Effects of exposure to short-term heat stress on male reproductive fitness in a soil arthropod

Ambient temperature is a key environmental factor influencing a variety of aspects of the ecology and evolution of ectotherms. Reproductive traits have been suggested to be more sensitive to thermal stress than other life history traits. This study investigated the direct and indirect effects of heat shock on male reproductive success in the widespread springtail Orchesella cincta. Male springtails were exposed to four temperature treatments: heat hardening (35.2 °C for 1 h), heat shock (37.2 °C for 1 h), heat hardening + heat shock (35.2 °C for 1 h, followed 15 h later by 37.2 °C for 1 h), and control (20 °C). The heat shock gene Hsp70 showed high expression in all the heat treatments, indicating that the treatments indeed induced thermal stress. Significant mortality was only found in the treatment with heat shock, both with and without heat hardening. A direct effect of heat treatment was found on time to first reproduction, which was significantly longer after heat shock (with or without heat hardening) than in the control treatment. There was no difference among treatments in the number of spermatophores produced in the first reproductive instar. Heat treatment also had indirect effects on male reproductive success. Females chose significantly more spermatophores from control males than from males that received heat shock, heat hardening or both. A high percentage of spermatophores produced by heat shocked males caused reproductive failure in females, but no significant differences among treatments were found.Our results suggest that not all traits were equally affected by the heat stress. Heat hardening did not protect reproductive traits against the negative effects of heat shock. The indirect effects of heat shock on reproduction may be equally important as the direct effects.     

Heat shock induces oxidative stress in rotan Perccottus glenii tissues

The effects of temperature transition from 19 to 32 °C on oxidative stress indices and activities of the main antioxidant enzymes were investigated in the rotan, Perccottus glenii. Levels of lipid peroxides (LOOH), thiobarbituric acid-reactive substances (TBARS), low- (L-SH) and high-molecular mass (H-SH) thiols and activities of superoxide dismutase (SOD) and catalase were measured in rotan brain, liver and muscle over 1–12 h of high-temperature exposure followed by 3 or 24 h lower (19 °C) temperature recovery. Heat shock exposure during 1 h transiently increased 1.5–3.2-fold LOOH levels in rotan tissues with subsequent suppression of their content; however, 12 h exposure again increased LOOH levels in the brain. TBARS content were elevated by 2–3-fold during the entire heat shock exposure in the brain and liver. Levels of both products of lipid peroxidation were generally near control values during return to 19 °C. L-SH content was lowered during heat shock exposure in the brain, transiently increased after 6 h in the liver and almost disappeared after longer treatment in the muscle. Liver H-SH content slightly decreased under heat shock exposure, but was elevated after 6 h in the brain and muscle. In the latter case, L-SH level was below control values during recovery. SOD activities increased 2-fold in the liver after 6–12 h heat shock. Liver catalase activities decreased at the same conditions. Generally, a quick response to suppression of lipid peroxidation and possible involvement of its products in the up-regulation of antioxidant enzymes seem to be key adaptations to high temperature.     

Hsp60 protein pattern in coral is altered by environmental changes in light and temperature

The heat shock protein Hsp60 exhibited marked oscillation during a 12-hour day period when the coral Turbinaria reniformis was maintained in the laboratory under constant conditions of light (200 μE) and temperature (27 °C). A biphasic pattern of Hsp60 was apparent, punctuated by a low protein level at the midpoint of the 12-hour day period. Oscillation of Hsp60 was also apparent when coral was kept in darkness in lieu of a scheduled light period. The pattern of Hsp60 was altered when coral was exposed to increased light intensity (400 μE) or temperature elevation (32 °C). These observations suggest that Hsp60 in coral exhibits oscillation that is altered by increased light and temperature elevation.     

Heat-shock-induced color-pattern changes of the blue pansy butterfly Junonia orithya: Physiological and evolutionary implications

