Methanogens, single-celled organisms that produce methane, are ideal candidates for studying temperature adaptation. Researchers from the Earth-Life Science Institute (ELSI) at Tokyo Institute of Technology analysed methanogenic genomes to understand how microorganisms adapt to varying temperatures. The findings could provide clues to the traits and functions present in the earliest microbes, and even shed light on whether microbial life originated in hot or cold environments. Interestingly, the study revealed that the first methanogens may have been similar to present-day organisms. Genome size was found to be more reliant on temperature than evolutionary history, with thermotolerant organisms having smaller, more evolutionarily “ancient” genomes than psychrotolerant organisms. Amino acid composition also varied among temperature groups, with thermotolerant methanogens having more charged amino acids and functional genes for ion transport, and psychrotolerants enriched in uncharged amino acids and proteins related to cellular structure and motility. These findings suggest that temperature adaptation is a gradual process occurring in fine steps rather than requiring large-scale changes.
The Genetics of Temperature Adaptation: Understanding Life’s Resilience to Extreme Conditions
Life on Earth has persisted despite extreme atmospheric conditions, chemical environments, and temperatures. From the time when Earth was too hot to support water, life has found a way to thrive. Today, life exists almost everywhere on the planet, demonstrating remarkable adaptability to changing environments. Among the many adaptations that enable this resilience, the ability to adjust to varying temperatures stands out. All life depends on chemical reactions, which are sensitive to temperature changes. Nevertheless, life can exist across a wide range of temperatures, from Antarctica to submarine volcanoes. So, how does life adapt to different temperatures?
Recently, a team of researchers led by Paula Prondzinsky and Shawn Erin McGlynn of the Earth-Life Science Institute (ELSI) at the Tokyo Institute of Technology has attempted to answer this question by studying a group of microorganisms called methanogens. Methanogens are single-celled organisms that produce methane and belong to a larger group called “Archaea.” They thrive in extreme temperatures ranging from -2.5 oC to 122 oC and are ideal candidates for studying temperature adaptation.
The researchers analysed and compared the genomes of different species of methanogens and divided them into three groups based on the temperatures they thrived in. These groups were thermotolerant (high temperatures), psychrotolerant (low temperatures), and mesophilic (ambient temperatures). The team then constructed a database of 255 genomes and protein sequences from the Genome Taxonomy Database and linked them to the growth temperature of 86 methanogens from laboratory collections using the Database of Growth TEMPeratures of Usual and Rare Prokaryotes.
This database helps us understand how life adapts to different temperatures. By examining the genomes of the three groups of methanogens, the researchers discovered genes that play a crucial role in temperature adaptation. For instance, thermotolerant methanogens have more genes involved in the stabilization of enzymes at high temperatures, while psychrotolerant methanogens have genes that code for enzymes that can function optimally at low temperatures. The mesophilic methanogens, which live in ambient temperatures, have a higher number of genes that regulate cell membranes and transporters, suggesting that these genes help them survive in fluctuating temperatures.
In conclusion, this study of methanogens has provided a better understanding of how life adapts to varying temperatures. By analysing and comparing genomes, the researchers have identified genes that help microorganisms thrive in extreme conditions. As scientists continue to study the genetics of temperature adaptation, we can gain insight into how life adapts to changing environments and how it may continue to do so in the future.
The Methanogenic Genome: How it Adapts to Temperature
Methanogens are single-celled organisms that produce methane and belong to a larger group called Archaea. They thrive in extreme temperatures ranging from -2.5 oC to 122 oC and are ideal candidates for studying temperature adaptation. In a recent study, researchers led by Paula Prondzinsky and Shawn Erin McGlynn of the Earth-Life Science Institute (ELSI) at the Tokyo Institute of Technology analysed the methanogenic genome to understand how these microorganisms adapt to varying temperatures.
Orthogroups: Shared and Unique Genes
The researchers used a software called OrthoFinder to establish different orthogroups—sets of genes descended from a single gene present in the last common ancestor of the species under consideration. They then segregated these orthogroups into core, shared, and unique categories. Their analyses revealed that about one third of the methanogenic genome is shared across all species. They also found that the amount of shared genes between species decreases with increasing evolutionary distance.
Genome Size and Evolution
Interestingly, the researchers found that thermotolerant organisms had smaller genomes and a higher fraction of core genome. These small genomes were also found to be more evolutionarily “ancient” than the genomes of psychrotolerant organisms. Since thermotolerant organisms were found in multiple groups, these findings indicate that the size of the genome is more reliant on temperature than on evolutionary history. They also suggest that as methanogen genomes evolved, they grew rather than shrank, which challenges the idea of “thermoreductive genome evolution,” i.e., that organisms remove genes from their genomes as they evolve into higher temperature locations.
