19 Domain Bacteria Examples: Detailed Explanations And Images


Bacteria are prokaryotic cells that contain unique rRNA sequences different from Archaea and Eukarya. They are encapsulated with cell membranes composed of peptidoglycan and unbranched fatty acid chains attached to glycerol molecules by ester linkages.

The different domain bacteria examples are as follows

  1. Aquificae
  2. Thermotogae
  3. Thermodesulfobacteria
  4. Deinococcus
  5. Chrysiogenetes
  6. Chloroflexi
  7. Nitrospira
  8. Deferribacteres
  9. Cyanobacteria
  10. Chlorobi
  11. Proteobacteria
  12. Firmicutes
  13. Actinobacteria
  14. Planctomycetes
  15. Chlamydiae
  16. Spirochaetes
  17. Acidobacteria
  18. Bacteroidetes
  19. Fusobacteria
  20. Fibrobacterota

Aquificae

The phylum Aquificae is considered the oldest branch of bacteria.

Aquifex pyrophilus is a Gram-negative rod-shaped, microaerophilic bacterium. This thermophilic bacterium can thrive in temperatures ranging from 85°C and 95°C. Aquifex is a lithoautotroph that utilizes hydrogen, thiosulfate, and sulfur along with oxygen as terminal electron acceptors. 

Thermotogae

The second oldest branch is the phylum Thermotogae. This phylum includes Gram-negative, rod-shaped thermophiles enclosed in an envelope that is extended from both the ends as a balloon. They flourish actively in geothermal regions.

Contrastingly, Thermotogae is a chemoheterotroph that can survive anaerobically on carbohydrates and protein.

domain bacteria examples
Outline of a Thermotoga maritima From Wikipedia

Thermodesulfobacteria

These are sulfur reducing bacteria that utilizes sulfate as electron acceptor for anaerobic respiration. These bacteria can breathe sulfate. Example Thermodesulfobacterium hydrogeniphilum is thermophilic sulfate-reducing bacteria.

Deinococcus

This group of bacteria is highly resistant to gamma rays and UV radiation. They have thick cell walls and can inhabit outer space for years. They have characteristic carotenoid pigment deinoxanthin which gives the bacterium pink color.

domain bacteria examples
Deinococcus radiodurans From Wikipedia

Deinococcus radiodurans is an important member of this phylum. It is a poly-extremophilic, non-endospore-forming bacterium that derives energy from organic compounds.

Chrysiogenetes

Chrysiogenes arsenatis is a member of this class that uses arsenate as a terminal electron acceptor. These anaerobic bacteria are usually found in arsenic-contaminated soils. They appear as rod-shaped motile cells with a single flagellum. They reduce arsenate to arsenite. It can utilize acetate, pyruvate, lactate, malate, and fumarate as its carbon source.

Chloroflexi

This phylum is now referred to as Chloroflexota which includes aerobic thermophilic bacteria, and anoxygenic phototrophs. They have a single membrane but appear as gram-negative after staining. These are green non-sulfur anoxygenic photosynthetic bacteria, that contain BChl a and c/d and carotenoids such as carotene, β—carotene, and myxocoxanthin as major photosynthetic pigments.

Nitrospira

It is a gram-negative bacterium that is capable of nitrite oxidation. It is helical in morphology and remains in aggregates. This chemolithoautotrophic bacterium is used in sewage water plants and reduces the emission of greenhouse gases. As it contains nitrite oxidoreductase genes thus it is mentioned as a nitrite oxidizer.

Deferribacteres

This group contains gram-negative anaerobic bacteria. They are rod-shaped and use iron, manganese, and nitrate for respiration. Geovibrio is a non-sporulating member of this class that uses sulfide, formate, and acetate as electron donors while sulfur, nitrate, and fumarate as electron acceptors.

Cyanobacteria

This group is the most diverse group of bacteria which contains about 2000 and more species. These gram-negative bacteria are also known as blue-green algae.

Cyanobacteria use chlorophyll a and photosystem I and II. The carbon reserve is glycogen and contains phycocyanin and phycoerythrin as pigments necessary for light reactions.  These pigments are stored in specialized organelles called phycobilisomes which are similar to chloroplasts of plants.

Some important cyanobacteria are as follows

Nostoc

These are filamentous cyanobacteria distributed in both terrestrial and aquatic ecosystems. It is often involved in symbiotic interaction with plants and helps in nitrogen fixation. These bacteria have heterocyst, a specialized cell responsible for nitrogen assimilation. Nostoc is widely used as a biofertilizer.

