BIOL 238 Review 2009

This page provides review questions for BIOL 238 (Spring 2009). Answers may be posted by students.

Chapter 17, 18

1. Compare and contrast the major divisions of bacteria. State an example of a species of each major division.

There are 7 major categories of bacteria:
1) Thermophiles live at very high temperatures and are some of the fastest growing cells on the planet. Deinococcus radiophilus is an example of a thermophile that is not only adapted to high temperatures but is also extremely resistant to radiation and has a very rapid rate of DNA repair.
These thermophile groups are "deep branching," that is, several branched off earlier than any of the other main groups known. Of course, we are always discovering new deep-branching groups.

2) Cyanobacteria, such as Anabaena flos-aquae, are oxygenic and nitrogen-fixing microbes. They contain many subcellular structures, including thylakoids, and can form spores.
What kind of spores? Cyanobacteria form particular kinds of spores called akinetes and baeocytes.
3) The gram-positive bacteria, like Staphylococcus aureus, possess a variety of attributes, ranging from no outer membrane to acid-fast cell walls to the ability to form spores and pahtogenicity.
4) Proteobacteria is a large category that can be further subdivided. Clostridium tetani and Helicobacter pylori are two examples of proteobacteria. Many use some form of litho- or phototrophy and some are pathogenic.
Helicobacter pylori is a good example of a Gram-negative proteobacteria. However, what group contains Clostridium tetani?
5) Bacteroidetes (i.e. B. thetaiomicron) are obligate anaerobes and major colonizers of the gut.
6) Spirochetes like Borrelia burgdorferi are also spiral in shape and have 2 flagella, one at either end, which are fully encased by the periplasm.
What kind of spiral form is typical of Spirochetes? How does it differ from "spirillum"? 7)Chlamydiae (C. trachomatis) are obligate intracellular parasites.

2. Explain an example of a major division of bacteria whose species show nearly uniform metabolism but differ widely in form. Explaine a different example of a division showing a common, distinctive form, but variety of metabolism.

Cyanobacteria and chlorobia are both phototrophs, obtaining energy from inorganic sources, although cyanobacteria alone produce oxygen. In addition, cyanobacteria typically use water as an electron donor, whereas chlorobia use H₂S. Cyanobacteria also have subcellular structures: thylakoids (where photosynthesis occurs), carboxysomes, and gas vesicles (from which oxygen escapes), and they may grow as filaments, as well as forming specialized spore cells called akinetes.
Yes, that sounds good. What do cyanobacteria release from the water, and how? Besides filaments, what cell and colony forms are found among cyanobacteria?

Chlorobia have no subcellular structures and do not grow as filaments or form akinetes.
Nitrospirae and spirochetes are both Gram-negative, free-living, spiral-shaped bacteria. However, nitrospirae are chemolithoautotrophs which oxidize nitrite to nitrate and take up inorganic carbon.
What is the difference between the spiral forms of nitrospirae and spirochetes?
Spirochetes are chemoheterotrophs which take up organic molecules like glucose for carbon.

3. Compare and contrast three different types of phototrophy found in bacteria.

4. Explain the pathology of three different gram-positive pathogens.

Clostridium tetani is a gram-positive bacteria that causes tetanus. It is contracted through contact of C. tetani spores with an open wound. If the environment of the wound is anaerobic, the spores will germinate and release a toxin that blocks the release of neurotransmitters from inhibitory interneurons, resulting in lockjaw and muscle contraction of primarily the neck. If left untreated, respiratory failure and death will soon follow.

Listeria are intracellular pathogens that can survive a relatively wide range of temperatures. They are absorbed into the blood stream from the GI tract. From there they enter the nervous system where they polymerize actin, resulting in conditions such as meningitis and septicemia, among others. These bacteria can even infect macrophages.

Mycobacterium tuberculosis, yet another gram-positive bacteria, follows a different route of pathogenesis. TB is spread via coughing and the release of infected droplets by the patient into the air, where they become dispersed and contact another victim. The particles then lie dormant in the lungs of the infected individual until enough bacteria accumulate to instigate an immune response. The bacteria infect the attacking macrophages. The bacteria continue to grow and divide within the macrophage and are spread to other macrophages when these immune cells aggregate in the deeper lung tissues. The infected macrophages develop into granulomas that wall off the infection. TB can be either active or dormant. If inactive, the bacteria remain within the granuloma. If active, the bacteria escape and cause lesions within the lungs.
Yes, the above mechanisms sound right.
5. Explain two different examples of bacterial-host mutualism.

Oscillatoria and Synechocystis are both cyanobacteria that are in mutualistic relationships with sponges. They supply up to 80% of the nutrional needs for the sponge and receive nutrients for themselves.

Lactobacillus acidophilus lives in the human intestine. It receives required nutrients and helps human health by inhibiting growth of pathogens.

Chapter 19

1. Compare and contrast the different major groups of archaea. Which ones grow in extreme heat or cold? Extreme salt? Produce methane?

