Kinetics of Spore Germination

1965 ◽  
Vol 89 (5) ◽  
pp. 1180-1185 ◽  
Author(s):  
Neil G. McCormick
Keyword(s):  
Spore Germination ◽  
Kinetics Of

scholarly journals Modelling spore germination and mycelium growth kinetics of fungi in yogurt-type environment

2012 ◽  
Author(s):  
Μαρία Γουγουλή
Keyword(s):  
Growth Kinetics ◽  
Spore Germination ◽  
Mycelium Growth ◽  
Kinetics Of

Η επιμόλυνση και η αποίκηση της γιαούρτης με μύκητες είναι ίσως το πιο σημαντικό πρόβλημα ποιότητας για τα προϊόντα γιαούρτης με σημαντικές οικονομικές επιπτώσεις για τη βιομηχανία γάλακτος. Το βασικό αντικείμενο της παρούσας διδακτορικής έρευνας ήταν η ανάπτυξη αποτελεσματικών εργαλείων ποσοτικής μυκητολογίας, τα οποία μπορούν να χρησιμοποιηθούν για τη βελτίωση των συστημάτων ελέγχου μυκήτων στην παραγωγή γιαούρτης. Το πρώτο μέρος της έρευνας επικεντρώθηκε στην ανάπτυξη μαθηματικών μοντέλων για την πρόβλεψη της επίδρασης της θερμοκρασίας και του επιπέδου εμβολίου στην ανάπτυξη 12 στελεχών διαφορετικών ειδών μυκήτων οι οποίοι απομονώθηκαν από το περιβάλλον παραγωγής γιαούρτης. Σημαντικές διαφορές παρατηρήθηκαν μεταξύ των στελεχών σχετικά με τη θερμοκρασιακή εξάρτηση της μυκηλιακής τους αύξησης. Με βάση τα αποτελέσματα, αναπτύχθηκε ένα λεπτομερές σχέδιο εφαρμογής των μοντέλων για την επιλογή των κατάλληλων συνθηκών των δοκιμών ελέγχου για την παρουσία μυκήτων στη γιαούρτη. Λαμβάνοντας υπόψη ότι οι διακυμάνσεις της θερμοκρασίας κατά τη διάρκεια της διανομής και αποθήκευσης της γιαούρτης αποτελούν συχνό φαινόμενο, τα μοντέλα που αναπτύχθηκαν αξιολογήθηκαν περαιτέρω σε δυναμικές συνθήκες θερμοκρασίας. Μετά τις παραπάνω μελέτες που διεξήχθησαν σε υψηλό επίπεδο πληθυσμού σπορίων, η έρευνα επεκτάθηκε στην αξιολόγηση και περιγραφή της συμπεριφοράς μυκήτων σε επίπεδο μεμονωμένων σπορίων. Μοντέλα που περιγράφουν τη συμπεριφορά μεμονωμένων σπορίων μυκήτων μπορεί να οδηγήσουν σε πιο ρεαλιστικές προβλέψεις, δεδομένου ότι στην πράξη η επιμόλυνση των τροφίμων με μύκητες συμβαίνει από πολύ χαμηλούς αριθμούς σπορίων. Η εκβλάστηση σπορίων