{{Short description|Shapes characteristic of certain bacteria and archaea}} [[File:Bacterial morphology diagram.svg|thumb|400px|alt=Chart displaying varieties of bacterial morphology: Cocci (coccus, diplococci, encapsulated diplococci, staphylococci, streptococci, sarcina, tetrad); Bacilli (bacillus, coccobacillus, diplobacilli, palisades, streptobacilli); Budding and appendages (hyphae, stalk); Others (enlarged rod, vibrio, comma form, club rod, helical form, corkscrew form, filamentous, spirochete)|Bacteria display a large diversity of cell morphologies and arrangements.]]
'''Bacterial cellular morphologies''' are the shapes that are characteristic of various types of bacteria and often key to their identification. Their direct examination under a light microscope enables the classification of these bacteria (and archaea).
Generally, the basic morphologies are spheres (coccus) and round-ended cylinders or rod shaped (bacillus). But, there are also other morphologies such as helically twisted cylinders (example ''Spirochetes''), cylinders curved in one plane (selenomonads) and unusual morphologies (the square, flat box-shaped cells of the Archaean genus ''Haloquadratum)''. Other arrangements include pairs, tetrads, clusters, chains and palisades.
==Types==
===Coccus=== thumb|300px|Arrangement of cocci bacteria thumb|''Staphylococcus'' bacteria {{redirect|Coccus|the insect genus|Coccus (insect)}} A '''coccus''' (plural ''cocci'', from the Latin ''coccinus'' (scarlet) and derived from the Greek ''kokkos'' (berry)), is any microorganism (usually bacteria)<ref name="Cole_1990">{{cite book | vauthors = Cole JR |title=17 - Streptococcus and Related Cocci |date= January 1990 | chapter = Diagnostic Procedure in Veterinary Bacteriology and Mycology | edition = Fifth |pages=211–220 | veditors = Carter GR, Cole JR |place=San Diego |publisher=Academic Press |language=en |doi=10.1016/b978-0-12-161775-2.50021-9 |isbn=978-0-12-161775-2 }}</ref> whose overall shape is spherical or nearly spherical.<ref name="Brock_2008">{{cite journal | vauthors = Zapun A, Vernet T, Pinho MG | title = The different shapes of cocci | journal = FEMS Microbiology Reviews | volume = 32 | issue = 2 | pages = 345–360 | date = March 2008 | pmid = 18266741 | doi = 10.1111/j.1574-6976.2007.00098.x | doi-access = free }}</ref><ref name="arrangement">{{cite book|last1=Pommerville|first1=J.C.|title=Fundamentals of Microbiology|date=2013|publisher=Jones & Bartlett|location=Sudbury, MA|isbn=978-1-4496-4796-4|page=106|edition= 10th}}</ref><ref name=":0">{{Cite book|title=Sherris medical microbiology|last=Ryan|first=Kenneth James|date=4 January 2018|isbn=978-1-259-85980-9|edition=7th|location=New York|publisher=McGraw-Hill Education|oclc=983825627}}</ref> Coccus refers to the shape of the bacteria and can contain multiple genera, such as staphylococci or streptococci. Cocci can grow in pairs, chains, or clusters, depending on their orientation and attachment during cell division. In contrast to many bacilli-shaped bacteria, most cocci bacteria do not have flagella and are non-motile.<ref name=":1">{{Cite book|title=Review of medical microbiology & immunology: a guide to clinical infectious diseases|last1=Levinson|first1=Warren|last2=Joyce|first2=Elizabeth A.|last3=Nussbaum|first3=Jesse|last4=Schwartz|first4=Brian S.|last5=Chin-Hong|first5=Peter|date=10 May 2018|isbn=978-1-259-64449-8|edition=15th|location=New York|publisher=McGraw-Hill Education|oclc=1032261353}}</ref>
Cocci is an English loanword of a modern or Neo-Latin noun, which in turn stems from the Greek masculine noun {{lang|grc|κόκκος}} ({{lang|grc-Latn|cóccos}}) meaning 'berry'.<ref>{{LSJ|ko/kkos|κόκκος|ref}}</ref>