Archaea which grow in extreme heat or cold are found in both phyla: Crenarchaeota and Euryarchaeota. Desulfurococcales and Sulfolobales are both groups of Crenarchaeota that grow at high temperatres and gain energy by reducing sulfur. Neither of these groups has a cell wall, and each has an S-layer present. Other thermophiles among the Crenarcheota are Thermoproteales, which also reduce sulfur, and Caldisphaerales, which either respire anaerobically or ferment. Yet there are certain Crenarchaeotes which live at psychrophilic temperatures: Cenararchaeum, which grows on deep-water sponges in Antarctic seawater, is a good example. Thermophiles among the eukaryotes include Thermococcales, anaerobic archaea which use sulfur as an electron acceptor, and Archaeoglobales, which reduce sulfate to sulfide and oxidize acetate to carbon dioxide. Thermoplasmatales are similar to Desulfurococcales and Sulfolobales: they have no cell wall. They have no S-layer either, and an amorphous shape.

Methanogens, archaea which produce methane by transferring electrons from H₂ to CO₂, are all Euryarchaeota which live in anaerobic environments such as landfills, rumen, flooded soil, and the human gut. Halophiles are Euryarchaeota which grow in extreme salt; in fact, they grow best at 4.3 M NaCl, at a pH of 7 or higher. The high GC content in their DNA prevents denaturation in high salt, and most are photoheterotrophs, with rhodopsins which capture light energy by a proton-motive force.

Be careful, "Euryarchaeota," not Eukaryotes.

2. Explain how archaea growing in extreme environments require specialized equipment for study.
These extreme environments near extremely hot vents are challenging to explore because they are a threat to the scientists survival. To take sample of these archae special submersive devices with robotic arms are used. An advanced version of this device can process the organisms DNA. This is very important because the organisms can not survive without their specialized enironment.

3. What kinds of archaea grow in "average" environment such as the soil? Or an animal digestive tract?

Methanogens are found commonly in the soil, landfills and animal digestive tracts. In humans, they constitute about 10% of anaerobes in our gut and might increase the amount of calories we gain from our food. In cattle however, they results in decreasing efficiency of meat production. Methane gas produced in landfills from methanogens is sometimes diverted to be used to produce energy. Methanogens must associate with bacteria to obtain the substrates required for methanogenesis.

In addition, crenarchaeota include archaea in "average" environments. There are many uncharacterized species that are associated with plant roots or live in the soil. Marine pelagic plankton in the open ocean include archaea as well.

Chapter 20

1. Compare and contrast the major divisions of eukaryotic microbes. Which groups include primary-symbiont algae? Secondary-symbiont algal protists? Single flagellum versus paired flagella? Motility (widespread) versus limited motility?.

1. Opisthokonta: singal basal flagellum on reproductive cells. Not protists, share deletion in key genes
2. Viridiplantae: include plants and algae, chloroplasts from primary endosymbiont. Includes Chlorophyta, of which the unicellular species have paired flagella.
3. Amoebozoa or Lobosea: lobe-shapes pseudopods, move by sol-gel transition of actin filaments. Includes slime molds.
4. Cercozoa: Filament-shaped pseudopods, some have a shell of inorganic material.
5. Alveolata: cortex contians flattened vesicles, Ciliophora reproduce by conjugation. Dinoflagellata are secondary or tertiary endosymbiont algae.
6. Heterokonta: pair of asymmetrical flagella, one shorter than the other, include sencondary-endosymbiont algae.
7. Euglenozoa or Discicristata: include Euglenida, which are free-living flagellate some of which contain a secondary endosymbiotic chloroplast
8. Excavata:flagellates that have lost mitochondria and Golgi apparatus through degenerative evolution.

2. Describe examples of eukaryotic microbes that have shells or plates of silicate or calcium carbonate.

Examples of eukaryotic microbes with shells include the Cercozoa, specifically radiolarians: shells make of silica with holes through which pseudopods radiate in all directions, and foraminiferans: generate shells of calcium carbonate laid down in helical succession, pseudopods extend from one opening. Diatoms are heterokonts that grow a bipartite shell called a frustule, which is composed of silica.

3. Explain mixotrophy. Why are so many marine protists mixotrophs?

Secondary endosymbiotic algae are often mixotrophic, meaning they use both phototrophy and heterotrophy. This allows them to live in a broader range of habitat: in deeper water light is not as available for photosynthesis, by using heterotrophy as well, they are able to obtain nutrients for a longer time span, at greater depths, and with a variety of environmental resources.

4. Why do eukaryotes show such as wide range of cell size? What selective forces favor large cell size, and what favors small cell size?

Chapter 21

1. Explain what is meant by symbiosis, mutualism, and parasitism. Show with specific examples how mutualism and parasitism have a lot in common, and how there are inbetween cases.

2. Compare and contrast the roles of microbes in the marine and soil ecosystems.

3. How does oxygen availability determine the community structure of the soil habitat? Of the aquatic (freshwater) sediment habitat?