μυκήτων παρατηρήθηκε μικροσκοπικά και τα δεδομένα εκβλάστησης μοντελοποιήθηκαν με τη βοήθεια πρωτογενών και δευτερογενών μοντέλων. Η εκβλάστηση των σπορίων μελετήθηκε, επίσης, σε διάφορες δυναμικές θερμοκρασιακές συνθήκες. Η σύγκριση μεταξύ των προβλεπόμενων και παρατηρούμενων δεδομένων έδειξαν ότι η εκβλάστηση των σπορίων επηρεάζεται έντονα από το βαθμό της θερμοκρασιακής μεταβολής, το ποσοστό των εκβλαστημένων σπορίων τη στιγμή της μεταβολής της θερμοκρασίας, καθώς και από το είδος του μύκητα. Η σχέση μεταξύ του χρόνου εκβλάστησης και του χρόνου φάσης προσαρμογής της μυκηλιακής ανάπτυξης μεμονωμένων σπορίων μελετήθηκε επίσης με συνδυασμό μικροσκοπικών και μακροσκοπικών τεχνικών. Η αύξηση ενός μεγάλου αριθμού μυκηλίων που προέρχονται από μεμονωμένα σπόρια μελετήθηκε μακροσκοπικά για τον προσδιορισμό του χρόνου φάσης προσαρμογής. Παρατηρήθηκε πως οι κατανομές των χρόνων φάσης προσαρμογής παρουσίασαν μία σημαντική χρονική καθυστέρηση σε σχέση με τις κατανομές του χρόνου εκβλάστησης. Προκειμένου να διερευνηθεί η πηγή της παραπάνω διαφοράς αναπτύχθηκε μια μικροσκοπική μέθοδος συνεχούς παρατήρησης παρέχοντας βίντεο με την συμπεριφορά των μεμονωμένων σπορίων μυκήτων από την εκβλάστηση μέχρι το σχηματισμό μυκήλιων. Εκτός από το επιστημονικό ενδιαφέρον για την κατανόηση της συμπεριφοράς των μυκήτων, τα ευρήματα αυτής της έρευνας μπορούν να εφαρμοστούν άμεσα από τη βιομηχανία γιαούρτης για τη βελτίωση των συστημάτων ελέγχου της ποιότητας. Για παράδειγμα, τα μοντέλα που αναπτύχθηκαν μπορούν να χρησιμοποιηθούν ως βάση για την επιλογή των κατάλληλων συνθηκών των δοκιμών πρόκλησης για την ανίχνευση μυκήτων σε γιαούρτη. Μέτρα ελέγχου ποιότητας βασισμένα σε επιστημονικά δεδομένα μπορούν να οδηγήσουν σε μια επιτυχημένη διαδικασία λήψης αποφάσεων για τη βελτίωση της ποιότητας. Επιπλέον, η ποσοτική περιγραφή της παραλλακτικότητας στη συμπεριφορά μεμονωμένων σπορίων μπορεί να χρησιμοποιηθεί για την εκτίμηση επικινδυνότητας της αλλοίωσης και την ανάπτυξη δραστικών συστημάτων διαχείρισης ποιότητας για προϊόντα τύπου γιαούρτης.