Important human diseases caused by coccoid bacteria include staphylococcal infections, some types of food poisoning, some urinary tract infections, toxic shock syndrome, gonorrhea, as well as some forms of meningitis, throat infections, pneumonias, and sinusitis.<ref name="Sherris_2004">{{cite book | veditors = Ryan KJ, Ray CG | title = Sherris Medical Microbiology | edition = 4th | publisher = McGraw Hill | year = 2004 | isbn = 0-8385-8529-9 }}</ref>
====Arrangements==== Coccoid bacteria often occur in characteristic arrangements and these forms have specific names as well;<ref name=Baron>{{cite book | vauthors = Salton MR, Kim KS | title = Structure. ''In:'' Baron's Medical Microbiology| editor = Baron S| display-editors = etal| edition = 4th | publisher = Univ of Texas Medical Branch | year = 1996 | id = [https://www.ncbi.nlm.nih.gov/books/NBK8477/ (via NCBI Bookshelf)] | isbn = 0-9631172-1-1}}</ref> listed here are the basic forms as well as representative bacterial genera:<ref name="arrangement"/> * Diplococci are pairs of cocci. * '''Streptococci''' are chains of cocci such as ''Streptococcus pyogenes''. * '''Staphylococci''' are irregular (grape-like) clusters of cocci (e.g. ''Staphylococcus aureus''). * '''Tetrads''' are clusters of four cocci arranged within the same plane such as ''Micrococcus sp.''). * '''Sarcina''' describes a pack-like cuboidal arrangement of eight cocci such as ''Sarcina ventriculi''.
====Gram-positive cocci==== The gram-positive cocci are a large group of bacteria with similar morphology. All are spherical or nearly so, but they vary considerably in size. Members of some genera are identifiable by the way cells are attached to one another: in pockets, in chains, or grape-like clusters. These arrangements reflect patterns of cell division and that cells stick together. ''Sarcina'' cells, for example, are arranged in cubical pockets because cell division alternates regularly among the three perpendicular planes. ''Streptococcus'' spp. resemble a string of beads because division always occurs in the same plane. Some of these strings, for example, ''S. pneumoniae'''','' are only two cells long. They are called ''diplococci.'' Species of ''Staphylococcus'' have no regular plane of division. They form grape-like structures.<ref name="Ingraham">{{Cite book|title=Introduction to Microbiology|url=https://archive.org/details/introductiontomi0000ingr|url-access=registration|first1=Catherine A.|last1=Ingraham|first2=John L.|last2=Ingraham|year=2000}}</ref>
The various gram-positive cocci differ physiologically and by habitat. ''Micrococcus'' spp. are obligate aerobes that inhabit human skin. ''Staphylococcus'' spp. also inhabit human skin, but they are facultative anaerobes. They ferment sugars, producing lactic acid as an end product. Many of these species produce carotenoid pigments, which color their colonies yellow or orange. ''Staphylococcus aureus'' is a major human pathogen. It can infect almost any tissue in the body, frequently the skin. It often causes nosocomial (hospital-acquired) infections.<ref name="Ingraham"/>
====Diplococci==== {{redirect-distinguish|Diplococcus|Diplodocus}} thumb|Structure b represents diplococcus bacteria
'''Diplococci''' are pairs of cocci. Examples of gram-negative diplococci are ''Neisseria'' spp. and ''Moraxella catarrhalis''. Examples of gram-positive diplococci are ''Streptococcus pneumoniae'' and ''Enterococcus'' spp.<ref name="(Ph.D.)2007">{{cite book|url=https://books.google.com/books?id=FPd38Gc33gwC&pg=PA395|title=Microbiology|author=Richard A. Harvey (Ph.D.)|publisher=Lippincott Williams & Wilkins|year=2007|isbn=978-0-7817-8215-9|pages=395–}}</ref><ref name=":0a">{{Cite web|url=https://sciencing.com/types-coccus-bacteria-8511915.html|title=Types of Coccus Bacteria|last=Gillespie|first=Claire|date=August 20, 2018|website=Sciencing|access-date=2019-12-01}}</ref> Presumably, diplococcus has been implicated in encephalitis lethargica.