Anabaena

Anabaena is another important genus of the cyanobacteria group that helps in nitrogen fixation. They contain heterocysts that convert nitrogen to organic ammonia and are often used as a biofertilizer in paddy fields.

domain bacteria examples
Anabaena From Wikipedia

Spirulina

This genus is a worldwide famous group of cyanobacteria which is referred to as superfood. It doesn’t contain a heterocyst. However, Spirulina is very popular as a dietary supplement as it stores a high amount of protein (65-70%). It is rich in chlorophyll and carotenoids which act as antioxidants and contain vitamins such as folic acid, Vit B2, and Vit B12 along with other necessary minerals.

domain bacteria examples
Spirulina From Wikipedia

Chlorobi

Representative members of this group are Chlorobium tepidum and Chlorobium vibrioforme. They are anaerobic photoautotrophs, green sulfur bacteria that utilizes reduced sulfur compounds for electrons and performs non-cyclic photosynthesis. They contain BChl c, BChl d, and BChl e.

Proteobacteria

Proteobacteria is also known as Pseudomonadota. This phylum includes gram-negative bacteria that perform anoxygenic photosynthesis.

Alpha proteobacteria

The major photosynthetic pigments are BChl a/b and carotenoids such as lycopene, and rhodopsin. They utilize reduced hydrogen and sulfur compounds as electron donors and use photosystem II for photosynthesis.

 

MethylobacteriumCan utilize C1 compounds, normally present in soil and water, facultative-aerobe
RhizobiumNitrogen-fixing soil bacteria associated with Leguminosae plant, motile cells
CaulobacterHeterotrophs and oligotrophs with rod or vibrio shaped cells
AgrobacteriumPlant pathogen causes tumors, chemoorganotroph, aerobic motile non-sporing rods
RickettsiaObligate intracellular parasites, pleomorphic
BrucellaPathogenic, coccobacillus with flagella
CoxiellaObligate parasites causes Q fever
RhodospirillumPhotoheterotrophs either aerobic or anaerobic
domain bacteria examples
Rhizobia nodules on Vigna unguiculata From Wikipedia

Beta proteobacteria

These purple non-sulfur bacteria contain bacteriochlorophylls and carotenoids as major photosynthetic pigments. They can survive in a wide range of environments by using various metabolic strategies. They make use of reduced nitrogen and sulfur forms as electron donors.

Bordetella Aerobic, nonmotile, coccobacillus parasites of mammals, need organic sulfur and nitrogen
NeisseriaPathogenic causes gonorrhea and meningitis, oxidases-positive, resident of mucosal membranes of mammals
BurkholderiaAerobic, straight rods with a single flagellum, with Poly-β-hydroxybutyrate as reserve material, causes cystic fibrosis
LeptothrixAerobic straight rods covered with a sheath containing iron and manganese oxides, present in clogged pipes
NitrosomonasAmmonia-oxidizing, obligate chemolithoautotroph
ThiobacillusAutotrophs, produce sulfate by oxidizing H2S, beneficial for plants
domain bacteria examples
Neisseria gonorrhoeae From Wikipedia

Gamma proteobacteria

AzotobacterAerobic bacterium, form cysts and helps in nitrogen fixation
EscherichiaFacultatively anaerobic in nature, oxidase-negative, converts formic acid to H2 and CO2, common parasites for mammals
MethylococcusMethane-utilizing aerobic bacterium, usually form cysts
HaemophilusFacultative or aerobic, oxidase-positive, fermentative bacterium, frequently present as parasites of mammals
PseudomonasChemoheterotrophs with aerobic respiration, common pathogens for animals and plants
domain bacteria examples
Escherichia From Wikimedia

Delta proteobacteria

BdellovibrioThis is an aerobic pathogenic bacterium that grows in the periplasmic space of other gram-negative bacteria.  
DesulfovibrioSulfur-reducing bacterium that inhabits polluted lakes and sewage lagoons
DesulfuromonasSulfur-reducing bacterium mostly present in anoxic freshwater environments
MyxococcusAerobic, motile bacterium usually present in soil and remain as dormant myxospores. These are micro predators and secret various digestive enzymes to lyse other bacterial cells.
domain bacteria examples
Desulfovibrio desulfuricans From Wikimedia

Epsilon proteobacteria

These are gram-negative rod-shaped microaerophilic proteobacteria.

CampylobacterThis genus comprises both pathogenic and non-pathogenic members. These are fermentative oxidase-positive bacteria often found in the intestinal tract and oral cavity of animals.
HelicobacterThese are both catalase and oxidase-positive, usually found in the gastrointestinal tract of humans.
domain bacteria examples
Campylobacter sp From Wikimedia

Zeta proteobacteria

This group is represented by Mariprofundus ferrooxydans. This bacterium is found in deep sea specially at hydrothermal vents as iron-oxidizing microorganism.

Firmicutes

This phylum contain gram-positive bacteria. Based on 16S rRNA analysis, this phylum contains bacteria with low G+C content.