Temperature shock to early pupae causes wing color-pattern changes in butterflies. These plastic changes are ascribed to the hemolymph level of the cold-shock hormone (CSH) in pupae as well as to other mechanisms. Here, we characterized heat-shock-induced color-pattern changes using the blue pansy butterfly Junonia orithya (Lepidoptera: Nymphalidae). In response to the 38-42 °C heat-shock treatments, parafocal elements (PFEs) were thinned and dislocated away from eyespots; this was the reverse of the direction of the cold-shock-induced changes. Somewhat surprisingly, in response to the lethal 44 °C heat shock, PFEs were modified as in the case of a cold-shock. These modifications were not affected by the removal of the head-prothorax portion of pupae. While the hemolymph-mediated transfer of the possible PFE-modification property induced by the 42 °C treatment was unsuccessful in the parabiosis experiment, the transfer of the factor induced by the 44 °C treatment was successful. In contrast, reduction of the blue background area was obtained not only by the 42 and 44 °C treatments but also by the injection of thapsigargin, a plant-derived stress inducer, in males. The result of this treatment was similar to the natural color patterns of other closely related Junonia species. We also observed an increase in orange coloration by the 42 °C treatment in females, and this change was similar to ecdysteroid-induced modifications. Taken together, the heat-shock-induced PFE modifications in J. orithya can be explained by the levels of CSH, and other modifications are likely to be caused by general stress responses and ecdysteroid effects. We conclude that phenotypic plasticity of the wing color patterns to heat shock results from a combined effect of at least a few different mechanisms. These mechanisms might have been exploited in the color-pattern evolution of some Junonia species.     

Bacillus mojavensis strain 32A, a bioflocculant-producing bacterium isolated from an Egyptian salt production pond

Bacillus mojavensis strain 32A that exhibited 96.11% flocculation efficiency for clay suspensions was selected from other 15 comparative strains. Under growth condition, strain 32A was able to produce 5.2 g/L of purified biopolymer. Its constituent was mainly polysaccharide and protein with proportional of 98.4-1.6% respectively. FTIR spectrum was confirming its chemical analysis. This biopolymer attain very fast sedimentation rate. The cost-effective biopolymer and CaCl₂ dosages were 3 mg/L and 5 ml/L respectively that posed 89.7% flocculation efficiency. These dosages were suitable only for clay concentrations ?5 g/L. The maximum flocculation efficiency of the biopolymer recorded at pH 1.0 of clay suspension. The too high (>75 °C) or too low (<25 °C) clay suspension temperature was unfavorable for the biopolymer flocculation performance. The biopolymer solution utilized high thermal stability over the temperature range of 5-60 °C. Furthermore, its pH stability recorded at pH range of 5-9.     

Expression of heat shock protein 70a mRNA in Bombyx mori diapause eggs

In an effort to understand whether heat shock protein 70 (Hsp70) participates in the environmental 5 °C signal reception/transduction toward breaking embryonic diapause of the silkworm Bombyx mori, we isolated a cDNA for Hsp70a and examined the expression of Hsp70a mRNA in B. mori diapause and nondiapause eggs by quantitative real-time PCR. Hsp70a mRNA gradually increased in diapause eggs continuously kept at 25 °C after oviposition to maintain diapause. When diapause eggs were exposed to the diapause-terminating condition of 5 °C beginning at 2 days post-oviposition, Hsp70a mRNA increased beginning at 5 days post-cold treatment. Even in nondiapause eggs, Hsp70a mRNA increased slightly with exposure to 5 °C. These results suggest that Hsp70a is involved in reception/transduction of the diapause-terminating (5 °C) signal via gene activation. The expression patterns of Hsp70a mRNA are discussed in relation to those of the cold-response gene Samui.     

Distinct chemical contaminants induce the synthesis of Hsp70 proteins in green microalgae Desmodesmus subspicatus: Heat pretreatment increases cadmium resistance

Using western-blotting techniques, we examined the effect of differently acting contaminants, such as anthracene (PAH), cadmium (heavy metal) and chloridazone (herbicide), as well as heat shock on the production of two Hsp70 proteins (cytoplasmic and stromal) in planktonic algae Desmodesmus subspicatus. All contaminants applied stimulated production of both Hsp70s in a concentration-dependent manner, but heat shock treatment turned out to be the most effective. Heat shock pretreatment (for 1 h at 40 °C) induced tolerance to cadmium in algal cells (measured by changes in growth rate), but not to anthracene or chloridazone. Two Hsp70s from D. subspicatus cells representing cytoplasmic and stromal proteins were purified by ATP-affinity chromatography.     

