The core interthreshold zone during exposure to red and blue light

Background

This study tested the hypothesis that the core interthreshold zone (CIZ) changes during exposure to red or blue light via the non-visual pathway, because it is known that light intensity affects the central nervous system. We conducted a series of human experiments with 5 or 10 male subjects in each experiment.

Methods

The air temperature in the climatic chamber was maintained at 20 to 24°C. The subjects wore suits perfused with 25°C water at a rate of 600 cm³/min. They exercised on an ergometer at 50% of their maximum work rate for 10 to 15 minutes until sweating commenced, and then remained continuously seated without exercise until their oxygen uptake increased. The rectal temperature and skin temperatures at four sites were monitored using thermistors. The sweating rate was measured at the forehead with a sweat rate monitor. Oxygen uptake was monitored with a gas analyzer. The subjects were exposed to red or blue light at 500 lx and 1000 lx in both summer and winter.

Results

The mean CIZs at 500 lx were 0.23 ± 0.16°C under red light and 0.20 ± 0.10°C under blue light in the summer, and 0.19 ± 0.20°C under red light and 0.26 ± 0.24°C under blue light in the winter. The CIZs at 1000 lx were 0.18 ± 0.14°C under red light and 0.15 ± 0.20°C under blue light in the summer, and 0.52 ± 0.18°C under red light and 0.71 ± 0.28°C under blue light in the winter. A significant difference (P <0.05) was observed in the CIZs between red and blue light at 1000 lx in the winter, and significant seasonal differences under red light (P <0.05) and blue light (P <0.01) were also observed at 1000 lx.

Conclusions

The present study demonstrated that dynamic changes in the physiological effects of colors of light on autonomic functions via the non-visual pathway may be associated with the temperature regulation system.     

THE PARACRYSTALLINE STATE OF THE RAT RED CELL

When washed rat red cells are kept in 3 per cent sodium citrate at low temperatures (4–9°C.), their resistance to osmotic hemolysis increases so that after several days they swell very little in hypotonic solutions (R = 0.15 to zero) and do not hemolyze even in distilled water. In this and in other respects they behave as if they were gelated or paracrystalline. The paracrystalline state is reversible, disappearing when the cells are warmed and rapidly reappearing when they are cooled, and the resistance to hypotonic hemolysis is not due to the cells reaching equilibrium with their environment by losing so much K that the concentrations become equal inside and out. The concentration of K remains about 25 times as great inside the cell as outside it in a hypotonic medium of T = 0.1, and the failure to swell and to hemolyze seems to be due to the activity of K in the interior of the paracrystalline cell approaching zero. The paracrystalline red cells are more resistant to saponin and digitonin hemolysis, and do not undergo the usual shape transformations, probably because they are too rigid. Hemolysis by saponin and similar lysins occurs without sphere formation, and after lysis is complete a granular debris is left behind. The paracrystalline cells show a diffuse birefringence with polarized light; on their being warmed, the birefringence disappears except at foci which are usually situated along the rim of the cell. The occurrence of the paracrystalline state accounts for the different amounts of swelling of red cells which have been observed in systems of the same degree of hypotonicity, and its relation to other metastable states of the red cell is discussed in connection with a tabulation of the metastable states of the mammalian red cell and their relation to one another. Changes in a membrane alone seem inadequate to account for the varied phenomena observed in connection with red cell behavior, the explanation of which appears to require a more detailed knowledge of the molecular architecture of the cell interior.     