In a soil habitat, aerobic species of microbes are found in the organic horizon and the aerated horizon, among decaying and decomposed matter, because there is plenty of oxygen available in these soil layers. Below the water table, species of anaerobes thrive, as this area is anoxic. In the bedrock, there are lithotrophs up to three km down. Obviously these microbes are anaerobic, and they must obtain their energy from inorganic sources, such as sulfur and hydrogen, because no organic minerals can reach the bedrock.

In a freshwater habitat, oxygen is available in the epilimnion, but not so much in the hypolimnion or the benthos; therefore, anaerobic organisms are found in the epilimnion. In the lower levels, anaerobic organisms are prevalent; photosynthetic sulfate reducers, in particular, are found in the hypolimnion.

4. Outline the metabolic processes of the bovine rumen microbial ecosystem.

Chapter 22

1. What are the common gases besides CO2 that contribute to global warming? What is the chemical basis for how these gases trap solar radiation as heat?

Nitrous oxide gas (N₂) can escape as a byproduct of denitrification in the presence of excess nitrate; as a greenhouse gas it generates 200 times the warming effect of carbon dioxide. Additionally, it can react with the upper atmosphere and break down the ozone layer. Methane is another potent greenhouse gas: it is produced by methanogens, especially in wetland habitats. Large amounts of methane are crystalized around vents, the sudden release of one of these stores could have a detrimental effect on global temperatures.

2. In the last fifty years, most of the wetlands off the coast of Louisiana have been destroyed. Is this destruction responsible for the increased run-off and pollutants in the Gulf of Mexico, as well as the notorious dead zone there Can dead zones ever be fully revived? What are the methods that used that cause the price of restoration to be $1 billion dollars per year?

Nitrogenous waste from agriculture all along the Mississippi River is eventually expelled off the coast of Louisiana. The excess of nitrogen fuels algal blooms, and when the algae die their bodies are consumed by heterotrophs that use up all of the available oxygen, causing hypoxia and ultimately dead zones. Wetlands are capable of denitrifying waste from agriculture, so their absence is a large factor contributing to the dead zones and pollution in the Gulf of Mexico.
Restoration of the dead zone would require all of the communities along river drainage areas to eliminate nitrogenous waste before disposal. This could be done either with wastewater treatment or wetland filtration.

3. It is interesting that the ocean's microbial communities could be responsible for over half of the biological uptake of atmospheric carbon. How soluble is CO2 is in water? Is it more soluble than oxygen gas in water?

4. How exactly is ammonium nitrate addition related to higher CO2 efflux in wetlands?
Ammonium nitrate is a common fertilizer used for agricultural purposes. When it runs off into water systems and makes its way into wetland regions it increases the rate of CO2 efflux of the area by increasing the amount of aerobic respiration of microbes. This then causes a positive feedback loop in the wetland with regards to CO2 production. The increased atmospheric CO2 from the microbial respiration increases the amount of CO2 available for plants to use in photosynthesis, which allows the plants to grow larger and establish more associations with microbes like micorrhizae. This results in higher CO2 output from the soil, which is one of the largest fluxes in the global carbon cycle.

5. Iron is limiting in oceans because the iron in the benthos, where it’s abundant, is inaccessible because it’s far away. In the benthic environment then, is iron not limiting because the microbes can access the sediment? What is typically limiting instead?

7. What is the microbial process in which nitrous oxide gas builds up?
The process in which nitrous oxide (N2O) gas builds up is nitrate respiration during the nitrification process of the nitrogen cycle. This happens most frequently in environments where heavy fertilization increases the amount of nitrate in the soil. During nitrate respiration, N2O is produced in excess and given off into the environment where it depetes the ozone layers and acts as a greenhouse gas.It depletes the ozone layer by reacting catalytically with ozone in the upper atmosphere.

N2O also builds up in marine dead zones, areas where eutrophication has resulted in the death of almost all of the organisms that lived there. Without oxygen, microbes are forced to utilize nitrate as an electron acceptor during anaerobic respiration. This process gives off a large amount of nitrate as well as N2O gas, which diffuses into the atmosphere and contributes to global warming by functioning as a greenhouse gas.

Chapter 23

1. What's the point of breeding a gnotobiotic animal? A gnotobiotic animal is an animal that satisfies one of two rules. It is either entirely germ-free, or all of the microbial species that colonize it are known. These animals are used to demonstrate how microbiotic organisms affect their host. They can be developed so that only particular microbiota are present and then observe any changes in the in the organism's function that may occur. In general, gnotobiotic organisms also demonstrate how microbiota are important to organisms as they show signs of poorly developed immune systems, low cardiac output, thin intestinal walls, and an increased susceptibility to pathogens.
Yes, that sounds right.

