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Polar Microbial Ecology: The Role of Microbes in the Functioning...
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Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Environmental Microbiology".

Deadline for manuscript submissions: closed (31 July 2020) | Viewed by 50838

Special Issue Editors

Dr. Angelina Lo Giudice

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Guest Editor
Institute of Polar Sciences of the National Research Council (CNR-ISP), 98122 Messina, Italy
Interests: microbial ecology of polar environments; biotechnology of cold-adapted bacteria; bacterial associations with benthic filter feeders; relationships between prokaryotes and chemical contamination
Special Issues, Collections and Topics in MDPI journals
Dr. Carmen Rizzo

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Guest Editor
Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, 98168 Messina, Italy
Interests: microbial ecology; bioprospecting; cold-adapted bacteria; microbial biodiversity; bioremediation; bacterial bioactive molecules; microbial communities associated with marine invertebrates
Special Issues, Collections and Topics in MDPI journals
Dr. Maurizio Azzaro

E-Mail Website
Guest Editor
Institute of Polar Sciences (ISP), National Research Council, Spianata S. Raineri 86, 98122 Messina, Italy
Interests: polar ecosystems; biogeochemical cycles, marine microbiology; microbial biodiversity; microbial ecology; microbial activities; monitoring of protected marine areas
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In polar environments, years of studies and research have allowed us to discover that beyond the austerity of ice, beyond the impetuous force of the winds and the rigidity of temperature, microbial life thrives by organizing itself in different and complex community structures, with the establishment of a delicate balance of interactions and unique metabolic pathways. Extreme environments are also among the most interesting targets for the discovery of new microbial species, not yet cultured and explored. Cold-adapted microbes not only face adversities to survive but actively contribute to the functioning of polar ecosystems and to their restoration. The development of high-throughput sequencing techniques has provided the ideal opportunity to really appreciate the polar microbial diversity, and sometimes it has also been useful for tracing back to ancient environmental conditions. However, this new basin of information has to go beyond mere taxonomic designation and should be used as key for the deep comprehension of ecological dynamics and to enhance the functional aspect linked to genomic diversity.

This Special Issue of Microorganisms invites you to join in by submitting contributions concerning the role of microbes in the functioning of extremely cold ecosystems, by including as main topics correlations between microbial diversity and polar environmental conditions, temporal and spatial changes in polar microbial communities, metagenomics and molecular advances in polar microbial ecology, relationships and symbiotic associations of cold-adapted microbes with their implications, biogeochemical processes in polar habitats, polar bioprospecting, role of polar microbes in restoration of environments, and biotechnological applications of these extremophiles.

Dr. Angelina Lo Giudice
Dr. Carmen Rizzo
Dr. Maurizio Azzaro
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Microorganisms is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • polar environments
  • microbial ecology
  • bioprospecting
  • cold-adapted microbes
  • biogeochemical cycles
  • biorestoration

Published Papers (12 papers)

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Research

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18 pages, 3674 KiB  
Article
Hot in Cold: Microbial Life in the Hottest Springs in Permafrost
by Tatiana V. Kochetkova, Stepan V. Toshchakov, Kseniya S. Zayulina, Alexander G. Elcheninov, Daria G. Zavarzina, Vasiliy Yu. Lavrushin, Elizaveta A. Bonch-Osmolovskaya and Ilya V. Kublanov
Microorganisms 2020, 8(9), 1308; https://doi.org/10.3390/microorganisms8091308 - 27 Aug 2020
Cited by 12 | Viewed by 3721
Abstract
Chukotka is an arctic region located in the continuous permafrost zone, but thermal springs are abundant there. In this study, for the first time, the microbial communities of the Chukotka hot springs (CHS) biofilms and sediments with temperatures 54–94 °C were investigated and [...] Read more.
