Mesophilic Strains Research Articles

Use of mesophilic Lactic Acid Bacteria in the manufacture of Feta cheese

The use of mesophilic lactic acid bacteria (LAB) in the manufacture of Feta cheese was studied. Five selected mesophilic strains, confirmed as Lactobacillus plantarum (2 strains), Lb. paracasei subsp. paracasein Lb. brevis and Lactococcus lactis subsp. lactis, isolated from ripened Feta and Teleme cheeses, were used in 7 different combinations, alone or in combination with Lb. delbrueckii subsp. bulgaricus and Streptococcus thermophilus (the control combination) for the manufacture of Feta cheese. Each combination of strains was used to prepare four different batches of Feta cheese, keeping all the other production parameters according to the traditional technology. The cheese batches were analyzed for bacteriological, chemical and sensory characteristics. The results showed that the populations of lactobacilli and lactococci increased from the beginning of the cheese manufacture reaching a population of more than 7.0 log10cfu/g. This level was maintained during the whole ripening period (60 days) and during the subsequent 60-day storage period. Only in batches prepared with the control combination F8 {Str. thermophilus I Lb. delbrueckii subsp. bulgaricus), did the population of LAB decline to 6.0 log10cfu/g at the end of the ripening period. Also, except for the yeast population which increased, in all other bacterial groups tested (coliforms, staphylococci, total contaminating bacteria, psychrotrophic bacteria, proteolytic and lipolytic bacteria) populations gradually decreased during the ripening period. Results of the chemical analysis showed a sharp increase in acidity (the cheese pH dropped to ca. 4.5 within 3-4 d) and, whereas the values of other chemical indices (moisture content, fat content and NaCl) were stabilized between the 15* and 30* day of ripening, proteolysis (nitrogen soluble in 12% TCA) and lipolysis (ADV) progressed throughout ripening. The assessment of the overall acceptance by the sensory panel was between "very good" and "excellent" for all cheeses. This suggests that the selected mesophilic starter cultures can be used alone or in combination with the traditional culture {Lb.delbrueckii subsp. bulgaricus I Str. thermophilus) in the production of Feta cheese, as the results of this work indicate that the wild (autochthonous) strains of Lb. plantarum and Lc. lactis subsp. Lactis are well adapted to the environmental conditions that prevail in Feta cheese. Batches prepared using these mesophilic starters received the highest score in the assessment of organoleptic quality of Feta cheese. Very good results were also obtained using the combination of the mesophilic starters Lb. brevis and Lc. lactis subsp. lactis or Lb. paracasei subsp. paracasei and Lc. lactis subsp. lactis alone or in combination with Lb. delbrueckii subsp. bulgaricus and Str. thermophilus.

Study of mesophilic Aeromonas salmonicida A527 strain sheds light on the species' lifestyles and taxonomic dilemma.

The Gram-negative bacterium Aeromonas salmonicida contains five subspecies: salmonicida, smithia, achromogenes, masoucida and pectinolytica. Pectinolytica is a mesophilic subspecies with the ability to thrive at a wide range of temperatures, including 37°C, while the four other subspecies are psychrophilic, restricted to lower temperatures. The psychrophilic subspecies are known to infect a wide range of fishes. However, there is no evidence of pathogenicity for the mesophilic subspecies pectinolytica. Study of the differences between the mesophilic and psychrophilic subspecies is hampered by the lack of completely sequenced and closed genomes from the mesophilic subspecies. A previous study reported that insertion sequences, which can induce genomic rearrangements at temperatures around 25°C, could be one of the determinants explaining the differences in lifestyle (mesophilic or psychrophilic) between the subspecies. In this study, the genome of mesophilic strain A527 of A. salmonicida was sequenced, closed and analyzed to investigate the mesophilic-psychrophilic discrepancy. This reference genome supports the hypothesis that insertion sequences are major determinants of the lifestyle differences between the A. salmonicida subspecies. Moreover, the phylogenetic analysis performed to position strain A527 within the taxonomy raises an issue regarding the intraspecies structure of A. salmonicida.

