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Chapter 3: Prokaryotic Diversity (habitats, relationships & microbiomes)
Lesson guide
3.1 Prokaryotic Habitats, Relationships, and Microbiomes
Identify and describe unique examples of prokaryotes in various habitats on
Earth.
- Hot Springs and Extreme Heat: o Prokaryotes can thrive in extreme heat, such as hot springs. For example, certain bacteria are metabolically flexible, switching energy sources based on availability, allowing survival in these extreme environments.
- Antarctic Ice Shield: o Prokaryotes can survive in freezing conditions like those in the Antarctic ice shield. Their resilience enables them to endure extremely low temperatures.
- High-Pressure Deep Environments: o Paracoccus denitrificans is an example of a bacterium capable of surviving extreme pressure, such as two miles underwater. It has even withstood simulated gravity forces equivalent to those on Jupiter.
- Salt Lakes: o Halobacteria, found in saline environments like the Dead Sea, decompose dead organic material (e.g., brine shrimp) and provide nutrients for young organisms like shrimp and flies.
- Soil Ecosystems: o Soil is rich in prokaryotic life, with one gram containing up to 10 billion microorganisms and about 1,000 species. Many soil bacteria metabolize substances from plant roots, contributing to soil formation and fertility.
- Human Body: o Prokaryotes are abundant on and within the human body. For instance, bacteria thrive in the mouth, nasal cavity, throat, ears, gastrointestinal tract, and vagina, as well as on skin, particularly in moist areas like the armpits and behind the ears.
- Atmosphere: o Prokaryotes exist even in the air, with up to 2,000 kinds of bacteria found in the atmosphere. This diversity rivals that of prokaryotes in soil.
- Man-Made Environments: o Certain bacteria play a crucial role in degrading toxic chemicals, helping to clean up polluted water and soil. Prokaryotes' remarkable adaptability and metabolic flexibility allow them to inhabit nearly every corner of the Earth, from extreme heat and pressure to freezing temperatures and highly saline conditions.
In what types of environments will you find prokaryotes?
Prokaryotes are ubiquitous , meaning they can be found in nearly every environment on Earth, including: Extreme environments: Hot springs, Antarctic ice, and areas of high pressure (e.g., two miles underwater). Soil: Up to 10 billion microorganisms per gram of soil, contribute to soil fertility and stability. Salt lakes: Halobacteria thrive in saline environments like the Dead Sea, breaking down organic material. Atmosphere: Prokaryotes are abundant in the air, with thousands of different kinds even in the upper atmosphere. Man-made environments: Some prokaryotes degrade toxic chemicals, aiding in environmental cleanup.
Where do you find prokaryotes on and in the human body?
Prokaryotes are abundant on and within the human body, with bacteria thriving in areas such as: Mouth, nasal cavity, throat, and ears. Gastrointestinal tract: Home to vast colonies that aid digestion and nutrient absorption. Vagina: Where they help maintain a healthy microbial balance. Skin: Especially in moist areas like the armpits, the navel, and behind the ears. Even drier skin areas host bacteria.
What important and vital roles do prokaryotes play? Give several examples.
The existence of prokaryotes is very important for the stability and thriving of ecosystems. They are often Metabolically flexible, which means that they might easily switch from one energy source to another, depending on the availability of the sources, or from one metabolic pathway to another. For example, certain prokaryotic cyanobacteria (blue-green algae) can switch from a conventional type of lipid metabolism, which includes the production of fatty aldehydes, to a different type of lipid metabolism that generates biofuel, such as fatty acids and wax esters. Groundwater bacteria store complex high-energy carbohydrates when grown in pure groundwater, but they metabolize these molecules when the groundwater is enriched with phosphates. Prokaryotes perform functions vital to life on earth by capturing (or “fixing”) and recycling elements like carbon and nitrogen. Ecological Roles: Nutrient cycling: o Carbon fixation: Converting carbon dioxide into organic compounds usable by plants and animals. Animals and plants rely on prokaryotes to convert carbon dioxide into organic carbon products that they can use.
