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Until a couple of decades ago, microbiologists thought of prokaryotes as isolated entities living apart. This model, however, does not reflect the true ecology of prokaryotes, most of which prefer to live in communities where they can interact. A biofilm    is a microbial community held together in a gummy-textured matrix, consisting primarily of polysaccharides secreted by the organisms, together with some proteins and nucleic acids. Biofilms grow attached to surfaces. Some of the best-studied biofilms are composed of prokaryotes, although fungal biofilms have also been described.

Biofilms are present almost everywhere. They cause the clogging of pipes and readily colonize surfaces in industrial settings. They have played roles in recent, large-scale outbreaks of bacterial contamination of food. Biofilms also colonize household surfaces, such as kitchen counters, cutting boards, sinks, and toilets.

Interactions among the organisms that populate a biofilm, together with their protective environment, make these communities more robust than are free-living, or planktonic, prokaryotes. The sticky substance that holds bacteria together also excludes most antibiotics and disinfectants, making biofilm bacteria hardier than their planktonic counterparts. Overall, biofilms are very difficult to destroy, because they are resistant to many of the common forms of sterilization.

Characteristics of prokaryotes

There are many differences between prokaryotic and eukaryotic cells. However, all cells have four common structures: a plasma membrane that functions as a barrier for the cell and separates the cell from its environment; cytoplasm, a jelly-like substance inside the cell; genetic material (DNA and RNA); and ribosomes, where protein synthesis takes place. Prokaryotes come in various shapes, but many fall into three categories: cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped) ( [link] ).

Scanning electron micrograph a shows ball-shaped cocci. Scanning electron micrograph b shows rod-shaped bacilli. Scanning electron micrograph c shows corkscrew-shaped spirilla.
Many prokaryotes fall into three basic categories based on their shape: (a) cocci, or spherical; (b) bacilli, or rod-shaped; and (c) spirilla, or spiral-shaped. (credit a: modification of work by Janice Haney Carr, Dr. Richard Facklam, CDC; credit c: modification of work by Dr. David Cox, CDC; scale-bar data from Matt Russell)

The prokaryotic cell

Recall that prokaryotes ( [link] ) are unicellular organisms that lack organelles surrounded by membranes. Therefore, they do not have a nucleus but instead have a single chromosome—a piece of circular DNA located in an area of the cell called the nucleoid. Most prokaryotes have a cell wall lying outside the plasma membrane. The composition of the cell wall differs significantly between the domains Bacteria and Archaea (and their cell walls also differ from the eukaryotic cell walls found in plants and fungi.) The cell wall functions as a protective layer and is responsible for the organism’s shape. Some other structures are present in some prokaryotic species, but not in others. For example, the capsule    found in some species enables the organism to attach to surfaces and protects it from dehydration. Some species may also have flagella (singular, flagellum) used for locomotion, and pili (singular, pilus) used for attachment to surfaces and to other bacteria for conjugation. Plasmids, which consist of small, circular pieces of DNA outside of the main chromosome, are also present in many species of bacteria.

Questions & Answers

Is there any other type of a eukaryotic cell.
Grace Reply
what is bionomial nomenclature
Rachaelda Reply
state the role of mitochondria
mitochondria ia power House of the cell. it provides energy and as ATP. Cells energy currency.
The scientific method of giving short names on the basis of genius and species.
it is introduce by carlous Lennieus
it is naming of living organism where by they are given two names one generic and the other specific name
what is element
Kofi Reply
Structure of water molecule and it's biological significance. .....help guys
what is the formula for chemical equetion
Justo Reply
Why mitochondria is called the power house of the congo the bahamas cell
Farrukh Reply
how can I learn this subject?
mascuud Reply
what's microscope?
Mathias Reply
A device used to study a very small specimen thst cannt br seen with the naked eyes for example cells, or microorganisms.
a medical device used to study cells bacteria viruses and parasites e.g electron microscope for studying cells.
exactly microscope
is an instrument use to view microorganisms such as viruses and bacteria
it is an instrument used to magnify micro-scopic organism
what does multi seminar mean
Grace Reply
many seminars
how many cells on the human
Amar Reply
how is genetic testing?
which party of an internal leaf which represent organ and tissue
3 trilleons cells on the human
name the groups of bacteria, what they cause and explain the components of bacterial cell
what are the three level of relationship that exist between organism?
trillions of cells
who many cell are in the human body
Ayasso Reply
trillions of cells
what causes coloring of skin variation
Prince Reply
what is your answer
Jonathan Reply
which qn
what is chemosynthesis
who many cell are in the human body
there are billion cells in human body
what are three stages of mitosis
they're alot cells in our body
what are the stages of mitosis
they are prophez methaphez anaphez. thelophez
anyone to explain each of the following,, prophase, metaphase, anaphase and telophase
what is a filial
Mbah Reply
denoting the offspring of a cross
what is the difference between chlorophyll and photosynthesis
Rahman Reply
Chloe is the green pigment found in green plants while photosynthesis is the process by which plant produce their own food
photosynthesis is the production of food by plant while chlorophyll is the green pigment that is found in chloroplast..
chrolophyll (green colouring matter in leaves) while photosynthesis (process by which green plants make their own food)
What isaac life
chlorophyll is the pigment that gives a plant its green color while photosynthesis is when a plant makes it's own food.
photo meaning light and synthesis meaning to make
what are the functions of parts of microscope
Bami Reply
base to provide support
only base what about the other
has only one function
Mirror ... used to reflect light
Which of the following is best at showing the life expandency of an individual within a a population
Daniel Reply
perianth is present in which gymnosperms ?
DebaXish Reply
perianth is present in which gymnos4perms ?
DebaXish Reply

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Source:  OpenStax, Bi 101 for lbcc ilearn campus. OpenStax CNX. Nov 28, 2013 Download for free at http://legacy.cnx.org/content/col11593/1.1
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