Question

What major physiological property unites species of Thermotoga, Aquifex, and Thermocrinis? (Sections 15.18, 15.19)

Short answer

All three genera—Thermotoga, Aquifex, and Thermocrinis—are thermophilic, meaning they thrive at high temperatures.

Step-by-step solution

- Understand the Specifics

Review Sections 15.18 and 15.19 in the textbook to understand the defining characteristics of Thermotoga, Aquifex, and Thermocrinis species. Take notes on their physiological traits.

- Identify Shared Properties

Compare thermophilic properties and environmental adaptations listed for each genus. Focus on traits they share, particularly those related to their physiological responses to high temperatures.

- Consolidate Findings

Summarize the common physiological property that all these species share based on the previous sections reviewed and notes taken.

Key concepts

Thermotoga

Thermotoga is a genus of thermophilic bacteria, meaning it thrives in high-temperature environments. These bacteria are notable for their unique outer membrane, which forms a sheath-like structure known as a ‘toga’. This toga is one of the reasons they are well-suited to hot environments.
They can be found in extreme conditions such as deep-sea hydrothermal vents and geothermal springs.
One of the key features of Thermotoga is its ability to perform anaerobic respiration, meaning it does not require oxygen to survive. Instead, it uses other molecules like sulfate, nitrate, or even hydrogen.

• Thermotoga maritima, a well-studied species, grows optimally at around 80°C, showcasing its impressive heat tolerance.

Moreover, Thermotoga species play a role in our understanding of early life on Earth due to their primitive metabolic and genetic traits.

Aquifex

Aquifex is another genus of thermophilic bacteria. Like Thermotoga, Aquifex species thrive in extremely high temperatures, often found in environments like hot springs and hydrothermal vents.
These bacteria are chemolithoautotrophs, meaning they obtain energy by oxidizing inorganic substances, such as hydrogen, and use carbon dioxide as their carbon source.

• Aquifex aeolicus is a well-known species that grows optimally at around 85°C.

Unlike Thermotoga, Aquifex species are more oxygen-tolerant and can perform oxygenic respiration. However, they prefer microaerophilic conditions, where oxygen levels are low.
Due to their ancient lineage, Aquifex bacteria provide key insights into the evolutionary processes of early bacterial life.

Thermocrinis

Thermocrinis is a genus of thermophilic bacteria similar to Thermotoga and Aquifex. Thermocrinis species are typically found in neutral to slightly alkaline hot springs.
These bacteria thrive at temperatures around 82°C, showing optimal growth at these extreme conditions. They form large filamentous structures, sometimes creating visible streamers in hot springs.

• Thermocrinis albus is an example of a species adapted to high temperatures.

Thermocrinis bacteria are known for their role in biogeochemical cycles, contributing to nutrient cycling in extreme environments. Their ability to adapt to hot and chemically diverse environments makes them subjects of interest for studying life's resilience and adaptability.

High-temperature adaptations

Thermophilic microorganisms like Thermotoga, Aquifex, and Thermocrinis have evolved several high-temperature adaptations, enabling them to survive and thrive in extreme environments.
These adaptations include:

• Heat-stable enzymes: Their proteins and enzymes are more stable at high temperatures, allowing cellular processes to continue without denaturation.
• Lipid membranes: Their cell membranes have specialized lipids, which maintain membrane integrity and fluidity at high temperatures.
• DNA stabilization: These microbes have mechanisms to protect their DNA from heat-induced damage, such as high GC content in their DNA, which provides additional stability.

Such adaptations not only help these organisms survive but also make them valuable in industrial applications where high temperatures are involved, such as bioremediation and biotechnology.