Classification of Bacteria (2023)

Classification of Bacteria (1)

Classification of bacteria helps scientists, medical microbiologists, and epidemiologists recognize different bacterial species and understand the effects of similar species. The following article will cover a scientific flowchart that will help you understand the different groups of bacteria clearly.

What drew me towards becoming a microbiologist was the world of unseen organisms. There are millions and millions of these microscopic organisms around and even within us. For a common man, there may not be much difference between a bacterium and a virus. Bacteria are unicellular microorganisms that come in different shapes. There are different kinds of bacteria, like beneficial bacteria as well as pathogenic bacteria. Beneficial bacteria help in fermentation of food and drink, making antibiotics, killing pests, and even digestion of food. Pathogenic bacteria, on the other hand, are the main reason for diseases. To be able to differentiate between the helpful and harmful bacteria, scientists have come up with a scientific classification of these organisms.

Classification of Bacteria of Medical Importance

(Video) Classification of Bacteria (Antibiotics - Lecture 1)

The classification helps in identification of organisms according to groups. These groups contain organisms that share common characteristics and traits from other organisms in a different group. The classification of bacteria of medical importance has been carried out according to the ‘Gram reaction’ all these years. Gram reaction is a medical staining test named after Christian Gram who came up with the process in 1884. He found out that these organisms have the ability to retain the crystal violet iodine complex after treating them with organic solvents like alcohol and acetone.

Organisms that are Gram-positive retain the stain color and look purple or blue-black under bright field microbiology. Those that cannot retain the dye complex need to be stained with a counterstain like carbol fuchsin and are called Gram-negative bacteria. Along with the Gram reaction, scientists also use the shape of bacteria to classify them. There are different types of bacteria shapes, like cocci (round), bacilli (stick or rod-shaped), or spiral.

Scientific Classification of Bacteria Based on Bergy’s Manual

Bergy’s Manual of Systematic Bacteriology is like the Holy Testament for microbiologists. This manual is the guiding light to identify bacterial species and understanding their characteristics. The manual was first published by David Hendricks Bergy in 1923, and helped in the classification based on their structure and functional characteristics. The following table contains the classification of bacteria by shape and function according to the Bergy’s Manual.

Kingdom Prokaryotae Division II -BacteriaMedically Important Bacterial GroupClassification by Shape and Function
Part 1Phototrophic bacteriaThese are aquatic bacteria that can produce carbohydrates from CO2 with the help of photosynthetic pigments
Part 2Gliding bacteriaThese are rods that can move by gliding in a layer of slime; these may form complex fruiting bodies
Part 3Sheathed bacteriaThese are rods that are surrounded by a sheath of iron or manganese oxides; some of these rods have flagella for movement.
Part 4Budding and/or appendages bacteriaThis is diverse group of rods that can reproduce by forming buds or appendages
Part 5SpirochetesThese are slender, helically-coiled bacteria that move by rotation or flexion of the cell
Part 6Spiral and curved bacteriaThese are helically curved rods that can move with a corkscrew-like motion
Part 7Gram-negative aerobic rods and cocciThese are rods and spheres that are aerobic Gram-negative bacteria
Part 8Gram-negative facultatively anaerobic rodsThese are rods that are Gram-negative and can survive in the absence of oxygen
Part 9Gram-negative anaerobic rodsThese are rods that are strictly anaerobic Gram-negative organisms
Part 10Gram-negative cocci and coccobacilliThese are spheres that are Gram-negative bacteria
Part 11Gram-negative anaerobic cocciThese are spheres that are strictly anaerobic Gram-negative organisms
Part 12Chemolithotrophic bacteriaThese bacteria use nitrogen, sulfur, and iron compounds for their energy and structural components
Part 13Methane-producing bacteriaThese are rods and spheres that obtain energy from carbohy­drates forming methane as an end product
Part 14Gram-positive cocciThese are spheres facultative Gram-positive organisms
Part 15Endospore-forming rods and cocciThese are rods and spheres that can form endospores during their life cycles
Part 16Gram-positive as porogenous rodsThese are rod-shaped bacteria that do not form spores and give Gram-positive porogenous rods
Part 17Actinomycetes and related organismsThis is a very large group of aerobic and anaerobic rods
Part 18The rickettsiaThese are small rod-shaped bacteria that are transmitted by arthropods, and can multiply only within a host cell that also includes chlamydiae
Part 19The mycoplasmasThese are very small, multi-shaped bacteria that lack a true cell wall
(Video) Taxonomy of Bacteria: Identification and Classification

Classification of Bacteria Flowchart

The following is a flowchart that contains names of most of the bacterial species under the specific groups according to their Gram reaction.