Composition of Amino Acids
The researchers’ analyses showed that methanogens grow across this wide range of temperatures without many special proteins. They found that specific amino acids were enriched in particular temperature groups. They also found compositional differences in the amino acids pertaining to their proteome charge, polarity, and unfolding entropy—all of which affect protein structure and its ability to function. In general, they found that thermotolerant methanogens have more charged amino acids and functional genes for ion transport, which are not present in psychrotolerants. Whereas psychrotolerants organisms are enriched in uncharged amino acids and proteins related to cellular structure and motility. However, the researchers could not pinpoint specific functions shared by all members of a temperature group, suggesting that temperature adaptation is a gradual process which occurs in fine steps rather than requiring large scale changes.
In conclusion, the study of methanogenic genomes provides insight into how microorganisms adapt to varying temperatures. The researchers found that shared genes between species decrease with increasing evolutionary distance, thermotolerant organisms have smaller genomes, and the composition of amino acids affects the organism’s ability to function at different temperatures. These findings challenge previous assumptions about thermoreductive genome evolution and suggest that temperature adaptation is a gradual process.
Methanogens as Key to Understanding the Origins of Life
A recent study by researchers from the Earth-Life Science Institute (ELSI) at Tokyo Institute of Technology sheds light on how the very first methanogens, which evolved when Earth was hostile to life, may have been similar to present-day microorganisms. The study examined methanogenic genomes to understand how microorganisms adapt to varying temperatures. The findings could provide clues to the traits and functions present in the earliest microbes, and even shed light on whether microbial life originated in hot or cold environments.
Methanogens: A Vital Link to Understanding the Origins of Life
Methanogens are single-celled organisms that produce methane and belong to a larger group called Archaea. They thrive in extreme temperatures ranging from -2.5 oC to 122 oC and are ideal candidates for studying temperature adaptation. According to Paula Prondzinsky, a researcher at ELSI, the study indicates that the first methanogens may have been similar to the organisms found on present-day Earth. This implies that methanogens could be a vital link to understanding the origins of life.
Orthogroups: Shared and Unique Genes
The researchers used a software called OrthoFinder to establish different orthogroups—sets of genes descended from a single gene present in the last common ancestor of the species under consideration. They then segregated these orthogroups into core, shared, and unique categories. Their analyses revealed that about one third of the methanogenic genome is shared across all species. They also found that the amount of shared genes between species decreases with increasing evolutionary distance.
Genome Size and Evolution
Interestingly, the researchers found that thermotolerant organisms had smaller genomes and a higher fraction of core genome. These small genomes were also found to be more evolutionarily “ancient” than the genomes of psychrotolerant organisms. Since thermotolerant organisms were found in multiple groups, these findings indicate that the size of the genome is more reliant on temperature than on evolutionary history. They also suggest that as methanogen genomes evolved, they grew rather than shrank, which challenges the idea of “thermoreductive genome evolution,” i.e., that organisms remove genes from their genomes as they evolve into higher temperature locations.
Composition of Amino Acids
The researchers’ analyses showed that methanogens grow across this wide range of temperatures without many special proteins. They found that specific amino acids were enriched in particular temperature groups. They also found compositional differences in the amino acids pertaining to their proteome charge, polarity, and unfolding entropy—all of which affect protein structure and its ability to function. In general, they found that thermotolerant methanogens have more charged amino acids and functional genes for ion transport, which are not present in psychrotolerants. Whereas psychrotolerants organisms are enriched in uncharged amino acids and proteins related to cellular structure and motility. However, the researchers could not pinpoint specific functions shared by all members of a temperature group, suggesting that temperature adaptation is a gradual process which occurs in fine steps rather than requiring large scale changes.
Tokyo Institute of Technology is at the forefront of research and higher education, hosting over 10,000 undergraduate and graduate students per year. It embodies the Japanese philosophy of “monotsukuri,” meaning “technical ingenuity and innovation,” and strives to contribute to society through high-impact research. The Earth-Life Science Institute (ELSI) at Tokyo Tech is one of Japan’s ambitious World Premiere International research centers, whose aim is to address the origin and co-evolution of the Earth and life. The World Premier International Research Center Initiative (WPI) promotes high research standards and outstanding research environments that attract frontline researchers from around the world. These centers are highly autonomous
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