3. How do defensins tell the difference between “good” bacteria and pathogens?

4. What are the benefits of an acidic skin? Of an acidic vaginal tract?

5. How are mast cells involved in immune response other than being differentiated with other immune cells?
Mast cells are involved in autoimmune and hypersensitivity responses as well as functioning to differentiate into other immune cells. One example of another function of mast cells can be seen in the acute inflammatory response. When an infection takes place in a person's tissue, bradykinin, a polypeptide that allows for extravasation, is released into the area. These molecules then bind mast cells and cause a calcium influx that triggers the mast cells to degranulate and release histamine into the area, which further increases the permeability of blood vessels. The bradykinins then attach to capillary cells, which produce prostaglandins, which stimulate nerve endings and produce a pain response.

Ultimately, another function of mast cells is to release inflammatory factors during particular processes.

6. Why do you think gnotobiotic animals have a lower cardiac output?

7. Why does an infection site heat up during vasodilation?

This helps create a localized fever in the region, which helps kill microbes infecting the area.

8. How do interferons work? How do they connect with the adaptive immune system?
Interferons are soluble proteinaceous cytokines that "interfere" with viral replication. They are often produced by eukaryotic cells in response to intracellular infections, infections by pathogens that grow within the cell. They are species specific, which means that interferons from one species won't be functional in another species, but they are nonspecific with regards to viruses. This means that they generally target different kinds of viruses. Furthermore, there are two classes of interferons:

Type I interferons preventatively bind receptors on the membranes of uninfected cells, thus rendering them resistant to viral infection. It can do this by promoting the production of two classes of proteins within the cell. The first of these proteins is an RNA-activated endoribonuclease, which functions to cleave viral RNA in the cell. The second class of proteins are protein kinases, that inactivate eIF2, a eukaryotic initiation factor that is necessary for translation.

Type II interferons work with the adaptive immune system by activating macrophages, natural killer T-cells, and T-cells to increase their production of major histocompatibility complex antigens they present on their cell surface. Presentation of antigens is important because many adaptive immune cells, including T-cells, need to bind MHC-presented antigens before they become activated. Once these cells are activated, they can deal with infections effectively.


9. Explain the difference between the innate and adaptive immune systems--and explain how they interconnect.

The innate immunity consists of physical barriers such as skin, chemical barriers such as stomach acid, and relatively nonspecific cellular responses to infection that engage if the physical and chemical barriers are breached (“hard-wired” in body). This protection is nonspecific. The adaptive immune system is designed to react to very specific structures call antigens, which are chemicals, compounds or structures foreign to body that elicits immune response. The connection between the adaptive immune system and innate immune system are microbes that possess a splippery capsule. Adaptive immunity synthesizes anticapsular antibodeies that help the innate immune mechanism of phagocytosis. The antibodies then bind the bacteria to the phagocytic tail-end antibody receptores, allowing phagocytosis to occur.

Chapter 24

1. Now that you know more about adaptive immunity, explain some examples of how the innate and adaptive immune systems interconnect. For instance, how does an innate system receiving a signal activate the adaptive immune system? How does an adaptive response to a pathogen activate an innate response component?

2. Explain the difference between the B-cell and T-cell immune systems--and explain how they interconnect.

3. Explain an example of an antigen-presenting cell within the adaptive immune response. In the adaptive immune system, dendritic cells are a type of antigen-presenting cell. Dendritic cells begin as white blood cells, also known as monocytes. Monocytes are capable of differentiating into dendritic cells and macrophages. As its name indicates, the dentritic cell has a highly branched morphology. These cells reside in the spleen and lymph nodes and can absorb and process small antigens. Once the antigens have been properly processed, the dentritic cell can display the antigen on its surface for recognition by T-cells.

Species to know for Test 3

For each species, state one or two broader categories of organism (such as gram-positive endospore-forming bacteria), the type of genome, type(s) of metabolism, habitat, and disease caused (if any).

Aeromonas hydrophila

Broader Categories: Gram-negative, anaerobic
Genome: Genes that contribute to its toxicity are cytotoxic enterotoxin gene (act), heat labile enterotoxins (Alt), and heat-stable cytotonic enterotoxins (Ast).
Metabolism: Heterotrophic, ferments glucose, digests gelatin, hemoglobin, and elastin.
Habitat: Exists in aerobic and anaerobic environments: aquatic environments, fish guts, food, human bloodstream and organs.
Disease: Causes many diseases in fish and amphibians, since it exists in aquatic environments. Can cause disease in humans, such as septiticemia, meningitis, pneumonia, and gastroenteritis.

Anabaena sp.


Broader Categories: Barrel-shaped cells. Filamentous cyanobacteria (blue-green algae) found as plankton.
Genome: 1 circular chromosome with 5368 protein-coding regions and 6 plasmids (from sequenced PCC 7120 strain).
Metabolism: Photoautotrophic, perform oxygenic photosynthesis. Form heterocysts (specialized nitrogen-fixing cells that convert nitrogen to ammonia) during nitrogen starvation.
Habitat: Freshwater and damp soil. Form symbiotic relationships with certain plants.
Disease: Produce neurotoxins, such as anatoxins (neuromuscular poisons), that are harmful to wildlife and farm animals.

