Archaea and Bacteria-The PROKARYOTES

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As late as 1977, all prokaryotes were put into one single kingdom called Monera. Taxonomists no longer accept that concept. Some prokaryotes are more closely related to eukaryotes than other prokaryotes. Most taxonomists now accept the concept of super kingdoms or domains. Two of the three domains are prokaryotes

General informationI. Three common shapes (cocci, bacilli, spirilla)II. Small 0.5-5 m

Which of the following is true? A) There are three domains in one kingdom. B) The Moneran Kingdom is recognized by taxonomists as the kingdom for single celled eukaryotes C) Archaea contains prokaryotic cells. D) Bacteria contains both prokaryotic cells and single celled eukaryotic cells.

ANS: CThe Domains Bacteria and Archaea contains only prokaryotic cells. The prokaryotes in the Archaea Domain are more closely related to eukaryotes. All eukaryotic celled organisms are in the Domain Eukarya.

III. Bacterial cell wall made of carbohydrate polymers that are connected by polypeptide chains (peptidoglycan). Gram-positive bacteria (stain purple with Gram-stain) have cell walls with just the peptidoglycan wall connected to plasma membrane. Gram-negative bacteria (stain pink) have peptidoglycan wall sandwiched between two membranes. The cell wall of Archae are made from polysaccharides and certain proteins but NOT peptidoglycans.

Some prokaryotes have a second layer outside the cell wall. -Capsule-sticky layer of carbohydrates or proteins. -Fimbriae-protein appendages that allows the prokaryote to attach to surfaces

Which of the following has a peptidoglycan cell wall?A) a prokaryote in the Archaea Domain B) plant cells C) fungal cells D) a prokaryote in the Bacteria Domain

ANS: DThe cells walls in the Bacteria Domain is composed of peptidoglycan which is carbohydrate connected by small polypeptide chains.

IV. Nucloid region-area where circular DNA chromosome is located. Chromosome lacks histones (some prokaryotes in Archae do). May also contain smaller circular pieces of DNA or plasmids.

V. Ribosomes are smaller than cytoplasmic eukaryotic ribosomes.

VI. Some prokaryotes have infoldings of the plasma membrane similar to cristae and some photosynthetic prokaryotes have internal membranes similar to thylakoid membranes.

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VII. Some prokaryotic cells have flagella. The flagellum is different from eukaryotic cells. It is a solid core of protein (1/10th width). It is driven by a system of rings in the cell wall. ATP pumps transports H+ out cell. When the H+ diffuse back in it powers the flagella which rotates like a helicopter rotor. Flagellated prokaryotes can exhibit taxis moving toward or away chemicals, nutrients or oxygen.

Which of the following is true?A) Prokaryotes have well defined organelles B) Prokaryotes have no internal membranes C) Some prokaryotes have membranes around the DNA D) Some prokaryotes have internal membranes for respiration or photosynthesis.

ANS: DSome prokaryotes have some membranes for respiration ( like the cristae) or for pigments for photosynthesis (like the thylakoid)

Reproduction-Reproduction is via binary fission. Bacteria can obtain genetic variation via conjugation, transformation, or transduction

Conjugation-(Lederberg & Tatum)

1. Conjugation-Certain bacteria that have been mutated, would need additonal nutrients in their media in order to grow. Bacteria without these mutations will grow on minimal media. E.Coli had been mutated and 2 different strains were found

#1- needed methonie and vitamin biotin but could make its own leucine and threonine.

#2-needed threonine and leucine but could not make its own methonine and vitamin biotin. When these two types were mixed, there emerged some new cells that had the ability to grow on minimal media. Conclusion: There had to be some exchange of genes or recombination of genes.

What causes the movement of prokaryotic flagella?A) Passive diffusion B) Active transport C) Facilitated diffusion D) Osmosis

ANS: BBoth active transport and passive diffusion are incorporated to make the flagella move. H+ ions are pumped out of the cell by ATP pumps (active transport) and as the H+ ion flow back into the cell (passive diffusion), the energy is used to move the flagella.

Recombination has occurred because the new cells can grow on minimal media. It was also discovered that in addition to the main chromosome, prokaryotic cells contained smaller circles of DNA (plasmids) which also contained genes.

The arrow points to a plasmid in a lysed E.Coli cell which is then magnified. This plasmid contains genes that makes the cell resistant to the antibiotic tetracycline.

Plasmids replicate independent of the main chromosome. These plasmids are being replicated.

In order for conjugation to occur there must be 2 different mating types F+ (male) and F- (female). F+ males have a plasmid (sex factor) which is replicated. When a F+ and F- meet, they form a cytoplasmic bridge or pilus. The copied F+ plasmid is transferred to F- making it F+.

