On the Nature of the Heat Resistance of Thermophilic Bacteria

The importance of inorganic ions for the heat stability of thermophilic bacteria was investigated. Cells of Bacillus stearothermophilus, strain 1503, were incubated at elevated temperatures in various media and the number of surviving organisms was determined at suitable intervals. The bacteria rapidly died at temperatures ordinarily employed for their cultivation if the surrounding medium lacked calcium ions. Besides calcium ions, potassium and phosphate ions and glucose, or some other energy source, seemed to be required for the heat stability of the cells. A chemically defined stabilizing medium with these components was developed for the above-mentioned strain. When any component of this medium was excluded, the heat resistance of this organism was lost. This medium had a stabilizing effect also on the cells of three other strains of B. stearothermophilus. These requirements suggest that the heat stability of thermophilic bacteria is attributable to an active transport of calcium ions from the environment into the cells.     

Properties of thermostable HtpR-mutant of Escherichia coli

A thermoresistant htpR mutant having a decreased level of proteolytic activity has been selected in E. coli strain K802 after the directed mutagenesis in vivo. The mutation results in the bacteriophage T7 RNA-polymerase stability, aminoglycosidephosphotransferase stability as well as in the decrease in the rate of proteolytic degradation of cytoplasmic proteins during the heat shock. The obtained mutant strain can, probably be used as a host for alien polypeptides production.     

Rice yield formation under high day and night temperatures—A prerequisite to ensure future food security

Increasing temperatures resulting from climate change dramatically impact rice crop production in Asia. Depending on the specific stage of rice development, heat stress reduces tiller/panicle number, decreases grain number per plant and lower grain weight, thus negatively impacting yield formation. Hence improving rice crop tolerance to heat stress in terms of sustaining yield stability under high day temperature (HDT), high night temperature (HNT), or combined high day and night temperature (HDNT) will bolster future food security. In this review article, we highlight the phenological alterations caused by heat and the underlying molecular-physiological and genetic mechanisms operating under different types of heat conditions (HDT, HNT, and HDNT) to understand heat tolerance. Based on our synthesis of HDT, HNT, and HDNT effects on rice yield components, we outline future breeding strategies to contribute to sustained food security under climate change.     

Impacts of a simulated heat wave on composition of a marine community

Extreme events, such as heat waves, are predicted to increase in frequency, duration, and severity as a consequence of climate change. However, global change research generally focuses on increases in mean temperatures and fails to address the potential impacts of increasingly severe heat waves. In addition, climate change may interact with another primary threat to biodiversity, non‐native species invasions. We assessed the impacts of a short‐term heat wave on the marine epibenthic fouling community of Bodega Harbor, California, USA, by exposing experimental mesocosms to a simulated heat wave in the laboratory and then monitoring community development in the field. We hypothesized that (1) juveniles would be more susceptible to heat waves than adults, (2) native species would be more susceptible than non‐native species, and (3) non‐native species would recover more quickly than native species. We observed no effect of the heat wave on juvenile species richness, either initially or during the recovery period, relative to communities at ambient seawater temperatures. In contrast, total adult species richness initially declined in response to the heat wave. Adult community composition also changed in heat‐wave treatments, with non‐natives representing the majority of species and occupying more cover than native species. The reduction in native richness associated with the heat wave persisted through the recovery period, whereas invasive richness was actually higher on heat‐wave versus ambient plates at 95 days. Heat waves have the potential to alter the composition of this community because of species‐, taxon‐, and/or origin‐specific responses; for example, non‐native bryozoans displayed greater resistance than native and non‐native tunicates. Recovery from the heat wave occurred via growth of resistant individuals and larval recruitment. Our study highlights the importance of considering species’ and community responses to heat waves, and not just mean predicted temperature increases, to evaluate the consequences of climate change.     

Relationship between genetic variation in thermal stability and electrophoretic mobility of mouse β-galactosidase

We have examined the relationships between the genetic determinants for mouse beta-galactosidase heat stability and electrophoretic mobility, in order to clarify previous reports indicating that a variation for enzyme heat stability is restricted to kidney while that for electrophoretic mobility is expressed in all tissues. We find that the two phenotypes show concordant strain distributions and cosegregate in genetic crosses. In contrast to a previous report, the thermal stability variation is expressed in all tissues, although the absolute rate of enzyme inactivation is tissue specific. The evidence supports the notion that a single beta-galactosidase structural locus is expressed in all tissues and that the differences in enzyme stability between tissues results from posttranslational enzyme modification.     

