Bacterial Diversity in Polar Habitats

Kirby, Bronwyn M.; Easton, Samantha; Tuffin, I. Marla; Cowan, Don A.

doi:10.1128/9781555817183.ch1

Cited by 5 publications

(6 citation statements)

References 128 publications

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“…High cell densities are also present in the Antarctic with figures of 5.4 to 7.9 × 10 7 cells per g of lake sediment [ 4 ], whereas in free waters, at Terra Nova Bay (Ross Sea) for example, cell counts vary from 0.1 to 15.7 × 10 5 cells mL −1 [ 5 ]. These cell densities, both in the Arctic and Antarctic oceans, are similar to those recorded in temperate habitats and correspond to microbial diversities much greater than those initially expected [ 6 ]. Such data testify to successful adaptations of microbial communities to extremely cold environments.…”

Section: Introductionsupporting

confidence: 78%

Psychrophily and Catalysis

Gerday

2013

Biology

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Polar and other low temperature environments are characterized by a low content in energy and this factor has a strong incidence on living organisms which populate these rather common habitats. Indeed, low temperatures have a negative effect on ectothermic populations since they can affect their growth, reaction rates of biochemical reactions, membrane permeability, diffusion rates, action potentials, protein folding, nucleic acids dynamics and other temperature-dependent biochemical processes. Since the discovery that these ecosystems, contrary to what was initially expected, sustain a rather high density and broad diversity of living organisms, increasing efforts have been dedicated to the understanding of the molecular mechanisms involved in their successful adaptation to apparently unfavorable physical conditions. The first question that comes to mind is: How do these organisms compensate for the exponential decrease of reaction rate when temperature is lowered? As most of the chemical reactions that occur in living organisms are catalyzed by enzymes, the kinetic and thermodynamic properties of cold-adapted enzymes have been investigated. Presently, many crystallographic structures of these enzymes have been elucidated and allowed for a rather clear view of their adaptation to cold. They are characterized by a high specific activity at low and moderate temperatures and a rather low thermal stability, which induces a high flexibility that prevents the freezing effect of low temperatures on structure dynamics. These enzymes also display a low activation enthalpy that renders them less dependent on temperature fluctuations. This is accompanied by a larger negative value of the activation entropy, thus giving evidence of a more disordered ground state. Appropriate folding kinetics is apparently secured through a large expression of trigger factors and peptidyl–prolyl cis/trans-isomerases.

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Section: Introductionsupporting

confidence: 78%

Psychrophily and Catalysis

Gerday

2013

Biology

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“…Nonetheless, we observed a very strong signal of homogeneous selection. As Antarctica is the coldest continent (Kirby et al, 2014), the extremely low temperature could be imposing strong homogeneous selection in this system, preventing community phylogenetic divergence despite the heterogeneous landscape of the CPWC. Furthermore, temperature preference is a trait shallowly conserved (Martiny et al, 2015), and could be influencing community assembly processes at the finer phylogenetic resolution of ASVs.…”

Section: Environmental Variables Related To Selection Processesmentioning

confidence: 99%

The ecological assembly of bacterial communities in Antarctic wetlands varies across levels of phylogenetic resolution

Quiroga

Valverde

Mataloni

et al. 2022

Environmental Microbiology

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Summary As functional traits are conserved at different phylogenetic depths, the ability to detect community assembly processes can be conditional on the phylogenetic resolution; yet most previous work quantifying their influence has focused on a single level of phylogenetic resolution. Here, we have studied the ecological assembly of bacterial communities from an Antarctic wetland complex, applying null models across different levels of phylogenetic resolution (i.e. clustering ASVs into OTUs with decreasing sequence identity thresholds). We found that the relative influence of the community assembly processes varies with phylogenetic resolution. More specifically, selection processes seem to impose stronger influence at finer (100% sequence similarity ASV) than at coarser (99%–97% sequence similarity OTUs) resolution. We identified environmental features related with the ecological processes and propose a conceptual model for the bacterial community assembly in this Antarctic ecosystem. Briefly, eco‐evolutionary processes appear to be leading to different but very closely related ASVs in lotic, lentic and terrestrial environments. In all, this study shows that assessing community assembly processes at different phylogenetic resolutions is key to improve our understanding of microbial ecology. More importantly, a failure to detect selection processes at coarser phylogenetic resolution does not imply the absence of such processes at finer resolutions.

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“…Most of the earth's ecosystems exist in permanently cold environments, including subzero environments, where the mean temperature never rises above 158C (Kirby et al, 2012). The discovery of living, growing communities of microbes in polar habitats has raised numerous questions with regards to how microbes grow and survive at cold temperatures.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of subzero growth in the cryophile Planococcus halocryophilus determined through proteomic analysis

Raymond-Bouchard

Chourey

Altshuler

et al. 2017

Environmental Microbiology

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The eurypsychrophilic bacterium Planococcus halocryophilus is capable of growth down to -15°C, making it ideal for studying adaptations to subzero growth. To increase our understanding of the mechanisms and pathways important for subzero growth, we performed proteomics on P. halocryophilus grown at 23°C, 23°C with 12% w/v NaCl and -10°C with 12% w/v NaCl. Many proteins with increased abundances at -10°C versus 23°C also increased at 23C-salt versus 23°C, indicating a closely tied relationship between salt and cold stress adaptation. Processes which displayed the largest changes in protein abundance were peptidoglycan and fatty acid (FA) synthesis, translation processes, methylglyoxal metabolism, DNA repair and recombination, and protein and nucleotide turnover. We identified intriguing targets for further research at -10°C, including PlsX and KASII (FA metabolism), DD-transpeptidase and MurB (peptidoglycan synthesis), glyoxalase family proteins (reactive electrophile response) and ribosome modifying enzymes (translation turnover). PemK/MazF may have a crucial role in translational reprogramming under cold conditions. At -10°C P. halocryophilus induces stress responses, uses resources efficiently, and carefully controls its growth and metabolism to maximize subzero survival. The present study identifies several mechanisms involved in subzero growth and enhances our understanding of cold adaptation.

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Bacterial Diversity in Polar Habitats

Cited by 5 publications

References 128 publications

Psychrophily and Catalysis

Psychrophily and Catalysis

The ecological assembly of bacterial communities in Antarctic wetlands varies across levels of phylogenetic resolution

Mechanisms of subzero growth in the cryophile Planococcus halocryophilus determined through proteomic analysis

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