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Cytophaga are motile aquatic bacteria that glide. Fusobacteria inhabit the human mouth and may cause severe infectious diseases. The largest genus of the CFB group is Bacteroides , which includes dozens of species that are prevalent inhabitants of the human large intestine, making up about 30% of the entire gut microbiome ( [link] ). One gram of human feces contains up to 100 billion Bacteroides cells. Most Bacteroides are mutualistic. They benefit from nutrients they find in the gut, and humans benefit from their ability to prevent pathogens from colonizing the large intestine. Indeed, when populations of Bacteroides are reduced in the gut—as often occurs when a patient takes antibiotics—the gut becomes a more favorable environment for pathogenic bacteria and fungi, which can cause secondary infections.

A micrograph of many rod shaped cells.
Bacteroides comprise up to 30% of the normal microbiota in the human gut. (credit: NOAA)

Only a few species of Bacteroides are pathogenic. B. melaninogenicus , for example, can cause wound infections in patients with weakened immune systems.

  • Why are Cytophaga , Fusobacterium , and Bacteroides classified together as the CFB group?

Planctomycetes

The Planctomycetes are found in aquatic environments, inhabiting freshwater, saltwater, and brackish water. Planctomycetes are unusual in that they reproduce by budding, meaning that instead of one maternal cell splitting into two equal daughter cells in the process of binary fission, the mother cell forms a bud that detaches from the mother cell and lives as an independent cell. These so-called swarmer cells are motile and not attached to a surface. However, they will soon differentiate into sessile (immobile) cells with an appendage called a holdfast that allows them to attach to surfaces in the water ( [link] ). Only the sessile cells are able to reproduce.

a) A micrograph of an oval cell with long projections attached to a root-shaped structure labeled holdfast. The oval cell is approximately 500 nm in diameter. B) A micrograph of a similar looking cell with a long projection that is not attached to a holdfast.
(a) Sessile Planctomycetes have a holdfast that allows them to adhere to surfaces in aquatic environments. (b) Swarmers are motile and lack a holdfast. (credit: modification of work by American Society for Microbiology)

[link] summarizes the characteristics of some of the most clinically relevant genera of nonproteobacteria.

Nonproteobacteria
Example Genus Microscopic Morphology Unique Characteristics
Bacteroides Gram-negative bacillus Obligate anaerobic bacteria; abundant in the human gastrointestinal tract; usually mutualistic, although some species are opportunistic pathogens
Cytophaga Gram-negative bacillus Motile by gliding; live in soil or water; decompose cellulose; may cause disease in fish
Fusobacterium Gram-negative bacillus with pointed ends Anaerobic; form; biofilms; some species cause disease in humans (periodontitis, ulcers)
Leptospira Spiral-shaped bacterium (spirochetes); gram negative-like (better viewed by darkfield microscopy); very thin Aerobic, abundant in shallow water reservoirs; infect rodents and domestic animals; can be transmitted to humans by infected animals’ urine; may cause severe disease
Sphingobacterium Gram-negative bacillus Oxidase positive; nonmotile; contain high amounts of sphingophospholipids; rarely cause disease in humans
Treponema Gram-negative-like spirochete; very thin; better viewed by darkfield microscopy Motile; do not grow in culture; T. pallidum (subspecies T. pallidum pallidum ) causes syphilis

Questions & Answers

what are the roles of microorganisms in human being
Buhari Reply
some causes disease, others are not disease causing
Clark
they're necessary in our digestive system+the skin,everywhere actually the number of them in the human body alone is higher(by millions)than the number of humans cells,they're indispensable in the food industry,others are fundamental to make medicines and more,what exactly are you asking about ?
BENNINI
What are the natural occurring elements found in organisms on earth?
Otu Reply
some of the naturally occurring elements found in organisms are carbon, nitrogen, hydrogen, oxygen
Yashi
thanks
Mariam
some of them are carbon, oxygen, nitrogen, hydrogen, phosphorus and sulfur
Jamal
what is Zika virus?
Somali Reply
Zika virus is a mosquito-borne flavivirus that was first identified in Uganda in 1947 in monkeys. 
Cumar
intracellular vesicles are found in
Akshay Reply
how do i report widal slide results
Isaac Reply
how food can be used as a substrate for the growth of microorganisms
Ashi Reply
what is the importance of understanding chemistry in the field of microbiology and food technology?
Charmaine Reply
What is different between eukaryotes and prokcaryotic
Abia Reply
main difference is that eukaryotic cells possess membrane bound organelles
Iqra
prokaryotes are primitive organisms that doesn't contain membrane bound nucleus or any orgenelle while in eukaryotes membrane bound orgenelles and nucleus is present
Yashi
what s anatomy
jane Reply
its mean body structure, function, and systems
gazi
study of internal structure of living things
Falere
anatomy is the study structure of the made human
isir
anotomy is the actual study of body internally and externally Which include how itis made. for what and what is need of this
Iqra
la science anatomie c'est la science qui nous aide à étudier l'homme
Baraka
okay
Baraka
Ancestor are they real
Rapheal Reply
yes of course
David
yes please
Clark
50 50, depending on the accuracy of the clan records.
Vincent
okay
Baraka
Why protist is not a kingdom of Linnaeus 'S taxonomy?
Neha Reply
I dont know
Jeewraj
Linnaeus used Aristotle's criteria for dividing living organisms into kingdoms. Plants are immobile and insensitive, while animals are mobile and sensitive. the creatures he saw through the microscope were mobile, so he attributed them to animals.
Lad
name the different types of media use in lab to detect the micro organisms
Shehzadi Reply
The different types of media used in the lab to detect the microorganisms is known as cell culture..
Tean
solid media or broth is used to grow and detect microorganisms
Pohor
what is microbiology
Baraka
the study of large living organisms
Pratibha
the study of organisms which are micro in range
Vency
what is autoclaving?
Yashi
process for sterilization
Vency
is a machine used on the process of sterilisation
Clark
what is difference between hot air oven and autoclave as they both are used for sterilization ?
Vency
autoclave basically do moist heat sterilization while hot air oven do sterilization by dry heat.....
Yashi
what is the microbe
HUSSAIN
which method out of these two is best?
Yashi
why human have microbe
HUSSAIN
Hi
Sadam
hi to all
Sadam
depends on what to sterilize
Vency
microbes
Md
what is knowledge
HUSSAIN
well idea
Daniel
what are the importance of microbiologe to a nurse
Enny Reply
it enable a nurse to know the weight and height of a patient
Abotu
it helps the nurse in way as to give first aid to patient on which basis doctor will take diagonos
Iqra
disagree with both of you
Akhtar
ok
Abotu
Your Own idea
Abotu
it helps a nurse to be able to counsel a patient /client
Abotu
cell culture
Tean
Types of micro organisms
Jennifer Reply
Who discovered plant and animal cell
Jennifer
Robert Hooke
Martha
Father of microbiology
Jennifer Reply
Antonie van Leeuwenhoek
Satarupa
Practice MCQ 3

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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