Variation with depth of the abundance, diversity and pigmentation of culturable bacteria in a deep ice core from the Yuzhufeng Glacier, Tibetan Plateau

Differential effects of winter cold stress on soil bacterial communities, metabolites, and physicochemical properties in two varieties of Tetrastigma hemsleyanum Diels & Gilg in reclaimed land

Tetrastigma hemsleyanum Diels & Gilg (TDG) has been recently planted in reclaimed lands in Zhejiang Province, China, to increase reclaimed land use. Winter cold stress seriously limits the growth and development of TDG and has become the bottleneck limiting the TDG planting industry. To investigate the defense mechanisms of TDG toward winter cold stress when grown on reclaimed land, a combined analysis of soil bacterial communities, metabolites, and physicochemical properties was conducted in this study. Significant differences were observed in the composition of soil bacterial communities, metabolites, and properties in soils of a cold-tolerant variety (A201201) compared with a cold-intolerant variety (B201810). The fresh weight (75.8% of tubers) and dry weight (73.6%) of A201201 were significantly higher than those of B201810. The 16S rRNA gene amplicon sequencing of soil bacteria showed that Gp5 (25.3%), Gemmatimonas (19.6%), Subdivision3 (16.7%), Lacibacterium (11.9%), Gp4 (11.8%), Gp3 (10.4%), Gp6 (7.0%), and WPS-1 (1.2%) were less common, while Chryseolinea (10.6%) were more common in A201201 soils than B201810 soils. Furthermore, linear discriminant analysis of effect size identified 35 bacterial biomarker taxa for both treatments. Co-occurrence network analyses also showed that the structures of the bacterial communities were more complex and stable in A201201 soils compared to B201810 soils. In addition, ultra-high-performance liquid chromatography coupled to mass spectrometry analysis indicated the presence of significantly different metabolites in the two soil treatments, with 10 differentially expressed metabolites (DEMs) (8 significantly upregulated by 9.2%-391.3% and 2 significantly downregulated by 25.1%-73.4%) that belonged to lipids and lipid-like molecules, organic acids and derivatives, and benzenoids. The levels of those DEMs were significantly correlated with the relative abundances of nine bacterial genera. Also, redundancy discriminant analysis revealed that the main factors affecting changes in the bacterial community composition were available potassium (AK), microbial biomass nitrogen (MBN), microbial biomass carbon (MBC), alkaline hydrolysis nitrogen (AHN), total nitrogen (TN), available phosphorus (AP), and soil organic matter (SOM). The main factors affecting changes in the metabolite profiles were AK, MBC, MBN, AHN, pH, SOM, TN, and AP. Overall, this study provides new insights into the TDG defense mechanisms involved in winter cold stress responses when grown on reclaimed land and practical guidelines for achieving optimal TDG production.IMPORTANCEChina has been undergoing rapid urbanization, and land reclamation is regarded as a viable option to balance occupation and compensation. In general, the quality of reclaimed land cannot meet plant or even cultivation requirements due to poor soil fertility and high gravel content. However, Tetrastigma hemsleyanum Diels & Gilg (TDG), extensively used in Chinese herbal medicine, can grow well in stony soils with few nutrients. So, to increase reclaimed land use, TDG has been cultivated on reclaimed lands in Zhejiang Province, China, recently. However, the artificial cultivation of TDG is often limited by winter cold stress. The aim of this study was to find out how TDG on reclaimed land deal with winter cold stress by looking at the bacterial communities, metabolites, and physicochemical properties of the soil, thereby guiding production in practice.

Cryosphere: a frozen home of microbes and a potential source for drug discovery

The world is concerned about the emergence of pathogens and the occurrence and spread of antibiotic resistance among pathogens. Drug development requires time to combat these issues. Consequently, drug development from natural sources is unavoidable. Cryosphere represents a gigantic source of microbes that could be the bioprospecting source of natural products with unique scaffolds as molecules or drug templates. This review focuses on the novel source of drug discovery and cryospheric environments as a potential source for microbial metabolites having potential medicinal applications. Furthermore, the problems encountered in discovering metabolites from cold-adapted microbes and their resolutions are discussed. By adopting modern practical approaches, the discovery of bioactive compounds might fulfill the demand for new drug development.