break down. In return, the human host benefits by absorbing the monosaccharides produced by the bacterium. Escherichia coli : Certain strains of E. coli are mutualistic, as they rely on the intestinal contents for nutrients, while humans derive essential vitamins like vitamin K, which is needed for blood clotting. Amensalism: Amensalism is a type of symbiotic relationship where one organism is harmed while the other is unaffected by the interaction. In amensalism, one organism suffers harm due to the interaction, while the other organism is not impacted. It’s a one-sided effect where the “victim” of the relationship is harmed, but the other does not gain or lose anything. Staphylococcus epidermidis and Propionibacterium acnes are examples of bacteria that produce bacteriocins, which can kill other bacteria. These bacteria are unaffected by the bacteriocins they produce, but they harm other bacterial species that might be present on the skin. Commensalism: Commensalism is a relationship where one organism benefits, while the other organism is neither helped nor harmed. In commensalism, the “beneficiary” of the relationship gains from the association, but the other organism experiences no significant effect (neither positive nor negative). Staphylococcus epidermidis : This bacterium benefits from living on the skin by consuming dead skin cells, while humans are unaffected. In some cases, the bacterium may also produce bacteriocins that protect the host from pathogenic bacteria. Neutralism: Neutralism refers to a type of symbiotic relationship in which both organisms coexist without having any effect on each other. Neutralism is a relatively rare and hypothetical scenario where the species involved do not influence each other’s survival or well-being. Both organisms coexist without any impact from the other. The coexistence of vegetating bacteria and dormant endospores, such as in Bacillus anthracis , can be considered neutralism. The endospores do not interact metabolically with the active bacteria, and neither group is affected by the other’s presence. Parasitism: Parasitism is a relationship where one organism benefits at the expense of the other. In this relationship, one organism (the parasite) harms the other (the host), often causing disease or damage. Parasitism always involves harm to the host. The parasite derives benefits (such as food, shelter, or reproduction opportunities) at the host's expense, often leading to disease or other health problems. In parasitism, the host’s health and resources are compromised. Many pathogenic prokaryotes, such as those responsible for diseases like tetanus, tuberculosis, and leprosy, exhibit parasitism. These bacteria invade the human body, causing harm through infection and the release of toxins.
Compare normal/commensal/resident microbiota to transient microbiota.
Resident Microbiota : These are microorganisms that live permanently or for long durations in and on the human body. They are often beneficial and may have a mutualistic
or commensal relationship with the host. For example, Staphylococcus epidermidis is part of the resident microbiota of the human skin. Transient Microbiota : These microorganisms are temporarily present on the body. They do not establish permanent residence and are often acquired from external sources (e.g., from the environment or from contact with other people). Transient microbiota can include pathogenic bacteria, which may cause infections if the body’s defenses are compromised.
What is the difference between cooperative and competitive interactions
regarding microorganisms? What are some examples of each type?
Cooperative Interactions : These occur when two or more populations of microorganisms benefit from living together. An example is the mutualistic relationship between humans and Bacteroides thetaiotaomicron , where both the bacterium and the human benefit from their association. Competitive Interactions : These occur when microorganisms compete for limited resources, such as nutrients or space. An example is when different bacterial species on the skin produce bacteriocins to outcompete other species, such as Propionibacterium acnes competing with other bacteria for space and resources.
What are pathogenic microorganisms?
Pathogenic microorganisms are harmful microorganisms that cause disease when they enter the human body. They may produce toxins or invade tissues, leading to infections and illnesses. Examples include bacteria such as Mycobacterium tuberculosis , which causes tuberculosis, and Clostridium tetani , which causes tetanus. Describe the human microbiome and why it might be important to human health.
Define microbiome.
The microbiome refers to the collection of all microorganisms (both prokaryotic and eukaryotic) that inhabit a specific environment, such as the human body. It includes bacteria, fungi, viruses, and other microbes. The microbiome is a complex ecosystem, consisting of trillions of microorganisms that live on and inside us, especially in areas like the gut, skin, mouth, respiratory tract, and other mucosal surfaces. These microorganisms interact with each other and with their host, playing critical roles in various bodily functions such as digestion, immunity, and protection against pathogens.
What is the difference between resident and transient microbiota
Resident microbiota are microorganisms that permanently live on and in the human body, playing roles in digestion, immunity, and protection against pathogens. Examples include the bacteria in the intestines (such as Bacteroides and Firmicutes ) and on the skin (such as Staphylococcus epidermidis ).
microbes in different body sites, such as the gut, mouth, skin, and respiratory tract. The HMP has led to important discoveries about how microbial communities contribute to diseases, immunity, digestion, and even mood regulation. It has also highlighted the complexity of the human microbiome and its impact on overall health.
What kinds of bacteria comprise the typical person’s microbiome?
The human microbiome is composed of a diverse range of bacteria, with the majority residing in the gastrointestinal (GI) tract, but there are also distinct populations in other areas like the skin, mouth, and respiratory tract. Some of the most common bacterial groups found in the human microbiome include: Firmicutes : A dominant group in the human gut, responsible for breaking down complex carbohydrates. They also help in the fermentation of fiber, contributing to energy production. Examples include Lactobacillus and Clostridia. Bacteroidetes : Another major group in the gut, which plays a role in digesting plant polysaccharides. Common genera include Bacteroides and Prevotella. Proteobacteria : Found in various body parts, these bacteria include species like Escherichia coli, which are part of the normal gut flora but can also become pathogenic under certain conditions. Actinobacteria : Important for producing certain vitamins and contributing to immune system regulation. Bifidobacterium is a well-known example found in the gut. Verrucomicrobia : These are also common in the human gut, and a well-known genus is Akkermansia, which plays a role in the metabolism of mucins (mucus components). Additionally, bacteria in the human mouth (such as Streptococcus, Prevotella), on the skin (Staphylococcus, Propionibacterium), and in other body areas contribute to the microbiome's diversity and functionality. Bacteroides and Firmicutes in the gut, which play a role in digestion and immunity. Staphylococcus epidermidis and Propionibacterium acnes on the skin. Lactobacillus species in the vagina, which help maintain a healthy pH and protect against infections.
