Bacteria

Sarah Schwarzschild

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General Bacteria Anatomy
(2)


Diagnostic Characteristics

Bacteria is one of two prokaryotic domains / Monera branches, the other being archaea. These organisms are usually unicellular, meaning they consist of only one cell. Like archaea, bacteria have no nuclear envelope (membrane enclosing the nucleus) or membrane-enclosed organelles (cell parts with specialized functions). Unlike other organisms, bacteria do not have any histones, a type of structural protein, associated with their DNA. Bacteria differ from archaea in that their cell walls contain peptidoglycan, constructed by modified sugar polymers cross linked by short polypeptides. Another major difference between the two domains is that they have different sequencing within their ribosomal RNA, which makes up part of a ribosome, a cell organelle. Bacteria have only one RNA polymerase (enzyme used to connect chain of ribonucleotides, the building blocks of RNA, during transcription, a cellular process), while archaea have three. Bacteria also have much less introns, the part of a gene that does not provide instructions for a protein, within their DNA (1).

Habitats
There are too many varying species of bacteria to confine them all within a certain habitat. Beause bacteria need very little to survive, they typically have enough to make everything else they need to grow and reproduce(14 VM). All they need is water (in the form of moisture), an energy source (such as sugar), and a few salts(14 VM). However, it is important to note that they cannot live in as extreme environments as archaea prokaryotes can (hot springs, salt ponds, etc.). So while they cannot live everywhere, they inhabit several different types of habitats (a bacteria's habitat depends on the species) (1).
Bacteria have many various adaptations that allow them to occupy a wide variety of habitats. Most species of bacteria are aerobic, meaning they require oxygen to thrive and reproduce. Other species of bacteria are anaerobic; meaning the presence of gaseous oxygen is unnecessary and usually detrimental for their ability to survive. Anaerobic bacteria occupy such habitats as deep underwater sediments, rock and solid ice. Bacteria however, are not extremophiles and therefore cannot thrive in environments with extreme conditions like hot springs and thermal vents on the ocean floor (5, NK).

Major Types
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A scanning electron microscope photograph of a strain of bacteria known as Staphylococcus epidermidis (15)(SS)

1. Proteobacteria- These bacteria are gram-negative, meaning they have more complex walls with less peptidoglycan. This group is very diverse, including photoautotrophs (use light energy to create organic compounds from carbon dioxide--photosynthesis), chemoautotrophs (needs carbon dioxide, but receives energy by oxidizing inorganic material), and heterotrophs (obtains organic material by consuming other organisms/their by-products), as well as both anaerobic (lacks oxygen) and aerobic (contains/utilizes oxygen) species. There are five subgroups: Alpha, Beta, Gamma, Delta, and Epsilon Proteobacteria (1).

This is a a dead specimen of a proteobacteria known as an Escherichia coli . (8, GR)

2. Chlamydias- These are parasites (pests that steal their nutrients from a host organism) that can survive only within the cells of animals, for they depend on their hosts for resources. This type of bacteria is unique, for it lacks peptidoglycan in its cell wall (1).
3. Spirochetes- These are helical-shaped heterotrophs. They rotate their internal filaments to produce a corkscrew-like movement (1).
4. Gram-Positive Bacteria- The majority of these bacteria are gram-positive, meaning they have simpler cell walls with a large amount of peptoglycan (1).Gram positive bacteria makeup the majority of the bacteria in the soil.(16)(SJB)
5. Cyanobacteria- These are photoautotrophs. Much like plants, they perform photosynthesis, so they tend to live in or around water (1).

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The cyanobacteria give the water in this New Zealand lake its green tint (OZ).
Basic Anatomy
Bacteria are almost always unicellular, meaning they are organisms made up of only one cell. Most bacterial cell walls contain peptidoglycan, constructed by modified sugar polymers cross linked by short polypeptides. This is how antibiotics kill harmful bacteria cells without damaging the cells of human beings. Antibiotics inhibit the synthesis of cross-links in peptidoglycan and prevent the formation of a functional cell wall. A capsule is a sticky substance that forms another protective layer in most bacteria. Capsules also help bacteria stick to different materials and other prokaryotes. Some bacteria move around by using different types of flagella (long cellular appendages specialized for locomotion). Many pili form on the outside surface of bacteria cells. Pili are surface appendages used to connect and hold bacteria to other bacteria or to other materials (1).
DNA in bacteria is found as a snarled fiber (one double-stranded DNA molecule in the form of a ring, often called a genophore) in a region known as the nucleoid region within the cytoplasm. Unlike other organisms, bacteria do not have any histones, a type of protein, associated with their DNA. Separate from the bacterial chromosome are plasmids, small rings of DNA that also carry a few genes. Plasmids can either help genetic recombination (inheritance of new characteristics from parents) known as F plasmids, or they can cary genes that help resist certian types of antibiotics (known as R plasmids). More genetic variation are caused by transposons (a piece of DNA that can copy itself and move the copy to another spot in the cell's genome) (1). (SV)
There are three basic shapes to bacteria: coccus, bacillus, and spirillium. The cocci (plural for cocci) are spherical in shape, the bacilli are rod-shaped, and the spirilla are shaped like a spiral. Bacteria can also be vibrio, which are bacteria that have a curved shape. There are also the spirochetes, which have a tighter spiral shape (like a corkscrew) than the spirilla (6). Another main difference between the spirilla and spirochetes is that the spirilla have a rigid cell all, while the spirochetes have a flexible one (7) [HZ].

