23 Filamentous Bacteria Examples: Detailed Explanations And Images

Filamentous bacteria are none other than the members of actinomycetes. They are unicellular organisms forming a branched network of filaments. They are anaerobic, gram-positive, colony forming bacteria. They are highly rich in G+C content.

Focus on filamentous bacteria examples:

  1. Actinomyces meyeri
  2. Actinomyces israelii
  3. Actinomyces gerencseriae 
  4. Actinomyces naeslundii
  5. Actinomyces viscosus, 
  6. Actinomyces odontolyticus
  7.  Actinomyces bovis
  8. Streptomyces coelicolor
  9. Streptomyces scabies
  10. Streptomyces venezuelae
  11. Nocardia brasiliensis
  12. Nocardia asteroides
  13. Dermatophilus congolensis
  14. Crenothrix polyspora
  15. Methylococcus capsulatus
  16. Methylocaldum szegediense
  17. Microthrix parvicella
  18. Propionibacterium propionicus
  19. Micromonospora
  20. Frankia
  21. Corynebacterium
  22. Mycobacterium
  23. Rhodococcus

Actinomyces meyeri

As they are unicellular filamentous bacteria that belong to the class actinomycetes. As per the reports, some members belonging to the Actinomyces genus are responsible to cause chronic inflammation in the lungs of human beings, called “actinomycosis“.

Actinomyces israelii

They are anaerobic, colonial, haematoxiphilic, filamentous gram+ve bacteria. They also cause the same pulmonary inflammation as they are commensal to the mouth and crypts of tonsils. They are also found in gastrointestinal tracts.

Actinomyces naeslundii

They are non-spore forming, facultative anaerobes which is a prominent oral bacteria causing emphyma in humans. They also cause an inflammatory problem in the endocardial layer of the heart.  They can easily grow at a temperature of 15 ° C to 40 ° C, with an optimum growth temperature of 37 °C

Actinomyces naeslundii - Wikipedia
Image credit: Wikipedia

Actinomyces viscosus

They are filamentous anaerobic pathogen of humans. They are acidogenic bacteria causing dental caries. Most commonly, it causes slow-growing, locally invasive, and destructive tissue damage in the oral neck, chest, abdomen, and pelvis region of human beings.

Actinomyces odontolyticus

This species of actinomyces is linked with cervicothoracic illness in humans. It was first isolated by Batty in 1958 in a patient with root lesions in the oral cavity. They are generally found in Asia and North America.

Actinomyces bovis

 It is the causative agent of the lumpy jaw in ruminants. It is a zoonotic organism that causes granulomas, abscesses, skin lesions, and bronchopneumonia in humans. Only when there is the destruction of the epithelial or mucosal surface it can penetrate deeper tissues of the cheeks.

Filamentous bacteria examples
Figure showing the
“Lumpy jaw in bovines”
Image credit: Flickr

Actinomyces gerencseriae

They are non-motile, gram positive bacilli and live in soil-biome and also in biological systems. They cause pathogenicity in humans as well as in cattle.

Streptomyces coelicolor

It is also an example of unicellular, spore-forming filamentous bacteria belonging to the phylum actinomycetes. Member of Streptomyces is responsible for much of the decomposition of organic matter in the soil and the “earthy” odour of the soil.

They become the research point of interest as they are “adaptable to environmental stress“. They emit blue/green pigments under alkaline conditions and red pigments under acidic conditions.

Streptomyces scabies

They are the main causal agent of potato scab in common potato crops. It passes through lenticels, wounds, and stomata and penetrates the tissue directly in young tubers. This can be prevented by avoiding the use of materials that add alkalinity to the soil, such as wood ash, fresh fertilizers and lime.

Streptomyces venezuelae

It is one of the gram-positive, unicellular, filamentous bacteria examples. It is mostly known for antibiotic production like chloramphenicol. The spores are somehow different from other members as they are rich in arginine and leucine contents.

Nocardia brasiliensis

They are aerobic, unicellular filamentous bacilli, ubiquitous in the environment but mainly found in soil. They can easily grow in temperature ranges between 25°C to 45°C. They are responsible to cause a disorder named “Nocardiosis” which infects the lungs, liver and central nervous system of humans

Nocardia asteroids

They are also filamentous bacteria examples. They are mostly aerobic, spore-forming, unicellular organisms. They are mostly involved in the septicity of bones and spinal cord region with mild muscular pain and are also found in respiratory tracts of the human population.