Classification of Bacteria of Medical Importance that give Gram-positive Reaction
This classification was carried out in 1984 and places cocci, endospore-forming and non-sporing rods, mycobacteria, and non-filamentous actinomycetes in this group.

Classification of Bacteria of Medical Importance that give Gram-negative Reaction
This classification was carried out in 1986 and placed spirochetes, spiral and curved, aerobic bacteria and facultatively aerobic rods, obligate anaerobic bacteria, aerobic and anaerobic cocci, sulfate and sulfur-reducing, rickettsias, clamydias, and mycoplasmas in this group.

The Kingdome Prokaryotae is divided into four divisions: Gracilicutes, Firmicutes, Tenericutes, Mendosicutes (Archeabacteria).

(Video) Bacterial Structure and Functions


  • Nocardioform Actinomycetes
  • Actinomycetes With Multilocar Sporangia
  • Actinoplanetes
  • Streptomyces and Related Genera
  • Maduromycetes
  • Thermomonospora and Related Genera
  • Thermoactinomycetes
  • Other Actinomycete Genera


  • The Methanogens
    • Cell Walls With Pseudomurein
      • Methanobacteriales
        • Methanobacteriaceae
          • Methanobacterium
          • Methanobrevibacter
      • Methanothermaceae
        • Methanothermus
    • Cell Walls With Pseudomurein
      • Methanococcales
        • Methanococcaceae
          • Methanococcus
      • Methanosarcinaceae
        • Methanococcaceae
          • Methanolacinia
          • Methanococcoides
          • Methanolobus
          • Methanothrix
      • Methanomicrobiales
        • Methanomicrobiaceae
          • Methanomicrobium
          • Methanogenium
          • Methanospirillum
        • Methanoplanaceae
          • Methanoplanus
        • Other Genera
          • Methanocorpusculum
          • Methanoculleus
          • Methanohalobium
          • Methanohalophilus
          • Methanosarcina
          • Methanosphaera
  • Archaeal Sulfate Reducers
    • Archaeoglobales
      • Archaeoglobaceae
        • Archaeoglobus
  • Extremely Halophilic, Aerobic Archaeobacteria
    • Halobacteriales
      • Halobacteriaceae
        • Haloarcula
        • Halobacterium
        • Halococcus
        • Haloferax
        • Natronobacterium
        • Natronococcus
  • Cell Wall-Less Archaeobacteria
    • Thermoplasma
  • Extremely Thermophilic and Hyperthermophilic So – Metabolizers
    • Cocci, Optimum Growth Below pH4
      • Desulfurolobus Metallosphaera
    • Sulfolobales
      • Sulfolobaceae
        • Acidianus
        • Sulfolobus
      • Rods That Use H2 as Energy Source
        • Pyrobaculum
      • Thermoproteales
        • Thermococcaceae
          • Thermofilum
          • Thermoproteus
      • Cocci or Disc-Shaped That Oxidize H2S
        • Hyperthermus
        • Staphylothermus
        • Thermodiscus
        • Desulfurococcaceae
          • Desulfurococcus
          • Pyrodictium
      • Thermococcales
        • Thermococcaceae
          • Thermococcus
          • Pyrococcus
  • Spirochetes
    • Spirochaetales
      • Spirochaetaceae
        • Borrelia
        • Cristispira
        • Spirochaeta
        • Treponema
      • Leptospiraceae
        • Leptospira
    • Other: Hindgut Spirochetes of Termites and Cryptocercus punctulatus (wood-eating cockroach)
  • Gram-positive Cocci
    • Aerobic, Catalase-Positive Genera
      • Deinobacter
      • Deinococcus
      • Marinococcus
      • Micrococcus
      • Planococcus
      • Saccharococcus
      • Staphylococcus
      • Stomatococcus
    • Aerotolerant, Catalase-Negative Genera
      • Aerococcus Enterococcus
      • Gemella
      • Lactococcus
      • Leuconostoc
      • Melissococcus
      • Pediococcus
      • Streptococcus (Pyogenic Hemolytic Streptococci, Oral Streptococci,Enterococci, Lactic Acid Streptococci, Anaerobic Streptococci)
      • Trichococcus
      • Vagococcus
    • Anaerobic, Catalase-Negative Genera
      • Coprococcus
      • Peptococcus
      • Peptostreptococcus
      • Ruminococcus
      • Sarcina
  • Endospore-Forming Gram-positive Rods and Cocci
    Desulfotomaculum (also dissimilatory sulfate reducer)
  • Endospore-Forming Gram-positive Rods and Cocci
    Desulfotomaculum (also dissimilatory sulfate reducer)