The distribution and drivers of microbial pigments in the cryoconite of four Tibetan glaciers

Microbial pigments play a significant role in glacier albedo reduction, thereby contributing to accelerated glacier retreat. The Tibetan Plateau has experienced rapid glacier retreat in recent decades due to global warming, yet there is limited understanding of microbial pigment distribution in the region. Here, we investigated the pigment concentration and composition in cryoconite from four glaciers. Our results showed that chlorophylls were the dominant pigments in Palong No. 4 (PL) and Jiemayangzong (JMYZ) glaciers located in the south of the Tibetan Plateau, while carotenoids were dominant in Qiangyong (QY) and Tanggula (TGL) glaciers located in the central region. Additionally, the chlorophyll b to chlorophyll a ratio, which is an indicator of the algae-to-cyanobacteria ratio, was higher in PL and JMYZ compared to QY and TGL. By using Random Forest Regression and Structural Equation Modelling, we determined that the concentrations of chlorophyll a, chlorophyll b, and carotenoids were associated with autotrophic bacteria relative abundance, climatic factors, and a combination of bacterial and climatic factors, respectively. This study is the first to describe the distribution of microbial pigments in cryoconite from Tibetan glaciers, providing additional support on the influence of algal pigment on glacier retreat.

A reduction in temperature induces bioactive red pigment production in a psychrotolerant Penicillium sp. GEU_37 isolated from Himalayan soil

Filamentous fungi are being globally explored for the production of industrially important bioactive compounds including pigments. In the present study, a cold and pH tolerant fungus strain Penicillium sp (GEU_37), isolated from the soil of Indian Himalaya, is characterized for the production of natural pigments as influenced by varying temperature conditions. The fungal strain produces a higher sporulation, exudation, and red diffusible pigment in Potato Dextrose (PD) at 15 °C as compared to 25 °C. In PD broth, a yellow pigment was observed at 25 °C. While measuring the effect of temperature and pH on red pigment production by GEU_37, 15 °C and pH 5, respectively, were observed to be the optimum conditions. Similarly, the effect of exogenous carbon and nitrogen sources and mineral salts on pigment production by GEU_37 was assessed in PD broth. However, no significant enhancement in pigmentation was observed. Chloroform extracted pigment was separated using thin layer chromatography (TLC) and column chromatography. The two separated fractions i.e., fractions I and II with Rf values 0.82 and 0.73, exhibited maximum light absorption, λ_max, at 360 nm and 510 nm, respectively. Characterization of pigments using GC-MS showed the presence of the compounds such as phenol, 2,4-bis (1,1-dimethylethyl) and eicosene from fraction I and derivatives of coumarine, friedooleanan, and stigmasterole in fraction II. However, LC-MS analysis detected the presence of derivatives of compound carotenoids from fraction II as well as derivative of chromenone and hydroxyquinoline as major compounds from both the fractions along with other numerous important bioactive compounds. The production of such bioactive pigments under low temperature conditions suggest their strategic role in ecological resilience by the fungal strain and may have biotechnological applications.

Research on safety and compliance of imported microbial inoculants using high-throughput sequencing

Microbial inoculants are widely used in wastewater treatment, soil remediation, and biological control. Safety and compliance for active constituents are considered to be the most important measures of imported microbial inoculants. Microbial inoculants composition was commonly identified by phenotypic culture, which is time-consuming and labor intense with occasionally false negative results provided, and can only be tested for specific species. High-throughput sequencing (HTS), known for its non-targeted detection of unknown species composition in samples, is suitable for composition consistency identification and biosafety analysis of imported microbial inoculants. In this study, the application of HTS for microflora distribution and resistance gene was verified in microbial inoculants for environmental protection and then applicated in imported microbial inoculants. Both Illumina- and Nanopore-based HTS methods identified the same dominant bacterial species successfully in the imported microbial inoculants. The main component of bacterial species was Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Enterococcus faecium, and further confirmed with traditional methods. The antibiotic resistance genes Bacillus subtilis mprF, bcrA, blt, lmrB, rphB, tet(L), tmrB, vmlR, ykkC, and ykkD were detected in all samples. Our results indicated that HTS processes the application potential to identify the active ingredients of microbial inoculants. Therefore, rapid and accurate identification of the microbial compositions in microbial formulation products is of high importance for port biosafety supervision.