Accumulation of potassium by human red cells

1. A method is described for measuring the accumulation of K at 37°C. by washed human red cells in glucose-containing systems in which the pH is kept constant, the K content of the cells being compared with that of the cells of systems which contain no added glucose but which are otherwise treated similarly. 2. In systems containing added glucose, the accumulation of K begins shortly after the cells have been warmed to 37°C., proceeds to a maximum which is reached after about 10 hours, and then falls exponentially. The maximum rate of accumulation is found during the first 3 hours. In systems which contain no added glucose, the K content of the cells appears to decrease exponentially with time for about 18 to 24 hours; thereafter the K content of the cells may decrease rapidly and the systems may show considerable hemolysis. Sometimes a small accumulation effect is observed during the first 2 to 3 hours; this may be the result of the washed cells not having been completely freed of glucose. 3. The accumulation process proceeds at its maximum rate at pH 7.4 to 7.6, which is also the pH at which the K loss from the red cells is at a minimum in systems containing no added glucose. 4. When red cells are stored at 4°C. for increasing lengths of time, the storage is accompanied by increasing K loss and the maximum rate of accumulation observed when the cells are warmed to 37°C. at first becomes greater. If the storage at 4°C. is continued for more than 3 to 4 days, the rate of the accumulation which occurs at 37°C decreases again, the accumulation mechanism showing progressive deterioration with time even at low temperatures. This deterioration has a counterpart in the progressive deterioration (deduced from the analysis of the curves relating K content and time) of the accumulation mechanism with time at 37°C. 5. The accumulation of K occurs at a maximum rate when the concentration of glucose in the system is between 50 and 200 mg./100 ml. Its temperature coefficient over the range 27–37°C. is 2.4. In the presence of glucose and at pH 7.6, accumulation of K takes place from isotonic mixtures of KCl and LiCl or of KCl and CsCl only a little less actively than from mixtures of KCl and NaCl; i.e., the accumulation of K under optimum conditions seems to be an active process which is at least partly independent of the excretion of Na.     

Heat stress reveals a specialized variant of the pachytene checkpoint in meiosis of Arabidopsis thaliana

Plant growth and fertility strongly depend on environmental conditions such as temperature. Remarkably, temperature also influences meiotic recombination and thus, the current climate change will affect the genetic make-up of plants. To better understand the effects of temperature on meiosis, we followed male meiocytes in Arabidopsis thaliana by live cell imaging under three temperature regimes: at 21°C; at heat shock conditions of 30°C and 34°C; after an acclimatization phase of 1 week at 30°C. This work led to a cytological framework of meiotic progression at elevated temperature. We determined that an increase from 21°C to 30°C speeds up meiosis with specific phases being more amenable to heat than others. An acclimatization phase often moderated this effect. A sudden increase to 34°C promoted a faster progression of early prophase compared to 21°C. However, the phase in which cross-overs mature was prolonged at 34°C. Since mutants involved in the recombination pathway largely did not show the extension of this phase at 34°C, we conclude that the delay is recombination-dependent. Further analysis also revealed the involvement of the ATAXIA TELANGIECTASIA MUTATED kinase in this prolongation, indicating the existence of a pachytene checkpoint in plants, yet in a specialized form.

Live cell imaging of plants exposed to different heat stresses provides a temporal framework of meiosis at high temperatures in wild-type and mutants for several meiotic recombination factors.     

Selective stimulation of Hsp27 and αB-crystallin but not Hsp70 expression by p38 MAP kinase activation

The levels of Hsp27 and αB-crystallin in C6 rat glioma cells, that had been heated at 43°C for 30 min with a subsequent culture for 16 h at 37°C, were markedly increased. The exposure of the cells to a low concentration (0.1–3 µg/ml) of anisomycin for a few hours after heat stress stimulated the accumulation of the small stress proteins Hsp27 and αB-crystallin, but not that of Hsp70. The levels of mRNAs for Hsp27 and αB-crystallin but not that for Hsp70 increased in cells that had been exposed to heat and subsequently for 2 h to 0.1–3 µg/ml anisomycin. The results of a reporter assay, using an αB-crystallin promotor fused to a luciferase reporter gene, suggested that the increase in level of αB-crystallin mRNA was due to the production of new mRNA. The activation of the binding of heat shock factors to heat shock elements induced in cells that had been heat stressed was barely affected by subsequent exposure to anisomycin at 0.3 µg/ml. The stimulatory effects of anisomycin were also observed in cells that had been exposed to NaAsO₂, or CdCl₂. The active form of p38 mitogen activated protein (MAP) kinase was increased in cell that had been subjected to heat shock and subsequent exposure to 0.3 µg/ml of anisomycin. The heat-induced accumulations of Hsp27 and αB-crystallin were also stimulated by cycloheximide, another stimulator of p38 MAP kinase. SB202190, a specific inhibitor of p38 MAP kinase, suppressed the stimulation by anisomycin of the heat stress-induced expressions of Hsp27 and αB-crystallin. These results suggest that the signal transduction pathway of the stress-induced expressions of Hsp27 and αB-crystallin in C6 glioma cells includes a process that is sensitive to p38 MAP kinase.     