Temperature-Dependent Alkyl Glycerol Ether Lipid Composition of Mesophilic and Thermophilic Sulfate-Reducing Bacteria

The occurrence of non-isoprenoid alkyl glycerol ether lipids in Bacteria and natural environments is increasingly being reported and the specificity and diagenetic stability of these lipids make them powerful biomarkers for biogeochemical and environmental studies. Yet the environmental controls on the biosynthesis of these peculiar membrane lipids remain poorly documented. Here, the lipid content of two mesophilic (Desulfatibacillum aliphaticivorans and Desulfatibacillum alkenivorans) and one thermophilic (Thermodesulfobacterium commune) sulfate-reducing bacteria—whose membranes are mostly composed of ether lipids—was investigated as a function of growth temperature (20–40°C and 54–84°C, respectively). For all strains, the cellular lipid content was lower at sub- or supra-optimal growth temperature, but the relative proportions of dialkyl glycerols, monoalkyl glycerols and fatty acids remained remarkably stable whatever the growth temperature. Rather than changing the proportions of the different lipid classes, the three strains responded to temperature changes by modifying the average structural composition of the alkyl and acyl chains constitutive of their membrane lipids. Major adaptive mechanisms concerned modifications of the level of branching and of the proportions of the different methyl branched lipids. Specifically, an increase in temperature induced mesophilic strains to produce less dimethyl branched dialkyl glycerols and 10-methyl branched lipids relative to linear structures, and the thermophilic strain to decrease the proportion of anteiso relative to iso methyl branched compounds. These modifications were in agreement with a regulation of the membrane fluidity. In one mesophilic and the thermophilic strains, a modification of the growth temperature further induced changes in the relative proportions of sn-2 vs sn-1 monoalkyl glycerols, suggesting an unprecedented mechanism of homeoviscous adaptation in Bacteria. Strong linear correlations observed between different ratios of alkyl glycerols and temperature allow to hypothesize the use of these specific lipids as indicators of temperature changes in the environment.

Diversity of Bacillus cereus strains in extended shelf life

Characterisation of 49 Bacillus cereus strains obtained from extended shelf life (ESL) milk and filler nozzles was done using (GTG)5 rep PCR fingerprinting, determining the presence of the virulence genes cytK, nheA, cer and hblA, and discrimination of psychrotrophic and mesophilic strains with 16S rDNA. Fourteen isolates were selected for 16S partial sequencing. Fingerprinting and sequencing showed evidence of filler nozzles contaminating ESL milk despite high heterogeneity existing between the isolates. While there is high prevalence of cer, hblA and nheA; cytK was not widely distributed. There was 100% and 8% prevalence of mesophilic and psychrotrophic signatures, respectively. Despite the large diversity of the B. cereus strains in this study, there is evidence that filler nozzles and raw milk are a source of contamination of B. cereus in ESL milk.

Fermentative hydrogen production from indigenous mesophilic strain Bacillus anthracis PUNAJAN 1 newly isolated from palm oil mill effluent

In the present study, a new mesophilic bacterial strain, identified as Bacillus anthracis strain PUNAJAN 1 was isolated from palm oil mill effluent (POME) sludge, and tested for its hydrogen production ability. Effect of physico-chemical factors such as temperature, initial pH, nitrogen source and carbon sources were investigated in order to determine the optimal conditions for hydrogen production. The maximum hydrogen yield of 2.42 mol H2/mol mannose was obtained at 35 °C and initial pH of 6.5. Yeast and mannose were used as the main carbon and nitrogen sources respectively in the course of the hydrogen production. Apart from synthetic substrate, specific hydrogen production potentials of the strain using POME was calculated and found to be 236 ml H2/g chemical oxygen demand (COD). The findings of this study demonstrate that the indigenous strain PUNAJAN 1 could be a potential candidate for hydrogen using POME as substrate.

Cytomorphological and nitrogen metabolic enzyme analysis of psychrophilic and mesophilic Nostoc sp.: a comparative outlook

Cyanobacterial diazotrophs play a significant role in environmental nitrogen economy despite their habitat either tropical or polar. However, the phenomenon by which it copes with temperature induced stress is poorly understood. Temperature response study of psychrophilic and mesophilic Nostoc strains explores their adaptive mechanisms. The selected psychrophilic and mesophilic strains were confirmed as Nostoc punctiforme and Nostoc calcicola respectively, by ultrastructure and 16S rDNA phylogeny. The psychrophilic strain has extensive glycolipid and polysaccharide sheath along with characteristic deposition of cyanophycin, polyhydroxybutyrate granules, and carboxysomes. This is possibly an adaptive strategy exhibited to withstand the freezing temperature and high intense of ultraviolet rays. The biomass measured in terms of dry weight, protein, and chlorophyll indicated a temperature dependant shift in both the psychrophilic and mesophilic strains and attained maximum growth in their respective temperature niches. At low temperature, psychrophilic organism exhibited nitrogenase activity, while mesophilic strains did not. The maximum glutamine synthetase activity was observed at 4 °C for psychrophilic and 37 °C for mesophilic strains. Activity at 4 °C in psychrophilic strains revealed their energetic mechanism even at low temperature. The nitrate and nitrite reductase of both psychrophilic and mesophilic strains showed maximum activity at 37 °C denoting their similar nitrogen assimilating mechanisms for combined nitrogen utilization. The activity studies of nitrogen fixation/assimilation enzymes have differential effects at varying temperatures, which provide valuable insights of physiological contribution and role of Nostoc strains in the biological nitrogen cycle.