Effects of water temperature change on immune function in surf clams, Mactra veneriformis (Bivalvia: Mactridae)

Surf clam, Mactra veneriformis is one of the crucial fishery resources in Korea. This study was performed to examine the immune functions of the surf clam under the stress of water temperature changes at 10 °C, 20 °C or 30 °C for 24 h. Viable bacterial counts (VBC), total haemocyte count (THC), phagocytic activity, lysozyme activity, NRR times and SOD activity were assessed in three different water temperature groups. Clams held at 10 °C decreased in THC, lysozyme activity and NRR times, but phagocytic activity was increased. The highest temperature (30 °C) significantly increased in THC, whereas it decreased in phagocytic activity, lysozyme activity and NRR times. In clams maintained at 20 °C, phagocytic activity, lysozyme activity and NRR times were increased whereas THC was somewhat decreased with respect to clams held at 30 °C. However, water temperature changes did not elicit any alteration of VBC and SOD activity. The present study demonstrates that acute water temperature change affects the haemocytic and haemolymphatic functions, reducing immunosurveillance in stressed surf clam, M. veneriformis.     

Heat inactivation of Escherichia coli K12 MG1655: Effect of microbial metabolites and acids in spent medium

Aim

The effect of spent medium, obtained after different time-temperature pre-histories, on the heat inactivation of Escherichia coli K12 MG1655 is studied.

Methods and results

Stationary E. coli cells were heated in BHI broth (initial pH 7.5) at different time-temperature scenarios, i.e., (1) 30 °C to 55 °C at 0.14 °C/min, (2) 30 °C to 42 °C at 0.14 °C/min and (3) 30 °C to 42 °C at 0.8 °C/min. After the heat treatment, spent medium was filter-sterilized, non-stressed cells were added and inactivation experiments took place at 54 °C and 58 °C. In all scenarios, increased resistance was observed. The main characteristics of the spent medium - compared to the unmodified BHI broth - are (1) the presence of proteins (proven via SDS-PAGE) and (2) a lower pH of approximately 6. Possibly, the increased resistance is due to these proteins and/or the lower pH. Further experiments revealed that each factor separately may lead to an increased heat resistance.

Conclusions

It can be concluded that this increased heat resistance resulted from both the presence of the heat shock proteins in the spent medium and the lowered pH. Experiments, which separate both effects, showed that mainly the lower pH resulted in the increased thermotolerance.

Significance and impact of study

This study may lead to a better understanding and control of the heat stress adaptation phenomenon as displayed by E. coli at lethal temperatures. Therefore, it contributes to an improved assessment of the effect of temperature during thermal processes in the food industry.     

Dermal gland secretion improves the heat tolerance of the brown dog tick, Rhipicephalus sanguineus, allowing for their prolonged exposure to host body temperature

Dermal glands (sensilla sagittiformia) secrete when brown dog ticks, Rhipicephalus sanguineus, are mechanically disturbed, presumably as a defensive mechanism. Recently, we observed that these glands secrete due to the pressure stimulation of engorgement. In this study, we examine how dermal gland secretion alters the physiology of R. sanguineus, particularly if this secretion is an important mechanism during blood feeding. The ability of ticks to retain water was not modified by dermal gland secretion, but heat tolerance was enhanced. Short-term heat shock was improved slightly (1 h at 50 °C to 1 h at 56 °C) and featured reduced injury responses and greater recovery after heat shock. When exposed to their host body temperature (37 °C) for prolonged periods, individuals that had secreted survived over 1 week longer than individuals that did not secrete. Dorsal application of squalene, the main component of dermal gland secretion, did not increase temperature tolerance, suggesting that the act of secreting rather than the physical properties of the secretion itself is responsible for the increase in heat tolerance. Based on our results, dermal gland secretion may be an essential mechanism in certain tick species (Amblyomma, Dermacentor, Hyalomma, Rhipicephalus, but not Ixodes) for tolerating body temperature and not succumbing to heat stress during the extended time periods of feeding on a mammalian host, serving as a mechanism to prevent heat damage from the host during feeding.     

An exceptionally stable Group II chaperonin from the hyperthermophile Pyrococcus furiosus

The hyperthermophilic archaeon Pyrococcus furiosus (Pf) grows optimally at 100 °C and encodes single genes for the Group II chaperonin (Cpn), Pf Cpn and α-crystallin homolog, the small Heat shock protein (sHsp). Recombinant Pf Cpn is exceptionally thermostable and remained active in high ionic strength, and up to 3 M guanidine hydrochloride (Gdn-HCl). Pf Cpn bound specifically to denatured lysozyme and ATP addition resulted in protection of lysozyme from aggregation and inactivation at 100 °C. While complexed to heat inactivated lysozyme, Pf Cpn showed enhanced thermostability and ATPase activity, and increased the optimal temperature for ATPase activity from 90 to 100 °C. Protein substrate binding also stabilized the 16-mer oligomer of Pf Cpn in 3 M Gdn-HCl and activated ATPase hydrolysis in 3-5 M Gdn-HCl. In addition, Pf Cpn recognized and refolded the non-native lysozyme released from Pf sHsp, consistent with the inferred functions of these chaperones as the primary protein folding pathway during cellular heat shock.     