Contamination analysis of Arctic ice samples as planetary field analogs and implications for future life-detection missions to Europa and Enceladus

Missions to detect extraterrestrial life are being designed to visit Europa and Enceladus in the next decades. The contact between the mission payload and the habitable subsurface of these satellites involves significant risk of forward contamination. The standardization of protocols to decontaminate ice cores from planetary field analogs of icy moons, and monitor the contamination in downstream analysis, has a direct application for developing clean approaches crucial to life detection missions in these satellites. Here we developed a comprehensive protocol that can be used to monitor and minimize the contamination of Arctic ice cores in processing and downstream analysis. We physically removed the exterior layers of ice cores to minimize bioburden from sampling. To monitor contamination, we constructed artificial controls and applied culture-dependent and culture-independent techniques such as 16S rRNA amplicon sequencing. We identified 13 bacterial contaminants, including a radioresistant species. This protocol decreases the contamination risk, provides quantitative and qualitative information about contamination agents, and allows validation of the results obtained. This study highlights the importance of decreasing and evaluating prokaryotic contamination in the processing of polar ice cores, including in their use as analogs of Europa and Enceladus.

An insight into the mechanisms of homeostasis in extremophiles

The homeostasis of extremophiles is one that is a diamond hidden in the rough. The way extremophiles adapt to their extreme environments gives a clue into the true extent of what is possible when it comes to life. The discovery of new extremophiles is ever-expanding and an explosion of knowledge surrounding their successful existence in extreme environments is obviously perceived in scientific literature. The present review paper aims to provide a comprehensive view on the different mechanisms governing the extreme adaptations of extremophiles, along with insights and discussions on what the limits of life can possibly be. The membrane adaptations that are vital for survival are discussed in detail. It was found that there are many alterations in the genetic makeup of such extremophiles when compared to their mesophilic counterparts. Apart from the several proteins involved, the significance of chaperones, efflux systems, DNA repair proteins and a host of other enzymes that adapt to maintain functionality, are enlisted, and explained. A deeper understanding of the underlying mechanisms could have a plethora of applications in the industry. There are cases when certain microbes can withstand extreme doses of antibiotics. Such microbes accumulate numerous genetic elements (or plasmids) that possess genes for multiple drug resistance (MDR). A deeper understanding of such mechanisms helps in the development of potential approaches and therapeutic schemes for treating pathogen-mediated outbreaks. An in-depth analysis of the parameters - radiation, pressure, temperature, pH value and metal resistance - are discussed in this review, and the key to survival in these precarious niches is described.

Cold-adaptive mechanism of psychrophilic bacteria in food and its application

Psychrophilic bacteria are a type of microorganisms that normally grow in low-temperature environments. They are usually found in extremely cold environments. However, as people's demand for low-temperature storage of food becomes higher, psychrophilic bacteria have also begun to appear in cold storage and refrigerators, which has become a food safety hazard. In this paper, the optimal cooling strategies of psychrophilic bacteria are reviewed from the aspects of the cell membrane, psychrophilic enzymes, antifreeze proteins, cold shock proteins, gene regulation, metabolic levels and antifreeze agents, and the principle of psychrophilic mechanism is briefly described. The application of thermophilic bacteria and its products adapted to cold environments in food fields are analyzed. The purpose of this paper is to provide ideas for future research on psychrophilic bacteria based on the mechanism and application of psychrophilic bacteria.

Culturable Bacterial Isolates from Arctic Soil shows High Biotechnological Potential

Polar microbiology remains as the most fascinating area of research which mainly focuses on exploration of psychrophilic organisms for having their cold-active enzymes of biotechnological potential. In this study, we have explored a culturable bacterial community and isolated 27 bacterial isolates with a different morphology from an unexplored site of Arctic region, for the possibility of identifying various active biomolecules. Screening of various isolates in a culture dependent manner helped us to identify strains capable of producing extracellular enzymes. The optimal growth parameters of most of the isolates are ranges between 18-22°C temperature, 3-5 days of incubation, 6-9 pH, and 3-5% (w/v) NaCl in LB media. It has also been found that among these isolates, 63% are able to produce lipase, 17% amylase, 7% xylanase and 7% isolates have responded for phosphatase activity but there are no isolates found for gelatinase and cellulase production ability. In addition, few isolates can also produce secretory protease, urease, β-galactosidase, etc. 16SrRNA gene sequence-based phylogeny revealed that the isolates belong to the genera of Psychrobacter, Planococcus, Halomonas, Arthrobacter, Oceanisphaera, Marinbacter, Pseudomonas, Algoriphagus. Strikingly, none of the Arctic isolates showed resistance towards commonly used antibiotics which indicates that the unexplored habitat is devoid of antibiotic exposure and so does the rise of antimicrobial resistance. The structure-function relationship of the isolated bioactive compounds from these isolates are the major focus of future research.