Dermatophilus congolensis

It is a gram-positive, non–acid-fast, facultative anaerobic saprophyte. As they are cosmopolitan so can be isolated from soil or water regions. They are mostly seen during heavy and long rainfall. They can cause pathogenicity in Rabbits. They are also a contagious agent for chronic bacterial skin problems known as Dermatophilosis.

Crenothrix polyspora

They are prokaryotic, gram-negative bacteria found in stagnant water containing a low concentration of Fe2+ and methane. They are responsible for the earthy smell in drinking water from ground source water bodies as they possess terpenoid geosmin, trans-1,10-dimethyl-trans-9-decalol and


Methylococcus capsulatus

They are methylotrophic, gram-negative aerobes. They can metabolise the methane gas as their source of energy and lowers the level of methane in the atmosphere. With this feature, they became the participating member of the conservation of the biosphere.

Methylocaldum szegediense

These are unicellular, filamentous, thermophilic methanotrophs. They are obligate anaerobes and are extremely hydrophobic due to the presence of mycolic acids on their cell walls.

Microthrix parvicella

They are prokaryotic, unicellular marine eubacteria. They are gram-positive, hydrophobic and also activated-sludge bacteria as they are the major participant in the filtration of water-sludge systems and water purification.

Propionibacterium propionicus

They are pleomorphic, anaerobic, gram-positive, human infecting bacteria. They produce some chemicals in trace amounts like carboxylic acids: propionic acid, acetic acid, formic acid, and succinic acid. They are also capable of nitrogen fixation.

The cell wall is made up of muramic acid, N-acetylglucosamine, glutamic acid, glycine, and L-diaminopimelic acid.

Propionibacterium - Wikipedia
Image credit: Wikipedia

Micromonospora noduli

They are gram-positive, branched, spore-forming aerobes. They are isolated from the root nodules of the Pisum sativum. It contains carotenoid mycelial pigments showing yellow, orange, red, purple, brown, or black colonies. They possess anticancer quinones, annsamycins, antimicrobial peptides, aminoglycosides and gentamycin complexes.


They are unicellular, aerobic, gram-positive, filamentous, free-living nitrogen-fixing bacteria. The cell wall is made up of meso diaminopimelic acid, glutamic acid, alanine, muramic acid, and glucosamine and is devoid of mycolic acid in composition.

Nitrogen fixation depends upon the availability of Ca2 + ions in host cells. They can convert atmospheric nitrogen into a biologically consumable form.

File:Frankia alni.jpg - Wikimedia Commons
Frankia forming the root nodules in higher plants
Image credit: Wikimedia commons


It is a prokaryotic, filamentous, fresh-water, motile cyanobacteria. The alkaloid neurotoxin antxa is a potent post-synaptic depolarizing neuromuscular inhibitor produced by the organism. Reproduction is mainly through binary fission or fragmentation.

Oscillatoria spp.
Image credit: Flickr


Members of this genus are photosynthetic, unbranched, colonial, filamentous bacteria. They possess a specific structure for nitrogen fixation” Heterocysts” into filaments. They reproduce through fragmentation and akinete formation.


Species of this genera are mostly unicellular, prokaryotic, filamentous, a club-shaped bacterium is known for pneumonic inflammation in human beings. They live in mice, rats, and voles as commensal organisms. A species Corynebacterium diphtheria is the main causal agent of diphtheria.

ff corynebacterium diphtheriae2 | 1973.Dr. P.B. Smith..This … | Flickr
Corynebacterium diphtheriae
Image credit: Flickr


They are gram-positive, catalase positive, non-motile, non-spore forming rod-shaped aerobes. They are mostly saprophytic to human beings. Mycobacterium tuberculosis is responsible for the ailment in the throat and lungs i.e. Tuberculosis.

Mycobacterium tuberculosis Bacteria, the Cause of TB | Flickr
Mycobacterium tuberculosis
Image credit: Flickr

Rhodococcus equi

It is a gram-positive encapsulated intracellular, soil-borne bacillus. They can metabolise aromatic compounds like toluene, naphthalene etc. They are potential members of the bioremediation of pollutants.

They are used in sewage treatment plants as they can form flocculation and fermentation by releasing gases. They can cause illness in the bone and joints.


This article is mainly focused on the examples of filamentous bacteria in which some are methane producing helps in flocculation formation in sewage treatment and to improve water quality. Few are the major nitrogen fixer and contribute to conservation in the biosphere while some are pathogenic to the biological systems like humans and cattle.

Anushree Verma

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