Evolution of the response to heat shock in genus Drosophila

Thermotolerance was studied in a wide spectrum of Drosophila species and strains originating from different climatic zones and considerably differing from one another in the ambient temperature of their habitats. The species that lived in hot climate have a higher thermotolerance. Most species of the virilis group exhibited positive correlation between the HSP70 accumulation after heat exposure and thermotolerance; however, this correlation was absent in some species and strains. For example, the D. melanogaster Oregon R strain, which had the highest sensitivity to heat shock (HS) among all strains and species studied, displayed the maximum level of HSP70 proteins after HS. The patterns of induction of various heat shock protein (HSP) families after heat exposure in a wide spectrum of Drosophila species were compared. The results obtained suggest that the HSP40 and low-molecular-weight HSPs (lmwHSPs) play a significant role in thermotolerance and adaptation to hot climate. Polymorphism in hsp70 gene clusters of Drosophila and variation in the numbers of gene copies and hsp70 isoforms in group virilis were found. The evolutionary role of the variation in the number of hsp70 gene copies observed in the strains and species of genus Drosophila is discussed.     

Some Properties of Heat-Resistant and Heat-Sensitive Strains of Clostridium perfringens I. Heat Resistance and Toxigenicity

Heat resistance at 100 C (D-values), sporulating ratios, toxigenicity for mice, and lecithinase activity (as micrograms per milliliter of enzyme, ascertained by the lecithovitellin reaction) were determined for four strains of Clostridium perfringens. A definite inverse relationship between thermal resistance and toxigenicity was found. The D-values ranged from 17.6 for the most heat-resistant strain to 0.3 for the strain possessing the least heat resistance, with corresponding lecithinase activities from 25 to 133 mug/ml of enzyme. The sporulating ratios did not differ greatly between the strains. The heat stability of the toxin was greater at 100 C than at 75 C. There was a noticeable difference between the heat stabilities of the toxin in the culture fluids of the heat-sensitive and heat-resistant strains at pH 7.0 when the toxic filtrates were held at 100 C. At a holding temperature of 75 C, a similar but lesser difference was observed at pH 5.5. Heat resistance and lecithinase activity did not change when a substrain of the least heat-resistant parent strain was obtained through heat selection by a single transfer, or when the most heat-resistant strain was transferred serially 12 times.     

High-level expression of a gene encoding the human complement factor C5a in Escherichia coli

The synthetic C5a gene was initially found to be expressed poorly in Escherichia coli. We undertook studies to determine the reasons for poor expression and to increase expression. The work was focused on the role of the mRNA structure in C5a expression and stability of its product in E. coli. We present data on the effects of varying the sequence at the 5' end of mRNA as well as different ribosome-binding sites on expression. Evaluation of the stability of C5a showed rapid degradation of C5a in wild-type E. coli (half-life 3-5 min). Screening of several protease-deficient strains of E. coli showed that C5a was much more stable in an htpR strain carrying a mutation in the sigma subunit of RNA polymerase that is specific for heat shock promoters. The mutation is associated with a proteolytic deficiency. The half-life of C5a was increased to 20 min. By manipulating the expression vector, the regulatory region for the C5a gene, the host strain, growth conditions and methods for recovering the protein, C5a levels were increased 300-fold over previously reported amounts to about 3% of total cellular protein.     

Isolation of Methylococcus Strain Resistant to Abnormal Climate Change to Reduce Methane Emissions from the Iranian Salt Lake

Abstract

An increase in the atmospheric concentration of methane greenhouse gas results in an increase in global warming, surface water evaporation, and amount of the solutes in relevant areas besides, it also causes climate change. In these situations, methanotrophs that are resistant to climate change and deserted conditions could be applied. Methylococcus, as one of the most extensively studied methanotrophs is highly resistant to salinity, a strain of which was isolated in this study from Hoz-e Soltan Salt Lake in Iran as an example influenced by climate change. Isolated strain was identified. To determine the ability of the bacteria for decrease of methane gas, the culture medium was analyzed by gas chromatography. Results showed that isolated strain is able to grow in salt proportion of 3.3% and acidic pH of 3.5 in vitro, reducing more than 75% of total methane gas within 10?days. In addition to nitrogen fixation ability of the strain, positive results obtained regarding drought tolerance and heat shock in this study confirmed that Methylococcus strains may be able to withstand environmental conditions of foreseeable future. Thus, to prevent methane emission in regions such as Hoz-e Soltan Salt Lake in Iran, more compatible methanotroph strains need to be identified and used.     

