4.5 Deeply Branching Bacteria
3 min read•june 18, 2024
are ancient microbes that offer a glimpse into Earth's early life. These organisms diverged from the last universal common ancestor long ago, adapting to extreme environments like and deep-sea vents.
These bacteria have unique traits that help them thrive in harsh conditions. They've developed heat-stable enzymes, acid-resistant cell walls, and efficient nutrient uptake systems. Studying their genomes and metabolic abilities sheds light on how life evolved and diversified over billions of years.
Evolutionary Significance and Adaptations of Deeply Branching Bacteria
Evolutionary significance of deeply branching bacteria
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- earliest lineages to diverge from ###last_universal_common_ancestor_()_0###
- LUCA hypothetical most recent common ancestor of all current life on Earth
- Deeply branching bacteria provide insights into characteristics and environment of early life forms (Archaea, Bacteria)
- Comparative analysis of deeply branching bacterial genomes helps infer minimal gene set and metabolic capabilities of LUCA
- Presence of deeply branching bacteria in extreme environments suggests LUCA may have inhabited similar conditions (, hot springs)
- Indicates early life on Earth likely evolved in high-temperature, , and nutrient-limited settings
- Study of deeply branching bacteria contributes to understanding the structure of the of life
Adaptations to extreme environments
- adaptations
- Heat-stable enzymes and proteins maintain function at high temperatures (90-100℃)
- Increased membrane stability through unique lipid composition (ether-linked lipids)
- Enhanced DNA repair mechanisms counteract thermal damage
- adaptations
- Highly efficient proton pumps maintain intracellular pH homeostasis
- Specialized cell wall structure withstands acidic conditions (pH < 3)
- Upregulation of stress response genes and chaperone proteins
- Anaerobic adaptations
- Utilization of alternative terminal electron acceptors for respiration (sulfur, nitrate)
- Presence of oxygen-sensitive enzymes and metabolic pathways (nitrogenase, hydrogenase)
- Specialized cofactors and redox proteins for fermentative metabolism (ferredoxin, rubredoxin)
- Adaptations to nutrient limitation
- High-affinity nutrient uptake systems for scavenging scarce resources
- Metabolic versatility to utilize wide range of substrates (H2, CO2, organic acids)
- Increased surface area-to-volume ratio for efficient nutrient acquisition (filamentous morphology)
Extremophiles and their adaptations
- : organisms thriving in extremely hot environments (>80°C)
- : microorganisms adapted to high-pressure environments, such as deep-sea habitats
- Some deeply branching bacteria use as their primary mode of energy production
Metabolic strategies of bacterial genera
- ()
- metabolism using hydrogen or reduced sulfur compounds as energy sources
- Carbon fixation through reductive tricarboxylic acid (rTCA) cycle
- Oxygen or nitrate as terminal electron acceptors
- ()
- Fermentative metabolism of sugars and peptides
- Hydrogen production through oxidation of reduced ferredoxin
- Sulfur reduction in some species
- ()
- Anaerobic sulfate reduction coupled with hydrogen oxidation
- Autotrophic carbon fixation through acetyl-CoA pathway
- ()
- Aerobic heterotrophic metabolism
- Utilization of organic compounds as carbon and energy sources (amino acids, sugars)
- Some species capable of anaerobic respiration using nitrate or metals as electron acceptors
- Chloroflexi (Chloroflexus)
- Anoxygenic phototrophy using type II photosynthetic reaction centers
- Carbon fixation through 3-hydroxypropionate bi-cycle
- Mixotrophic growth on organic compounds in absence of light (acetate, pyruvate)
- Some species exhibit , contributing to their metabolic diversity
Key Terms to Review (31)
Acetothermus: Acetothermus is a genus of thermophilic, anaerobic bacteria that thrive in high-temperature environments. These bacteria are known for their unique metabolic processes involving acetate as a primary substrate.
