tools for the detection of bacterial spores. [ABSTRACT FROM AUTHOR]

Methods for microbial inactivation are important in the food industry; however, conventional external heating (CH) reduces food quality. Accordingly, the nonthermal effects of ohmic heating (OH) on Bacillus subtilis spores in a sodium chloride aqueous solution at 101°C (i.e., the boiling point), as well as the effects of electric field intensity and frequency during OH, were investigated. Survival kinetics were compared between OH and external CH. The inactivation effect on B. subtilis was greater for all electric field conditions (5, 10, and 20 V/cm) than for CH. In particular, 20 V/cm showed a significantly higher inactivation effect ( P < 0.05) on B. subtilis than those of CH at 8, 10, 12, 14, and 16 min. The survival data were fitted to various primary kinetic models. In the Weibull model and the log-linear model, there were significant differences ( P < 0.05) in the rate parameters δ and kmax between OH at 20 V/cm and CH. However, there were no significant differences ( P > 0.05) in survival kinetics between 20, 40, and 60 kHz; B. subtilis spores were inactivated more efficiently as the frequency increased. B. subtilis spores were almost completely inactivated at 14 to 16 min for the 60-kHz treatment, but spores were still alive at 20 and 40 kHz for the same treatment times. These results demonstrated that OH inactivates B. subtilis spores more effectively than CH. OH conditions with high electric field intensities and high frequencies resulted in efficient B. subtilis spore inactivation. [ABSTRACT FROM AUTHOR]

[Display omitted] • UVc effect explored on spore metabolites: DPA and its salt CaDPA. • Photoproducts of DPA characterized fluorescence using emission. • Spectroscopy and DPA assay demonstrated the instability of photoproducts. • New insights into photoproducts production by mass spectrometry. • Novel microscopy methodology implemented for photoproducts vizualization. Bacterial spores can cause significant problems such as food poisoning (like neurotoxin or emetic toxin) or serious illnesses (like anthrax or botulism). This dormant form of bacteria, made of several layers of barriers which provide extreme resistance to many abiotic stresses (radiation, temperature, pressure, etc.), are difficult to investigate in situ. To better understand the biological and chemical mechanisms involved and specific to spores resistance, the acquisition of environmental parameters is necessary. For that purpose, our research has been focused on the detection and analysis of a unique spore component, dipicolinic acid (DPA), used as the main in situ metabolite for sporulating bacteria detection. In its native form, DPA is only weakly fluorescent but after Ultraviolet irradiation at the wavelength of 254 nm (UVc), DPA photoproducts (DPAp) exhibit a remarkable fluorescence signal. These photoproducts are rarely identified and part of this study gives new insights offered by mass spectrometry (MS) in the determination of DPA photoproducts. Thanks to DPA assay techniques and fluorescence spectrometry, we highlighted the instability of photoproducts and introduced new assumptions on the effects of UVc on DPA. Studies in spectroscopy and microscopy allowed us to better understand these native probes in bacterial spores and will allow the implementation of a new method for studying the physico-chemical parameters of spore resistance. [ABSTRACT FROM AUTHOR]

Clostridium species and Bacillus spp. are spore-forming bacteria that cause hospital infections. The spores from these bacteria are transmitted from patient to patient via healthcare workers' hands. Although alcohol-based hand rubbing is an important hand hygiene practice, it is ineffective against bacterial spores. Therefore, healthcare workers should wash their hands with soap when they are contaminated with spores. However, the extent of health care worker hand contamination remains unclear. The aim of this study is to determine the level of bacterial spore contamination on healthcare workers' hands. The hands of 71 healthcare workers were evaluated for bacterial spore contamination. Spores attached to subject's hands were quantitatively examined after 9 working hours. The relationship between bacterial spore contamination and hand hygiene behaviors was also analyzed. Bacterial spores were detected on the hands of 54 subjects (76.1%). The mean number of spores detected was 468.3 CFU/hand (maximum: 3300 CFU/hand). Thirty-seven (52.1%) and 36 (50.7%) subjects were contaminated with Bacillus subtilis and Bacillus cereus , respectively. Nineteen subjects (26.8%) were contaminated with both Bacillus species. Clostridium difficile was detected on only one subject's hands. There was a significant negative correlation between the hand contamination level and the frequency of handwashing ( r = −0.44, P < 0.01) and a significant positive correlation between the hand contamination level and the elapsed time since last handwashing ( r = 0.34, P < 0.01). Healthcare workers' hands may be frequently contaminated with bacterial spores due to insufficient handwashing during daily patient care. [ABSTRACT FROM AUTHOR]