Induced thermotolerance under nonisothermal treatments of a heat sensitive and a resistant strain of Staphylococcus aureus in media of different pH

AIMS: The aim was to assess the induced thermotolerance under nonisothermal treatments of two strains of Staphylococcus aureus in media of different pH. METHODS AND RESULTS: Staphylococcus aureus ATCC 25923 was more heat resistant than S. aureus ATCC 13565 at any pH investigated under isothermal conditions. At pH 7.4, the D58 value of the resistant strain was approx. 30 times greater. Both strains showed a higher heat resistance at pH 4.0 than at pH 7.4. In contrast, under nonisothermal treatments (0.5-2 degrees C min(-1)), both strains were more heat resistant when treated at pH 7.4 than at pH 4.0 due to heat adaptation at the higher pH. At the slowest heating up rate tested at pH 7.4, the initially heat-sensitive strain nearly reached the thermotolerance of the heat-resistant strain. CONCLUSIONS: The induced thermotolerance under nonisothermal treatments depended on the treatment medium pH and the microbial strain tested. The induced thermotolerance in a sensitive strain can be greater than in a heat-resistant strain, showing similar resistance under nonisothermal conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: This work shows data of interest about mechanisms of microbial resistance and adaptation to heat. Moreover, it contributes to the development of more adequate combined processes for food preservation.     

Characteristics of the induction of aldehyde dehydrogenase in rat liver

The activity of rat liver supernatant aldehyde dehydrogenase is increased by phenobarbital treatment in one selected strain (RR) but not in another strain (rr) of animals derived from randomally bred populations (Deitrich, Collins, and Erwin (1972) J. Biol. Chem., 247, 7232). Before 14 days of age, increased enzyme activity after phenobarbital treatment is minimal but between 30 and 60 days of age there is a maximal increase in activity after phenobarbital treatment. Using animals of this age, it was shown that both cycloheximide and actinomycin D block this response to phenobarbital. Phenobarbital treatment decreases heat stability of crude preparations of the enzyme from RR rats, but increases heat stability of the enzyme from rr animals.     

Heat-shock response and its contribution to thermotolerance of the nitrogen-fixing cyanobacterium<Emphasis Type="Italic"> Anabaena</Emphasis> sp. strain L-31

Compared to Escherichia coli, the nitrogen-fixing soil cyanobacterium Anabaena sp. strain L-31 exhibited significantly superior abilities to survive prolonged and continuous heat stress and recover therefrom. Temperature upshift induced the synthesis of heat-shock proteins of similar molecular mass in the two microbes. However, in Anabaena sp. strain L-31 the heat-shock proteins (particularly the GroEL proteins) were synthesised throughout the stress period, were much more stable and accumulated during heat stress. In contrast, in E. coli the heat-shock proteins were transiently synthesised, quickly turned over and did not accumulate. Nitrogenase activity of Anabaena cells of sp. strain L-31 continuously exposed to heat stress for 7 days rapidly recovered from thermal injury, although growth recovery was delayed. Exposure of E. coli cells to >4.5 h of heat stress resulted in a complete loss of viability and the ability to recover. Marked differences in the synthesis, stability and accumulation of heat-shock proteins appear to distinguish these bacteria in their thermotolerance and recovery from heat stress.     

Assessing the contribution of bacteria to the heat tolerance of experimentally evolved coral photosymbionts

Coral reefs are extremely vulnerable to ocean warming, which triggers coral bleaching—the loss of endosymbiotic microalgae (Symbiodiniaceae) from coral tissues, often leading to death. To enhance coral climate resilience, the symbiont, Cladocopium proliferum was experimentally evolved for >10 years under elevated temperatures resulting in increased heat tolerance. Bacterial 16S rRNA gene metabarcoding showed the composition of intra- and extracellular bacterial communities of heat-evolved strains was significantly different from that of wild-type strains, suggesting bacteria responded to elevated temperatures, and may even play a role in C. proliferum thermal tolerance. To assess whether microbiome transplantation could enhance heat tolerance of the sensitive wild-type C. proliferum, we transplanted bacterial communities from heat-evolved to the wild-type strain and subjected it to acute heat stress. Microbiome transplantation resulted in the incorporation of only 30 low-abundance strains into the microbiome of wild-type cultures, while the relative abundance of 14 pre-existing strains doubled in inoculated versus uninoculated samples. Inoculation with either wild-type or heat-evolved bacterial communities boosted C. proliferum growth, although no difference in heat tolerance was observed between the two inoculation treatments. This study provides evidence that Symbiodiniaceae-associated bacterial communities respond to heat selection and may contribute to coral adaptation to climate change.     