  • Regular, Nonsporing Gram-positive Rods
  • Irregular, Nonsporing Gram-positive Rods
    Butyrivibrio (has thin, Gram-positive walls, but stains as negative)
    Gardnerella (has thin, Gram-positive walls but stains as negative)
    Lachnospira (has thin, Gram-positive walls but stains as negative)
  • Aerobic/Microaerophilic, Motile, Helical/Vibrioid Gram-negative Bacteria
  • Nonmotile (or rarely), Gram-negative Curved Bacteria
    • Spirosomaceae
      • Flectobacillus
      • Runella
    • Spirosoma
    • Other Genera
      • Ancyclobacter
      • Brachyarcus
      • Cyclobacterium
      • Meniscus
      • Microcyclus
      • Pelosigma
  • Gram-negative Aerobic Rods and Cocci
    • Pseudomonadaceae
      • Frateuria
      • Pseudomonas
      • Xanthomonas
      • Zooglea
    • Azotobacteriaceae
      • Azomonas
      • Azotobacter
    • Rhizobiaceae
      • Agrobacterium
      • Bradyrhizobium
      • Phyllobacterium
      • Rhizobium
    • Methylococcaceae
      • Methylococcus
      • Methylomonas
    • Acetobacteraceae
      • Acetobacter
      • Gluconobacter
    • Halobacteriaceae
      • Halobacterium
      • Halococcus
    • Legionellaceae
      • Legionella
    • Neisseriaceae
      • Acinetobacter
      • Kingella
      • Moraxella
      • Neisseria
    • Other Genera
      • Acidiphilium
      • Acidomonas
      • Acidothermus
      • Afipia
      • Agromonas
      • Alcaligenes
      • Alteromonas
      • Aminobacter
      • Aquaspirillum
      • Azorhizobium
      • Beijerinckia
      • Bordetella
      • Brucella
      • Chromohalobacter
      • Chryseomonas
      • Comoamonas
      • Cupriavidas
      • Deleya
      • Derxia
      • Ensifer
      • Erythrobacter
      • Flavimonas
      • Flavobacterium
      • Francisella
      • Halomonas
      • Hydrogenophaga
      • Janthinobacterium
      • Lampropedia
      • Marinobacter
      • Marinomonas
      • Mesophilobacter
      • Methylobacillus
      • Methylobacterium
      • Methylophaga
      • Methylophilus
      • Methylovorus
      • Morococcus
      • Oceanospirillum
      • Oligella
      • Paracoccus
      • Phenylobacterium
      • Psychrobacter
      • Rhizobacter
      • Roseobacter
      • Rugamonas
      • Serpens
      • Sinorhizobium
      • Sphingobacterium
      • Thermoleophilum
      • Thermomicrobium
      • Thermus
      • Variovorax
      • Volcaniella
      • Weeksella
      • Xanthobacter
      • Xylella
      • Xylophilus
      • Zoogloea
  • Facultatively Anaerobic Gram-negative Rods
    • Enterobacteriaceae
      • Arsenophonus
      • Budvicia
      • Buttiauxella
      • Cedecea
      • Citrobacter
      • Edwardsiella
      • Enterobacter
      • Erwinia
      • Escherichia
      • Ewingella
      • Hafnia
      • Klebsiella
      • Kluyvera
      • Leclercia
      • Leminorella
      • Moellerella
      • Morganella
      • Obesumbacterium
      • Pantoea
      • Pragia
      • Proteus
      • Providencia
      • Rahnella
      • Salmonella
      • Serratia
      • Shigella
      • Tatumella
      • Xenorhabdus
      • Yersinia
      • Yokenella
    • Vibrionaceae
      • Aeromonas
      • Enhydrobacter
      • Photobacterium
      • Plesiomonas
      • Vibrio
    • Pasturellaceae
      • Actinobacillus
      • Haemophilus
      • Pasteurella
    • Other Genera
      • Calymmatobacterium
      • Cardiobacterium
      • Cedecea
      • Eikenella
      • Gardnerella (has thin, Gram-positive walls but stains as negative)
      • Kluyvera
      • Obesumbacterium
      • Rahnella
      • Streptobacillus
      • Tatumella
      • Xenorhabdus
      • Chromobacterium
      • Zymomonas
  • Gram-negative Anaerobic, Straight, Curved, and Helical Rods
    • Bacteroidaceae
      • Acetivibrio
      • Acetoanaerobium
      • Acetofilamentum
      • Acetogenium
      • Acetomicrobium
      • Acetothermus
      • Acidaminobacter
      • Anaerobiospirillum
      • Anaerorhabdus
      • Anaerovibrio
      • Bacteroides
      • Butyrivibrio (has thin, Gram-positive walls but stains as negative)
      • Centipeda
      • Fervidobacterium
      • Fibrobacter
      • Fusobacterium
      • Haloanaerobium
      • Halobacteroides
      • Ilyobacter