Aquifex sp.

Broader categories: gram-negative, generally rod-shaped, thermophilic, non spore forming, aerobe. Genome: Densely packed genome with overlapping genes. No introns or splicing proteins. Genome is about 1/3 the size of that of E. coli. Metabolism: Autotrophic chemolithotrophs that fix carbon from the environment and draw energy from inorganic chemical sources. Uses oxygen as terminal electron acceptor when it oxidizes hydrogen to form water “aquifex=water forming.” They can also use sulfur or thiosulfate to produce H2S instead of water. Some aquifcales aren’t aerobic, however, and reduce nitrogen instead of oxygen. In this case the reaction ends with H2. Habitat: Near volcanoes or hot springs Diseases Caused: None

Aspergillus sp.

Broader Categories: Over 185 species of this genus Genome: Largely incomplete Metabolism: Highly aerobic. Pathogenic species obtain nutrients from host, while non-pathogenic species obtain nutrients from soil, wood, and plant detritus. Habitat: Grow as molds in oxygen-rich environments and carbon-sources. Some species are capable of living in nutrient-depleted environments as well. Disease: About 20 species are pathogenic in humans and animals. Aspergillus fumigatus and Aspergillus flavus cause invasive pulmonary aspergillosis and is often fatal.

Bacillus anthracis

Broader Categories: Gram-positive, rod-shaped, form endo-spores and biofilms
Genome: 1 circular chromosome with over 5 million b.p. 2 circular plasmids: pxO1 and pxO2. These plasmids encode main virulent factors.
Metabolism: Facultative anaerobe and must grow in medium with essential nutrients including C and N sources. Upon nutrient deprivation, endospores form (requires oxygen to form) and can live in inhospitable envrionments for many years. Can grow into vegetative cells in aqueous environment with adequate nutrients.
Habitat: Live in soils world-wide and is the main habitat.
Disease: Anthrax disease. Infectious endospores harm host by germinating for vegetative growth. During growth the bacteria produce toxins in the body of humans and animals. The slime capsule enables it to resist phagocytosis. 3 main forms of the disease: cutaneous, pulmonary, and gastrointestinal. Can cause death in 2-48 hours.

Bacillus subtilis

Broader Categories: Gram-positive, rod-shaped, form stress-resistant endospores Genome: 1 circular chromosome with 4100 genes coding for proteins. Metabolism: Can grow in aerobic and anaerobic conditions. Uses fermentation and nitrate ammonification to make ATP in the absence of oxygen. Habitat: Soil and vegetation at mesophilic temperatures. Disease: Non-pathogenic. Responsible for spoilage of food, since contamination often results in decomposition, but it rarely causes food-poisoning.

Bacillus thuringiensis

Broader Categories: Gram-positive, spore-forming, rod-shaped Genome: 1 circular chromosome with 5.2-5.8 Megabases. Contains many plasmids. Metabolism: Facultative anaerobe (makes ATP by aerobic respiration if oxygen is present, but can switch to fermentation). Habitat: Soil. It is used in 90% of pesticides. Fends off insects by producing crystal proteins (Cry proteins). Disease: Species-specific, non-pathogenic to humans, making it an environmentally-friendly insecticide. Cry toxin grows and sporulates in alkaline gut o finsect, which aids in its ability to infect the insect gut. The gut breaks down and the insect eventually dies.

Bacteroides thetaiotaomicron

Broader Categories: Gram-negative, anaerobic, human-bacterial symbiosis model Genome: 1 circular chromosome made of d.s. DNA, consists of 4776 proein-coding genes, 90% of which are essential in the binding and import of various polysaccharides. Metabolism: Starch (all 3 forms) is primary carbohydrate used as its source of C and Energy. Polysaccharides bind to the cell surface before undergoing hydrolysis. Habitat: Adult intestine-allows humans to degrade plant polysaccharides Disease: Serious infections include intra-abdominal sepsis and bacteremia. It is resistant to many antimicrobial agents.

Borrelia burgdorferi

Broader Categories: Sprial-shaped with 2 flagella Genome: A linear chromosome with 910,725 b.p. with 853 genes. 17 linear and circular plasmids. Metabolism: Require specific nutritional requirements making it difficult to culture in vitro. Habitat: Live extracellularly and adapts to various host animals (tick, rodents, birds) by regulating various lipoproteins on thier surface. Disease: Lyme disease and recurring fever.

Chlamydia sp.