ClpB1 Overproduction in Synechocystis sp. Strain PCC 6803 Increases Tolerance to Rapid Heat Shock

ClpB1 is a heat shock protein known to disaggregate large protein complexes. Constitutive, 16-fold ClpB1 overproduction in the cyanobacterium Synechocystis sp. strain PCC 6803 increased cell survival by 20-fold when cultures were heated quickly (1°C/s) to 50°C and delayed cell death by an average of 3 min during incubation at high temperatures (>46°C). Cooverexpression of ClpB1 and another heat shock protein, DnaK2, further increased cell survival. According to immunocytochemistry results, ClpB1 is dispersed throughout the cytoplasm but is concentrated in specific areas and is more prevalent near thylakoid membranes. However, ClpB1 overproduction does not lead to a change in the morphology, chlorophyll content, or photosystem ratio. Whereas electron microscopy demonstrated that apparent protein aggregation occurred after heat treatment in the control strain, protein aggregate size was maintained in the ClpB1 overexpresser. Constitutive ClpB1 overproduction allows an earlier response to heat shock and protects from rapid heating of cultures.     

Sodium movement in high sodium feline red cells

The transport of Na in the cat red cells has been studied under various experimental conditions. The unidirectional radioactive Na influx increased with increasing temperature until it reached a maximum value at 37°C ± 2°C and then decreased with a further increase in temperature. Errors stated in this paper represent 1.0 standard errors of the mean. The apparent activation energy was calculated in the region between 25 and 37°C and was found to be 4.9 ± 0.5 kcal/mole. Copper at a concentration of 0.04 mM inhibited this influx by 65%. When cells were suspended in isosmotic KCl buffer, cell volume was found to decrease initially with time. This unusual behavior is discussed in terms of Na to K preference of the cell membrane. In cat red cells, Na influx was found to increase about 13-fold when cell volume was decreased from 1.16 normal to 0.87. This effect could not be reproduced when the medium osmolarity was changed only by the addition of urea, a permeating molecule. On the other hand, K influx was found to decrease from 0.24 ± 0.03 mEq/liters RBC, hr at a relative cellular volume equal to 1.0 to 0.11 ± 0.01 mEq/liters RBC, hr at a cell volume of 0.75. Na influx in human red cells did not show any significant dependence on cell volume. The properties of Na movement in the cat red cells are compared to those of human red cells.     

Transposon insertion mutation of Antarctic psychrotrophic fungus for red pigment production adaptive to normal temperature

Polar regions are rich in microbial and product resources. Geomyces sp. WNF-15A is an Antarctic psy chrotrophic filamentous fungus producing high quality red pigment with potential for industrial use. However, efficient biosynthesis of red pigment can only realize at low temperature, which brings difficult control and high cost for the large-scale fermentation. This study aims to develop transposon insertion mutation method to improve cell growth and red pigment production adaptive to normal temperature. Genetic manipulation system of this fungus was firstly developed by antibiotic marker screening, protoplast preparation and transformation optimization, by which transformation efficiency of ∼50% was finally achieved. Then transposable insertion systems were established using Helitron, Fot1, and Impala transposons. The transposition efficiency reached 11.9%, 9.4%, and 4.6%, respectively. Mutant MP1 achieved the highest red pigment production (OD₅₂₀ of 39) at 14°C, which was 40% higher than the wild-type strain. Mutant MP14 reached a maximum red pigment production (OD₅₂₀ of 14.8) at 20°C, which was about twofold of the wild-type strain. Mutants MP2 and MP10 broke the repression mechanism of red pigment biosynthesis in the wild-type and allowed production at 25°C. For cell growth, eight mutants grew remarkably better (12%∼30% biomass higher) than the wild-type at 25°C. This study established an efficient genetic manipulation and transposon insertion mutation platform for polar filamentous fungus. It provides reference for genetic breeding of psychrotrophic fungi from polar and other regions.     

Heat Stress Responses in Cultured Plant Cells : Heat Tolerance Induced by Heat Shock versus Elevated Growing Temperature

Using cultured pear (Pyrus communis cv Bartlett) cells, heat tolerance induced by heat shock was compared to that developed during growth at high temperature. After growth at 22°C, cells exposed to 38°C for 20 minutes (heat shock) showed maximum increased tolerance within 6 hours. Cells grown at 30°C developed maximum heat tolerance after 5 to 6 days; this maximum was well below that induced by heat shock. Heat shock-induced tolerance was fully retained at 22°C for 2 days and was only partly lost after 4 days. However, pear cells acclimated at 30°C lost all acquired heat tolerance 1 to 2 days after transfer to 22°C. In addition, cells which had been heat-acclimated by growth at 30°C showed an additional increase in heat tolerance in response to 39°C heat shock. The most striking difference between heat shock and high growth temperature effects on heat tolerance was revealed when tolerance was determined using viability tests based on different cell functions. Growth at 30°C produced a general hardening, i.e. increased heat tolerance was observed with all three viability tests. In contrast, significantly increased tolerance of heat-shocked cells was observed only with the culture regrowth test. The two types of treatment evoke different mechanisms of heat acclimation.     