Chukotka is an arctic region located in the continuous permafrost zone, but thermal springs are abundant there. In this study, for the first time, the microbial communities of the Chukotka hot springs (CHS) biofilms and sediments with temperatures 54–94 °C were investigated and analyzed by NGS sequencing of 16S rRNA gene amplicons. In microbial mats (54–75 °C), phototrophic bacteria of genus Chloroflexus dominated (up to 89% of all prokaryotes), while Aquificae were the most numerous at higher temperatures in Fe-rich sediments and filamentous “streamers” (up to 92%). The electron donors typical for Aquificae, such as H2S and H2, are absent or present only in trace amounts, and the prevalence of Aquificae might be connected with their ability to oxidize the ferrous iron present in CHS sediments. Armatimonadetes, Proteobacteria, Deinococcus-Thermus, Dictyoglomi, and Thermotogae, as well as uncultured bacteria (candidate divisions Oct-Spa1-106, GAL15, and OPB56), were numerous, and Cyanobacteria were present in low numbers. Archaea (less than 8% of the total community of each tested spring) belonged to Bathyarchaeota, Aigarchaeota, and Thaumarchaeota. The geographical location and the predominantly autotrophic microbial community, built on mechanisms other than the sulfur cycle-based ones, make CHS a special and unique terrestrial geothermal ecosystem. Full article
(This article belongs to the Special Issue Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems)
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15 pages, 1148 KiB  
Article
Novel Psychrophiles and Exopolymers from Permafrost Thaw Lake Sediments
by Ilaria Finore, Adrien Vigneron, Warwick F. Vincent, Luigi Leone, Paola Di Donato, Aniello Schiano Moriello, Barbara Nicolaus and Annarita Poli
Microorganisms 2020, 8(9), 1282; https://doi.org/10.3390/microorganisms8091282 - 22 Aug 2020
Cited by 11 | Viewed by 2977
Abstract
Thermokarst lakes are one of the most abundant types of microbial ecosystems in the circumpolar North. These shallow basins are formed by the thawing and collapse of ice-rich permafrost, with subsequent filling by snow and ice melt. Until now, permafrost thaw lakes have [...] Read more.
Thermokarst lakes are one of the most abundant types of microbial ecosystems in the circumpolar North. These shallow basins are formed by the thawing and collapse of ice-rich permafrost, with subsequent filling by snow and ice melt. Until now, permafrost thaw lakes have received little attention for isolation of microorganisms by culture-based analysis. The discovery of novel psychrophiles and their biomolecules makes these extreme environments suitable sources for the isolation of new strains, including for potential biotechnological applications. In this study, samples of bottom sediments were collected from three permafrost thaw lakes in subarctic Québec, Canada. Their diverse microbial communities were characterized by 16S rRNA gene amplicon analysis, and subsamples were cultured for the isolation of bacterial strains. Phenotypic and genetic characterization of the isolates revealed affinities to the genera Pseudomonas, Paenibacillus, Acinetobacter,Staphylococcus and Sphingomonas. The isolates were then evaluated for their production of extracellular enzymes and exopolymers. Enzymes of potential biotechnological interest included α and β-glucosidase, α and β-maltosidase, β-xylosidase and cellobiohydrolase. One isolate, Pseudomonas extremaustralis strain 2ASCA, also showed the capability to produce, in the loosely bound cell fraction, a levan-type polysaccharide with a yield of 613 mg/L of culture, suggesting its suitability as a candidate for eco-sustainable alternatives to commercial polymers. Full article
(This article belongs to the Special Issue Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems)
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25 pages, 2942 KiB  
Article
Regulation of Microbial Activity Rates by Organic Matter in the Ross Sea during the Austral Summer 2017
by Renata Zaccone, Cristina Misic, Filippo Azzaro, Maurizio Azzaro, Giovanna Maimone, Olga Mangoni, Giannetta Fusco, Alessandro Ciro Rappazzo and Rosabruna La Ferla
Microorganisms 2020, 8(9), 1273; https://doi.org/10.3390/microorganisms8091273 - 21 Aug 2020
Cited by 5 | Viewed by 1793
Abstract
The active prokaryotic communities proliferate in the ecosystems of the Antarctic Ocean, participating in biogeochemical cycles and supporting higher trophic levels. They are regulated by several environmental and ecological forcing, such as the characteristics of the water masses subjected to global warming and [...] Read more.