Acetothermus paucivorans: Acetothermus paucivorans is a species of thermophilic, anaerobic bacterium that thrives in high-temperature environments. It is part of the deeply branching bacteria group, known for its evolutionary significance and unique metabolic pathways.
Acidophilic: Acidophilic refers to organisms that thrive in highly acidic environments, typically with a pH range between 0 and 5. These organisms have evolved specialized mechanisms to survive and grow in conditions that would be lethal to most other life forms.
Anaerobic: Anaerobic refers to the absence of oxygen and the processes that occur in the absence of oxygen. It is a key term in the context of 4.5 Deeply Branching Bacteria, as these ancient microorganisms often thrive in anaerobic environments.
Aquifex: Aquifex is a genus of bacteria that are hyperthermophilic and chemolithoautotrophic, thriving in extreme environments such as hot springs and hydrothermal vents. They are among the deepest-branching bacteria, offering insights into early life on Earth.
Aquificae: Aquificae is a phylum of bacteria known for being hyperthermophilic and deeply branching, meaning they are among the earliest forms of life. They thrive in extreme environments such as hot springs and hydrothermal vents.
Barophiles: Barophiles are organisms that thrive in high-pressure environments, such as the deep ocean. These microbes have adaptations that allow them to survive and grow under the immense pressure found in the depths of the ocean.
Chemolithoautotrophic: Chemolithoautotrophs are a type of organism that obtain their energy through the oxidation of inorganic chemical compounds, such as hydrogen, sulfur, or iron, and use carbon dioxide as their sole source of carbon for biosynthesis. This metabolic strategy is a key feature of deeply branching bacteria, which are some of the earliest life forms on Earth.
Chemosynthesis: Chemosynthesis is a process by which certain organisms use inorganic chemical reactions to obtain energy for the synthesis of organic compounds, similar to the way plants use photosynthesis to convert sunlight into usable energy. This process is particularly important for deeply branching bacteria that thrive in environments without access to sunlight.
Conan the Bacterium: Conan the Bacterium, scientifically known as Deinococcus radiodurans, is an extremophilic bacterium renowned for its extraordinary resistance to radiation and other environmental stresses. It is a model organism for studying DNA repair mechanisms and microbial survival in extreme conditions.
Deeply branching bacteria: Deeply branching bacteria are a group of bacteria that occupy the earliest branches of the phylogenetic tree. They thrive in extreme environments and provide insights into early life on Earth.
Deeply Branching Bacteria: Deeply Branching Bacteria, also known as the Deeply Rooted Bacteria, are a group of prokaryotes that occupy some of the earliest and most primitive branches on the tree of life. These bacteria exhibit unique evolutionary characteristics that provide insights into the origins and early diversification of life on Earth.
Deinococcus radiodurans: Deinococcus radiodurans is an extremophilic bacterium known for its extraordinary resistance to ionizing radiation and other environmental stresses. It is often called the world's toughest bacterium due to its ability to survive extreme conditions.
Deinococcus-Thermus: Deinococcus-Thermus is a deeply branching bacterial phylum known for its members' remarkable resistance to environmental stressors such as radiation, desiccation, and extreme temperatures. This phylum represents one of the earliest diverging lineages of bacteria, providing insights into the evolution and adaptation of life on Earth.
Extremophiles: Extremophiles are microorganisms that thrive in environmental conditions considered extreme, such as high or low temperatures, high pressure, high salinity, or high acidity. These hardy organisms have evolved unique adaptations that allow them to survive and even flourish in settings that would be lethal to most other forms of life.
Horizontal Gene Transfer: Horizontal gene transfer (HGT) is the transfer of genetic material between organisms other than via reproduction. It is a key process that allows the rapid spread of traits, such as antibiotic resistance, across different species of prokaryotes, and is an important mechanism driving evolution and adaptation in microbial communities.