Starvation-Induced Thermal Tolerance as a Survival Mechanism in a Psychrophilic Marine Bacterium

Carbon-starved cultures of strain Ant-300, a psychrophilic marine vibrio isolated from the Antarctic Convergence, were compared with their nonstarved counterparts for resistance to heat. Specifically, starved and unstarved cells were exposed to 17°C, which is 4°C above the maximum growth temperature, and compared with cells maintained at the optimum temperature (5 to 7°C). Total cell counts, direct viable-cell counts, and plate counts were monitored. At a temperature of 17°C, viability (as indicated by plate counts) was lost within 40 h, with direct viable-cell counts indicating less than 5% viability at this time. However, when cells were carbon starved for 1 week prior to heat challenge, significant plateability was maintained for more than 6 days; direct viable-cell counts of starved cells maintained at 17°C indicated the presence of viable cells for at least 12 days. Because starvation is the normal physiological state of copiotrophic, heterotrophic bacteria in oligotrophic marine waters, these data suggest that starvation conditions may be a significant factor in providing heat tolerance to psychrophiles.     

Cold Shock and Its Effect on Ribosomes and Thermal Tolerance in Listeria monocytogenes

Differential scanning calorimetry (DSC) and fatty acid analysis were used to determine how cold shocking reduces the thermal stability of Listeria monocytogenes. Additionally, antibiotics that can elicit production of cold or heat shock proteins were used to determine the effect of translation blockage on ribosome thermal stability. Fatty acid profiles showed no significant variations as a result of cold shock, indicating that changes in membrane fatty acids were not responsible for the cold shock-induced reduction in thermal tolerance. Following a 3-h cold shock from 37 to 0°C, the maximum denaturation temperature of the 50S ribosomal subunit and 70S ribosomal particle peak was reduced from 73.4 ± 0.1°C (mean ± standard deviation) to 72.1 ± 0.5°C (P ≤ 0.05), indicating that cold shock induced instability in the associated ribosome structure. The maximum denaturation temperature of the 30S ribosomal subunit peak did not show a significant shift in temperature (from 67.5 ± 0.4°C to 66.8 ± 0.5°C) as a result of cold shock, suggesting that either 50S subunit or 70S particle sensitivity was responsible for the intact ribosome fragility. Antibiotics that elicited changes in maximum denaturation temperature in ribosomal components also elicited reductions in thermotolerance. Together, these data suggest that ribosomal changes resulting from cold shock may be responsible for the decrease in D value observed when L. monocytogenes is cold shocked.     

The specific heat and the heat of compression of human red cells,sickled red cells,and paracrystalline rat red cells

The investigation of two thermal properties of red cells throws some light on whether sickling is a process involving the crystallization of a relatively insoluble hemoglobin. These properties are the specific heat and the heat of compression, both of which would be expected to become numerically less if the hemoglobin of the red cell were to crystallize. In the case of paracrystalline rat red cells, which give spacings at 45 A and 58 A by x-ray diffraction, the specific heat is reduced to 85 per cent of that of the normal red cells, and the heat of compression is only about 75 per cent of that found for the normal red cell. In the case of the red cell sickled by a reduction of the O₂ tension, the specific heat and the heat of compression are substantially the same as found for the normal red cell. This is an argument against sickling being the result of a crystallization process, and supports the observation that sickled cells do not give x-ray spacings. The result is compatible, on the other hand, with sickling being the result of the formation of an oriented and birefringent gel.     