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Above is the basic anatomy of a bacterium. The capsule helps the cell maintain it's shape and helps protect against environmental stresses. The cell wall is present in all prokaryotic cells except the mycoplasmas. There are over 15,00 ribosomes per cell. The single stranded DNA is contained in a cirular molecule in the center of the cell. Most bacteria have plasmids, extra DNA, which they can pass back and forth between eachother easily. Most activity occurs in the protein, chemical rich cytoplasm- such as metabolism, reproduction and protein manufacturing (9) AR.


Transport of Materials
Some bacteria are photoautotrophs that perform photosynthesis to take in carbon dioxide and produce glucose and oxygen. Others are chemoautotrophs which need carbon dioxide and which oxidize (remove electrons from) inorganic materials to get energy. Photoheterotroph bacteria use light energy to make ATP (energy source), but they need to take in organic carbon. Lastly there are chemoheterotroph bacteria that need to take in organic material for energy and for carbon. Chemoheterotrophs are either saprobes (decomposers) that absorb nutrients from dead organic matter or parasites that get their nutrients from the body of living hosts. Bacteria are also vital to different nutrient cycles; life depends on bacteria and their ability to metabolize inorganic molecules within nutrient cycles. Certain bacteria perform the nitrogen fixation step of the nitrogen cycle. Other aerobic bacteria use oxygen for cellular respiration, which is part of the oxygen cycle (1).
Bacteria take up nutrient material (like carbon dioxide,etc.) through their membrane. Bacteria usually use active transport, which is the process of moving substances across a membrane against its electrochemical gradient or concentration gradient (meaning the substance moves from an area of lower concentration to an area of higher concentration) with specific transport proteins embedded in the membrane. This process is referred to as active because it requires energy to work (1).

Reproduction
Bacteria reproduce asexually (only one parent; reproduce through division of a single cell) using binary fission, a certain type of cell division. This process can be as fast as twenty minutes, which explains why bacteria can reach such high population densities. Because they are prokaryotic, bacteria never perform meiosis, cell division within sexually reproductive organisms that produces cells with half the amount of chromosomes the parent cells have, or mitosis, nuclear cell division within eukaryotes. While they are not sexual, bacteria can still transfer genes between one another through one of three different processes: transformation, conjugation, and transduction. During transformation, one bacteria cell will receives genes from the surrounding environment, which enables some genetic transfer between bacteria. During conjugation the genes are directly transferred between the two bacteria (use pili to stick together and get in position). During transduction, viruses, called bacteriophages in this case, transfer genes between bacteria. The preferred temperature, pH level, salt concentration, and nutrient sources, etc. for optimal reproduction (binary fission), varies with each bacterial species (1).
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Augusta High School
(HS 4)




Continued binary fission can result in a colony of bacteria, as shown in the picture below:
A colony of bacteria. (ER) http://www.hubtesting.net/yahoo_site_admin/assets/images/bacteria.94120838_std.jpg
A colony of bacteria. (ER) http://www.hubtesting.net/yahoo_site_admin/assets/images/bacteria.94120838_std.jpg
Environmental Adaptations
Bacteria branched off from archaea billions of years ago. Even though bacteria seem to have much more in common with archaea than they do with any eukaryotes, their membrane lipids are more like eukaryotic membrane lipids (type of organic macromolecule) in structure (contain unbranched hydrocarbons). Also, Bacteria are like eukaryotes in that they cannot grow successfully at temperatures greater than 100 degrees Celsius, like archaea can. Bacterial adaptations can be dangerous, for now bacterial diseases are becoming a large problem due to the rapid evolution of antibiotic resistant strains of pathogenic (disease-causing) bacteria (1).

Bacteria have a couple different ways of adapting to environmental changes (including antibiotics). The first way is called inherent (natural) resistance, where the bacteria are naturally resistant to environmental changes. For example, the antibiotic Penicillin is not effective against gram-negative bacteria because the bacteria has an extra outer membrane, causing difficulty for the Penicillin to enter the cell. The second was is called acquired resistance, which is usually due to a change in the genetic make-up of the bacteria. Outside pressures can cause a mutation, resulting in different genetic make-up, or they can cause the bacteria to respond to the pressure and change their genetic make-up. For example, the protist Vibrio parahaemolyticus will adopt a different means of transportation when switched from a
watery environment to a more viscous envirmonment. When bacteria are reacting to a sudden change, they will express or repress certain genes (3) (DP).