Hot Springs: Hot springs are natural springs that produce water at temperatures significantly higher than the surrounding environment. They are often found in areas with geothermal activity, where heat from the Earth's interior is brought to the surface, resulting in the release of hot water or steam. Hot springs are particularly relevant in the context of deeply branching bacteria, as they provide a unique and extreme environment that supports the growth of specialized microbial communities.
Hydrothermal Vents: Hydrothermal vents are underwater geological features formed by the escape of superheated, mineral-rich water from the Earth's crust. They are found in areas of active seafloor spreading and are important in the context of deeply branching bacteria, as they provide a unique and extreme environment for the evolution of some of the most primitive life forms on the planet.
Hyperthermophiles: Hyperthermophiles are microorganisms that thrive in extremely high temperatures, typically above 80°C (176°F). They are often found in environments such as hot springs and hydrothermal vents.
Hyperthermophiles: Hyperthermophiles are a group of microorganisms that thrive in extremely hot environments, typically at temperatures above 80°C (176°F). These organisms possess unique adaptations that allow them to survive and grow in such extreme conditions, making them a fascinating subject of study in the fields of microbiology, extremophile biology, and evolutionary biology.
Hyperthermophiles are found in various environments, including deep-sea hydrothermal vents, hot springs, and geothermal areas, and they play a crucial role in the understanding of the origins of life and the limits of life on Earth. Their study is particularly relevant to the topics of 3.3 Unique Characteristics of Prokaryotic Cells, 4.5 Deeply Branching Bacteria, 4.6 Archaea, and 9.4 Temperature and Microbial Growth.
Last universal common ancestor (LUCA): The Last Universal Common Ancestor (LUCA) is the most recent common ancestor of all current life on Earth, estimated to have lived around 3.5 to 3.8 billion years ago. It represents a key node in the tree of life from which all prokaryotic and eukaryotic organisms diverged.
LUCA: LUCA stands for Last Universal Common Ancestor, the most recent population of organisms from which all organisms now living on Earth have a common descent. LUCA is not a specific organism but rather a concept used to trace the evolutionary history of life.
Phylogenetic tree: A phylogenetic tree is a diagram that represents the evolutionary relationships among various biological species based on their genetic characteristics. It helps in understanding how different species, including deeply branching bacteria, are related through common ancestors.
Phylogenetic Tree: A phylogenetic tree is a diagram that depicts the evolutionary relationships and ancestry of different species or organisms. It is a visual representation of the hypothesized evolutionary history and the degree of relatedness between various life forms based on their shared characteristics and genetic similarities.
Thermodesulfobacteria: Thermodesulfobacteria are a class of deeply branching bacteria that are known for their ability to reduce sulfate and other sulfur compounds for energy production, often in high-temperature environments.
Thermodesulfobacterium: Thermodesulfobacterium is a genus of thermophilic, anaerobic, sulfate-reducing bacteria that are considered to be deeply branching members of the bacterial domain, representing one of the earliest evolutionary lineages.
Thermophilic: Thermophilic refers to organisms that thrive in high-temperature environments, typically with optimal growth temperatures between 45°C and 80°C. These organisms are adapted to survive and function in conditions that would be lethal for most other life forms.
Thermotoga: Thermotoga is a genus of hyperthermophilic bacteria characterized by their unique outer membrane structure, resembling a toga. These bacteria thrive in extremely high-temperature environments, such as hydrothermal vents.
Thermotogae: Thermotogae are a phylum of hyperthermophilic bacteria characterized by their unique toga-like outer membrane. These bacteria are known for thriving in extremely hot environments such as hydrothermal vents.
Thermus: Thermus is a genus of deeply branching bacteria known for their ability to thrive in extremely hot environments. These thermophilic bacteria are considered to be among the most primitive and ancient forms of life on Earth, providing valuable insights into the origins and evolution of life.
Toga: The Toga phylum comprises a group of deeply branching bacteria characterized by their ancient evolutionary lineage and unique metabolic pathways. They are known for their ability to thrive in extreme environments.