      • Lachnospira (has thin, Gram-positive walls but stains as negative)
      • Leptotrichia
      • Malonomonas
      • Megamonas
      • Mitsuokella
      • Oxalobacter
      • Pectinatus
      • Pelobacter
      • Porphyromonas
      • Prevotella
      • Propionigenium
      • Propionispira
      • Rikenella
      • Roseburia
      • Ruminobacter
      • Sebaldella
      • Selenomonas
      • Sporomusa
      • Succinimonas
      • Succinivibrio
      • Syntrophobacter
      • Syntrophosmonas
      • Thermobacteroides
      • Thermospipho
      • Thermotoga
      • Tissierella
      • Wolinella
      • Zymophilus
    • Dissimulatory Sulfate- or Sulfur-Reducing Bacteria
      • Desulfobacter
      • Desulfobacterium
      • Desulfobulbus
      • Desulfococcus
      • Desulfomicrobium
      • Desulfomonas
      • Desulfomonile
      • Desulfonema
      • Desulfosarcina
      • Desulfotomaculum (also endospore-forming)
      • Desulfovibrio
      • Desulfurella
      • Desulfuromonas
      • Thermodesulfobacterium
    • Anaerobic Gram-negaitve Cocci
      • Veillonellaceae
        • Acidaminococcus
        • Megasphaera
        • Syntrophococcus
        • Veillonella
  • Rickettsias and Chlamydias
    • Rickettsiales
      • Rickettsiaceae
        • Cowdria
        • Coxiella
        • Ehrlichia
        • Neorickettsia
        • Rickettsia
        • Rickettsiella
        • Rochalimaea
        • Wolbachia
      • Bartonellaceae
        • Bartonella
        • Grahamella
      • Anaplasmataceae
        • Aegyptianella
        • Anaplasma
        • Eperythrozoon
        • Haemobartonella
    • Chlamydiales
      • Chlamydiaceae
        • Chlamydia
  • Mycoplasmas
    • Mycoplasmataceae
      • Mycoplasma
      • Ureaplasma
    • Acholeplasmataceae
      • Acholeplasma
    • Spiroplasmataceae
      • Spiroplasma
    • Other Genera
      • Anaeroplasma
      • Asteroleplasma
      • Thermoplasma
  • Endosymbionts
    • Endosymbionts of Protozoa
      • Caedibacter
      • Holospora
      • Lyticum
      • Pseudocaedibacter
      • Tectibacter
    • Endosymbionts of Insects (blood sucking, plant sap-sucking, cellulose and stored grain feeders, and insects feeding on complex diets
      • Blattabacterium
    • Endosymbionts of Fungi and Invertebrates other than Arthropods (Fungi, Sponges, Coelenterates, Helminthes, Annelids, Marine worms and mollusks
    • Endosymbionts of Protozoa, ciliates, flagellates, and amoebas
      • Caedibacter
      • Holospora
      • Lyticum
      • Pseudocaedibacter
      • Tectibacter
    • Endosymbionts of Insects (blood sucking, plant sap-sucking, cellulose and stored grain feeders, and insects feeding on complex diets
      • Blattabacterium
    • Endosymbionts of Fungi and Invertebrates other than Arthropods (Fungi, Sponges, Coelenterates, Helminthes, Annelids, Marine worms and mollusks
    • Endosymbionts of Protozoa, ciliates, flagellates, and amoebas
      • Caedibacter
      • Holospora
      • Lyticum
      • Pseudocaedibacter
      • Tectibacter
  • Mycobacteria
    • Mycobacteriaceae
      • Mycobacterium
  • Nocardioforms
  • Anoxygenic Phototrophic Bacteria
    • Purple Sulfur Bacteria: Internal Sulfur Granules
      • Chromatiaceae
        • Amoebobacter
        • Chromatium
        • Lamprobacter
        • Lamprocystis
        • Thiocapsa
        • Thiocystis
        • Thiodictyon
        • Thiopedia
        • Thiospirillum
    • Purple Sulfur Bacteria: External Sulfur Granules
      • Ectothiorhodospiraceae
        • Ectothiorhodopsin
        • Ectothiorhodospira
    • Purple Nonsulfur Bacteria
      • Rhodobacter
      • Rhodyclus
      • Rhodomicrobium
      • Rhodopila
      • Rhodopseudomonas
      • Rhodospirillum
    • Green Nonsulfur Bacteria
      • Heliobacillus
      • Heliobacterium
    • Green Sulfur Bacteria
      • Anacalochloris
      • Chlorobium
      • Chloroherpeton
      • Pelodictyon
      • Prosthecochloris
    • Multicellular Filamentous Green Bacteria
      • Chloroflexus
      • Chloronema
      • Heliothrix
      • Oscillochloris
    • Anaerobic Chemotrophic Bacteria
      • Erythrobacter
  • Oxygenic Phototrophic Bacteria
    • Cyanobacteria
      • Chroococcales