The active prokaryotic communities proliferate in the ecosystems of the Antarctic Ocean, participating in biogeochemical cycles and supporting higher trophic levels. They are regulated by several environmental and ecological forcing, such as the characteristics of the water masses subjected to global warming and particulate organic matter (POM). During summer 2017, two polynyas in the Ross Sea were studied to evaluate key-microbiological parameters (the proteasic, glucosidasic, and phosphatasic activities, the microbial respiratory rates, the prokaryotic abundance and biomass) in relation to quantitative and qualitative characteristics of POM. Results showed significant differences in the epipelagic layer between two macro-areas (Terra Nova Bay and Ross Sea offshore area). Proteins and carbohydrates were metabolized rapidly in the offshore area (as shown by turnover times), due to high enzymatic activities in this zone, indicating fresh and labile organic compounds. The lower quality of POM in Terra Nova Bay, as shown by the higher refractory fraction, led to an increase in the turnover times of proteins and carbohydrates. Salinity was the physical constraint that played a major role in the distribution of POM and microbial activities in both areas. Full article
(This article belongs to the Special Issue Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems)
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19 pages, 2036 KiB  
Article
Microbial Communities in Permafrost Soils of Larsemann Hills, Eastern Antarctica: Environmental Controls and Effect of Human Impact
by Ivan Alekseev, Aleksei Zverev and Evgeny Abakumov
Microorganisms 2020, 8(8), 1202; https://doi.org/10.3390/microorganisms8081202 - 07 Aug 2020
Cited by 16 | Viewed by 4419
Abstract
Although ice-free areas cover only about 0.1% of Antarctica and are characterized by harsh environmental conditions, these regions provide quite diverse conditions for the soil-forming process, having various physical and geochemical properties, and also assuring different conditions for living organisms. This study is [...] Read more.
Although ice-free areas cover only about 0.1% of Antarctica and are characterized by harsh environmental conditions, these regions provide quite diverse conditions for the soil-forming process, having various physical and geochemical properties, and also assuring different conditions for living organisms. This study is aimed to determine existing soil microbial communities, their relationship with soil parameters and the influence of anthropogenic activity in Larsemann Hills, Eastern Antarctica. The soil microbiome was investigated at different locations using 16S rRNA gene pyrosequencing. The taxonomic analysis of the soil microbiomes revealed 12 predominant bacterial and archaeal phyla—Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, Gemmatimonadetes, Verrucomicrobia, Planctomycetes, Bacteroidetes, Armatimonadetes, Firmicutes, Cyanobacteria, Thaumarchaeota. Some specific phyla have been also found in sub-surface horizons of soils investigated, thus providing additional evidence of the crucial role of gravel pavement in saving the favorable conditions for both soil and microbiome development. Moreover, our study also revealed that some bacterial species might be introduced into Antarctic soils by human activities. We also assessed the effect of different soil parameters on microbial community in the harsh environmental conditions of Eastern Antarctica. pH, carbon and nitrogen, as well as fine earth content, were revealed as the most accurate predictors of soil bacterial community composition. Full article
(This article belongs to the Special Issue Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems)
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15 pages, 3094 KiB  
Article
Uncovered Microbial Diversity in Antarctic Cryptoendolithic Communities Sampling Three Representative Locations of the Victoria Land
by Claudia Coleine, Nuttapon Pombubpa, Laura Zucconi, Silvano Onofri, Benedetta Turchetti, Pietro Buzzini, Jason E. Stajich and Laura Selbmann
Microorganisms 2020, 8(6), 942; https://doi.org/10.3390/microorganisms8060942 - 23 Jun 2020
Cited by 12 | Viewed by 3665
Abstract
The endolithic niche represents an ultimate refuge to microorganisms in the Mars-like environment of the Antarctic desert. In an era of rapid global change and desertification, the interest in these border ecosystems is increasing due to speculation on how they maintain balance and [...] Read more.