Importance of Bacteria (10, DJ)
Many humans are aware of bacteria's negative effects on human life. Many bacteria cause diseases, but many prevent disease as well. Bacteria produce and provide us with Vitamin K, a vitamin we cannot produce ourselves. Bacteria are also involved in vaccines. In addition to health, bacteria are involved in many food processes like creating yogurt, cheese, and vinegar. Aside from humans, bacteria affect the environment as they play a key role in making soil fertile by the process of nitrogen-fixation. (10, DJ) Bacteria often have a symbiotic relationship with plants, attaching to the plant's roots and converting nitrogen in the air that is unavailible to the plants into nitrates and nitrites that plants can use. Some bacteria can also convert nitrogen in the opposite way, releasing the nitrogen back into the atmosphere. Bacteria also play a role in cycling carbon and sulfur. Bacteria help to decompose organisms so that their organic components can be recylced (12) (RK).
It is said almost 99% of bacteria are helpful. Some are in the digestive tract of humans and help in digestion. Some bacteria are on our skin and protect us from the spread of some fungus. (YS)
Also, there are some types of bacteria that can help clean oil spills. They are able to degrade crude oil metabolically. These bacteria have been found off the coast of Spain. (13) (JAC)


Review Questions:1) Although Bacteria and Archaea seem to be similar, which characteristics of Bacteria differentiate them from Archaea? (BL)
2. What occurs during the reproduction stages of transformation, conjugation, and transduction within a Bacteria? (Jesse Carmen)
3. What is the difference between inherent resistance and acquired resistance?(RJS)
4. What are the similarities and differences between photoautotrophs, chemoautotrophs, photoheterotrophs, and chemoheterorophs? (Nangia)
5. How can bacteria affect human life? (BMB)

Work Cited:

1.) Campbell, Neil A., and Jane B. Reece. Biology. Boston: Benjamin-Cummings Company, 2001.

2.) Watts, Anthony. "The Doomsday Bomb: Bacteria or Nuclear." Watts Up With That? 10 Dec. 2006. 24 Nov. 2008 <http://www.norcalblogs.com/watts/2006/12/the_doomsday_bomb_bacteria_or.html>.

3.)
"Bacterial Adaptation." World of Microbiology and Immunology. Ed. K. Lee Lerner and Brenda Wilmoth Lerner. Detroit: Gale, 2002. 1 Dec. 2008 <http://www.bookrags.com/research/bacterial-adaptation-wmi/>.

(4) "Binary Fision (Reproduction) in Bacteria." Biology. Augusta High School. 3 Dec. 2008 <http://www.augusta.k12.wi.us/.../class/bio/img003.jpg>.

(5) Waggoner, Ben. "Bacteria." Www.ucmp.berkeley.edu. Berkley Free Clinic. 4 Dec. 2008.
(6) "Bio102 Bacteria." 7 Dec. 2008 <http://www.scribd.com/doc/14600/Bio102-bacteria>.
(7) "Spirochetes and Spirilla." Cliffs Notes. 7 Dec. 2008 <http://www.cliffsnotes.com/WileyCDA/CliffsReviewTopic/Spirochetes-and-Spirilla.topicArticleId-8524,articleId-8441.html>.
(8) Blackwell, Meredith, Rytas Vilgalys, Timothy Y. James, and John W. Taylor. "Fungi." Tree of Life. 2005. 7 Dec. 2008 <http:// www.tolweb.org/proteobacteria/2302>.
(9) "Bacteria." MSN Encarta. 7 Dec. 2008. <http://www.scienceclarified.com/images/uesc_02_img0069.jpg>.
(10) "Bacteria." MSN Encarta. 8 Dec. 2008. <http://encarta.msn.com/encyclopedia_761574409_5/Bacteria.html>.
(11) "Helpful and Harmful Types of Bacteria". 5 Dec. 2008. http://www.buzzle.com/articles/helpful-and-harmful-types-of-bacteria.html
(12) Waggoner, Ben. "Bacteria: LIfe History and Ecology." University of California at Berkeley.1994. 14 Dec. 2008 http://www.ucmp.berkeley.edu/bacteria/bacterialh.html..
(13) "A Hope for Oil Spill Bioremediation." Science Daily. 17 May 2005. Science Daily. 14 Dec. 2008 <http://www.sciencedaily.com/releases/2005/05/050517063708.htm>.
(14) 15 Dec 2008 <http://www.emcc.edu/cmtdoc/Bacteria%20are%20everywher1.htm>
(15) Scharf, David. "Staph Bacteria." Scharf Photo.com. 17 Dec. 2008 <http://www.scharfphoto.com/fine_art_prints/archives/199812-026-staph-bacteria.jpg>.
(16) http://www.horizonpress.com/gateway/gram-positive-bacteria.html
Page Edited by: DP; Hilary Stepansky, NK, Sarah Vlach, Hanna Z. GR, AR, Daisy Joo, Yasheka Sharma, Omer Zaidi, Rachel Kornetsky, Josh Czik, SS, Becca Levenson, Sam Blatchford, Jesse Carmen, Meru Nangia, Brittany Marcus-Blank