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ABSTRACT: Microscopic conformation, growth behaviour and freezing sensitivity of seven strains of Geotrichum candidum, a ripening starter, were studied and compared according to their macroscopic morphotypes. It has been shown that the thallus forming units (TFU)×ml-1/OD600nm ratio as a function of time is an interesting parameter to follow G. candidum sporulation through the growth behaviour. Microscopic conformation, growth behaviour and freezing sensitivity are clearly strain specific and mostly related to their corresponding morphotypes "yeast", "mould" or "intermediate". The two "mould" strains that sporulate weakly (UCMA103, UCMA499) showed a low survival rate to freezing stress whereas the "yeast" strains expressed a significant resistance owing to the arthrospore abundance. Interestingly, one strain (UCMA96) which appeared on solid medium in accord with the "mould" morphotype respond similarly to freezing stress.
Journal of Dairy Research 11/2010; 77(4):425-31. · 1.34 Impact Factor
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ABSTRACT: Any modification of the environment that leads to a physiological, genetic, or epigenetic adaptive response in microorganisms may be considered as a stress. Historically, forms of stresses affecting biological structures were classified either as non-thermal, such as osmotic, oxidative, or acid stress or as thermal stress, hot or cold. Currently, the classification in biology is as abiotic, including physical and chemical stress, or biotic. The aim of this mini-review is to show, through the example of microorganisms, that the response to stress can be considered, in biology, as a global phenomenon, which can be extended to anthropogenic pressure.
Microbes and Environments 01/2008; 23(1):20-3. · 1.91 Impact Factor
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ABSTRACT: This study aimed to relate the acquisition of different antibiotic resistances and the corresponding physiological responses to cold stress of Lactobacillus delbrueckii subsp. bulgaricus strain CFL1. Six resistant mutants were spontaneously obtained and studied depending on the target of the antibiotic: (i) bacitracin and vancomycin (Bac(R), Van(R), wall synthesis), (ii) novobiocin (Nov(R), DNA replication), and (iii) kanamycin, spiramycin, streptomycin (Kan(R), Spi(R), Str(R), RNA translation). The mutations modified the growth and the cold stress response at three different physiological levels: (i) Van(R) and Spi(R) mutants showed significant lower growth rates compared to the wild type strain. (ii) Van(R) and Bac(R) mutants displayed a slightly higher resistance to a freezing-thawing challenge whereas Str(R) and Spi(R) mutants were more sensitive compared to the wild type. (iii) The recovery of acidification activity after freezing and during frozen storage was improved by considering the Nov(R) strain, but not with the Van(R) and Spi(R) mutants. Thus, acquisition of some antibiotic resistance by spontaneous mutation led to modification of the cold stress response. The hypothesis of a unique cellular thermostat is discussed regarding the diversity of the tested antibiotics.
Cryobiology 09/2007; 55(1):19-26. · 2.06 Impact Factor
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ABSTRACT: Freezing of prokaryotic and eukaryotic microorganisms is the main interest in the study of cold stress responses of living organisms. In parallel, applications which arise from this approach are of two types: (i) optimization of the frozen starters used in food processing; and (ii) improvement of the ex situ preservation of microorganisms in collections. Currently, cryopreservation of microorganisms in collections is carried out in cryotubes, and bibliographical references related to freezing microorganisms packaged in straws are scarce. In this context, a preliminary study was completed to evaluate the technological potential of ionomeric resin straws compared to polycarbonate cryo-tubes. Survival under freezing stress was tested on three microorganisms selected for their biotechnological interest: two lactic acid bacteria, Lactococcus lactis subsp. cremoris and Lactobacillus delbrueckii subsp. bulgaricus and a deuteromycete fungus, Geotrichum candidum. The stress was carried out by repeated freezing-thawing cycles to artificially accelerate the lethal effect of freezing on the microorganisms. Two main results were obtained: (i) the survival rate values (per freezing-thawing cycle) seems to depend on the thermal type of the studied microorganism, and (ii) there was no, under our experimental conditions, significant difference between straws and tubes. However, conservation in the resin straws lead to a slight increase in the survival of L. cremoris and G. candidum compared to microtubes. In those conditions, straws seems an alternative system to securely store frozen microorganisms with three main characteristics: (i) a high resistance to thermal stress, (ii) a safe closing by hermetic weld, and (iii) a system for inviolable identification.
Journal of Microbiological Methods 06/2004; 57(2):181-6. · 2.09 Impact Factor
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ABSTRACT: Geotrichum candidum is a yeast-like fungus used as ripening starter in cheese making. The present study focused on chemical stress pretreatments affecting survival of G. candidum ATCC 204307 to freeze-thaw stress. Cryotolerance of G. candidum cells was induced by pretreatment with NaCl, CaCl2, or MgCl2, indicating heterologous phenotypic adaptation to freeze-thaw stress (- 20 to 25 degrees C) by osmotic stress. Furthermore, the nystatin, an antifungal compound, was shown to be a cryotolerance inducer.
International Journal of Food Microbiology 07/2002; 76(3):215-21. · 3.33 Impact Factor
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Microbiology 04/2002; 148(Pt 3):625. · 3.06 Impact Factor
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ABSTRACT: The lactic acid bacterium,Lactococcus lactis subsp.lactis IL1403 was subjected to defferent cold temperatures for various times. Physiological experiments showed that this strain had an improved survival capacity in stationary phase as the temperature decreased. Two-dimensional electrophoresis of proteins extracted from cold-temperature exposed cultures showed that a dozen proteins are overexpressed up to threefold compared with exposure at 30C. Most of these proteins are overexpressed first, temporarily and second, in the first 10 h after the transfer to 8C. These observations indicate that response to cold stress inL. lactis subsp.lactis is an active phenomenon.
Current Microbiology 09/1994; 29(4):213-216. · 1.82 Impact Factor
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ABSTRACT: Heat shock inLactococcus lactis subsp.lactis may induce as many as 16 proteins after a temperature shift from 30 to 40C. Five induced proteins were found to be immunologically related to theEscherichia coli GroEL, DnaK, DnaJ, and GrpE proteins, and to theBacillus subtilis
43 factor. From these initial studies we conclude that, inL. lactis subsp.lactis, a heat shock response similar to that known to occur in other prokaryotes might exist.
Current Microbiology 04/1992; 24(5):281-284. · 1.82 Impact Factor
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ABSTRACT: Repair of ultraviolet-light-induced DNA damage inStreptococcus lactis has been examined. The wild-type strain and its derivative Lac– possess a dark repair system (maximal increase in survival of 4-fold). Enzymatic photoreactivation exists in the two strains but a weaker photoreactivability was found in the Lac– derivative (4 and 2-fold, respectively). Concomitant reduction of UV-induced mutagenesis (Rifr marker) was also studied during these two repair phenomena. The absence of dark repair after saturation of photoreactivation suggests that photoreactivation is much more efficient with pyrimidine dimers as substrate.
Journal of Industrial Microbiology and Biotechnology 12/1988; 4(1):13-17. · 2.73 Impact Factor