Broader Categories: Gram-negative, aerobic, coccoid or rod-shaped Genome: C. trachomatis-1,042,519 b.p. with 894 protein-coding sequences (70 genes are not homologous to sequences on the C. pneumoniae genome). C. pneumoniae- 1,230,230 b.p. (186 genes are not homologous to sequences on the C. trachomatis genome) Metabolism: Cannot synthesize its own ATP, so they cannot be grown on artificial medium and require growing cells to remain viable. Habitat: C. trachomatis-human host cells, C. suis- swine host cells, C. muridarum- mice and hamster host cells. Infectious elementary body form induces endocytosis upon contact with host cell. Once inside, the elementary body germinates to vegetative form, and divides every 2-3 hrs. It then reverts back to the elementary form and is released by the cell through exocytosis. Disease: C. trahomatis causes chlamydia and is the most common STD in the world. C. pneumoniae causes pneumonia and bronchitis

Clostridium botulinum

Broader Categories: Gram-positive, rod-shaped, anaerobic, spore-former Genome: Genome size of 4039 kbp, which is larger than most Gram-positive genomes, indicating the extra genomic requirements needed for sporulation and pathogenic toxin production Metabolism: Lie dormant in very adverse environments. Spores can begin to grow in favorable conditions: non-halophilic salinity and anaerobic conditions. Grows at mesophilic temps. Habitat: Soils and improperly canned food products Disease: A-G subtypes produce different botulin toxin- al except C and D subtypes are human pathogens. The toxin prevents propagation of action potentials to the muscle fibers- causing paralysis by inhibiting muscle contraction. Fatalities usually occur due to asphyxiation

Chloroflexus sp.

Corynebacterium diphtheriae

Escherichia coli

Broader Categories: Gram-negative, rod-shaped, aerobic Genome: 1 circular chromosome, (4300 coding sequences) with 1800 known proteins. Some contain circular plasmid. Metabolism: Facultative anaerobe. Uses mixed-acid fermentation in anaerobic conditions. Growth driven by aerobic or anaerobic respiration using a large variety of redox pairs: oxidation of pyruvic acid, formic acid, hydrogen, and amino acids and reduction of oxygen, nitrate, dimethyl sulfoxide, trimethylamine N-oxide. Habitat: Lower intestines of human and mammals, where it aids in digestion processes: vitamin K production, food breakdown and absorption Disease: E. coli O157:H7 (enterohemorrhagic strain) causes food poisoning- leading to bloody diarrhea and kidney failure due to its production of Shiga-like toxin. Also can cause urinary tract infections by ascending infections of the urethra.

Geobacter metallireducens

Broader Categories: Gram-negative, rod-shaped, possesses flagella, and pili Genome: 1 circular chromosome encoding 3621 genes. Plasmid encodes 13 genes, 1 of which is addiction module toxin (gives resistance to bacteria and another encoding plasmid stabilization system protein (allows bacteria to adapt to new environmental conditions) Metabolism: First organism with the ability to oxidize organic compounds and metals (iron, radioactive metals like Uranium, and petroleum compounds) into environmentally benign carbon dioxide while using iron oxide and other available metals an electron acceptors. Habitat: anaerobic conditions in soils and aquatic sediments Disease: Non-pathogenic

Pseudomonas aeruginosa

Broader categories: Gram-negative, rod-shaped, does not produce spores. Habitat: due to its capability to synthesize arginine, P. aeruginosa proliferates in anaerobic conditions. It can be found in environments such as soil, water, humans, animals, plants, sewage, and hospitals. Metabolism: Aerobic respiration. P. aeruginosa can metabolize on hundreds of other things besides arginine, and can respire on nitrate (although it does much better on O2).Genome: a single and supercoiled circular chromosome in the cytoplasm. Disease(s) caused: Causes disease in immuno-compromised patients, such as those with cystic fibrosis, cancer, or AIDS. It further weakens the patient, allowing the patient to become more susceptible to other diseases. Usually this kills the patient. P. aeruginosa forms biofilms in the lung of cystic fibrosis patients; it is the major cause of death in these individuals.

Broader Categories: Gram-negative, rod-shaped, and contains 1 flagella Genome: It contains a 5.2 to 7 million base pairs and a single, supercoiled circular chromosome in the cytoplasm with many plasmids contributing to its pathogenicity. Metabolism: Facultative aerobe, with its preferred metabolism being aerobic respiration by transferring electrons from glucose to oxygen. Habitat: Ubiquitous in that it can live in both human and inanimate environments. This is possible mainly because of the vast array of enzymes that allow uptake of diverse forms of nutrients. Pathogenicity: Disease-causing agent to immuno-compromised individuals (cystic fibrosis patients) or indivuals in a trauma (burn victims). It tends to form biofilms and cause tissue damage through its virulence factors.

Halobacterium sp.