        • Chamaespiphon
        • Cyanothece
        • Gloeobacter
        • Gloeocapsa
        • Gloethece
        • Microcystis
        • Myxobaktron
        • Synechococcus
        • Synechocystis
      • Pleurocapsales
        • Chroococcidiopsis
        • Dermocarpa
        • Dermocarpella
        • Myxosarcina
        • Pleurocapsa
        • Xenococcus
      • Oscillatoriales
      • Arthrospira
      • Crinalium
      • Lyngbya
      • Microcoleus
      • Oscillatoria
      • Pseudanabaena
      • Spirulina
      • Starria
      • Trichodesmium
    • Nostocales
      • Nostocaceae
        • Anabaena
        • Aphanizomenon
        • Cylindrospermum
        • Nodularia
        • Nostoc
      • Scytonemataceae
        • Scytonema
      • Rivulariaceae
        • Calothrix
    • Stigonematales
      • Chlorogloeopsis
      • Fischerella
      • Geitleria
      • Stigonema
    • Prochlorales
      • Prochloraceae
        • Prochloron
        • Prochlorothrix
  • Aerobic Chemolithotrophic Bacteria and Associated Organisms
    • Nitrifying Bacteria
      • Nitrobacteraceae
    • Nitrate-oxidizing bacteria
      • Nitrobacter
      • Nitrococcus
      • Nitrospina
      • Nitrospira
    • Ammonia-oxidizing bacteria
      • Nitrosococcus
      • Nitrosolobus
      • Nitrosomonas
      • Nitrosospira
      • Nitrosovibrio
    • Colorless sulfur-oxidizing bacteria
      • Acidiphilium
      • Macromonas
      • Thermothrix
      • Thiobacillus
      • Thiobacterium
      • Thiodendron
      • Thiomicrospira
      • Thiosphaera
      • Thiospira
      • Thiovulum
    • Obligate Chemolithotrophic Hydrogen Bacteria
      • Hydrogenobacter
    • Iron- and Manganese-oxidizing and/or -Depositing Bacteria
      • Siderocapsaceae
        • Aquaspirillum
        • Bilophococcus
        • Gallionella (both iron-oxidizing and appendaged)
        • Leptospirillum
        • Metallogenium
        • Naumaniella
        • Ochrobium
        • Siderocapsa
        • Siderococcus
        • Sulfobacillus
    • Budding and/or Appendaged Bacteria
      (Appendaged Bacteria are indicatated by *)
      • Prosthecate Bacteria
        • Ancalomicrobium
        • Asticcacaulus*
        • Caulobacter*
        • Dichotomicrobium*
        • Filomicrobium*
        • Hirschia
        • Hyphomicrobium*
        • Hyphomonas*
        • Labrys
        • Pedomicrobium
        • Prosthecobacter*
        • Prosthecomicrobium
        • Stella
        • Verrucomicrobium*
      • Planctomycetales
        • Gemmata
        • Pirelulla
      • Non prosthecate Budding Bacteria
        • Angulomicrobium
        • Blastobacter
        • Ensifer
        • Gemmiger
        • Isosphaera
        • Planctomyces
  • Nonbudding Bacteria
  • Morphologically Unusual Budding Bacteria (involved in iron and manganese deposition)
  • Sheathed Bacteria
  • Nonphotosynthetic, Nonfruiting Gliding Bacteria
  • Single-celled, Rod-shaped Gliding Bacteria
    • Cytophagales
      • Cytophagaceae
        • Capnocytophaga
        • Chitinophaga
        • Cytophaga
        • Flexibacter
        • Flexithrix
        • Microscilla
        • Sporocytophaga
        • Thermonema
    • Lysobacterales
      • Lysobacteriaceae
        • Lysobacter
  • Flattened, Filamentous Gliding Bacteria
    • Simonsiellaceae
      • Alysiella
      • Simonsiella
  • Sulfur-Oxidizing Gliding Bacteria
    • Beggiatoales
      • Beggiatoaceae
        • Achromatium
        • Beggiatoa
        • Thioploca
        • Thiospirillopsis
        • Thiothrix
  • The Pelonemas
    • Pelonemataceae
      • Achroonema
      • Desmanthus
      • Pelonema
      • Peloploca
    • Other Genera
      • Agitococcus
      • Desulfonema
      • Herpetosiphon
      • Isosphaera
      • Leucothrix
      • Saprospira
      • Toxothrix
      • Vitreoscilla
  • Gliding, Fruiting Bacteria
    • Archangiaceae
      • Archangium
    • Cystobacteraceae
      • Cystobacter
      • Melittangium
      • Stigmatella
    • Myxococcales
      • Myxococcaceae
        • Myxococcus
      • Polyangiaceae
        • Chondromyces
        • Nannocystis
        • Polyangium
      • Other Genera
        • Angiococcus
        • Corallococcus
        • Haploangium
        • Sorangium