Production of an acidic and thermostable lipase of the mesophilic fungus Penicillium simplicissimum by solid-state fermentation

The production of a lipase by a wild-type Brazilian strain of Penicillium simplicissimum in solid-state fermentation of babassu cake, an abundant residue of the oil industry, was studied. The enzyme production reached about 90 U/g in 72 h, with a specific activity of 4.5 U/mg of total proteins. The crude lipase showed high activities at 35–60 °C and pH 4.0–6.0, with a maximum activity at 50 °C and pH 4.0–5.0. Enzyme stability was enhanced at pH 5.0 and 6.0, with a maximum half-life of 5.02 h at 50 °C and pH 5.0. Thus, this lipase shows a thermophilic and thermostable behavior, what is not common among lipases from mesophilic filamentous fungi. The crude enzyme catalysed the hydrolysis of triglycerides and p-nitrophenyl esters (C4:0–C18:0), preferably acting on substrates with medium-chain fatty acids. This non-purified lipase in addition to interesting properties showed a reduced production cost making feasible its applicability in many fields.     

Thermal stability properties of an antifreeze protein from the desert beetle Microdera punctipennis

An insect antifreeze protein gene Mpafp698 was cloned by the RT-PCR approach from the desert beetle Microdera punctipennis. The gene was constructed and heterogeneously expressed in Escherichia coli as fusion proteins, His-MpAFP698, glutathione S-transferase (GST)-MpAFP698, and maltose-binding protein (MBP)-MpAFP698. The thermostability and thermal hysteresis activity of these proteins were determined, with the aim of elucidating the biological characteristics of this protein. The approximate thermal hysteresis (TH) value of the purified His-MpAFP698 was 0.37 °C at 0.84 mg/ml, and maintained approximately 95.7% of the TH activity at 100 °C for 5 min. Furthermore, heat incubation showed that MBP-MpAFP698 was 10 °C more thermostable than MBP protein, indicating that MpAFP698 could, to some extent, improve the thermal stability of the fused partner MBP protein. This study suggests that MpAFP698 has a high thermal stability and could be used to improve the thermal stability of the less stable proteins by producing fusion proteins, which could be used for biotechnological purposes.     

A method for enzyme quenching in microbial metabolome analysis successfully applied to gram-positive and gram-negative bacteria and yeast

Although microbial metabolome analysis has now become a widely used method, no generally applicable quenching method has been published so far. Either the methods were established for only one defined organism or the metabolite coverage was quite low. In the current work, a novel, reliable, and robust quenching method for different types of organisms is described. Compared with the commonly used quenching procedure with 60% methanol (−50 °C), we obtained improved results for three examined organisms with different cell wall and membrane structures using a 40% ethanol/0.8% sodium chloride solution (−20 °C). Increased metabolite levels were achieved for 60-80% of all identified compounds. Moreover, the estimated standard error of the relative concentrations of 120-160 different substances was only 14 ± 4% compared with 17 ± 3% in unquenched samples and 24 ± 7% in samples quenched with methanol for the different tested organisms.     

Response of juvenile diamond-backed terrapins (Malaclemys terrapin) to an aquatic thermal gradient

In many ectotherms, selection of environmental thermal niches may positively affect growth, nutrient assimilation rates, immune system function, and ultimately survival. Temperature preference in some turtle species may be influenced by environmental conditions, including acclimation temperature. We tested for effects of acclimation temperature (22 °C, 27 °C) on the selected temperature and movement patterns of 14 juvenile Malaclemys terrapin (Reptilia: Emydidae) in an aquatic thermal gradient of 14–34 °C and in single-temperature (22 °C, 27 °C) control tests. Among 8–10 month old terrapins, acclimation temperature influenced activity and movement patterns but did not affect temperature selection. In thermal gradient and single-temperature control tests, turtles acclimated to 27 °C used more tank chambers and relocated between chambers significantly more frequently than individuals acclimated to 22 °C. However, acclimation temperature did not affect temperature selection: both 22- and 27 °C-acclimated turtles selected the warmest temperature (34 °C), and avoided the other temperatures available, during thermal gradient tests. These results suggest that young M. terrapin are capable of detecting small temperature increments and prefer warm temperatures that may positively influence growth and metabolism.