Class : Mollicutes
AcholeplasmaMostly present in vertebrates, with optimum temp 30-37°C
AnaeroplasmaInhabit rumen of bovine and anaerobes
EntomoplasmaUsually present in insects and plants with optimal growth at 30°C
MycoplasmaPresent in humans and animals with 37°C optimal temperature, require sterol for its growth
SpiroplasmaHelical filaments grow at 30-37°C in insects and plants
UreaplasmaCapable of hydrolysis of urea, present in human and animal
Class : Clostridia
ClostridiumAnaerobic, chemoorganotrophs with oval or spherical endospores, rod-shaped pleomorphic, catalase negative 
HeliobacteriumAnaerobic, photoheterotrophs with BChl g
Class : Bacilli
BacillusAerobic or facultative chemoorganotrophs with straight rod-shaped, have endospores, catalase-positive
EnterococcusFacultative spherical or ovoid cells, catalase-negative and undergoes fermentation, produce lactate with any gas, present in fecal matter
LactobacillusFacultative or microaerophilic, non-sporing, fermentative, catalase-negative
StaphylococcusChemoorganotrophs, catalase-positive, pathogenic, present in the skin and mucosal membrane of humans
StreptococcusFermentative, produce lactate without any gas, catalase-negative, hemolysis-positive, parasites of animals

Actinobacteria

This is a fascinating group of bacteria that produces characteristic secondary metabolites with anticancer, and anti-helminthic properties. Their life cycle involves the development of filamentous hyphae that carry spores.

ArthrobacterAerobic, present as rod-shaped cells (young) or small cocci (old), catalase-positive, mostly present in the soil
CorynebacteriumFacultatively anaerobes, fermentative, oxidase-positive
MicrococcusAerobic, present as tetrads or irregular cocci, catalase-positive, mammalian skin resident and also present in soil
MycobacteriumAerobic, slightly curved rods, catalase-positive, present in soil and water, sometimes pathogenic in nature
StreptomycesAerobic, branched vegetative mycelium with aerial mycelium containing spore, can utilize various organic compounds
FrankiaAerobic or microaerophilic, branched vegetative mycelium with no aerial mycelium, usually present as symbionts with plants
domain bacteria examples
Micrococcus luteus From Wikimedia

Planctomycetes

This group of bacteria is widely distributed in both aquatic and terrestrial environments. They play a significant role in carbon and nitrogen cycles and can survive under limited carbon and nitrogen sources. They lack the peptidoglycan layer and have separate internal compartments.

These anaerobes are capable of oxidizing ammonia to nitrogen inside a specialized organelle called anammoxosome which bears similarities with eukaryotic mitochondria.

Chlamydiae

This group comprises obligate intracellular parasites; some are pathogenic while others remain as symbionts of humans and animals. It also lacks a peptidoglycan layer. Example Chlamydia pneumoniae which causes pneumonia, and Chlamydia trachomatis that causes chlamydia.

domain bacteria examples
Chlamydia trachomatis From Shutterstock

Spirochaetes

These are double membraned gram-negative bacteria with distinct corkscrew shapes. This group has distinct flagella known as endoflagella that is anchored at the end of the bacteria cell. It has a twisting motion. Most of the species are pathogenic in nature.

domain bacteria examples
Spirochete From Shutterstock

Acidobacteria

This phylum represents gram-negative, acidophilic soil bacteria. Mostly present in hot springs and metal contaminated soils. In soil, it represents 52% of the total soil bacteria community. It contains bacteriochlorophyll a and carotenoids such as Echinenone, lycopene, ɣ- and β- carotene. It utilizes organic compounds such as acetate and succinate as electron donors

domain bacteria examples
Acidobacterium From Wikipedia

Bacteroidetes

These can be either pathogenic or symbiotic bacteria. These are gram-negative, rod-shaped bacteria. Some species can degrade complex polysaccharides of plants such as starch, and cellulose. They exhibit protease and urease activity.

domain bacteria examples
Bacteroides biacutis From Wikipedia

Fusobacteria

These are obligate anaerobes with rod-shaped morphology. Species of this phylum colonizes the mucosal membrane of the humans and causes tonsilitis and peritonsillar abscess.

Fibrobacterota

This phylum includes bacteria that are capable of degrading cellulose and usually present in the rumen of bovine animals. This phylum is represented by two members Fibrobacter succinogenes and Fibrobacter intestinalis.

Summary

Domain bacteria comprises a diverse group of micro organisms that utilizes various metabolic strategies. Through such metabolic processes, these can thrive anywhere starting from deep sea hydrothermal vents to outer space. They can utilize organic and inorganic carbon sources. Some are pathogenic, commensal while others are beneficial to plants.

Paurabi Das

I am a doctoral student of CSIR- CIMAP, Lucknow. I am devoted to the field of plant metabolomics and environmental science. I have completed my graduation from the University of Calcutta with expertise in Molecular Plant Biology and Nanotechnology. I am an ardent reader and incessantly developing concepts in every niche of biological sciences. I have published research articles in peer-reviewed journals of Elsevier and Springer. Apart from academic interests, I am also passionate about creative things such as photography and learning new languages. Let’s connect over Linkedin https://www.linkedin.com/in/paurabi-das-cimap26/

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