Dark fermentative hydrogen and ethanol production from biodiesel waste glycerol using a co-culture of Escherichia coli and Enterobacter sp.

In previous comparative studies, Enterobacter spH1 was selected as the best hydrogen and ethanol producer (Knothe, 2010). Here, glycerol fermentation was compared between three other strains: Escherichia coli CECT432, Escherichia coli CECT434 and Enterobacter cloacae MCM2/1. E. coli CECT432 was found to perform best with a H2 productivity of 69.1mM (1307mL/L). A co-culture of this E. coli CECT432 strain with the earlier selected Enterobacter spH1 showed a 3.1-fold higher H2 productivity (4767mL/L) from pure glycerol and higher biomass production. Remarkably, the hydrogen yield per mol of glycerol also increased from 0.61 to 1.26molH2/molglycerol. The co-culture was also tested using waste glycerol from biodiesel. Waste glycerol was characterized and found to consist of (w/v): glycerol 47.5%, water 40.5%, ash content 4.8% and non-glycerol organic matter (MONG) 7.2%. The amount of total soluble organic carbon (TOC) in the crude glycerol was 317g/L. A maximum H2 yield and ethanol yield of 1.53 and 1.21mol/mol glycerol was obtained on the waste glycerol, respectively. These yields are the highest reported to date using mesophilic strains. The strains metabolized the crude glycerol without any purification step. The ability to produce H2 without prior purification of the waste glycerol is attractive because it avoids extra costs in the process.

In vitro synthesis of polyhydroxyalkanoates using thermostable acetyl-CoA synthetase, CoA transferase, and PHA synthase from thermotorelant bacteria

Thermostable enzymes are required for the rapid and sustainable production of polyhydroxyalkanoate (PHA) invitro. The invitro synthesis of PHA using the engineered thermostable synthase PhaC1SG(STQK) has been reported; however, the non-thermostable enzymes acetyl-CoA synthetase (ACS) and CoA transferase (CT) from mesophilic strains were used as monomer-supplying enzymes in this system. In the present study, acs and ct were cloned from the thermophilic bacteria Pelotomaculum thermopropionicum JCM10971 and Thermus thermophilus JCM10941 to construct an invitro PHA synthesis system using only thermostable enzymes. ACS from P.thermopropionicum (ACSPt) and CT from T.thermophilus (CTTt) were confirmed to have high thermostability, and their optimal temperatures were around 60°C and 75°C, respectively. The invitro PHA synthesis was successfully performed by ACSPt, CTTt, PhaC1SG(STQK), and poly(3-hydroxybutyrate) [P(3HB)] was synthesized at 45°C. Furthermore, the yields of P(3HB) and P(lactate-co-3HB) at 37°C were 1.4-fold higher than those of the invitro synthesis system with non-thermostable ACS and CT from mesophilic strains. Overall, the thermostable ACS and CT were demonstrated to be useful for the efficient invitro PHA synthesis at relatively high temperatures.

Biomass production and removal of ammonium and phosphate by Chlorella sp. in sludge liquor at natural light and different levels of temperature control.

Microalgae cultivation for biomass production and nutrient removal implies the use of natural light and minimal control of the temperature for obtaining a low cost production. The aim of this study was to quantify the effect of temperature control at natural light on biomass productivity and removal of NH4-N and PO4-P of a mesophilic strain of Chlorella. Chlorella sp. was grown in reject water of anaerobically digested municipal sludge, sludge liquor, inside a greenhouse compartment (Ås, Norway, 59°N) using batch cultures (300 mL). Five experiments were conducted from May to September, and effects of different levels of temperature control and diurnal variations were investigated. The highest biomass productivities (0.45 g L−1 day−1) in the linear growth phase were obtained at daily light integrals ≥12 mol day−1 m−2. Results showed that the average temperature was of more importance than the night or day temperature range. At average temperatures <22 °C for cultures with no temperature control, the productivity decreased by 23 and 39 % compared to cultures with full temperature control (24–25 °C). In one experiment, the productivity was reduced at no temperature control due to prolonged high daytime temperatures (>32 °C) and were followed by a lower NH4-N removal rate. Otherwise, temperature had little effect on NH4-N removal. The level of temperature control did not affect removal of PO4-P. Cellular starch content varied from ~15–38 % in the evening and was generally lower at no temperature control. In the morning the starch content was reduced to ~4–12 % with no difference between the different levels of temperature control. (~4–12 %).

