Proteomic expression of microfungal ripening starter Geotrichum candidum submitted to cold stress is strain-dependent: studies using 2d-dige technology and samespots software analysis.

Geotrichum candidum is a micro-fungus widely used as a ripening starter in cheese making. In anthropogenic environments such as dairy industries, this microorganism is subjected to many environmental and technological stresses including low temperature exposure. Our aim was to study the proteomic response of G.

Relationship between growth behaviour, micro and macroscopic morphologies and freezing sensitivity of the ripening starter Geotrichum candidum is strain specific and mostly related to the morphotypes: the arthrospores/hyphae parameter.

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.

Response to environmental stress as a global phenomenon in biology: the example of microorganisms.

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.

Improvement of the cryopreservation of the fungal starter Geotrichum candidum by artificial nucleation and temperature downshift control.

Food industry tends towards the use of controlled microorganisms in order to improve its technologies including frozen starter production. The fungus Geotrichum candidum, which is currently found in various environments, is widely used as ripening agent in some specific cheese making process. In order to optimize the cryopreservation of this microorganism, freezing experiments were carried out using a Peltier cooler-heater incubator, which permits to control the temperature downshift from +20 to -10 degrees C in time period ranges from 20 to 40min depending on the experiments.

Cryotolerance of Lactobacillus delbrueckii subsp. bulgaricus CFL1 is modified by acquisition of antibiotic resistance.

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).

Resin straw as an alternative system to securely store frozen microorganisms.

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.

Nystatin and osmotica as chemical enhancers of the phenotypic adaptation to freeze-thaw stress in Geotrichum candidum ATCC 204307.

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.

Phenotypic adaptation to freeze-thaw stress of the yeast-like fungus Geotrichum candidum.

The effect of cold stress on Geotrichum candidum was investigated at chill and freezing temperatures. Specific growth rates were determined at various temperatures and plotted according to the Ratkowsky and Arrhenius equations. The obtained profiles led to the determination of characteristics including the activation energy and notional minimum temperatures.

Cryoprotectants lead to phenotypic adaptation to freeze-thaw stress in Lactobacillus delbrueckii ssp. bulgaricus CIP 101027T.

This study was conducted to investigate the ability of cryoprotective chemicals to induce phenotypic cryoadaptation in Lactobacillus delbrueckii ssp. bulgaricus CIP 101027T. Tolerance to negative temperature stress (freezing at -20 degrees C and thawing at 37 degrees C) was induced by pretreatment with Me(2)SO, glycerol, lactose, sucrose, and trehalose.

Cold stress responses in mesophilic bacteria.

The diversity of the prokaryotes that have been studied, combined with the many different effects of low temperature, has led to an extensive literature concerning cold stress responses in mesophilic bacteria. The aim of this review is to discuss the effects of cold on the behavior of bacteria. The following three responses will be described: (i) biochemical modifications consisting first of membrane fatty acid desaturation and second of the synthesis of cold stress proteins, (ii) physiological responses of the cells to permit growth at low temperatures above 0 degrees C and cryotolerance at lower temperatures, and (iii) control of the cold shock response at a transcriptional and/or translational level.

Differentiation between cold shock proteins and cold acclimation proteins in a mesophilic gram-positive bacterium, Enterococcus faecalis JH2-2.

Transfer of Enterococcus faecalis to a cold temperature (8 degrees C for 4 to 30 h) led to increased expression of 11 cold shock proteins (CSPs). Furthermore, this mesophilic prokaryote synthesized 10 cold acclimation proteins, five of them distinct from CSPs, during continuous growth (4 days) at the same temperature (8 degrees C).

Physiological response of Enterococcus faecalis JH2-2 to cold shock: growth at low temperatures and freezing/thawing challenge.

Growth at low positive temperatures and induced phenotypic resistance to extreme cold temperature (freezing/thawing cycles) of Enterococcus faecalis were investigated. The effect of low temperatures on the specific growth rates was studied; use of Arrhenius profile and Ratkovsky 'square-root' model allowed determination of the 'temperature characteristic' (mu approximately equal to 13,800 cal mol-1), the critical temperature (Tcrit approximately equal to 17.9 degrees C) and the notional minimum growth temperature (T0 approximately equal to 3.

Induction of thermotolerance by chemical agents in Lactococcus lactis subsp. lactis IL1403.

Like in other organisms tested to date, adapted cells of Lactococcus lactis subsp. lactis IL1403 pretreated at 42 degrees C for 30 min develop a thermotolerant state, i.e.

Characterization of the heat shock response in Enterococcus faecalis.

We have characterized the general properties of the heat shock response of the Gram-positive hardy bacterium Enterococcus faecalis. The heat resistance (60 degrees C or 62.5 degrees C, 30 min) of log phase cells of E.

Is thermotolerance correlated to heat-shock protein synthesis in Lactococcus lactis subsp. lactis?

Exposure of Lactococcus lactis subsp. lactis cells to a heat shock at 40 degrees C for 30 min induces thermotolerance, the increased ability of bacterial cells to survive exposure to lethal temperature (52 degrees C for 25 min). This transient state of thermal resistance is accompanied, as in Escherichia coli, by the synthesis of a new set of specific proteins termed heat-shock proteins (Hsps).

Heat shock induces thermotolerance and inhibition of lysis in a lysogenic strain of Lactococcus lactis.

In this preliminary work, the heat shock response of lactic acid bacteria was investigated and characterized. Log-phase Lactococcus lactis cells pre-incubated at 40 degrees C before heat challenge at 52 degrees C for 30 min demonstrated increased thermotolerance as compared with cells pre-incubated at 30 degrees C. The response persisted for at least 60 min.

Identification of a RecA-like protein in Lactococcus lactis.

We have identified in Lactococcus lactis, an analogue of Escherichia coli RecA protein. Physiological responses such as ultraviolet (UV) and chemical mutagenesis and induction of prophage have been characterized and suggest the existence of RecA-like functions in this commercially important species. The putative RecA protein was detected at the position of an apparent molecular weight of 39 kDa by Western blot analysis by using antiserum against E coli RecA protein.

Response of Lactococcus (Streptococcus) lactis to N-methyl-N'-nitro-N-nitrosoguanidine: absence of adaptive response.

Pretreatment of cells of Lactococcus lactis subsp. lactis with low levels of N-methyl-N'-nitro-N-nitrosoguanidine does not reduce the cytotoxic and mutagenic effects caused by high concentration of this agent. This observation indicates that there is no efficient inducible error-free repair system for alkylation damage similar to the 'adaptive response' described in detail for Escherichia coli.