The endolithic niche represents an ultimate refuge to microorganisms in the Mars-like environment of the Antarctic desert. In an era of rapid global change and desertification, the interest in these border ecosystems is increasing due to speculation on how they maintain balance and functionality at the dry limits of life. To assure a reliable estimation of microbial diversity, proper sampling must be planned in order to avoid the necessity of re-sampling as reaching these remote locations is risky and requires tremendous logistical and economical efforts. In this study, we seek to determine the minimum number of samples for uncovering comprehensive bacterial and fungal diversity, comparing communities in strict vicinity to each other. We selected three different locations of the Victoria Land (Continental Antarctica) at different altitudes and showing sandstone outcrops of a diverse nature and origin—Battleship promontory (834 m above sea level (a.s.l.), Southern VL), Trio Nunatak (1,470 m a.s.l., Northern VL) and Mt New Zealand (3,100 m a.s.l., Northern VL). Overall, we found that a wider sampling would be required to capture the whole amplitude of microbial diversity, particularly in Northern VL. We concluded that the inhomogeneity of the rock matrix and the stronger environmental pressure at higher altitudes may force the communities to a higher local diversification. Full article
(This article belongs to the Special Issue Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems)
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16 pages, 6090 KiB  
Article
Investigating Algal Communities in Lacustrine and Hydro-Terrestrial Environments of East Antarctica Using Deep Amplicon Sequencing
by Yuu Hirose, Takuhei Shiozaki, Masahiro Otani, Sakae Kudoh, Satoshi Imura, Toshihiko Eki and Naomi Harada
Microorganisms 2020, 8(4), 497; https://doi.org/10.3390/microorganisms8040497 - 31 Mar 2020
Cited by 7 | Viewed by 5453
Abstract
Antarctica has one of the most extreme environments on Earth, with low temperatures and low nutrient levels. Antarctica’s organisms live primarily in the coastal, ice-free areas which cover approximately 0.18% of the continent’s surface. Members of Cyanobacteria and eukaryotic algae are important primary [...] Read more.
Antarctica has one of the most extreme environments on Earth, with low temperatures and low nutrient levels. Antarctica’s organisms live primarily in the coastal, ice-free areas which cover approximately 0.18% of the continent’s surface. Members of Cyanobacteria and eukaryotic algae are important primary producers in Antarctica since they can synthesize organic compounds from carbon dioxide and water using solar energy. However, community structures of photosynthetic algae in Antarctica have not yet been fully explored at molecular level. In this study, we collected diverse algal samples in lacustrine and hydro-terrestrial environments of Langhovde and Skarvsnes, which are two ice-free regions in East Antarctica. We performed deep amplicon sequencing of both 16S ribosomal ribonucleic acid (rRNA) and 18S rRNA genes, and we explored the distribution of sequence variants (SVs) of these genes at single nucleotide difference resolution. SVs of filamentous Cyanobacteria genera, including Leptolyngbya, Pseudanabaena, Phormidium, Nodosilinea, Geitlerinama, and Tychonema, were identified in most of the samples, whereas Phormidesmis SVs were distributed in fewer samples. We also detected unicellular, multicellular or heterocyst forming Cyanobacteria strains, but in relatively small abundance. For SVs of eukaryotic algae, Chlorophyta, Cryptophyta, and Ochrophyta were widely distributed among the collected samples. In addition, there was a red colored bloom of eukaryotic alga, Geminigera cryophile (Cryptophyta), in the Langhovde coastal area. Eukaryotic SVs of Acutuncus antarcticus and/or Diphascon pingue of Tardigrada were dominant among most of the samples. Our data revealed the detailed structures of the algal communities in Langhovde and Skarvsnes. This will contribute to our understanding of Antarctic ecosystems and support further research into this subject. Full article
(This article belongs to the Special Issue Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems)
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14 pages, 1774 KiB  
Article
Understanding the Response of Nitrifying Communities to Disturbance in the McMurdo Dry Valleys, Antarctica
by Maria Monteiro, Mafalda S. Baptista, Joana Séneca, Luís Torgo, Charles K. Lee, S. Craig Cary and Catarina Magalhães
Microorganisms 2020, 8(3), 404; https://doi.org/10.3390/microorganisms8030404 - 13 Mar 2020
Cited by 12 | Viewed by 3004
Abstract
Polar ecosystems are generally limited in nitrogen (N) nutrients, and the patchy availability of N is partly determined by biological pathways, such as nitrification, which are carried out by distinctive prokaryotic functional groups. The activity and diversity of microorganisms are generally strongly influenced [...] Read more.