In this study, we develop a characterization of bacterial spore resistance to NIR pulsed light under modalities traditionally used in multiphoton microscopy. Energy dose and laser power are both key parameters in spore and bacterial cell inactivation. Surprisingly, spores and vegetative cells seem to show a similar sensitivity to pulsed NIR, spores being only 2-fold more resistant than their vegetative counterparts. This work enables us to eliminate certain hypotheses concerning the main driver of spore inactivation processes. Our findings suggest that damage leading to inactivation is mainly caused by photochemical reactions characterized by multiple possible pathways, including DNA damage or oxidation processes. • Pulsed Near Infrared Radiation can lead to bacterial spore inactivation. • Unusual close inactivation rate are observed between bacterial spore and vegetative cells. • Photochemicals damage are proposed as the main driver of spore inactivation. [ABSTRACT FROM AUTHOR]

A new generation of high pressure homogenizers reaching up to 400 MPa offers opportunities for spore inactivation and high pressure sterilization of foods. A Stansted Fluid Power ultra-high pressure homogenization (UHPH) unit was tested to inactivate bacterial spores in a model buffer system. Bacillus subtilis PS832 and Geobacillus stearothermophilus ATCC7953 spores’ thermal resistances were assessed (D, z-value and E a ). The pressure and valve temperature were monitored during UHPH. Residence times under pressure and high temperature were estimated and enabled comparison with thermal inactivation, indicating the estimated thermal contribution to inactivation. Spore germination was also assessed but no germination was observed. Up to five log 10 B. subtilis and two log 10 G. stearothermophilus spores were inactivated by the harshest treatments (> 300 MPa –T valve > 145 °C for ~ 0.24 s). The inactivation profiles were similar to the predicted thermal inactivation suggesting that the valve temperature might be a dominant parameter leading to bacterial spore inactivation. Industrial relevance This work showed the UHPH potential for spore inactivation and the need of highly thermoresistant surrogates for process validation, for instance, G. stearothermophilus ATCC7953 spores. Both these findings are highly relevant for industrial application as, to date, no surrogate for this process was suggested while the first patents for the technology transfer to industry are being issued. [ABSTRACT FROM AUTHOR]

Abstract: Spores of Geobacillus stearothermophilus and Bacillus subtilis adhering to the surface of stainless steel (SS) and polypropylene (PP) were subjected to rinsing in water or NaOH solution to study their removability. The spores were made adherent through deposition from suspension under humid and dry conditions. The humid condition kept the surface wet throughout the deposition, whereas the dry condition made them dry up finally. Experimental results demonstrated that drying significantly enhanced both quantity and strength of the spore adhesion for both types of surface. No removal of the spores adhering to surfaces exposed to dry environment was observed through water rinsing with shear force application. Even with 0.2% NaOH, they were hardly removed irrespective of temperature. Although 1% NaOH removed or inactivated most of spores on SS surface, it left considerable viable spores on PP surface. Thus enhanced alkali tolerance was indicated for spores adhering to surfaces, especially made of PP, exposed to dry environment. [Copyright &y& Elsevier]

Abstract: Both atmospheric pressure plasma and photo-catalyst metal oxide titanium dioxide (TiO2) are well known for their microorganism inactivation and chemical material decomposition abilities. In this work, radio-frequency atmospheric pressure plasma and TiO2 are used together to inactivate Bacillus subtilis spores that have a very high degree of environmental resistance to ultra-violet (UV) photons and heat. The combinational use of the plasma and TiO2 demonstrates an enhanced performance of B. subtilis spore inactivation by showing a decrease in the decimal reduction time of as large as 40% compared with the use of plasma alone. A significant increase of hydroxyl (OH) and excited oxygen atomic emission line (O I) intensities in the presence of TiO2 suggests that the atmospheric pressure plasma assisted by TiO2 is very effective at generating reactive oxygen radicals, which is known to be a dominant factor in bacterial spore inactivation. Possible TiO2 activation mechanism by the plasma is investigated. [Copyright &y& Elsevier]

Abstract: Germination of Clostridium perfringens is known to be triggered by nutrients such as l-alanine and inosine, and facilitated by CO2, however the role of CO2 has not been fully understood. During the studies of the germination-specific protease GSP, we found that CO2 could be replaced by bicarbonate or weakly acidic pH (pH 6.0–6.5). We also found that the spores obtained from the C. perfringens S40 overproducing GSP could germinate without CO2. Moreover, the spores could germinate in the absence of nutrients, when the spores were incubated with bicarbonate or under weakly acidic pH. GSP, which might consist of three homologous proteases, CspA, CspB, and CspC, is one of the key enzymes involved in the spore germination, and converts the pre-mature form of the spore cortex-lytic enzyme, SleC, to the mature form. Maturation of SleC in the spores obtained from the mother strain of C. perfringens S40 requires nutrients plus bicarbonate or weakly acidic pH. In contrast, mature SleC was found in the spores obtained from the cells overpoducing GSP, when the spores were treated by nutrients, bicarbonate or weakly acidic pH. Each nutrients, bicarbonate and weakly acidic pH can trigger the germination of the spores obtained from C. perfringens cells overproducing GSP. [Copyright &y& Elsevier]