scholarly journals Germination, Outgrowth, and Vegetative-Growth Kinetics of Dry-Heat-Treated Individual Spores ofBacillusSpecies

2018 ◽  
Vol 84 (7) ◽  
Author(s):  
Lin He ◽  
Zhan Chen ◽  
Shiwei Wang ◽  
Muying Wu ◽  
Peter Setlow ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Spore Germination ◽  
Differential Interference Contrast Microscopy ◽  
Content Type ◽  
Dry Heat ◽  
Heat Treated ◽  
Contrast Microscopy ◽  
Interference Contrast Microscopy ◽  
Dry Heat Treatment ◽  
Kinetics Of

ABSTRACTDNA damage kills dry-heated spores ofBacillus subtilis, but dry-heat-treatment effects on spore germination and outgrowth have not been studied. This is important, since if dry-heat-killed spores germinate and undergo outgrowth, toxic proteins could be synthesized. Here, Raman spectroscopy and differential interference contrast microscopy were used to study germination and outgrowth of individual dry-heat-treatedB. subtilisandBacillus megateriumspores. The major findings in this work were as follows: (i) spores dry-heat-treated at 140°C for 20 min lost nearly all viability but retained their Ca2+-dipicolinic acid (CaDPA) depot; (ii) in most cases, dry-heat treatment increased the average times and variability of all major germination events inB. subtilisspore germination with nutrient germinants or CaDPA, and in one nutrient germination event withB. megateriumspores; (iii)B. subtilisspore germination with dodecylamine, which activates the spore CaDPA release channel, was unaffected by dry-heat treatment; (iv) these results indicate that dry-heat treatment likely damages spore proteins important in nutrient germinant recognition and cortex peptidoglycan hydrolysis, but not CaDPA release itself; and (v) analysis of single spores incubated on nutrient-rich agar showed that while dry-heat-treated spores that are dead can complete germination, they cannot proceed into outgrowth and thus not to vegetative growth. The results of this study provide new information on the effects of dry heat on bacterial spores and indicate that dry-heat sterilization regimens should produce spores that cannot outgrow and thus cannot synthesize potentially dangerous proteins.IMPORTANCEMuch research has shown that high-temperature dry heat is a promising means for the inactivation of spores on medical devices and spacecraft decontamination. Dry heat is known to killBacillus subtilisspores by DNA damage. However, knowledge about the effects of dry-heat treatment on spore germination and outgrowth is limited, especially at the single spore level. In the current work, Raman spectroscopy and differential interference contrast microscopy were used to analyze CaDPA levels in and kinetics of nutrient- and non-nutrient germination of multiple individual dry-heat-treatedB. subtilisandBacillus megateriumspores that were largely dead. The outgrowth and subsequent cell division of these germinated but dead dry-heat-treated spores were also examined. The knowledge obtained in this study will help understand the effects of dry heat on spores both on Earth and in space, and indicates that dry heat can be safely used for sterilization purposes.

scholarly journals Kinetics of Germination of Wet-Heat-Treated Individual Spores of Bacillus Species, Monitored by Raman Spectroscopy and Differential Interference Contrast Microscopy

2011 ◽  
Vol 77 (10) ◽  
pp. 3368-3379 ◽  
Author(s):  
Guiwen Wang ◽  
Pengfei Zhang ◽  
Peter Setlow ◽  
Yong-qing Li
Keyword(s):  
Heat Treatment ◽  
Raman Spectroscopy ◽  
Spore Germination ◽  
Great Majority ◽  
Lytic Enzyme ◽  
Differential Interference Contrast ◽  
Content Type ◽  
Heat Treated ◽  
Wet Heat ◽  
Kinetics Of

ABSTRACTRaman spectroscopy and differential interference contrast (DIC) microscopy were used to monitor the kinetics of nutrient and nonnutrient germination of multiple individual untreated and wet-heat-treated spores ofBacillus cereusandBacillus megaterium, as well as of several isogenicBacillus subtilisstrains. Major conclusions from this work were as follows. (i) More than 90% of these spores were nonculturable but retained their 1:1 chelate of Ca2+and dipicolinic acid (CaDPA) when incubated in water at 80 to 95°C for 5 to 30 min. (ii) Wet-heat treatment significantly increased the time,Tlag, at which spores began release of the great majority of their CaDPA during the germination ofB. subtilisspores with different nutrient germinants and also increased the variability ofTlagvalues. (iii) The time period, ΔTrelease, betweenTlagand the time,Trelease, at which a spore germinating with nutrients completed the release of the great majority of its CaDPA, was also increased in wet-heat-treated spores. (iv) Wet-heat-treated spores germinating with nutrients had higher values ofIrelease, the intensity of a spore's DIC image atTrelease, than did untreated spores and had much longer time periods, ΔTlys, for the reduction inIreleaseintensities to the basal value due to hydrolysis of the spore's peptidoglycan cortex, probably due at least in part to damage to the cortex-lytic enzyme CwlJ. (v) Increases inTlagand ΔTreleasewere also observed when wet-heat-treatedB. subtilisspores were germinated with the nonnutrient dodecylamine, while the change inIreleasewas less significant. (vi) The effects of wet-heat treatment on nutrient germination ofB. cereusandB. megateriumspores were generally similar to those onB. subtilisspores. These results indicate that (i) some proteins important in spore germination are damaged by wet-heat treatment, (ii) the cortex-lytic enzyme CwlJ is one germination protein damaged by wet heat, and (iii) the CaDPA release process itself seems likely to be the target of wet-heat damage which has the greatest effect on spore germination.