Polar ecosystems are generally limited in nitrogen (N) nutrients, and the patchy availability of N is partly determined by biological pathways, such as nitrification, which are carried out by distinctive prokaryotic functional groups. The activity and diversity of microorganisms are generally strongly influenced by environmental conditions. However, we know little of the attributes that control the distribution and activity of specific microbial functional groups, such as nitrifiers, in extreme cold environments and how they may respond to change. To ascertain relationships between soil geochemistry and the ecology of nitrifying microbial communities, we carried out a laboratory-based manipulative experiment to test the selective effect of key geochemical variables on the activity and abundance of ammonia-oxidizing communities in soils from the McMurdo Dry Valleys of Antarctica. We hypothesized that nitrifying communities, adapted to different environmental conditions within the Dry Valleys, will have distinct responses when submitted to similar geochemical disturbances. In order to test this hypothesis, soils from two geographically distant and geochemically divergent locations, Miers and Beacon Valleys, were incubated over 2 months under increased conductivity, ammonia concentration, copper concentration, and organic matter content. Amplicon sequencing of the 16S rRNA gene and transcripts allowed comparison of the response of ammonia-oxidizing Archaea (AOA) and ammonia-oxidizing Bacteria (AOB) to each treatment over time. This approach was combined with measurements of 15NH4+ oxidation rates using 15N isotopic additions. Our results showed a higher potential for nitrification in Miers Valley, where environmental conditions are milder relative to Beacon Valley. AOA exhibited better adaptability to geochemical changes compared to AOB, particularly to the increase in copper and conductivity. AOA were also the only nitrifying group found in Beacon Valley soils. This laboratorial manipulative experiment provided new knowledge on how nitrifying groups respond to changes on key geochemical variables of Antarctic desert soils, and we believe these results offer new insights on the dynamics of N cycling in these ecosystems. Full article
(This article belongs to the Special Issue Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems)
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20 pages, 5787 KiB  
Article
Diversity of Bacterial Biosynthetic Genes in Maritime Antarctica
by Adriana Rego, António G. G. Sousa, João P. Santos, Francisco Pascoal, João Canário, Pedro N. Leão and Catarina Magalhães
Microorganisms 2020, 8(2), 279; https://doi.org/10.3390/microorganisms8020279 - 18 Feb 2020
Cited by 9 | Viewed by 4456
Abstract
Bacterial natural products (NPs) are still a major source of new drug leads. Polyketides (PKs) and non-ribosomal peptides (NRP) are two pharmaceutically important families of NPs and recent studies have revealed Antarctica to harbor endemic polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) [...] Read more.