Broader categories: rod-shaped, halophilic, candidate for life on Mars. Genome: 1 large chromosome and 2 plasmids (3 circular replicons). Metabolism: aerobic, but not glucose degradation. Habitat: highly saline lakes. Disease: non-pathogenic

Helicobacter pylori

Broader Categories: Gram-negative, spiral-shaped, 6-8 flagella at one end Genome: Single circular chromosome with genes that encode urease, membrane cytotoxins, and the cag pathogenicity island. Metabolism: Glucose is the only carbohydrate used by H. pylori and is metabolized through the ED pathway. Pyruvate is synthesized from D-amino acids, lactate, L-alanine, and L-serine, rather than glucose. Fermentation of pyruvate yields acetate. Urease converts urea into ammonia and bicarbonate to buffer the low pH of the stomach. Habitat: The lining of the stomach and duodenum, where it is well adapted to a pH of 2 or less. Pathogenicity: Peptic ulcers and gastritis

Lactobacillus sp.

Lactococcus sp.

Broader categories: spherical, gram positive. Genome: 1 circular chromosome with 2, 365, 589 bp, where 86 % of the genome code for protein, 1.4 % for RNA, and 12.6 % for noncoding region. 64.2 % of the genes code for known functional proteins, and 20.1 % of the genes for known protein with unknown function. Metabolism: aerobic or anaerobic, often use lactic acid fermentation. Habitat: plant surfaces, digestive tract of cows. Disease: non-pathogenic.

Leptospira

Broader Categories: spirochete, spiral-shaped with one or both ends usually hooked, of the family Leptospiraceae, and the genus Leptospira. Very thin and must be observed through darkfield microscopy. Genome: Consists of a large chromosome and a small chromosome, with about 4768 total genes. Metabolism: aerobic using oxygen as the final electron acceptor. Energy is gained primarily through long-chain fatty acids. Carbohydrates are not used as a source of carbon, but can be synthesized through the TCA cycle. Habitat: Occupies diverse environments, habitats, and life cycles. Stagnant waters are its natural environment. Prefers slightly alkaline environment. Prefers a temp of 28-30 degrees C bu can grow at temp. as low as 11-13 degrees C. Pathogenicity: Leptospirosis is potentially deadly in both humans and animals. In humans it can cause symptoms of fever, chills, sore muscles, vomiting, jaundice, red eyes, abdominal pain, diarrhea, or rashes. It is typically spread through contact with water, food, or urine of an infected animal.

Methanococcus sp.

Broader categories: gram-negative, cocci-shaped, archaea domain, thermophilic and mesophilic. Genome: 1 circular chromosome with 1 large extra-chromosomal element and 1 small extra-chromosomal element. Metabolism: autotrophic, anaerobic, reduces carbon dioxide with hydrogen gas to generate methane. Habitat: can grow up to pressures of 200 atm, temperature ranges between 48-94 degrees C, with optimal growth at 85 degrees C. Disease: non-pathogenic.

Mycobacterium tuberculosis

Mycoplasma pneumoniae sp.

Broader categories: spherical without a cell wall, highly pathogenic--osmotic instability. Genome: 1 small circular chromosome. Metabolism: major nutrients come from mucosal epithelial cells of the host, many proposed metabolic pathways. Habitat: not found in the environment but can be cultured in medium-rich agar. Disease: highly pathogenic; parasitizes epithelial cells in the respiratory tract.

Nitrospira sp.

Paramecium sp.

Broader categories: Eukaryotic ciliated unicellular organisms. Genome: Linear. Metabolism: Paramecium eject trichocyts to help capture their prey. They commonly eat bacteria, yeasts, algae, and small protozoa. Paramecium are also heterotrophs. Habitat: Aquatic environments, usually in stagnant warm water. Some Paramecium species form symbiotic relationships with green algae or bacteria. The bacteria/algae live in the cytoplasm of the Paramecium and perform photosynthesis. Disease: Non-pathogenic

Plasmodium falciparum

Broader Categories: Protazoan parasite Genome: It contains a 23-megabase nuclear genome consisting of 14 chromosomes, encoding about 5,300 genes, and is the most A/T rich genome sequenced to date Metabolism: Uses intracellular hemoglobin as a food source. Anaerobic glycolisis with pyruvate being converted to lactate. Habitat: Requires both human and mosquito hosts Pathogenicity: Causative agent of malaria

Prochlorococcus sp.

Broader Categories: Single-celled cyanobacteria Genome: It is about 1.67 Mega-base pairs long with 1,694 predicted protein-coding regions Metabolism: photoautotrophic Habitat: Oceans Pathogenicity: Non-pathogenic

Rhodobacter sp.

Broader categories: quorum-sensing bacteria, flagella motility. Genome: unique complexities-2 chromosomes, 1 large and 1 small, circular chromosomes. Metabolism: photosynthesis mostly, also capable of lithotrophy, aerobic, and anaerobic respiration pathways. Habitat: aquatic and marine environments. Disease: non-pathogenic.
Which photosystem does it use? Does it conduct phototrophy anaerobically, or in the presence of oxygen?

Rhodopseudomonas sp.

Rhodospirillum rubrum
Which photosystem does it use?
Rickettsia sp.