Role of dipicolinic acid in resistance and stability of spores of Bacillus subtilis with or without DNA-protective alpha/beta-type small acid-soluble proteins

Dipicolinic acid (DPA) comprises approximately 10% of the dry weight of spores of Bacillus species. Although DPA has long been implicated in spore resistance to wet heat and spore stability, definitive evidence on the role of this abundant molecule in spore properties has generally been lacking. Bacillus subtilis strain FB122 (sleB spoVF) produced very stable spores that lacked DPA, and sporulation of this strain with DPA yielded spores with nearly normal DPA levels. DPA-replete and DPA-less FB122 spores had similar levels of the DNA protective alpha/beta-type small acid-soluble spore proteins (SASP), but the DPA-less spores lacked SASP-gamma. The DPA-less FB122 spores exhibited similar UV resistance to the DPA-replete spores but had lower resistance to wet heat, dry heat, hydrogen peroxide, and desiccation. Neither wet heat nor hydrogen peroxide killed the DPA-less spores by DNA damage, but desiccation did. The inability to synthesize both DPA and most alpha/beta-type SASP in strain PS3664 (sspA sspB sleB spoVF) resulted in spores that lost viability during sporulation, at least in part due to DNA damage. DPA-less PS3664 spores were more sensitive to wet heat than either DPA-less FB122 spores or DPA-replete PS3664 spores, and the latter also retained viability during sporulation. These and previous results indicate that, in addition to alpha/beta-type SASP, DPA also is extremely important in spore resistance and stability and, further, that DPA has some specific role(s) in protecting spore DNA from damage. Specific roles for DPA in protecting spore DNA against damage may well have been a major driving force for the spore's accumulation of the high levels of this small molecule.     

Analysis of Heat Shock Proteins and Thermotolerance in a Thermoresistant Strain of Drosophila melanogaster

Here we studied the response to heat shock in a desert D. melanogasterstrain TT capable of living and propagating at 32°C and the standard Oregon R strain. The TT strain proved to be more resistant to extreme temperatures. On the other hand, the observed high thermotolerance of the strain was not accompanied by a higher level of HSP70 synthesis. Conversely, reliably smaller amounts of HSP70 were synthesized in the TT strain as compared to Oregon R under all shock temperatures except the critical one (39.5°C). Differences in both the structure of HSP70genes and the pattern of all heat shock proteins have been observed between the studied strains. The role of the heat shock system in the adaptation to hyperthermia is discussed.     

Resilience to extreme temperature events: acclimation capacity and body condition of a polymorphic fish in response to thermal stress

Considerable attention has been given to the potential impacts of global climate change on biodiversity. In the present study, we combine understudied themes by examining the ability of a freshwater fish (polymorphic for heat‐sensitivity) to respond to short‐term thermal stress mimicking an extreme temperature event. We simultaneously measured the effect of thermal stress on the body condition of heat‐sensitive and heat‐tolerant forms to evaluate an existing hypothesis regarding the underlying mechanism by which temperature affects the maintenance of genetic variation in this species. Surprisingly, the heat‐sensitive allelic variant increased in body condition equally as much as a heat‐tolerant variant under acute heat stress. More importantly, the heat‐sensitive variant exhibited a significant response to thermal stress, with an upward shift of greater than 2 °C in critical thermal maximum. Our findings suggest a complexity to the relationship between thermal stress and male body condition that may depend on an interaction with other factors such as resource level. Although the evolutionary fate of species with respect to climate change is typically evaluated in terms long‐term adaptive response, short‐term selection events could drastically reduce fitness and reduce evolutionary potential. Our results suggest that heat‐sensitive species may have considerably greater resilience to the short‐term, extreme perturbations to the environment that are expected under climate change. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 504–510.     