Phenotypic expression of a genetic property introduced by deoxyribonucleate

The time course of the appearance of cells showing a new phenotype, following treatment with a specific DNA, has been analyzed. A plot as a function of time of the number of cells showing the new property closely resembles the summation under a normal distribution curve. Describing the appearance of the new phenotype in these terms permits the definition of two parameters, the mean time, and the standard deviation of the distribution curve. This distribution is not affected either by the DNA concentration with which the transformable population has been treated, or by the streptomycin concentration with which the transformed population has been challenged. Interruptions of the expression process, by cooling to 20° or 0°C., serve only to displace the expression curves, without changing their shape, while small reductions in temperature change both the mean time of expression and the standard deviation of the distribution curve. On the basis of these observations a number of hypotheses have been examined concerning the mechanism whereby transforming DNA manifests a phenotypic alteration in the transformed cells. It can be concluded that there exist at least two stages in the process of expression. The completion of the first stage, causing the randomization, occurs with a mean time of about 60 minutes, and a terminal step, that of the transition of phenotype, occurs in less than 3 minutes.     

Translational thermotolerance in Saccharomyces cerevisiae

While protein synthesis is rapidly inactivated in Saccharomyces cerevisiae, cells shifted from log growth at 30°C to 43°C, a 1-h 37°C treatment given to cells just prior to the shift to 43°C partially blocks this inactivation. By contrast, such a pre-heat shock treament has no protective effect on translational inactivation at 45°C or higher. Cells allowed to approach stationary phase not only develop an enhanced thermotolerance relative to log cells but also exhibit a pronounced resistance to inactivation of protein synthesis at 43°C as well as at 45°C. We have found that this ‘translational thermotolerance’ can also be induced in S. cerevisiae by briefly treating log phase cells at 30°C with cycloheximide. Using such a procedure to induce stabilization of protein synthesis at 43°C, we have been able to show that heat shock-induced proteins are not responsible for the establishment of this protective effect. This work shows that enhanced thermotolerance can be induced in log cells even after a shift to 43°C, as long as a prior translational thermotolerance has been established. Futhermore, we show that the capacity of plateau cells to maintain translation at 43°C contributes significantly to their state of enhanced thermotolerance.     

The Effect of Temperature on the Uptake of Radiosulfate by Rat Renal Tissue from Radiosulfate-Containing Solutions in Vitro

Kidney cortex slices incubated in vitro at 0°C. accumulate radiosulfate from the incubation medium. This process differs from the previously described uptake of radiosulfate by renal tissue incubated at 38°C., for instance, in the lesser sensitivity of the uptake at 0°C. to differential effects of Na⁺ as compared with K⁺ ions, and of sucrose as compared with glucose. Phlorizin inhibits radiosulfate accumulation at 0°C., whereas it enhances the uptake at 38°C. Effects of the cations K⁺ and Na⁺ and of phlorizin at temperatures intermediate between 0° and 38°C. have been studied. Parallels have been noted between the accumulative processes for radiosulfate of kidney slices maintained at 0°C. and of mitochondria isolated from rat liver and kidney cortex. These similarities may be attributed to an important role of radiosulfate uptake by mitochondria in slice accumulation of radiosulfate in the cold.     

Effects of Hydration Level and Heat Stress on Thermoregulatory Responses,Hematological and Blood Rheological Properties in Growing Pigs

Heat stress is one of the major limiting factors of production efficiency in the swine industry. The aims of the present study were 1) to observe if hemorheological and hematological parameters could be associated to physiological acclimation during the first days of heat stress exposure and 2) to determine if water restriction could modulate the effect of thermal heat stress on physiological, hematological and hemorheological parameters. Twelve Large White male pigs were divided into an ad libitum and a water restricted group. All pigs were submitted to one week at 24°C (D-7 to D-1). Then, at D0, temperature was progressively increased until 32°C and maintained during one week (D1 to D7). We performed daily measurements of water and feed intake. Physiological (i.e., skin temperature, rectal temperature, respiratory rate), hematological and hemorheological parameters were measured on D-6, D-5, D0, D1, D2 and D7. Water restriction had no effect on physiological, hematological and hemorheological parameters. The first days of heat stress caused an increase in the three physiological parameters followed by a reduction of these parameters suggesting a successful acclimation of pigs to heat stress. We showed an increase in hematocrit, red blood cell aggregation and red blood cell aggregation strength during heat stress. Further, we observed an important release of reticulocytes, an increase of red blood cell deformability and a reduction of feed intake and blood viscosity under heat stress. This study suggests that physiological acute adaptation to heat stress is accompanied by large hematological and hemorheological changes.     