scholarly journals Characterization of the Dynamic Germination of Individual Clostridium difficile Spores Using Raman Spectroscopy and Differential Interference Contrast Microscopy

2015 ◽  
Vol 197 (14) ◽  
pp. 2361-2373 ◽  
Author(s):  
Shiwei Wang ◽  
Aimee Shen ◽  
Peter Setlow ◽  
Yong-qing Li
Keyword(s):  
Raman Spectroscopy ◽  
Gastrointestinal Tract ◽  
Clostridium Difficile ◽  
Spore Germination ◽  
Bile Salts ◽  
Differential Interference Contrast ◽  
Gram Positive ◽  
Content Type ◽  
Kinetics Of ◽  
Dic Microscopy

ABSTRACTThe Gram-positive spore-forming anaerobeClostridium difficileis a leading cause of nosocomial diarrhea. Spores ofC. difficileinitiate infection when triggered to germinate by bile salts in the gastrointestinal tract. We analyzed germination kinetics of individualC. difficilespores using Raman spectroscopy and differential interference contrast (DIC) microscopy. Similar toBacillusspores, individualC. difficilespores germinating with taurocholate plus glycine began slow leakage of a ∼15% concentration of a chelate of Ca2+and dipicolinic acid (CaDPA) at a heterogeneous timeT1, rapidly released CaDPA atTlag, completed CaDPA release atTrelease, and finished peptidoglycan cortex hydrolysis atTlysis.T1andTlagvalues for individual spores were heterogeneous, but ΔTreleaseperiods (Trelease−Tlag) were relatively constant. In contrast toBacillusspores, heat treatment did not stimulate spore germination in the twoC. difficilestrains tested.C. difficilespores did not germinate with taurocholate or glycine alone, and different bile salts differentially promoted spore germination, with taurocholate and taurodeoxycholate being best. Transient exposure of spores to taurocholate plus glycine was sufficient to commit individual spores to germinate.C. difficilespores did not germinate with CaDPA, in contrast toB. subtilisandC. perfringensspores. However, the detergent dodecylamine inducedC. difficilespore germination, and rates were increased by spore coat removal although cortex hydrolysis did not followTrelease, in contrast withB. subtilis.C. difficilespores lacking the cortex-lytic enzyme, SleC, germinated extremely poorly, and cortex hydrolysis was not observed in the fewsleCspores that partially germinated. Overall, these findings indicate thatC. difficileandB. subtilisspore germination exhibit key differences.IMPORTANCESpores of the Gram-positive anaerobeClostridium difficileare responsible for initiating infection by this important nosocomial pathogen. When exposed to germinants such as bile salts,C. difficilespores return to life through germination in the gastrointestinal tract and cause disease, but their germination has been studied only with population-wide measurements. In this work we used Raman spectroscopy and DIC microscopy to monitor the kinetics of germination of individualC. difficilespores, the commitment of spores to germination, and the effect of germinant type and concentration, sublethal heat shock, and spore decoating on germination. Our data suggest that the order of germination events inC. difficilespores differs from that inBacillusspores and provide new insights intoC. difficilespore germination.

Direct observations of radiation-enhanced transformations in glass

1983 ◽  
Vol 41 ◽  
pp. 354-355
Author(s):  
J. F. DeNatale ◽  
D. G. Howitt
Keyword(s):  
Glass Matrix ◽  
Diffusion Mechanism ◽  
Bubble Formation ◽  
Silicate Glasses ◽  
Phase Decomposition ◽  
Direct Observations ◽  
Thin Foils ◽  
Oxygen Bubble ◽  
Electron Energy Loss ◽  
Kinetics Of

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.

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