Glacial Ice Age Shapes Microbiome Composition in a Receding Southern European Glacier

Glaciers and their microbiomes are exceptional witnesses of the environmental conditions from remote times. Climate change is threatening mountain glaciers, and especially those found in southern Europe, such as the Monte Perdido Glacier (northern Spain, Central Pyrenees). This study focuses on the reconstruction of the history of microbial communities over time. The microorganisms that inhabit the Monte Perdido Glacier were identified using high-throughput sequencing, and the microbial communities were compared along an altitudinal transect covering most of the preserved ice sequence in the glacier. The results showed that the glacial ice age gradient did shape the diversity of microbial populations, which presented large differences throughout the last 2000 years. Variations in microbial community diversity were influenced by glacial conditions over time (nutrient concentration, chemical composition, and ice age). Some groups were exclusively identified in the oldest samples as the bacterial phyla Fusobacteria and Calditrichaeota, or the eukaryotic class Rhodophyceae. Among groups only found in modern samples, the green sulfur bacteria (phylum Chlorobi) stood out, as well as the bacterial phylum Gemmatimonadetes and the eukaryotic class Tubulinea. A patent impact of human contamination was also observed on the glacier microbiome. The oldest samples, corresponding to the Roman Empire times, were influenced by the beginning of mining exploitation in the Pyrenean area, with the presence of metal-tolerant microorganisms. The most recent samples comprise 600-year-old ancient ice in which current communities are living.

Carotenoid Cocktail Produced by An Antarctic Soil Flavobacterium with Biotechnological Potential

Carotenoids are highly important in pigmentation, and its content in farmed crustaceans and fish correlates to their market value. These pigments also have a nutritional role in aquaculture where they are routinely added as a marine animal food supplement to ensure fish development and health. However, there is little information about carotenoids obtained from Antarctic bacteria and its use for pigmentation improvement and flesh quality in aquaculture. This study identified carotenoids produced by Antarctic soil bacteria. The pigmented strain (CN7) was isolated on modified Luria–Bertani (LB) media and incubated at 4 °C. This Gram-negative bacillus was identified by 16S rRNA analysis as Flavobacterium segetis. Pigment extract characterization was performed through high-performance liquid chromatography (HPLC) and identification with liquid chromatography–mass spectrometry (LC–MS). HPLC analyses revealed that this bacterium produces several pigments in the carotenoid absorption range (six peaks). LC–MS confirms the presence of one main peak corresponding to lutein or zeaxanthin (an isomer of lutein) and several other carotenoid pigments and intermediaries in a lower quantity. Therefore, we propose CN7 strain as an alternative model to produce beneficial carotenoid pigments with potential nutritional applications in aquaculture.

Cold Active Lipases: Biocatalytic Tools for Greener Technology

Lipases are enzymes that catalyze the ester bond hydrolysis in triglycerides with the release of fatty acids, mono- and diglycerides, and glycerol. The microbial lipases account for $400 million market size in 2017 and it is expected to reach $590 million by 2023. Many biotechnological processes are expedited at high temperatures and hence much research is dealt with thermostable enzymes. Cold active lipases are now gaining importance in the detergent, synthesis of chiral intermediates and frail/fragile compounds, and food and pharmaceutical industries. In addition, they consume less energy since they are active at low temperatures. These cold active lipases have not been commercially exploited so far compared to mesophilic and thermophilc lipases. Cold active lipases are distributed in microbes found at low temperatures. Only a few microbes were studied for the production of these enzymes. These cold-adapted enzymes show increased flexibility of their structures in response to freezing effect of the cold habitats. This review presents an update on cold-active lipases from microbial sources along with some structural features justifying high enzyme activity at low temperature. In addition, recent achievements on their use in various industries will also be discussed.

Linking genomic and physiological characteristics of psychrophilic Arthrobacter to metagenomic data to explain global environmental distribution

BACKGROUND

Microorganisms drive critical global biogeochemical cycles and dominate the biomass in Earth's expansive cold biosphere. Determining the genomic traits that enable psychrophiles to grow in cold environments informs about their physiology and adaptive responses. However, defining important genomic traits of psychrophiles has proven difficult, with the ability to extrapolate genomic knowledge to environmental relevance proving even more difficult.

RESULTS

Here we examined the bacterial genus Arthrobacter and, assisted by genome sequences of new Tibetan Plateau isolates, defined a new clade, Group C, that represents isolates from polar and alpine environments. Group C had a superior ability to grow at -1°C and possessed genome G+C content, amino acid composition, predicted protein stability, and functional capacities (e.g., sulfur metabolism and mycothiol biosynthesis) that distinguished it from non-polar or alpine Group A Arthrobacter. Interrogation of nearly 1000 metagenomes identified an over-representation of Group C in Canadian permafrost communities from a simulated spring-thaw experiment, indicative of niche adaptation, and an under-representation of Group A in all polar and alpine samples, indicative of a general response to environmental temperature.