<ref>{{Cite news | url=https://news.bbc.co.uk/2/hi/health/3930727.stm | title=Mystery of the forgotten plague| date=2004-07-27}}</ref> The genus ''Neisseria'' belongs to the family Neisseriaceae. This genus, ''Neisseria'', is divided into more than ten different species, but most of them are gram negative and coccoid. The gram-negative, coccoid species include: ''Neisseria cinerea'', ''N. gonorrhoeae'', ''N. polysaccharea'', ''N. lactamica'', ''N. meningitidis'', ''N. mucosa'', ''N. oralis'' and ''N. subflava''. The most common of these species are the pathogenic ''N. meningitidis'' and ''N. gonorrhoeae''.<ref>{{Cite web|url=https://www.gbif.org/species/3220214|title=Neisseria Trevisan, 1885|website=www.gbif.org|language=en|access-date=2019-12-02}}</ref>
The genus ''Moraxella'' belongs to the family ''Moraxellaceae''. This genus, ''Moraxellaceae'', comprises gram-negative coccobacilli bacteria: ''Moraxella lacunata'', ''M. atlantae'', ''M. boevrei'', ''M. bovis'', ''M. canis'', ''M. caprae'', ''M. caviae'', ''M. cuniculi'', ''M. equi'', ''M. lincolnii'', ''M. nonliquefaciens'', ''M. osloensis'', ''M. ovis'', ''M. saccharolytica'', and ''M. pluranimalium''.<ref>{{Cite web|url=https://lpsn.dsmz.de/species/moraxella-catarrhalis|title=Moraxella|website=LPSN|access-date=2019-12-02}}</ref> However, only one has a morphology of diplococcus, ''M. catarrhalis'', a salient pathogen contributing to infections in the human body.<ref>{{Cite book|title=Epidemiology and pathogenesis of Moraxella catarrhalis colonization and infection|author=Verhaegh, S.J.C. (Suzanne)|date=2011-06-01|publisher=Lippincott Williams & Wilkins |isbn=978-0-397-51568-4|oclc=929980928}}</ref>
The species ''Streptococcus pneumoniae'' belongs to the genus ''Streptococcus'' and the family ''Streptococcaceae''. The genus ''Streptococcus'' has around 129 species and 23 subspecies<ref>{{Cite web|url=https://lpsn.dsmz.de/genus/streptococcus|title=Streptococcus|website=LPSN|access-date=2019-12-02}}</ref> that benefit many microbiomes on the human body. There are many species that show non-pathogenic characteristics; however, there are some, like ''S. pneumoniae'', that exhibit pathogenic characteristics in the human body.<ref>{{Cite web|url=https://www.gbif.org/species/111218319|title=Streptococcus pneumoniae (Klein, 1884) Chester, 1901|website=www.gbif.org|language=en|access-date=2019-12-02|archive-date=2020-04-01|archive-url=https://web.archive.org/web/20200401122032/https://www.gbif.org/species/111218319}}</ref><ref name=":0a" />
The genus ''Enterococcus'' belongs to the family ''Enterococcaceae''. This genus is divided into 58 species and two subspecies.<ref>{{Cite web|url=https://lpsn.dsmz.de/genus/enterococcus|title=Enterococcus|website=LPSN|access-date=2019-12-02}}</ref> These gram-positive, coccoid bacteria were once thought to be harmless to the human body. However, within the last ten years, there has been an influx of nosocomial pathogens originating from ''Enterococcus'' bacteria.<ref>{{Cite journal|last1=Fisher|first1=Katie|last2=Phillips|first2=Carol|date=2009|title=The ecology, epidemiology and virulence of Enterococcus|journal=Microbiology|volume=155|issue=6|pages=1749–1757|doi=10.1099/mic.0.026385-0|pmid=19383684|issn=1350-0872|doi-access=free}}</ref><ref name=":0a" />
===Bacillus=== A '''bacillus''' ({{plural form}}: '''bacilli'''), also called a '''bacilliform bacterium''' or often just a '''rod''' (when the context makes the sense clear), is a rod-shaped bacterium or archaeon. Bacilli are found in many different taxonomic groups of bacteria. However, the name ''Bacillus'', capitalized and italicized, refers to a specific genus of bacteria. The name Bacilli, capitalized but not italicized, can also refer to a less specific taxonomic group of bacteria that includes two orders, one of which contains the genus ''Bacillus''. When the word is formatted with lowercase and not italicized, 'bacillus', it will most likely be referring to shape and not to the genus. Bacilliform bacteria are also often simply called rods when the bacteriologic context is clear.<ref>{{cite web|url=http://classes.midlandstech.edu/carterp/courses/bio225/chap04/lecture2.htm |access-date=8 August 2016 |title=The Size, Shape, And Arrangement Of Bacterial Cells |publisher=Midlands Technical College |archive-url=https://web.archive.org/web/20160809135552/http://classes.midlandstech.edu/carterp/courses/bio225/chap04/lecture2.htm |archive-date=9 August 2016 }}</ref>