The advantage of using high pressure (HP) cycling treatment compared with continuous HP treatment was investigated for the inactivation of bacterial spores. The effects of parameters such as pulse number, pressure level, treatment temperature, compression and decompression rates, and time between pulses were evaluated. For this purpose, Bacillus subtilis and B. cereus spores (108 and 106 CFU/mL respectively) were suspended in 2-(N-morpholino) ethanesulfonic acid (MES) buffer solution, tryptone salt (TS) buffer solution, or infant milk and treated by HP cycling at 300–400 MPa, at 38–60 °C, for 1–5 pulses. Pressure cycling reduced the number of viable spores by 1.8 and 5.9 log respectively for B. subtilis and B. cereus species. Continuous HP treatments were performed at the same pressure and temperature for similar treatment durations. Our results showed that the spore inactivation ratio was correlated with the cumulative exposure time to pressure rather than to effects of the cycling process. Greater spore inactivation caused by HP cycling was observed only when faster compression and decompression rates were applied, probably due to adiabatic heating. A three-step kinetic model was developed, which seemed to support our hypothesis regarding the mechanisms of inactivation by pressure cycling and continuous HP treatments. The resistance of bacterial spores to HP limits the industrial applications to refrigerated food products. In this study, we investigated the use of pressure cycling as a means to improve spore baroinactivation at moderate temperatures (T < 60 °C). We showed that cycling pressure does not significantly increase bacterial spore inactivation in comparable treatment duration, but certainly increases material fatigue in HP vessels. Thus, under moderate temperature, cycling pressure treatment is not industrially relevant. • The highest inactivation was 1.8 and 5.9 log for B. subtilis and B. cereus spores respectively. • Spore inactivation was mainly related to the pressure holding time and not to the cycling effect. • A three-step kinetic model with a good fit was developped for spore inactivation by pressure cycling. • Higher inactivation with slow compression kinetic due to holding time under pressure during compression time [ABSTRACT FROM AUTHOR]

Abstract: The formation of spore clumps of Bacillus coagulans and Bacillus licheniformis during high-pressure carbon dioxide treatment (HCT) was investigated. As the treatment time increased, the number of spore clumps increased. After 120 min, single spore decreased to 20–35% of the population. Addition of a surfactant decreased the hydrophobicity of spore surface and increased both the number of single spores and the rate of inactivation ratio of B. coagulans and B. licheniformis spores. [Copyright &y& Elsevier]

Effect of high pressure gaseous carbon dioxide treatment (HGCT) at 6.5 MPa, 35 °C on the germination of bacterial spores was investigated. Germination of bacterial spores was estimated by the decrease of heat tolerance. Approximately, 40% of Bacillus coagulans and 70% of Bacillus licheniformis were germinated by HGCT for 120 min at 35 °C, respectively. Germination was confirmed by phase contrast microscopy. The effect of hydrostatic pressure treatment (HPT) at 6.5 MPa, 35 °C on the germination of B. coagulans and B. licheniformis spores were also investigated. Spores did not germinate by HPT alone at 6.5 MPa for 120 min. [Copyright &y& Elsevier]

Anthrax is a bioterror agent because of its toxicity and the tolerance of its bacterial spores. Thus, researchers have attempted to develop various nanomaterials to detect dipicolinic acid (DPA), a biomarker of bacterial spores. Nanomaterials containing lanthanide ions have received considerable attention, owing to their potential to exhibit high sensitivity and selectivity in the detection of DPA via chelation with molecules. However, the fluorescent signals of the lanthanide complex are quenchable because the nanomaterials simultaneously absorb the excitation and emission light. For the precise detection of DPA, pure signals have to be obtained from the complex by alleviating the quenching effect of the nanomaterials. In this study, we develop a structure with terbium ion (Tb3+)-coordinated magnetite (Fe 3 O 4) nanoparticle to detect DPA. Tb3+ can be detached from the magnetite during chelation with the DPA, and the complex can emit the unencumbered signals with improved detection limit through the application of a magnetic field. The detection system exhibits a significantly lower detection limit (5.4 nM) than the infectious dosage of anthrax (60 μM) with high selectivity and chemical stability. This study informs the improvement of detection limits via the separation of nanomaterials and lanthanide complex. ga1 • Design of terbium (Tb) ion-coordinated magnetite (Fe 3 O 4) nanoparticles. • Tb ion is detached from magnetite and chelated with dipicolinic acid simultaneously. • Facile approach to detect unencumbered-fluorescent signal applying a magnetic field. • Low detection limit of 5.4 nM with high selectivity. [ABSTRACT FROM AUTHOR]