Bacterial natural products (NPs) are still a major source of new drug leads. Polyketides (PKs) and non-ribosomal peptides (NRP) are two pharmaceutically important families of NPs and recent studies have revealed Antarctica to harbor endemic polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) genes, likely to be involved in the production of novel metabolites. Despite this, the diversity of secondary metabolites genes in Antarctica is still poorly explored. In this study, a computational bioprospection approach was employed to study the diversity and identity of PKS and NRPS genes to one of the most biodiverse areas in maritime Antarctica—Maxwell Bay. Amplicon sequencing of soil samples targeting ketosynthase (KS) and adenylation (AD) domains of PKS and NRPS genes, respectively, revealed abundant and unexplored chemical diversity in this peninsula. About 20% of AD domain sequences were only distantly related to characterized biosynthetic genes. Several PKS and NRPS genes were found to be closely associated to recently described metabolites including those from uncultured and candidate phyla. The combination of new approaches in computational biology and new culture-dependent and -independent strategies is thus critical for the recovery of the potential novel chemistry encoded in Antarctica microorganisms. Full article
(This article belongs to the Special Issue Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems)
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17 pages, 3160 KiB  
Article
Effects of a Simulated Acute Oil Spillage on Bacterial Communities from Arctic and Antarctic Marine Sediments
by Carmen Rizzo, Roberta Malavenda, Berna Gerçe, Maria Papale, Christoph Syldatk, Rudolf Hausmann, Vivia Bruni, Luigi Michaud, Angelina Lo Giudice and Stefano Amalfitano
Microorganisms 2019, 7(12), 632; https://doi.org/10.3390/microorganisms7120632 - 30 Nov 2019
Cited by 25 | Viewed by 3737
Abstract
Background: The bacterial community responses to oil spill events are key elements to predict the fate of hydrocarbon pollution in receiving aquatic environments. In polar systems, cold temperatures and low irradiance levels can limit the effectiveness of contamination removal processes. In this study, [...] Read more.
Background: The bacterial community responses to oil spill events are key elements to predict the fate of hydrocarbon pollution in receiving aquatic environments. In polar systems, cold temperatures and low irradiance levels can limit the effectiveness of contamination removal processes. In this study, the effects of a simulated acute oil spillage on bacterial communities from polar sediments were investigated, by assessing the role of hydrocarbon mixture, incubation time and source bacterial community in selecting oil-degrading bacterial phylotypes. Methods: The bacterial hydrocarbon degradation was evaluated by gas chromatography. Flow cytometric and fingerprinting profiles were used to assess the bacterial community dynamics over the experimental incubation time. Results: Direct responses to the simulated oil spill event were found from both Arctic and Antarctic settings, with recurrent bacterial community traits and diversity profiles, especially in crude oil enrichment. Along with the dominance of Pseudomonas spp., members of the well-known hydrocarbon degraders Granulosicoccus spp. and Cycloclasticus spp. were retrieved from both sediments. Conclusions: Our findings indicated that polar bacterial populations are able to respond to the detrimental effects of simulated hydrocarbon pollution, by developing into a more specialized active oil degrading community. Full article
(This article belongs to the Special Issue Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems)
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15 pages, 3478 KiB  
Article
The Effect of Nitrogen Content on Archaeal Diversity in an Arctic Lake Region
by Jinjiang Lv, Feng Liu, Wenbing Han, Yu Wang, Qian Zhu, Jiaye Zang, Shuang Wang, Botao Zhang and Nengfei Wang
Microorganisms 2019, 7(11), 543; https://doi.org/10.3390/microorganisms7110543 - 08 Nov 2019
Cited by 3 | Viewed by 2460
Abstract
The function of Arctic soil ecosystems is crucially important for the global climate, and nitrogen (N) is the major limiting nutrient in these environments. This study assessed the effects of changes in nitrogen content on archaeal community diversity and composition in the Arctic [...] Read more.
The function of Arctic soil ecosystems is crucially important for the global climate, and nitrogen (N) is the major limiting nutrient in these environments. This study assessed the effects of changes in nitrogen content on archaeal community diversity and composition in the Arctic lake area (London Island, Svalbard). A total of 16S rRNA genes were sequenced to investigate archaeal community composition. First, the soil samples and sediment samples were significantly different for the geochemical properties and archaeal community composition. Thaumarchaeota was an abundant phylum in the nine soil samples. Moreover, Euryarchaeota, Woesearchaeota, and Bathyarchaeota were significantly abundant phyla in the three sediment samples. Second, it was found that the surface runoff caused by the thawing of frozen soil and snow changed the geochemical properties of soils. Then, changes in geochemical properties affected the archaeal community composition in the soils. Moreover, a distance-based redundancy analysis revealed that NH4+–N (p < 0.05) and water content were the most significant factors that correlated with the archaeal community composition. Our study suggests that nitrogen content plays an important role in soil archaeal communities. Moreover, archaea play an important role in the carbon and nitrogen cycle in the Arctic lake area. Full article
(This article belongs to the Special Issue Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems)
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Review

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30 pages, 1706 KiB  
Review
Physiological and Molecular Responses to Main Environmental Stressors of Microalgae and Bacteria in Polar Marine Environments
by Chiara Lauritano, Carmen Rizzo, Angelina Lo Giudice and Maria Saggiomo
Microorganisms 2020, 8(12), 1957; https://doi.org/10.3390/microorganisms8121957 - 09 Dec 2020
Cited by 19 | Viewed by 5484
Abstract
The Arctic and Antarctic regions constitute 14% of the total biosphere. Although they differ in their physiographic characteristics, both are strongly affected by snow and ice cover changes, extreme photoperiods and low temperatures, and are still largely unexplored compared to more accessible sites. [...] Read more.
