MutT from the fish pathogen Aliivibrio salmonicida is a cold-active nucleotide-pool sanitization enzyme with unexpectedly high thermostability

Distinct gut microbial communities and functional predictions in divergent ophiuroid species: host differentiation, ecological niches, and adaptation to cold-water habitats

IMPORTANCE

Gastrointestinal microorganisms are critical to the survival and adaptation of hosts, and there are few studies on the differences and functions of gastrointestinal microbes in widely distributed species. This study investigated the gut microbes of two ophiuroid species (Ophiura sarsii and its subspecies O. sarsii vadicola) in cold-water habitats of the Northern Pacific Ocean. The results showed that a combination of host and environmental factors shapes the intestinal microbiota of ophiuroids. There was a high similarity in microbial communities between the two groups living in different regions, which may be related to their similar ecological niches. These microorganisms played a vital role in the ecological success of ophiuroids as the foundation for their adaptation to cold-water environments. This study revealed the complex relationship between hosts and their gut microbes, providing insights into the role they play in the adaptation and survival of marine species.

Eurypsychrophilic acidophiles: From (meta)genomes to low-temperature biotechnologies

Low temperature and acidic environments encompass natural milieus such as acid rock drainage in Antarctica and anthropogenic sites including drained sulfidic sediments in Scandinavia. The microorganisms inhabiting these environments include polyextremophiles that are both extreme acidophiles (defined as having an optimum growth pH < 3), and eurypsychrophiles that grow at low temperatures down to approximately 4°C but have an optimum temperature for growth above 15°C. Eurypsychrophilic acidophiles have important roles in natural biogeochemical cycling on earth and potentially on other planetary bodies and moons along with biotechnological applications in, for instance, low-temperature metal dissolution from metal sulfides. Five low-temperature acidophiles are characterized, namely, Acidithiobacillus ferriphilus, Acidithiobacillus ferrivorans, Acidithiobacillus ferrooxidans, “Ferrovum myxofaciens,” and Alicyclobacillus disulfidooxidans, and their characteristics are reviewed. Our understanding of characterized and environmental eurypsychrophilic acidophiles has been accelerated by the application of “omics” techniques that have aided in revealing adaptations to low pH and temperature that can be synergistic, while other adaptations are potentially antagonistic. The lack of known acidophiles that exclusively grow below 15°C may be due to the antagonistic nature of adaptations in this polyextremophile. In conclusion, this review summarizes the knowledge of eurypsychrophilic acidophiles and places the information in evolutionary, environmental, biotechnological, and exobiology perspectives.

Active site architecture of an acetyl xylan esterase indicates a novel cold adaptation strategy

SGNH-type acetyl xylan esterases (AcXEs) play important roles in marine and terrestrial xylan degradation, which are necessary for removing acetyl side groups from xylan. However, only a few cold-adapted AcXEs have been reported, and the underlying mechanisms for their cold adaptation are still unknown because of the lack of structural information. Here, a cold-adapted AcXE, AlAXEase, from the Arctic marine bacterium Arcticibacterium luteifluviistationis SM1504^T was characterized. AlAXEase could deacetylate xylooligosaccharides and xylan, which, together with its homologs, indicates a novel SGNH-type carbohydrate esterase family. AlAXEase showed the highest activity at 30 °C and retained over 70% activity at 0 °C but had unusual thermostability with a T_m value of 56 °C. To explain the cold adaption mechanism of AlAXEase, we next solved its crystal structure. AlAXEase has similar noncovalent stabilizing interactions to its mesophilic counterpart at the monomer level and forms stable tetramers in solutions, which may explain its high thermostability. However, a long loop containing the catalytic residues Asp200 and His203 in AlAXEase was found to be flexible because of the reduced stabilizing hydrophobic interactions and increased destabilizing asparagine and lysine residues, leading to a highly flexible active site. Structural and enzyme kinetic analyses combined with molecular dynamics simulations at different temperatures revealed that the flexible catalytic loop contributes to the cold adaptation of AlAXEase by modulating the distance between the catalytic His203 in this loop and the nucleophilic Ser32. This study reveals a new cold adaption strategy adopted by the thermostable AlAXEase, shedding light on the cold adaption mechanisms of AcXEs.

Cold survival strategies for bacteria, recent advancement and potential industrial applications

Microorganisms have evolved themselves to thrive under various extreme environmental conditions such as extremely high or low temperature, alkalinity, and salinity. These microorganisms adapted several metabolic processes to survive and reproduce efficiently under such extreme environments. As the major proportion of earth is covered with the cold environment and is exploited by human beings, these sites are not pristine anymore. Human interventions are a great reason for disturbing the natural biogeochemical cycles in these regions. The survival strategies of these organisms have shown great potential for helping us to restore these pristine sites and the use of isolated cold-adapted enzymes from these organisms has also revolutionized various industrial products. This review gives you the insight of psychrophilic enzyme adaptations and their industrial applications.

Gene analysis and structure prediction for the cold-adaption mechanism of trypsin from the krill Euphausia superba (Dana, 1852)

BACKGROUND

The ability of Antarctic krill, Euphausia superba (Dana, 1852), to thrive in a cold environment comes from its capacity to synthesize cold-adapted enzymes. Its trypsin, as a main substance in the metabolic reactions, plays a key role in the adaption to low temperatures. However, the progress of research on its cold-adaption mechanism is being influenced due to the limited information on its gene and spatial structure.

RESULTS

We studied the gene of E. superba trypsin with transcriptome sequencing first, and then discussed its cold-adaption mechanism with the full gene and predicted structure basing on bioinformatics. The results showed the proportion of certain residues played important roles in the cold-adaptation behavior for trypsin. Furthermore, a higher proportion of random coils and reduced steric hindrance might also be key factors promoting its cold adaption.

CONCLUSION

This research aimed to reveal the cold-adaption mechanism of E. superba trypsin and provide support for basic research on molecular modification by site-directed mutagenesis of complementary DNA used to produce new and improved recombinant variants with cold adaption. Furthermore, it may broaden its commercial application on minimizing undesirable changes elevated at higher temperature in food processing and in treatment of trauma and inflammation in medicine. © 2017 Society of Chemical Industry.

Discovery, Molecular Mechanisms, and Industrial Applications of Cold-Active Enzymes

Cold-active enzymes constitute an attractive resource for biotechnological applications. Their high catalytic activity at temperatures below 25°C makes them excellent biocatalysts that eliminate the need of heating processes hampering the quality, sustainability, and cost-effectiveness of industrial production. Here we provide a review of the isolation and characterization of novel cold-active enzymes from microorganisms inhabiting different environments, including a revision of the latest techniques that have been used for accomplishing these paramount tasks. We address the progress made in the overexpression and purification of cold-adapted enzymes, the evolutionary and molecular basis of their high activity at low temperatures and the experimental and computational techniques used for their identification, along with protein engineering endeavors based on these observations to improve some of the properties of cold-adapted enzymes to better suit specific applications. We finally focus on examples of the evaluation of their potential use as biocatalysts under conditions that reproduce the challenges imposed by the use of solvents and additives in industrial processes and of the successful use of cold-adapted enzymes in biotechnological and industrial applications.