Survey on proteolytic activity and diversity of proteinase genes in mesophilic lactobacilli

Lactocepins or CEPs are large cell wall bound extracellular proteinases of lactic acid bacteria, involved in protein breakdown and utilization. They are responsible for many health-promoting traits of food products fermented with these organisms, but also essential for probiotic effects of certain strains. Different mesophilic strains selected within the species Lactobacillus zeae, Lb. casei, Lb. rhamnosus, and Lb. plantarum were analyzed for their proteolytic activity towards main fractions of milk proteins—caseins and whey proteins. The strains showing excellent proteolytic features were further examined for presence of corresponding proteinase gene(s). It was found that Lb. zeae LMG17315 possessed catalytic domains of three distinct proteinase genes, unique feature in Lb. casei group, which are similar but not identical to previously characterized prtP and prtR genes. Lb. casei neotype strain ATCC393 was also analysed and based on obtained results its reclassification in taxon Lb. zeae is supported. In addition, we report catalytic domain of prtR-type gene in Lb. plantarum LMG9208, which is first such report in this species, and it is first time that this gene is reported outside Lb. casei group.

Bioleaching of Sphalerite by the Native Mesophilic Iron-oxidizing Bacteria from a Lead-Zinc Tailing

An isolated native mesophilic iron-oxidizing bacteria, acidithiobacillus ferrooxidans, was used to extract zinc by the bioleaching method from a typical lead-zinc tailing. Experiments were carried out by mixed culture of the mesophilic strain in the shake flasks and the different influencing factors such as pH, temperature, inoculation cell number, as well as slurry concentration on the process of bioleaching were investigated. The results indicated that the extraction efficiency of zinc was relevant with these variables and more than 70% of sphalerite was dissolved on the condition of with pH 2.0, initial ferrous concentration of 10g/L and slurry concentration of 10wt.% during 25 d, while without bacteria, 22% of Zn was merely extracted.

Characteristics of &lt;i&gt;Acidibacillus&lt;/i&gt; Spp.: A Novel Genus of Acidophilic Iron-Oxidising &lt;i&gt;Firmicutes&lt;/i&gt;

Strains of acidophilic bacteria, isolated from different global locations, were shown to be representatives of a novel genus within theFirmicutesphylum. All isolates oxidised and reduced iron and catalysed the oxidative dissolution of pyrite. Together they formed two distinct phylogenetic clusters, one of which included mesophilic strains that did not oxidise sulfur, and the other thermotolerant/moderately thermophilic strains that could oxidise sulfur. The novel genusAcidibacillusis proposed for these new isolates, to includeA. ferrooxidans(mesophilic iron-oxidising strains) andA.sulfooxidans(moderately thermophilic iron-and sulfur-oxidising strains) as candidate species.

Antimicrobial properties of chitosan solutions, chitosan films and gelatin-chitosan films

The antimicrobial properties of chitosan solutions and films against selected bacteria and the effect of chitosan incorporation into gelatin films were studied. The bactericidal effect of chitosan solutions increased with time and temperature of sample incubation. Two psychrotrophic strains Pseudomonas fluorescens and Listeria innocua were more sensitive to chitosan than mesophilic strains Escherichia coli and Staphylococcus aureus. The growth of bacteria under chitosan discs was inhibited. In the case of two component gelatin-chitosan films strong antimicrobial effect was also observed.