CONCLUSION

The findings illustrate a capacity to define genomic markers of specific taxa that potentially have value for environmental monitoring of cold environments, including environmental change arising from anthropogenic impact. More broadly, the study illustrates the challenges involved in extrapolating from genomic and physiological data to an environmental setting. Video Abstract.

Microbial Community Structure Driven by a Volcanic Gradient in Glaciers of the Antarctic Archipelago South Shetland

It has been demonstrated that the englacial ecosystem in volcanic environments is inhabited by active bacteria. To know whether this result could be extrapolated to other Antarctic glaciers and to study the populations of microeukaryotes in addition to those of bacteria, a study was performed using ice samples from eight glaciers in the South Shetland archipelago. The identification of microbial communities of bacteria and microeukaryotes using 16S rRNA and 18S rRNA high throughput sequencing showed a great diversity when compared with microbiomes of other Antarctic glaciers or frozen deserts. Even the composition of the microbial communities identified in the glaciers from the same island was different, which may be due to the isolation of microbial clusters within the ice. A gradient in the abundance and diversity of the microbial communities from the volcano (west to the east) was observed. Additionally, a significant correlation was found between the chemical conditions of the ice samples and the composition of the prokaryotic populations inhabiting them along the volcanic gradient. The bacteria that participate in the sulfur cycle were those that best fit this trend. Furthermore, on the eastern island, a clear influence of human contamination was observed on the glacier microbiome.

Light stimulates anoxic and oligotrophic growth of glacial Flavobacterium strains that produce zeaxanthin

Bacteria that inhabit glaciers usually produce carotenoids. Here, we report that a group of zeaxanthin-producing glacial Flavobacterium exhibited light-promoted growth. Of the tested 47 strains, 45 showed increased growths but two died under illumination at 50 μmol photon m^-2 s^-1. Light stimulation occurred mainly in either anoxic or nutrient-poor cultures, while the same levels of light promotion were found for that grown at 14 and 7 °C. Pigment assays identified overrepresentative zeaxanthin but trace retinal in the light promoted 45 strains, while flexirubin was exclusively in the light-lethal two. Genomic analysis revealed the gene cluster for zeaxanthin synthesis in the 45 strains, in which 37 strains also harbored the proteorhodopsin gene prd. Transcriptomic analysis found that light-induced expressions of both the zeaxanthin synthesis and proteorhodopsin genes. Whereas, deletion of the prd gene in one strain did not diminish light promotion, inhibition of zeaxanthin synthesis did. In comparison, no light promotion was determined in a glacier Cryobacterium luteum that produced a non-zeaxanthin-type carotenoid. Therefore, light stimulation on the glacial Flavobacterium is mostly likely related to zeaxanthin, which could provide better photoprotection and sustain membrane integrity for the organisms living in cold environments.

First report on antibiotic resistance and antimicrobial activity of bacterial isolates from 13,000-year old cave ice core

Despite the unique physiology and metabolic pathways of microbiomes from cold environments providing key evolutionary insights and promising leads for discovering new bioactive compounds, cultivable bacteria entrapped in perennial ice from caves remained a largely unexplored life system. In this context, we obtained and characterized bacterial strains from 13,000-years old ice core of Scarisoara Ice Cave, providing first isolates from perennial ice accumulated in caves since Late Glacial, and first culture-based evidences of bacterial resistome and antimicrobial compounds production. The 68 bacterial isolates belonged to 4 phyla, 34 genera and 56 species, with 17 strains representing putative new taxa. The Gram-negative cave bacteria (Proteobacteria and Bacteroidetes) were more resistant to the great majority of antibiotic classes than the Gram-positive ones (Actinobacteria, Firmicutes). More than 50% of the strains exhibited high resistance to 17 classes of antibiotics. Some of the isolates inhibited the growth of clinically important Gram-positive and Gram-negative resistant strains and revealed metabolic features with applicative potential. The current report on bacterial strains from millennia-old cave ice revealed promising candidates for studying the evolution of environmental resistome and for obtaining new active biomolecules for fighting the antibiotics crisis, and valuable cold-active biocatalysts.