The Arctic and Antarctic regions constitute 14% of the total biosphere. Although they differ in their physiographic characteristics, both are strongly affected by snow and ice cover changes, extreme photoperiods and low temperatures, and are still largely unexplored compared to more accessible sites. This review focuses on microalgae and bacteria from polar marine environments and, in particular, on their physiological and molecular responses to harsh environmental conditions. The data reported in this manuscript show that exposure to cold, increase in CO2 concentration and salinity, high/low light, and/or combination of stressors induce variations in species abundance and distribution for both polar bacteria and microalgae, as well as changes in growth rate and increase in cryoprotective compounds. The use of -omics techniques also allowed to identify specific gene losses and gains which could have contributed to polar environmental adaptation, and metabolic shifts, especially related to lipid metabolism and defence systems, such as the up-regulation of ice binding proteins, chaperones and antioxidant enzymes. However, this review also provides evidence that -omics resources for polar species are still few and several sequences still have unknown functions, highlighting the need to further explore polar environments, the biology and ecology of the inhabiting bacteria and microalgae, and their interactions. Full article
(This article belongs to the Special Issue Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems)
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17 pages, 647 KiB  
Review
Microbial Nitrogen Cycling in Antarctic Soils
by Max Ortiz, Jason Bosch, Clément Coclet, Jenny Johnson, Pedro Lebre, Adeola Salawu-Rotimi, Surendra Vikram, Thulani Makhalanyane and Don Cowan
Microorganisms 2020, 8(9), 1442; https://doi.org/10.3390/microorganisms8091442 - 21 Sep 2020
Cited by 21 | Viewed by 8136
Abstract
The Antarctic continent is widely considered to be one of the most hostile biological habitats on Earth. Despite extreme environmental conditions, the ice-free areas of the continent, which constitute some 0.44% of the total continental land area, harbour substantial and diverse communities of [...] Read more.
The Antarctic continent is widely considered to be one of the most hostile biological habitats on Earth. Despite extreme environmental conditions, the ice-free areas of the continent, which constitute some 0.44% of the total continental land area, harbour substantial and diverse communities of macro-organisms and especially microorganisms, particularly in the more “hospitable” maritime regions. In the more extreme non-maritime regions, exemplified by the McMurdo Dry Valleys of South Victoria Land, nutrient cycling and ecosystem servicing processes in soils are largely driven by microbial communities. Nitrogen turnover is a cornerstone of ecosystem servicing. In Antarctic continental soils, specifically those lacking macrophytes, cold-active free-living diazotrophic microorganisms, particularly Cyanobacteria, are keystone taxa. The diazotrophs are complemented by heterotrophic bacterial and archaeal taxa which show the genetic capacity to perform elements of the entire N cycle, including nitrification processes such as the anammox reaction. Here, we review the current literature on nitrogen cycling genes, taxa, processes and rates from studies of Antarctic soils. In particular, we highlight the current gaps in our knowledge of the scale and contribution of these processes in south polar soils as critical data to underpin viable predictions of how such processes may alter under the impacts of future climate change. Full article
(This article belongs to the Special Issue Polar Microbial Ecology: The Role of Microbes in the Functioning of Extremely Cold Ecosystems)
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