Adaptation to thermotolerance in Rhizopus coincides with virulence as revealed by avian and invertebrate infection models, phylogeny, physiological and metabolic flexibility

Mucormycoses are fungal infections caused by the ancient Mucorales. They are rare, but increasingly reported. Predisposing conditions supporting and favoring mucormycoses in humans and animals include diabetic ketoacidosis, immunosuppression and haematological malignancies. However, comprehensive surveys to elucidate fungal virulence in ancient fungi are limited and so far focused on Lichtheimia and Mucor. The presented study focused on one of the most important causative agent of mucormycoses, the genus Rhizopus (Rhizopodaceae). All known clinically-relevant species are thermotolerant and are monophyletic. They are more virulent compared to non-clinically, mesophilic species. Although adaptation to elevated temperatures correlated with the virulence of the species, mesophilic strains showed also lower virulence in Galleria mellonella incubated at permissive temperatures indicating the existence of additional factors involved in the pathogenesis of clinical Rhizopus species. However, neither specific adaptation to nutritional requirements nor stress resistance correlated with virulence, supporting the idea that Mucorales are predominantly saprotrophs without a specific adaptation to warm blooded hosts.

Risungbinella pyongyangensis gen. nov., sp. nov., a mesophilic member of the family Thermoactinomycetaceae isolated from an agricultural soil sample.

A mesophilic strain, designed MC 210T, was isolated from an agricultural soil sample from Pyongyang, Democratic People's Republic of Korea, and its taxonomic position was investigated by using a polyphasic approach. The novel strain grew well on PYI medium, and no diffusible pigments were produced. The optimum temperature for growth was 37 °C. The aerial mycelium was well developed, but not fragmented. The strain was Gram-reaction-positive and non-motile and formed endospores on the aerial mycelium. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain MC 210T belongs to the family Thermoactinomycetaceae. Strain MC 210T showed 16S rRNA gene sequence similarities of 92.90 and 92.54% to the type strains of Geothermomicrobium terrae and Shimazuella kribbensis, respectively. The cell wall of strain MC 210T contained meso-diaminopimelic acid, glutamic acid and alanine as the diagnostic amino acids, and whole-cell hydrolysates contained glucose, arabinose and galactose. Strain MC 210T contained anteiso-C13 : 0, iso-C14 : 0, C14 : 0, anteiso-C15 : 0, C16 : 0 and iso-C13 : 0 as the major cellular fatty acids. The main polar lipids were phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, two unknown aminophospholipids, an unknown aminolipid, three unknown phospholipids and five unknown polar lipids. The predominant menaquinone was MK-7.The G+C content of the genomic DNA was 42.1 mol%. On the basis of our phylogenetic, physiological and chemotaxonomic data, strain MC 210T is considered to represent a novel genus and species, for which we propose the name Risungbinella pyongyangensis gen. nov., sp. nov., in the family Thermoactinomycetaceae. The type strain of Risungbinella pyongyangensis is MC 210T (CCTCC AA 2013021T = NRRL B-59118T).

Thermophilic production of polyhydroxyalkanoates by a novel Aneurinibacillus strain isolated from Gudao oilfield, China.

Polyhydroxyalkanoates (PHAs) are usually biosynthesized using mesophilic strains, but the fermentation processes often suffer from bacterial contamination. This work reports the screening of thermophilic bacteria capable of producing PHAs under elevated temperatures to reduce the contamination risk. Strain XH2 was isolated from an oilfield and identified as Aneurinibacillus sp. by morphology, physiological-biochemical characterization, and 16S rDNA phylogenetic analysis. This strain can produce PHA granules, which was detected by Nile red staining and transmission electron microscopic imaging. At 55 °C, 111.6 mg l(-1) of PHA was produced in a fermentation medium containing glucose, peptone, and yeast extract. If peptone was removed from the medium, the yield of PHA would be enhanced by 2.4 times. The main monomers of the PHA product were identified to be 3-hydroxybutyrate and 3-hydroxyvalerate with a molar ratio of 17.2:1 by gas chromatography-mass spectroscopy (GC-MS) and nuclear magnetic resonance analyses. Two minor homologues, 3-hydroxyoctanoate, and 3-hydroxy-4-phenylbutanoate, were tentatively identified by GC-MS as well. This is the first report of thermophilic PHA bacterial producer from the Firmicutes phylum.

Augmented biogas production from protein-rich substrates and associated metagenomic changes

This study demonstrates that appropriate adaptation of the microbial community to protein-rich biomass can lead to sustainable biogas production. The process of acclimation to these unusual mono-substrates was controlled by the protease activity of the microbial community. Meat extract (C/N=3.32) and kitchen waste (C/N=12.43) were used as biogas substrates. Metagenome analysis highlighted several mesophilic strains that displayed a preference for protein degradation. Bacillus coagulans, Bacillus subtilis and Pseudomonas fluorescens were chosen for detailed investigation. Pure cultures were added to biogas reactors fed solely with protein-rich substrates. The bioaugmentation resulted in a 50% increase in CH4 production even without any acclimation. The survival and biological activity of the added bacteria were followed in fed-batch fermenters by qPCR. Stable biogas production was observed for an extended period of time in laboratory CSTR reactors fed with biomass of low C/N.