Saccharomyces cerevesiae

Broader Categories: Best known as brewer's and baker's yeast, used as a model system due to its short generation time (1.5-2 hrs. at 30 degrees C), can be easily cultured, easily transformed which allows the addition or deletion of genes, and is a eukaryote so it shares much of the non-coding DNA stretches found in higher order eukaryotes Genome: Single, linear, d.s. DNA, with little repeated sequences and less the 5% of the sequences have introns. Metabolism: Heterotrophs that use both aerobic respiration and fermentation and obtain their energy from glucose. Habitat: The natural habitat is the surface of fruits. Industrially, it is used in baking and brewing and is considered an ale yeast, or top yeast. Pathogenicity: Is used as a probiotic in humans. However, new evidence may suggest that the use of S. cerevesiae probiotics could potentially be harmful, causing the infection of S. cerevesiae fungemia.

Salmonella enterica

Broader Categories: Gram-negative, rod-shaped, flagellated Genome: Circular chromosome with a one to a few plasmids (depending on the 1 of 2,000 serovars that comprise S. enterica. Metabolism: aerobic respiration Habitat: Reptile and amphibian microbiota. It is also found in red meat, poultry, and raw egg shells Pathogenicity: Salmonella enterica serovar Typhi is the causative agent of typhoid fever. Salmonella enterica serovar Typhimurium generally causes gastroenteritis. Its major virulent factor is its secreted proteins, such as adhesins that help colonize the host and are involved in biofilm formation.

Serratia marcescens

Broader Categories: Gram-negative, rod-shaped, motile, of the family Enterobacteriaceae. Genome: Singular circular chromosome. Few plasmids Metabolism: Facultative anaerobe, but uses primarily fermentation to obtain Energy. Nitrate is usually the final electron acceptor. Habitat: Found in diverse environments from water and soil to plants and animals. One of the most common contaminant on laboratory Petri dishes. Pathogenicity: A wide variety of diseases can result mainly in immuno-compromised individuals, such as bacteremia, meningitis, urinary tract infections, osteomyelitis, ocular infections, and endocarditis. It is resistant to penicillin and ampicillin, due to R-factors on plasmids encoding genes involved in antibiotic resistance and is able to produce biofilms.

Sinorhizobium meliloti

Staphylococcus epidermidis

Broader Categories: Gram positive, spherical, arrange in grape-like clusters, resistant to all penicillins and methicillin. Genome: The chromosome length is 2,616,530 bp and contains a few plasmids, depending on the strain. Metabolism: Facultative anaerobe that can grow by aerobic respiration or by fermentation. Most strains can reduce nitrate. Habitat: The skin and in mucous membranes of animals. Has the ability to produce slime and biofilms, which enable it to grow on biomedical devices. Pathogenicity: The primary virulence factor is its ability to form biofilms. With the increased use of intravascular catheters, the rate of infection has increased. It is more resistant to antibiotics that most other species.

Staphylococcus aureus

Broader categories: gram positive, spherical, immobile. Genome: 1 circular genome, resistance for antibiotics are encoded by a transposon. Metabolism: EMP and Pentose-Phosphate pathways. Lactate is the end product of anaerobic glucose metabolism. Acetate and carbon dioxide are the end products of aerobic metabolism. Habitat: skin, mucous membranes of animals. Disease: skin infections, invasive diseases, toxic shock syndrome (TSS).

Streptococcus sp.

Broader Categories: Gram positive, spherical, can be found in chains or in pairs, immobile. Genome: 1 circular chromosome. Metabolism: Many species of Streptococcus are facultative anaerobes, while others are obligate anaerobes. Habitat: Part of normal animal flora. Can become pathogenic and infect humans and other animals. They often imitate aspects of their host organism to avoid being detected. Disease: Can cause step throat, necrotizing fasciitis, scarlet fever, rheumatic fever, postpartum fever, and streptococcal toxic shock syndrome. Some species of Streptococcus can cause pneumonia.

Streptomyces sp.

Vibrio cholerae

Broader Categories: Gram-negative, bent rod shaped, one polar flagellum. Genome: Two circular chromosomes. Metabolism: Fermentative and respiratory. Habitat: Aquatic environments. Disease: Responsible for cholera in humans, which is characterized by diarrhea and vomiting leading to dehydration. The bacteria secrete a toxin that ultimately causes an increase in cyclic AMP levels that stimulates ion transport in the cells lining the intestine. This is followed by water leaving the intestinal cells to compensate for the change in osmolarity.

Vibrio fischeri

Broader Categories: Rod shaped, gram-negative. Genome: Two circular chromosomes with 2,284,050 bp and a plasmid. The lux operon controls bioluminescence. Metabolism: Heterotrophic. Habitat: Found in marine environments in a symbiotic relationship or as free-living. It can also be parasitic and saprophytic. Often found in the Hawaiian squid, Euprymna scolopes, where the bacteria bioluminesce in the light organ. The squid protects the bacteria from predators and provides nutrients, while the bacteria’s light eliminates the squid’s shadow, protecting it from predators. Disease: Other Vibrio species can cause human infections.