Pseudomonadota is a phylum of bacteria associated with nutrient cycling, human and environmental health. Some like the E. coli, gonorrhea and plague bacteria can be harmful; some have strong ecological functions.
Here's a glance at the six main classes: Acidithiobacillia, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Hydrogenophilia, and Zetaproteobacteria.
Extremists like many Acidithiobacillus are found in harsh environments. Alphaproteobacteria sp. are essential for nitrogen uptake by plants and increasing soil fertility, and Zetaproteobacteria can consume heavy metals.
1. Acidithiobacillia
Traits and Qualities
The Acidithiobacillia are extremophiles, happy in acidic environments or low pH. These bacteria are chemolithotrophic, gaining energy from inorganic compounds such as sulfur, iron or hydrogen.
These are metal-munching microbes. Acidithiobacillia oxidize iron and sulfur, helping them survive in low pH conditions.
Habitat
Found in highly acidic environments, these bacteria prosper in acid mine drainage systems and sulfur-rich geothermal springs. Places with pH lower than 3, like Tinto River in Spain, have dense populations of Acidithiobacillia.
Nutrition
They feed on reduced sulfur compounds and ferrous iron. Their diet consists primarily of inorganic compounds. They oxidize iron and sulfur ions, releasing energy essential for their growth and activities.
Uses in Nature & Industry
Acidithiobacillia contribute to weathering rocks, making metals like copper and gold more accessible for other organisms. Their actions release nutrients to enhance soil and aquatic environments.
Bioleaching: Species like Acidithiobacillus ferrooxidans are used in mining to extract metals such as copper and gold via biomining techniques.
Acid Mine Drainage Remediation: Can help break down harmful compounds in mine waste.
Acidithiobacillus ferroxidans may be found in company of other extremophiles like Cupriavidus metallidurans, the copper-eating gold producer, or archaea such as Pyrococcus furiosus from the Isle of Vulcano.
Hazards
Their activities add to environmental acidification and metal pollution. While beneficial in nutrient cycling, Acidithiobacillia overgrowths can lead to environmental health decline. Acid mine drainage caused by the bacteria can decrease water quality and degrade aquatic ecosystems.
Benefits
Despite their harsh living conditions, they're a key to understanding microbial survival in extreme environments, and long-term applications in astrobiology.
These bacteria are also used in bioleaching, an efficient process for extracting metals from ores. They can recover up to 95% of copper in mining operations.
2. Alphaproteobacteria
Traits and Qualities
Alphaproteobacteria are highly adaptable and include both free-living and symbiotic species. They're known for metabolic versatility and important functions in nitrogen fixation.
Also capable of photosynthesis, Alphaproteobacteria exhibit remarkable metabolic versatility. This wide range allows them to exist abundantly in many environments.
Habitat
Alphaproteobacteria live in soil, freshwater, marine ecosystems, and in host organisms as symbionts or pathogens. In symbiotic relations with plants the bacteria dwell in root nodules of legumes.
They help with nitrogen acquisition. Despite the vast need for nitrogen in plant life, this element rarely occurs in consumable form in the environment.
When a plant sprouts it sends out signals to attract these bacteria. They dwell in the safety of the plant's roots, and break nitrogen into simpler compounds the plant can uptake, like ammonium or ammonia.
Nutrition
Alphaproteobacteria are phototrophs, heterotrophs or nitrogen fixers, using both organic and inorganic materials. Some use sunlight for energy as in photosynthesis, while others break down organic matter in soil.
Legumes are famously friendly with these bacteria. They benefit from a 20-30% increase in nitrogen availability when Alphaproteobacteria stay for a visit.
Uses in Nature & Industry
Nitrogen Fixation: Rhizobium is the species most beneficial to leguminous plants, enhancing soil fertility by converting atmospheric nitrogen into ammonia. Without it, plants would wither and die. Crop rotation with legumes also results in healthier yields of other plants.
Bioremediation: Sphingomonas species degrade toxic compounds, aiding in environmental cleanup.
Hazards
Pathogenic species like Rickettsia, responsible for diseases such as typhus and Rocky Mountain spotted fever, are notable threats. Despite their benefits, certain Alphaproteobacteria, like Rickettsia, can be harmful. Insects transmit Rickettsia, leading to diseases such as typhus and spotted fever.
Points of Interest
The ancestral species of mitochondria belong to this group. Mitochondria are special compartments or organelles best known for breakdown of food molecules to turn out ATP, a molecular fuel for the rest of the cell.
Some Alphaproteobacteria are being explored for biofuel development, offering the potential to convert agricultural waste into renewable energy.
3. Betaproteobacteria
Traits and Qualities
Betaproteobacteria are metabolically and ecologically diverse, including free-living, symbiotic, and pathogenic species. They are often associated with nutrient cycling.
Betaproteobacteria are identified by their wide array of metabolic capabilities. Many can break down complex organic compounds to build organic-rich environments.
Habitat
Found in soil, water bodies, and within host organisms, these bacteria thrive in freshwater and marine environments. They're abundant in decomposing organic matter, as in swamps or landfills.
Nutrition
Many are chemolithoautotrophs, oxidizing nitrogen, sulfur, or hydrogen compounds for energy. Mostly heterotrophs, they are unable to make their own food as plants do.
Betaproteobacteria rely on organic substances for energy. They're power decomposers, recycling nutrients back into ecosystems.
Uses in Nature & Industry:
Role in Nitrogen Cycle: Nitrosomonas participates in nitrification, converting ammonia to nitrite.