You will find there are many reference journals as well as books that will provide you with further information related to scientific classification of bacteria. Hope the above paragraphs have helped solved some of your queries and doubts related to bacterial classification.

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(Video) Classification of Bacteria


What are the classification of bacteria? ›

Bacteria are classified into five groups according to their basic shapes: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes). They can exist as single cells, in pairs, chains or clusters.

What are the 3 classifications of bacteria? ›

Bacillus (Rod-shaped) Spirilla or spirochete (Spiral) Coccus (Sphere)

What are the 7 levels of classification for bacteria? ›

In prokaryotic taxonomy, the overall classification system is a hierarchic grouping. It concerns from highest to the lowest: domain, phylum, class, order, family, genus, species, and subspecies. Prokaryotic systematics is a scientific discipline that evolves with the technological tools that become available.

Why is classification of bacteria important? ›

Bacteria are classified and identified to distinguish one organism from another and to group similar organisms by criteria of interest to microbiologists or other scientists. The most important level of this type of classification is the species level. A species name should mean the same thing to everyone.

Who gave classification of bacteria? ›

Bacteria as prokaryotes

In the late 1970s American microbiologist Carl Woese pioneered a major change in classification by placing all organisms into three domains—Eukarya, Bacteria (originally called Eubacteria), and Archaea (originally called Archaebacteria)—to reflect the three ancient lines of evolution.

Who first classified bacteria? ›

Leeuwenhoek's 1677 paper, the famous 'letter on the protozoa', gives the first detailed description of protists and bacteria living in a range of environments.

What are the 2 major classification of bacteria? ›

Bacteria can be separated into two major divisions by their reaction to Gram's stain, and exhibit a range of shapes and sizes from spherical (cocci) through rod shaped (bacilli) to filaments and spiral shapes.

What are 4 types of bacteria? ›

There are four common forms of bacteria-coccus,bacillus,spirillum and vibrio.
  • Coccus form:- These are spherical bacteria. ...
  • Bacillus form:- These are rod-shaped bacteria. ...
  • Spirilla form:- These are spiral-shaped bacteria that occur singly.
  • Vibrio form:- These are comma-shaped bacteria.

What are 5 examples of bacteria? ›

Examples include Listeria monocytogenes, Pesudomonas maltophilia, Thiobacillus novellus, Staphylococcus aureus, Streptococcus pyrogenes, Streptococcus pneumoniae, Escherichia coli, and Clostridium kluyveri.

How many bacteria types are there? ›

How Many Named Species of Bacteria are There? There are about 30,000 formally named species that are in pure culture and for which the physiology has been investigated.

What are characteristics of bacteria? ›

There are three notable common traits of bacteria, 1) lack of membrane-bound organelles, 2) unicellular and 3) small (usually microscopic) size. Not all prokaryotes are bacteria, some are archaea, which although they share common physicals features to bacteria, are ancestrally different from bacteria.

Is the classification system? ›

The classification system is the system used for the scientific classification of organisms and other activities in science based on the characteristics, behaviors, and methods used.

What is the main importance of classification? ›

Classification is needed for convenient study of living organisms. It is necessary for knowing the different varieties of organisms. It helps in the correct identification of various organisms. It helps to know the origin and evolution of organisms.