Bacilli usually divide in the same plane and are solitary, but can combine to form diplobacilli, streptobacilli, and palisades.<ref>{{cite web|url=http://www2.nemcc.edu/bkirk/Template%201/MICROCHAPTER4NOTES.htm |archive-url=https://web.archive.org/web/20120923190032/http://www2.nemcc.edu/bkirk/Template%201/MICROCHAPTER4NOTES.htm |archive-date=23 September 2012 |title=Chapter 4: Functional Anatomy Of Prokaryotic And Eukaryotic Cells}}</ref> * Diplobacilli: Two bacilli arranged side by side with each other. * Streptobacilli: Bacilli arranged in chains. * Coccobacillus: Oval and similar to coccus (circular shaped bacterium).<ref>{{cite web|url=http://faculty.ccbcmd.edu/courses/bio141/lecguide/unit1/shape/shape.html|title=Sizes, Shapes, and Arrangements of Bacteria|author=Kaiser GE|publisher=The Community College of Baltimore County|access-date=8 August 2016|archive-date=11 August 2019|archive-url=https://web.archive.org/web/20190811021638/http://faculty.ccbcmd.edu/courses/bio141/lecguide/unit1/shape/shape.html}}</ref>
There is no connection between the shape of a bacterium and its color upon Gram staining; there are both gram-positive rods and gram-negative rods. MacConkey agar can be used to distinguish among gram-negative bacilli such as ''E. coli'' and salmonella.<ref name="urlGram Negative Bacilli">{{cite web |url=http://education.med.nyu.edu/courses/old/microbiology/courseware/infect-disease/Gram_Neg_Byacilli5.html |title=Gram Negative Bacilli |archive-url=https://web.archive.org/web/20090314013352/http://education.med.nyu.edu/courses/old/microbiology/courseware/infect-disease/Gram_Neg_Bacilli5.html |archive-date=14 March 2009 |publisher=NYU School of Medicine}}</ref>
====Arrangements==== Bacilli usually divide in the same plane and are solitary, but can combine to form diplobacilli, streptobacilli, and palisades.<ref name="pmid17098054">{{cite book | vauthors = Harry E, Monahan L, Thompson L | title = Bacterial cell division: the mechanism and its precision | series = International Review of Cytology | volume = 253 | pages = 27–94 | date = 2006 | pmid = 17098054 | doi = 10.1016/S0074-7696(06)53002-5 |isbn=978-0-12-373597-3 }}</ref>
* Diplobacilli: Two bacilli arranged side by side with each other. * Streptobacilli: Bacilli arranged in chains.<ref name="Brock_2008" /><ref name="Cole_1990" />
==== Gram-positive examples ==== {{main|Gram-positive bacteria}} * ''Actinomyces'' * ''Bacillus'' * ''Clostridium'' * ''Corynebacterium'' * ''Listeria'' * ''Propionibacterium''
==== Gram-negative examples ==== {{main|Gram-negative bacteria}} * ''Bacteroides'' * ''Citrobacter'' * ''Enterobacter'' * ''Escherichia'' * ''Klebsiella'' * ''Pseudomonas'' * ''Proteus'' * ''Salmonella'' * ''Serratia'' * ''Shigella'' * ''Vibrio'' * ''Yersinia''
===Coccobacillus=== [[File:Coxiella burnetii 01.JPG|thumb|''Coxiella burnetii'' (TEM)]]
A '''coccobacillus''' (plural '''coccobacilli'''), or '''bacillococcus''', is a type of bacterium with a shape intermediate between cocci (spherical bacteria) and bacilli (rod-shaped bacteria). Coccobacilli, then, are very short rods which may be mistaken for cocci.<ref>{{Cite web|url=https://microbeonline.com/gram-negative-cocci-coccobacilli-medical-significance-list-bacteria-diseases/|title=Gram-Negative Cocci and Coccobacilli of Medical Significance; List of Bacteria and Diseases|first=Acharya|last=Tankeshwar|date=April 11, 2016}}</ref> The word ''coccobacillus'' reflects an intermediate shape between ''coccus'' (spherical) and ''bacillus'' (elongated).<ref name="Brock_2008" />