Tanned or Burned: The Role of Fire in Shaping Physical Seed Dormancy

Plant species with physical seed dormancy are common in mediterranean fire-prone ecosystems. Because fire breaks seed dormancy and enhances the recruitment of many species, this trait might be considered adaptive in fire-prone environments. However, to what extent the temperature thresholds that break physical seed dormancy have been shaped by fire (i.e., for post-fire recruitment) or by summer temperatures in the bare soil (i.e., for recruitment in fire-independent gaps) remains unknown. Our hypothesis is that the temperature thresholds that break physical seed dormancy have been shaped by fire and thus we predict higher dormancy lost in response to fire than in response to summer temperatures. We tested this hypothesis in six woody species with physical seed dormancy occurring in fire-prone areas across the Mediterranean Basin. Seeds from different populations of each species were subject to heat treatments simulating fire (i.e., a single high temperature peak of 100°C, 120°C or 150°C for 5 minutes) and heat treatments simulating summer (i.e., temperature fluctuations; 30 daily cycles of 3 hours at 31°C, 4 hours at 43°C, 3 hours at 33°C and 14 hours at 18°C). Fire treatments broke dormancy and stimulated germination in all populations of all species. In contrast, summer treatments had no effect over the seed dormancy for most species and only enhanced the germination in Ulex parviflorus, although less than the fire treatments. Our results suggest that in Mediterranean species with physical dormancy, the temperature thresholds necessary to trigger seed germination are better explained as a response to fire than as a response to summer temperatures. The high level of dormancy release by the heat produced by fire might enforce most recruitment to be capitalized into a single post-fire pulse when the most favorable conditions occur. This supports the important role of fire in shaping seed traits.     

The State of Water in Human and Dog Red Cell Membranes

The apparent activation energy for the water diffusion permeability coefficient, P_d, across the red cell membrane has been found to be 4.9 ± 0.3 kcal/mole in the dog and 6.0 ± 0.2 kcal/mole in the human being over the temperature range, 7° to 37°C. The apparent activation energy for the hydraulic conductivity, L_p, in dog red cells has been found to be 3.7 ± 0.4 kcal/mole and in human red cells, 3.3 ± 0.4 kcal/mole over the same temperature range. The product of L_p and the bulk viscosity of water, η, was independent of temperature for both dog and man which indicates that the geometry of the red cell membrane is not temperature-sensitive over our experimental temperature range in either species. In the case of the dog, the apparent activation energy for diffusion is the same as that for self-diffusion of water, 4.6–4.8 kcal/mole, which indicates that the process of water diffusion across the dog red cell membrane is the same as that in free solution. The slightly, but significantly, higher activation energy for water diffusion in human red cells is consonant with water-membrane interaction in the narrower equivalent pores characteristic of these cells. The observation that the apparent activation energy for hydraulic conductivity is less than that for water diffusion across the red cell membrane is characteristic of viscous flow and suggests that the flow of water across the membranes of these red cells under an osmotic pressure gradient is a viscous process.     

Response of Lactobacillus helveticus PR4 to Heat Stress during Propagation in Cheese Whey with a Gradient of Decreasing Temperatures

The heat stress response was studied in Lactobacillus helveticus PR4 during propagation in cheese whey with a gradient of naturally decreasing temperature (55 to 20°C). Growth under a gradient of decreasing temperature was compared to growth at a constant temperature of 42°C. Proteinase, peptidase, and acidification activities of L. helveticus PR4 were found to be higher in cells harvested when 40°C was reached by a gradient of decreasing temperature than in cells grown at constant temperature of 42°C. When cells grown under a temperature gradient were harvested after an initial exposure of 35 min to 55°C followed by decreases in temperature to 40 (3 h), 30 (5 h 30 min), or 20°C (13 h 30 min) and were then compared with cells grown for the same time at a constant temperature of 42°C, a frequently transient induction of the levels of expression of 48 proteins was found by two-dimensional electrophoresis analysis. Expression of most of these proteins increased following cooling from 55 to 40°C (3 h). Sixteen of these proteins were subjected to N-terminal and matrix-assisted laser desorption ionization-time of flight mass spectrometry analyses. They were identified as stress proteins (e.g., DnaK and GroEL), glycolysis-related machinery (e.g., enolase and glyceraldehyde-3-phosphate dehydrogenase), and other regulatory proteins or factors (e.g., DNA-binding protein II and ATP-dependent protease). Most of these proteins have been found to play a role in the mechanisms of heat stress adaptation in other bacteria.