What do u mean by classification? ›

The method of arranging the organisms into groups is called classification. When we classify things, we put them into groups based on their characteristics.

What is classification and why is it important? ›

Classifying is an investigative approach that involves sorting objects or events into groups or categories. Classification and identification are important because they allow us to better understand relationships and connections between things. They also help scientists to communicate clearly with each other.

What are the importance of bacteria? ›

The bacteria in our bodies help degrade the food we eat, help make nutrients available to us and neutralize toxins, to name a few examples[7]; [8]. Also, they play an essential role in the defense against infections by protecting colonized surfaces from invading pathogens[8]; [9].

How are bacteria named? ›

The current nomenclature for bacterial species requires a capital letter for the genus name and an epithet beginning by a lowercase letter for the species name [7]. Genera and epithet should be Latin or Latinized; the specific epithet is an adjective that must agree with the gender of the generic name [7].

What was bacteria first name? ›

The first ever living organism on Earth was a bacteria known as cyanobacteria.

Where are bacteria found? ›

Bacteria are found almost everywhere on Earth and are vital to the planet's ecosystems. Some species can live under extreme conditions of temperature and pressure. The human body is full of bacteria, and in fact is estimated to contain more bacterial cells than human cells.

Who is the father of bacteria biology? ›

Antonie Phillips van Leewenhoek circa1759 is known as the father of microbiology and the microscope due to his early study of bacteria. He was a Dutch scientist. Antonie Van Leeuwenhoek a Dutch, who saw microbes when he was polishing lens he saw microbes.

Why are bacteria animals? ›

No, bacteria are not animals. Although bacteria does share some characteristics with animals, for example, bacteria produces a typical nucleic acid that are found in parts of the human pancreas, spleen, and sperm. There are 39 trillion bacterial cells in the human body, which make up about 30% of our cell composition.

What are the structure of bacteria? ›

In bacteria, the cell wall forms a rigid structure of uniform thickness around the cell and is responsible for the characteristic shape of the cell (rod, coccus, or spiral). Inside the cell wall (or rigid peptidoglycan layer) is the plasma (cytoplasmic) membrane; this is usually closely apposed to the wall layer.

What are the 10 types of bacteria? ›

Top Ten Bacteria
  • Deinococcus radiodurans.
  • Myxococcus xanthus. ...
  • Yersinia pestis. ...
  • Escherichia coli. ...
  • Salmonella typhimurium. ...
  • Epulopiscium spp. The big boy of the kingdom – about as large as this full stop. ...
  • Pseudomonas syringae. Dreaming of a white Christmas? ...
  • Carsonella ruddii. Possessor of the smallest bacterial genome known, C. ...
5 Dec 2008

What are the 5 most common bacteria? ›

The top five germs that cause illnesses from food eaten in the United States are:
  • Norovirus.
  • Salmonella.
  • Clostridium perfringens.
  • Campylobacter.
  • Staphylococcus aureus (Staph)
18 Mar 2020

What are 2 examples of bacteria? ›

Examples of bacteria that cause infections include Streptococcus, Staphylococcus, and E. coli.

What are the size of bacteria? ›

Bacteria display a wide diversity of shapes and sizes. Most bacteria are 0.2μm (micron) in diameter and 2−8μm (micron) in length. Bacterial cells are about one-tenth the size of eukaryotic cells.

What are common types of bacteria? ›

The bacteria and viruses that cause the most illnesses, hospitalizations, or deaths in the United States are described below and include:
  • Campylobacter.
  • Clostridium perfringens.
  • E. coli.
  • Listeria.
  • Norovirus.
  • Salmonella.
22 Mar 2021

What are the 6 parts of bacteria? ›

Bacterial Structure

Structure of a typical bacterium. The numbered parts are: (1) pilus, (2) plasmid, (3) ribosome, (4) cytoplasm, (5) cytoplasmic membrane, (6) cell wall, (7) capsule, (8) nucleoid, and (9) flagellum (Source: LadyofHats [Public domain] via Wikimedia Commons).

How many bacteria are in a human? ›

What is the microbiome? In any human body there are around 30 trillion human cells, but our microbiome is an estimated 39 trillion microbial cells including bacteria, viruses and fungi that live on and in us.

What do you mean by bacteria? ›

Note: Microscopic single-celled organisms lacking a distinct nucleus are known as bacteria. They may be shaped like spheres, rods, or spirals. They inhabit virtually all environments, including soil, water, organic matter, and the bodies of animals.