''Haemophilus influenzae'', ''Gardnerella vaginalis'', and ''Chlamydia trachomatis'' are coccobacilli. ''Aggregatibacter actinomycetemcomitans'' is a Gram-negative coccobacillus prevalent in subgingival plaques. ''Acinetobacter'' strains may grow on solid media as coccobacilli. ''Bordetella pertussis'' is a Gram-negative coccobacillus responsible for causing whooping cough. ''Yersinia pestis'', the bacterium that causes plague, is also a coccobacillus.<ref>{{Cite book |last=Collins |first=Frank M. |url=https://www.ncbi.nlm.nih.gov/books/NBK7627/|title=Medical Microbiology |date=1996 |publisher=University of Texas Medical Branch at Galveston |isbn=978-0-9631172-1-2 |editor-last=Baron |editor-first=Samuel |edition=4th|location= |chapter=Pasteurella, Yersinia, and Francisella |pmid=21413268 |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK7798/}}</ref>
''Coxiella burnetii'' is also a coccobacillus.<ref name="McCaul_1981">{{cite journal | vauthors = McCaul TF, Williams JC | title = Developmental cycle of Coxiella burnetii: structure and morphogenesis of vegetative and sporogenic differentiations | journal = Journal of Bacteriology | volume = 147 | issue = 3 | pages = 1063–1076 | date = September 1981 | pmid = 7275931 | pmc = 216147 | doi = 10.1128/jb.147.3.1063-1076.1981 }}</ref><ref name="urlpersistent rickettsial disease">{{cite web |last=Walters |first=Sherry |editor-last=Thacker |editor-first=Leon |title=Q-fever (Coxiella burnetti) Zoonoses: An historical and persistent rickettsial disease |url=http://www.addl.purdue.edu/newsletters/2004/spring/qfever.htm |website=Purdue University Animal Disease Diagnostic Laboratory|date=Spring 2004|access-date=22 September 2025}}</ref> Bacteria from the genus ''Brucella'' are medically important coccobacilli that cause brucellosis. ''Haemophilus ducreyi'', another medically important Gram-negative coccobacillus, is observed in sexually transmitted disease, chancroid, of Third World countries.<ref>{{Cite book |last1=Schaechter |first1=Moselio |url=https://books.google.com/books?id=1Zl70SLDU3oC |title=Schaechter's Mechanisms of Microbial Disease |last2=DiRita |first2=Victor J. |last3=Dermody |first3=Terence |publisher=Lippincott Williams & Wilkins |year=2007 |isbn=978-0-7817-5342-5 |editor-last=Schaechter |editor-first=Moselio |edition=4 |location=Philadelphia, Pa. |page=666 |editor-last2=Engleberg |editor-first2=N. Cary}}</ref>
===Spiral=== '''Spiral bacteria''' are another major bacterial cell morphology.<ref name="Brock_2008" /><ref>{{cite journal | vauthors = Young KD | title = The selective value of bacterial shape | journal = Microbiology and Molecular Biology Reviews | volume = 70 | issue = 3 | pages = 660–703 | date = September 2006 | pmid = 16959965 | pmc = 1594593 | doi = 10.1128/MMBR.00001-06 }}</ref><ref>{{cite book |first1=Maria |last1=Csuros |first2=Csaba |last2=Csuros |date=1999 |title=Microbiological Examination of Water and Wastewater |location=Boca Raton, Florida |publisher=CRC Press |pages=16–17 |isbn=978-1-56670-179-2 }}</ref><ref>{{cite journal |last=Young |first=Kevin D. |date=September 2006 |title=The Selective Value of Bacterial Shape |journal=Microbiology and Molecular Biology Reviews |volume=70 |issue=3 |pages=660–703 |doi=10.1128/MMBR.00001-06 |pmid=16959965 |pmc=1594593}}</ref> Spiral bacteria can be sub-classified as spirilla, spirochetes, or vibrios based on the number of twists per cell, cell thickness, cell flexibility, and motility.<ref name="Foundations">{{cite book|last1=Talaro|first1=Kathleen|url=https://books.google.com/books?id=4hhgYEJZfisC&q=spirillum%20and%20spirochete&pg=PA108|title=Foundations in Microbiology|date=2007|publisher=McGraw-Hill|isbn=978-0-07-126232-3|edition=6th International|pages=108–109|access-date=11 September 2017}}</ref>