Development and stability of a heat‐stable formulation of carbetocin for the prevention of postpartum haemorrhage for use in low and middle‐income countries

Postpartum haemorrhage is a leading cause of maternal death worldwide. Oxytocin, currently the drug of choice for prevention of PPH, requires constant refrigeration. In pursuit of an alternative medicine, Ferring Pharmaceuticals have developed a heat‐stable formulation of carbetocin, an oxytocin analogue. This study aimed to define that formulation, and to investigate its stability under ICH climate zone IV conditions (30°C/75% relative humidity) for at least 3 years and at extreme temperatures, such as 60°C, for shorter periods of time. The development resulted in a heat‐stable carbetocin formulation consisting of 0.1 mg/mL carbetocin in sodium succinate buffer, mannitol, and methionine. The optimum pH was determined to be pH 5.45 (5.25–5.65). The generated stability data of this formulation show that ≥95% purity of the peptide was maintained for a minimum of 3 years at 30°C, 6 months at 40°C, 3 months at 50°C and 1 month at 60°C. In addition, the heat‐stable carbetocin formulation was not sensitive to freezing or light. The reported highly stable peptide formulation facilitates the distribution in low and middle‐income countries, where maintaining cold chain distribution is difficult. Ferring Pharmaceuticals, the World Health Organization, and MSD # for Mothers have established a collaboration to develop this heat‐stable formulation of carbetocin for the prevention of post‐partum hemorrhage in women after vaginal childbirth, with the aim of making the medicine available in the public sector of developing countries that have a high burden of maternal mortality.     

Evolution of the Response to Heat Shock in Genus Drosophila

Thermotolerance was studied in a wide spectrum of Drosophilaspecies and strains originating from different climatic zones and considerably differing from one another in the ambient temperature of their habitats. The species that lived in hot climate have a higher thermotolerance. Most species of the virilisgroup exhibited positive correlation between the HSP70 accumulation after heat exposure and thermotolerance; however, this correlation was absent in some species and strains. For example, the D. melanogasterOregon R strain, which had the highest sensitivity to heat shock (HS) among all strains and species studied, displayed the maximum level of HSP70 proteins after HS. The patterns of induction of various heat shock protein (HSP) families after heat exposure in a wide spectrum of Drosophila species were compared. The results obtained suggest that the HSP40 and low-molecular-weight HSPs (lmwHSPs) play a significant role in thermotolerance and adaptation to hot climate. Polymorphism in hsp70 gene clusters ofDrosophila and variation in the numbers of gene copies andhsp70 isoforms in group viriliswere found. The evolutionary role of the variation in the number of hsp70 gene copies observed in the strains and species of genusDrosophilais discussed.     

Halotolerant, alkaliphilic urease-producing bacteria from different climate zones and their application for biocementation of sand

Microbially induced calcium carbonate precipitation (MICP) is a phenomenon based on urease activity of halotolerant and alkaliphilic microorganisms that can be used for the soil bioclogging and biocementation in geotechnical engineering. However, enrichment cultures produced from indigenous soil bacteria cannot be used for large-scale MICP because their urease activity decreased with the rate about 5 % per one generation. To ensure stability of urease activity in biocement, halotolerant and alkaliphilic strains of urease-producing bacteria for soil biocementation were isolated from either sandy soil or high salinity water in different climate zones. The strain Bacillus sp. VUK5, isolated from soil in Ukraine (continental climate), was phylogenetically close in identity (99 % of 16S rRNA gene sequence) to the strain of Bacillus sp. VS1 isolated from beach sand in Singapore (tropical rainforest climate), as well as to the strains of Bacillus sp. isolated by other researchers in Ghent, Belgium (maritime temperate climate) and Yogyakarta, Indonesia (tropical rainforest climate). Both strains Bacillus sp. VS1 and VUK5 had maximum specific growth rate of 0.09/h and maximum urease activities of 6.2 and 8.8 mM of hydrolysed urea/min, respectively. The halotolerant and alkaliphilic strain of urease-producing bacteria isolated from water of the saline lake Dead Sea in Jordan was presented by Gram-positive cocci close to the species Staphylococcus succinus. However, the strains of this species could be hemolytic and toxigenic, therefore only representatives of alkaliphilic Bacillus sp. were used for the biocementation studies. Unconfined compressive strengths for dry biocemented sand samples after six batch treatments with strains VS1and VUK5 were 765 and 845 kPa, respectively. The content of precipitated calcium and the strength of dry biocemented sand at permeability equals to 1 % of initial value were 12.4 g Ca/kg of dry sand and 454 kPa, respectively, in case of biocementation by the strain VS1. So, halotolerant, alkaliphilic, urease-producing bacteria isolated from different climate zones have similar properties and can be used for biocementation of soil.