Bioremediation: Capable of degrading environmental pollutants such as hydrocarbons (e.g., oil spills).
They decompose organic matter, participating in nutrient cycling in ecosystems. Their activity helps maintain soil fertility.
Hazards
Bordetella pertussis causes whooping cough in humans. Burkholderia pseudomallei is responsible for the tropical disease melioidosis. Neisseria gonorrhoeae is the bacterium causing gonorrhea.
While Betaproteobacteria are beneficial for decomposition, some species like Burkholderia cause disease in plants and humans. Infections from Burkholderia can lead to pneumonia and other serious health conditions.
Betaproteobacteria facilitate energy flow between primary producers and consumers in ecosystems. They're used in bioremediation and can reduce organic pollutants by up to 70%.
4. Gammaproteobacteria
Traits and Qualities
This is the most well-known and diverse group within Pseudomonadota, with several species important to medicine and industry. Their diverse metabolic pathways allow them to process a variety of organic materials.
Habitat
Found virtually everywhere, from oceans to soil and animal intestines. These bacteria inhabit soils, aquatic environments, and organisms, often found in areas impacted by human activities. For instance, they often thrive in wastewater treatment facilities.
Nutrition
This genus includes phototrophs like purple sulfur bacteria who convert sunlight, heterotrophs and chemolithotrophs. Gammaproteobacteria can use sugars, proteins, and hydrocarbons for energy. They easily adapt to nutrient sources, including waste.
Uses in Nature & Industry:
Disease Agents: Includes pathogenic species such as Escherichia coli (intestinal infections, though some strains are harmless) and Salmonella.
Food Fermentation: Certain Pseudomonas species contribute to dairy fermentation.
Bioluminescence: Vibrio fischeri forms symbiotic relationships with marine hosts, producing light through bioluminescence.
They aid in nutrient cycling, breaking down organic material to release nutrients vital for other organisms. They're important in agriculture and wastewater treatment, improving overall ecosystem health.
Hazards
Many Gammaproteobacteria are pathogens causing diseases like cholera (Vibrio cholerae), bubonic plague (Yersinia pestis) and typhoid fever (Salmonella Typhi).
Though many are beneficial, some can be pathogenic. Escherichia coli and Salmonella can cause foodborne illnesses affecting millions.
Bacterial Trivia
Some Pseudomonas species produce pigments such as pyocyanin, which has antimicrobial properties. Gammaproteobacteria are involved in innovative biotechnology applications, like engineering strains to produce biofuels from organic waste, potentially reducing reliance on fossil fuels.
5. Hydrogenophilia
Traits and Qualities
Hydrogenophilia are chemolithotrophic bacteria capable of metabolizing hydrogen gas (H2). Their ability to metabolize hydrogen helps maintain ecological balance.
Habitat
Found in hydrogen-rich environments, including geothermal vents, volcanic areas, and deep-sea ecosystems. Hydrogenophilia are predominantly found in geothermal springs and hydrothermal vents, environments rich in hydrogen gas.
Nutrition
Their primary energy source is hydrogen gas, often carbon dioxide as a carbon source. They consume hydrogen and inorganic compounds for energy.
Uses in Nature & Industry
Biogeochemical Cycling: They're important to hydrogen and carbon cycling in extreme environments.
Biotechnology Potential: Their enzymes may be explored for hydrogen fuel production.
These bacteria help control hydrogen sulfide pollution, industriously helping to detoxify environments. Their activities also contribute to sulfur cycling.
Hazards
No harmful effects or pathogenic members are currently known. While they largely benefit their ecosystems by regulating pollution, their presence can also signal elevated hydrogen levels, which can point to underlying environmental issues.
Model Microbes
Hydrogenophilia is considered a model group for studying microbial life in early Earth conditions and potentially on other planets. Researchers are investigating Hydrogenophilia for renewable hydrogen fuel production, with potential to support sustainable energy goals globally.
Hydrogenophilus thermoluteolus, a facultative chemolithoautotroph first isolated from a hot spring, is found in 2004 in ice core samples from 3 km deep in Antarctica's Lake Vostok. This suggests a geothermal system under the lake or non-thermophilic strains of Hydrogenophilus in the ice.
6. Zetaproteobacteria
Traits and Qualities
Zetaproteobacteria are iron-oxidizing bacteria. They're important to iron cycling within aquatic environments, and contribute to the creation of rust.
Habitat
They're primarily found in deep-sea hydrothermal vents with abundant iron and oxygen. Marine ecologies in iron-rich coastal sediments provide them with ideal habitats. Zetaproteobacteria thrive in low-oxygen conditions.
Nutrition
They oxidize ferrous iron (Fe2+) to ferric iron (Fe3+) for energy. These bacteria use iron as their main energy source, converting ferrous iron to ferric iron, a process crucial in iron-rich ecosystems.
Uses in Nature & Industry
Iron Cycling: Play a critical role in global iron cycling in marine environments.
Microbial Engineering: Potential applications in bioremediation of iron-polluted areas.
Their iron-oxidizing activities are vital for maintaining iron levels in seawater, impacting overall marine health and nutrient availability.
Hazards
Not known to have pathogenic species. While important for biogeochemical processes, their ability to oxidize iron can result in biofouling, which poses problems for marine infrastructure.
Interesting Facts
Zetaproteobacteria build intricate structures or "iron mats" on the ocean floor, which support unique ecosystems dependent on iron oxidation.
Zetaproteobacteria are under study for their potential in bioremediation and biotechnology, revealing insights into their ecological and industrial applications.
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