Bacteria are known to evolve specific traits to survive in their ideal environment.<ref name="Tan_2022">{{cite journal | vauthors = Tan YS, Zhang RK, Liu ZH, Li BZ, Yuan YJ | title = Microbial Adaptation to Enhance Stress Tolerance | journal = Frontiers in Microbiology | volume = 13 | article-number = 888746 | date = 2022 | pmid = 35572687 | pmc = 9093737 | doi = 10.3389/fmicb.2022.888746 | doi-access = free }}</ref> Bacteria-caused illnesses hinge on the bacteria's physiology and their ability to interact with their environment, including the ability to shapeshift. Researchers discovered a protein that allows the bacterium ''Vibrio cholerae'' to morph into a corkscrew shape that likely helps it twist into — and then escape — the protective mucus that lines the inside of the gut.<ref name="Tan_2022" />
====Spirillum==== [[File:ARS Campylobacter jejuni.jpg|125px|thumb|''Campylobacter jejuni'' is a common pathogen of bacterial food-related gastrointestinal illness.]] A spirillum (plural spirilla) is a rigid spiral bacterium that is gram-negative and frequently has external amphitrichous or lophotrichous flagella.<ref name="Foundations" /> Examples include: * Members of the genus ''Spirillum'' * ''Campylobacter'' species, such as ''Campylobacter jejuni'', a foodborne pathogen that causes campylobacteriosis * ''Helicobacter'' species, such as ''Helicobacter pylori'', a cause of peptic ulcers
====Spirochetes==== [[File:Treponema pallidum.jpg|thumb|150px|right|Thin spirochete ''Treponema pallidum'' bacteria, the causative agent of syphilis magnified 400 times.]] A spirochete (plural spirochetes) is a very thin, elongate, flexible, spiral bacteria that is motile via internal periplasmic flagella inside the outer membrane.<ref name="Foundations" /> They comprise the phylum Spirochaetes. Owing to their morphological properties, spirochetes are difficult to Gram-stain but may be visualized using dark field microscopy or Warthin–Starry stain.<ref>{{cite book |year=2008 |chapter=Chapter 53: Histology and histochemical stains |editor1-last=Humphrey |editor1-first=Peter A. |editor2-last=Dehner |editor2-first=Louis P. |editor3-last=Pfeifer |editor3-first=John D. |title=The Washington Manual of Surgical Pathology |location=Philadelphia |publisher=Lippincott Williams & Wilkins |page=680 |isbn=978-0-7817-6527-5 }}</ref> Examples include: * ''Leptospira'' species, which cause leptospirosis. * ''Borrelia'' species, such as ''Borrelia burgdorferi'', a tick-borne bacterium that causes Lyme disease * ''Treponema'' species, such as ''Treponema pallidum'', subspecies of which causes treponematoses, including syphilis
===Helical=== ''Helicobacter'' species are helically shaped, the most common example of which is ''Helicobacter pylori''.<ref name="Constantino">{{cite journal |vauthors=Constantino MA, Jabbarzadeh M, Fu HC, Bansil R |title=Helical and rod-shaped bacteria swim in helical trajectories with little additional propulsion from helical shape |journal=Sci Adv |volume=2 |issue=11 |article-number=e1601661 |date=November 2016 |pmid=28138539 |pmc=5262464 |doi=10.1126/sciadv.1601661 |url=}}</ref> A helical shape is seen to be better suited for movement of bacteria in a viscous medium.<ref name="Young">{{cite journal | vauthors = Young KD | title = The selective value of bacterial shape | journal = Microbiol Mol Biol Rev | volume = 70 | issue = 3 | pages = 660–703 | date = September 2006 | pmid = 16959965 | pmc = 1594593 | doi = 10.1128/MMBR.00001-06 | url = }}</ref>
== See also == * Bacterial morphological plasticity * Ferdinand Cohn – gave first named shapes of bacteria
== References == {{reflist|2}}
== External links == * [http://www.bacteria-world.com/bacteria-pictures.htm Bacteria Picture Gallery]
{{bacteria}} {{anatomy}}
Category:Bacteria Category:Morphology (biology)