Bacterial spores are a major challenge in industrial decontamination processes owing to their extreme resistance. High-pressure (HP) of 150 MPa at 37 °C can trigger the germination of spores, making them lose their extreme resistance. Once their resistance is lost, germinated spores can easily be inactivated by a mild decontamination step. The implementation of this gentle germination-inactivation strategy is hindered by the presence of a subpopulation of so-called high-pressure superdormant (HPSD) spores, which resist germination or germinate only very slowly in response to HP. It is essential to understand the properties of HPSD spores and the underlying causes of superdormancy to tackle superdormant spores and further develop germination-inactivation strategies involving HP. This study investigated factors influencing the prevalence of HPSD spores and successfully isolated them by combining buoyant density centrifugation and fluorescence-activated cell sorting, which allowed further characterisation of HPSD spores for the first time. The prevalence of HPSD spores was shown to be strongly dependent on the HP dwell time, with increasing treatment times reducing their prevalence. Spore mutants lacking major germinant receptors further showed a highly increased prevalence of HPSD spores; 93% of the spores remained dormant even after a prolonged HP dwell time of 40 min. In contrast to nutrient germination, sublethal heat treatment of 75 °C for 30 min prior to pressure treatment did not induce spore activation and increase germination. The isolated HPSD spores did not show visible structural differences compared to the initial dormant spores when investigated with transmission electron microscopy. Re-sporulated HPSD spores showed similar germination capacity compared to the initial dormant spores, indicating that HPSD spores are most likely not genetically different from the rest of the population. Moreover, the majority of HPSD spores germinated when exposed a second time to the same germination treatment; however, the germination capacity was lower than that of the initial population. The fact that the majority of spores lost superdormancy when exposed a second time to the same trigger makes it unlikely that there is one factor that determines whether a spore germinates with a certain HP treatment or not. Instead, it seems possible that there are other reversible or cumulative causes. This study investigated the factors influencing spore HP superdormancy to improve the understanding of HPSD spores with regard to their stability, germination capacity, and potential underlying causes of spore HP superdormancy. This knowledge will contribute to the development of HP-based germination-inactivation strategies for gentle but effective spore control. • High-pressure superdormant (HPSD) bacterial spores were isolated. • The stability, microscopic structure, and germination capacity were characterised. • HPSD spores have similar size and cortex width compared to dormant spores. • Spore high-pressure superdormancy is most likely not due to a genetic change. • The cause of superdormancy is likely cumulative or transient. [ABSTRACT FROM AUTHOR]

• The MOFs functionalized palygorskite hybrid as a novel multicolor fluorescence nanoprobe was manufactured. • The results indicated that the limit of detection (LOD) of this multicolor fluorescence nanoprobe was as low as 9.3 nM. • The nanoprobe can realize the real-time detection through the smartphone with a color-scanning application. • 4. The practicability of this nanoprobe was further verified by detecting DPA released by non-infectious Bacillus subtilis. The metal-organic frameworks (MOFs) functionalized palygorskite (Pal) hybrid as a novel multicolor fluorescence probe for the detection of bacterial spore biomarker-dipicolinic acid (DPA), had been prepared via in-situ growth. The MOFs can effectively encapsulate dye molecules on the surface of Pal, and the rich carboxyl groups on its surface can coordinate with europium ions (Eu3+), forming a highly sensitive recognition group. The results indicated that the limit of detection (LOD) of this multicolor fluorescence probe was as low as 9.3 nM and was obviously lower than the amount of anthrax spores infecting the human body (60 μM). Moreover, a wide linear range from 0 to 35 μM was obtained. The high specific surface area of Pal, as well as the permanent porosity and suitable binding sites of Eu3+-doped MOFs may play a major role in the sensitivity and linear detection range. The multicolor fluorescence strategy made full use of the diversity of fluorescence signals collected by dye molecules and lanthanide ions, which can realize the real-time and on-site detection through the smartphone with a color-scanning application (APP). The practicability of this probe was further verified by detecting DPA released by non-infectious Bacillus subtilis. [ABSTRACT FROM AUTHOR]