Gryllotalpicola soli sp. nov., isolated from soil

A novel Gram-stain-positive, short rod-shaped, non-flagellated and mesophilic strain, KIS12-7(T), isolated from a soil sample collected from Daecheong-Island in Ongjin County, Republic of Korea, was studied using a polyphasic approach. Phylogenetic trees based on the 16S rRNA gene sequence revealed that the novel strain was a member of the genus Gryllotalpicola, showing more than 97.0 % sequence similarity with Gryllotalpicola daejeonensis RU-04(T) (98.0 %), Gryllotalpicola koreensis RU-16(T) (97.7 %) and Gryllotalpicola kribbensis PU-02(T) (97.3 %). However, DNA-DNA relatedness values demonstrated that strain KIS12-7(T) could be clearly distinguished from closely related species of the genus Gryllotalpicola. The cell-wall peptidoglycan of strain KIS12-7(T) was of the type B2 and the acyl type was acetyl. The predominant menaquinones were MK-11 and MK-10. Polar lipids were diphosphatidylglycerol, phosphatidylglycerol, one unknown phosphoglycolipid, one unknown glycolipid, one unknown phospholipid and one unknown lipid. The G+C content of the genomic DNA was 72.1 mol%. On the basis of the evidence presented, strain KIS12-7(T) is a representative of a novel species of the genus Gryllotalpicola, and the name Gryllotalpicola soli sp. nov. is proposed; the type strain is KIS12-7(T) ( = DSM 27182(T) = KACC 17302(T) = NBRC 109659(T)).

Downward-Shifting Temperature Range for the Growth of Snow-Bacteria on Glaciers of the Tibetan Plateau

Fifty-seven snow-bacteria strains were isolated from the snow of the Zadang and Mengdagangri Glaciers located in the central and southern part of the Tibetan Plateau, respectively. 16S rRNA gene sequence analysis showed that strains isolated from the Zadang Glacier belonged to the Alphaproteobacteria, Gammaproteobacteria, Actinobacteria, Firmicutes and Bacteroidetes, and were dominated by the Firmicutes. Strains from the Mengdagangri Glacier belonged to the Actinobacteria, Alphaproteobacteria and Gammaproteobacteria, and were dominated by the Actinobacteria. Sixty-one percent of the isolates were colored with pigment. Sixty-nine percent of isolates from the Zadang Glacier were psychrotolerants, and there were no psychrophiles. We compared the growth-temperature range of 26 snow-bacteria strains to their closest mesophilic type strains and found that 46% of them had an optimum growth-temperature at or lower than 20°C, and 65% were all able to grow at 0°C. However, only 5.3% of mesophilic strains had optimum growth-temperatures at or lower than 20°C, and 9% could grow at 0°C. Snow-bacteria shift their growth-temperature downward; and doing this, in terms of the minimum and optimum temperatures for growth, might be an important strategy for them to adapt to low temperature after they have been deposited on the glacier. Our results suggested that, in order to adapt from mesophilic environments to a cold habitat, snow-bacteria widen their temperature range for growth, convert from mesophiles to psychrotolerants, but not to psychrophiles. In addition, eight isolates formed pigmented colonies, while their mesophilic counterparts were achromogenic. This helped us to confirm through comparative analysis that pigmented microorganisms were more abundant in high-altitude glaciers than in mesophilic environments.

Thermotolerance in Saccharomyces cerevisiae is linked to resistance to anhydrobiosis

We have demonstrated that a thermotolerant yeast strain (Saccharomyces cerevisiae TS1) is much more resistant to dehydration–rehydration treatments than a mesophilic strain of S. cerevisiae. Yeast resistance to dehydration–rehydration was found to be similar in cells from exponential and stationary growth phases. Under controlled rehydration conditions involving gradual rehydration in water vapour, yeast cell viability was maintained at 90–95%. When S. cerevisiae TS1 cells were pre-grown at 37°C and then dried, controlled rehydration lead to restoration of plasma membrane integrity, indicating important differences in cell envelope architechture of mesophilic and thermotolerant yeast strains. Comparison of such strains provides new insight into anhydrobiosis in eukaryotic cells.