Bacterial community characterization of Batura Glacier in the Karakoram Range of Pakistan

High-altitude cold habitats of the Karakoram are rarely explored for their bacterial community characterization and metabolite productions. In the present study, bacterial communities in ice, water, and sediments of Batura Glacier were investigated using culture-dependent and culture-independent methods. Twenty-seven cold-adapted bacterial strains (mostly psychrotrophic) were isolated using R2A, Tryptic Soy Agar (TSA), and Luria-Bertani (LB) media, at 4 °C and 15 °C. Most of the isolates exhibited growth at a wide range of temperature (4-35 °C), pH (5-12), and salinity (1-6%). Among the bacterial isolates, 52% were identified as Gram-positive and the remaining 48% represented as Gram-negative. The results of phylogenetic analysis indicated that all the culturable bacteria belonged to 3 major phylogenetic groups, i.e., Actinobacteria (48%), Bacteroidetes (26%), and Proteobacteria (22%), while Flavobacterium (26%), Arthrobacter (22%), and Pseudomonas (19%) were represented as the dominant genera. Similarly, Illumina amplicon sequencing of 16S rRNA genes after PCR amplification of DNA from the whole community revealed dominance of the same phylogenetic groups, Proteobacteria, Actinobacteria, and Bacteroidetes, while Arthrobacter, Mycoplana, Ochrobactrum, Kaistobacter, Janthinobacterium, and Flavobacterium were found as the dominant genera. Among the culturable isolates, 70% demonstrated activity for cellulases, 48% lipases, 41% proteases, 41% DNases, and only 7% for amylases. Most of the glacial isolates demonstrated antimicrobial activity against other microorganisms including the multiple-drug-resistant strains of Candida albicans, Klebsiella pneumoniae, Acinetobacter sp., and Bacillus sp. 67% of Gram-negative while 46% of Gram-positive glacial bacteria were resistant to trimethoprim/sulfamethoxazole. Resistance against methicillin and vancomycin among the Gram-positive isolates was 23% and 15%, respectively, while 11% of the Gram-negative isolates exhibited resistance against both colistin sulfate and nalidixic acid.

Pigment production by cold-adapted bacteria and fungi: colorful tale of cryosphere with wide range applications

Pigments are an essential part of everyday life on Earth with rapidly growing industrial and biomedical applications. Synthetic pigments account for a major portion of these pigments that in turn have deleterious effects on public health and environment. Such drawbacks of synthetic pigments have shifted the trend to use natural pigments that are considered as the best alternative to synthetic pigments due to their significant properties. Natural pigments from microorganisms are of great interest due to their broader applications in the pharmaceutical, food, and textile industry with increasing demand among the consumers opting for natural pigments. To fulfill the market demand of natural pigments new sources should be explored. Cold-adapted bacteria and fungi in the cryosphere produce a variety of pigments as a protective strategy against ecological stresses such as low temperature, oxidative stresses, and ultraviolet radiation making them a potential source for natural pigment production. This review highlights the protective strategies and pigment production by cold-adapted bacteria and fungi, their industrial and biomedical applications, condition optimization for maximum pigment extraction as well as the challenges facing in the exploitation of cryospheric microorganisms for pigment extraction that hopefully will provide valuable information, direction, and progress in forthcoming studies.

Psychrophilic lifestyles: mechanisms of adaptation and biotechnological tools

Cold-adapted microorganisms inhabiting permanently low-temperature environments were initially just a biological curiosity but have emerged as rich sources of numerous valuable tools for application in a broad spectrum of innovative technologies. To overcome the multiple challenges inherent to life in their cold habitats, these microorganisms have developed a diverse array of highly sophisticated synergistic adaptations at all levels within their cells: from cell envelope and enzyme adaptation, to cryoprotectant and chaperone production, and novel metabolic capabilities. Basic research has provided valuable insights into how these microorganisms can thrive in their challenging habitat conditions and into the mechanisms of action of the various adaptive features employed, and such insights have served as a foundation for the knowledge-based development of numerous novel biotechnological tools. In this review, we describe the current knowledge of the adaptation strategies of cold-adapted microorganisms and the biotechnological perspectives and commercial tools emerging from this knowledge. Adaptive features and, where possible, applications, in relation to membrane fatty acids, membrane pigments, the cell wall peptidoglycan layer, the lipopolysaccharide component of the outer cell membrane, compatible solutes, antifreeze and ice-nucleating proteins, extracellular polymeric substances, biosurfactants, chaperones, storage materials such as polyhydroxyalkanoates and cyanophycins and metabolic adjustments are presented and discussed.