What is the scientific name of bacteria? ›

current name. Bacteria. Genbank common name: eubacteria.

What are the four functions of bacteria? ›

What are the functions of good bacteria?
  • Supplements the digestive process to break down food.
  • Produces vitamins, short chain fatty acids and proteins utilized by the body.
  • Protects against overgrowth of pathogenic bacteria and yeast.
  • Strengthens immune function.
  • Creates beneficial nutrients that prevent weight gain.

What are the basics of bacteria? ›

Bacteria are single-celled microorganisms that lack a nuclear membrane, are metabolically active and divide by binary fission. Medically they are a major cause of disease. Superficially, bacteria appear to be relatively simple forms of life; in fact, they are sophisticated and highly adaptable.

What is bacteria structure and function? ›

It is a gel-like matrix composed of water, enzymes, nutrients, wastes, and gases and contains cell structures such as ribosomes, a chromosome, and plasmids. The cell envelope encases the cytoplasm and all its components. Unlike the eukaryotic (true) cells, bacteria do not have a membrane enclosed nucleus.

What are the types of classification? ›

The three types of classification are Artificial classification, Natural classification, and Phylogenetic classification.

What are the uses of classification? ›

Classifications are the most frequently used—and most useful—prediction types. Classifications are predictions that separate data into groups. Binary Classification produces “yes-no” or “in-out” answers when there are only two choices.

What is natural classification? ›

Natural classification involves grouping organisms based on similarities first and then identifying shared characteristics. According to a natural classification system, all members of a particular group would have shared a common ancestor.

What is level of classification? ›

There are seven major levels of classification: Kingdom, Phylum, Class, Order, Family, Genus, and Species. The two main kingdoms we think about are plants and animals.

What is basis of classification? ›

The basis for the biological classification scheme is similarity of morphology (shape) and phylogeny (evolutionary history). In addition, the processes that led to these similarities are also used in biological classification.

What are the benefits of classification? ›

Advantages of classification of organisms:
  • It facilitates the identification of organisms.
  • It explains how different creatures interact with one another.
  • It aids in the comprehension of organism evolution.
  • It helps to understand how animals, plants, and other living creatures are related and how they can benefit humans.

What is classification in PDF? ›

Document classification is often a first step in processing incoming documents, e.g. pdf files or jpg files received via email. For further processing and to reduce the response time, documents have to be classified by type and ideally, be forwarded to the right agent.

What are classification examples? ›

If you have a group of things, such as fruits or geometric shapes, you can classify them based on the property that they possess. For example, you can classify the apples in one category, the bananas in another, and so on. Similarly, geometric shapes can be classified as triangles, quadrilaterals, and so on.

What is the purpose of classification in biology? ›

Classification is used in biology for two totally different purposes, often in combination, namely, identifying and making natural groups. The specimen or a group of similar specimens must be compared with descriptions of what is already known.

What are two classifications of bacteria? ›

Bacteria can be separated into two major divisions by their reaction to Gram's stain, and exhibit a range of shapes and sizes from spherical (cocci) through rod shaped (bacilli) to filaments and spiral shapes.

What are the 4 main types of bacteria? ›

There are four common forms of bacteria-coccus,bacillus,spirillum and vibrio.
  • Coccus form:- These are spherical bacteria. ...
  • Bacillus form:- These are rod-shaped bacteria. ...
  • Spirilla form:- These are spiral-shaped bacteria that occur singly.
  • Vibrio form:- These are comma-shaped bacteria.

How do you remember the classification of bacteria? ›

Bacteria can also be classified based on their shapes.
Use the mnemonic “CLAP”:
  1. C – Clostridium.
  2. L – Lactobacillus.
  3. A – Actinomyces.
  4. P – Propionibacterium.

What are the 4 classifications of germs? ›

Germs: Bacteria, Viruses, Fungi, and Protozoa.

How many types of bacteria are there? ›


How do you remember the 7 classifications? ›

To help remember the levels of biological classification, James taught his students the mnemonic sentence “King Philip Came Over For Good Spaghetti” (Kingdom, Phylum, Class, Order, Family, Genus, Species).

What is the most common way to classify bacteria? ›

The most basic method used for identifying bacteria is based on the bacterium's shape and cell arrangement. This section will explain the three morphological categories which all bacteria fall into - cocci, bacilli, and spirilla.

What are the classification of infection? ›

The four different categories of infectious agents are bacteria, viruses, fungi, and parasites.

What are the three classification of viruses? ›

Based on their host, viruses can be classified into three types, namely, animal viruses, plant viruses, and bacteriophages.


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