The population never completely is converted to F+ because

1. F- can undergo bacterial reproduction (fission) faster than F+ can conjugate.

2. The formation of the pilus, allows for cetain viruses to attack, and they only attack F+ cells.

Some F+ plasmids are inserted into the main chromosome becoming Hfr (high frequency recombinants). When Hfr conjugates with F-, the entire main chromosome is replicated.

Conjugating bacteria with the pilli connecting the cells to one another to exchange DNA.

However during transfer only part of the chromosome is transferred.

The gene for Hfr is usually at the end of the chromosome, so that the receiving cell F- will stay an F-. The longer the pilus stays together, the more genes transferred.

Which of the following mating types have the ability to conjugate and produce a cell with genetic variationA) F- x F- B) F+ x F+ C) Hfr x F- D) F+ x F-

ANS: DTwo mating types can undergo conjugation F- (female) x F+ (male). The F+ has the sex plasmid which is transferred to the F- female. The second mating type is F- (female) x Hfr (male). The Hfr cell has the sex plasmid integrated into the main circular chromosome.

Autonomous plasmids-Plasmids that never integrate themselves into the chromosome. They may carry genes that include antibiotic resistance or a virulence factor. Plasmids have the ability to replicate themselves so that a prokaryotic cell may have 1,000 to 3,000 copies of it.

2. Transformation- Involves prokaryotic cells taking up extraneous DNA from the environment. Genetic engineering uses this technique in transforming bacteria and using engineered plasmids.

3.Transduction- Bacterial cells obtaining DNA via a viral vector.

The rapid reproduction, mutations, and genetic recombination allows for a great variety in their metabolic pathways. In fact, every possible mode of nutrition in the living world is found in prokaryotes:

-Photoautotroph-does photosynthesis and uses CO2 as its carbon source

-Chemoautotroph-uses CO2 to make organic compounds on its own and uses chemicals like H2S and NH3 for energy instead of light

-Photoheterotroph-uses light for energy but obtains carbon from an organic source.

-Chemoheterotroph-uses organic compounds for both an energy source and carbon source. Most are decomposers or pathogens that break organic compounds down.

What is the process called in which prokaryotic cells take up extraneous DNA from the environment?A) conjugation B) transformation C) transduction D) binary fission

ANS: BTransformation is the process called in which prokaryotic cells take up extraneous DNA from the environment. Conjugation involves two prokaryotic cells with different mating types. Transduction involves a viral vector, and binary fission is the asexual reproduction of prokaryotic cells.

Types of cell respiration-Obligate aeorbes must use oxygen for cell respiration or will die without it

-Obligate anaerobe- oxygen is not used for cell respiration and the cell is actually poisoned by it.

-Faculative anaerobes-can use oxygen when present or do fermentation if oxygen is not present.

Nitrogen fixationSome prokaryotes have the ability to “fix” atmospheric nitrogen (N2) into ammonia NH3. Then the ammonia can be converted into nitrates and nitrites. The nitrogen compounds then can be converted into amino acids. Important part of nitrogen cycle. Some prokaryotes live in symbiotic relationships with this pathway. The root nodules of legumes contain nitrogen fixing bacteria.

Types of photosynthesis-Some prokaryotes are photosynthetic. There are two types of photosynthesis in prokaryotes Type I that gives off O2 as a by product.

Contains photosystem I and II like higher plantsContains chlorophyll a like higher plantsSplits water6 CO2 + 6 H2O -> C6H12O6 + 6 O2

Type II that does not give off O2 as a by product. Contains only photosystem IContains bacteriochloropyll Splits hydrogen sulfideCO2 + 2H2S -> (CH2O)n + 2 S

How would you classify a prokaryotic cell that can uses CO2 to make organic compounds on its own and uses chemicals like H2S and NH3 for energy instead of light? A) photoautotroph B) photoheterotroph C) chemoheterotroph D) chemoautotroph

 

ANS: D-Photoautotroph-does photosynthesis and uses CO2 as its carbon source -Chemoautotroph-uses CO2 to make organic compounds on its own and uses chemicals like H2S and NH3 for energy instead of light  -Photoheterotroph-uses light for energy but obtains carbon from an organic source. -Chemoheterotroph-uses organic compounds for both an energy source and carbon source. Most are decomposers or pathogens that break organic compounds down.

Domain Bacteria-Supergroups1. Proteobacteria-Gram negative with 5 subgroups. Metabolic diverse photoautotrophs, chemoautotrophs, and heterotrophs. Some are aerobic while others are anaerobes.2. Chlamydias-Obligate pararsites only live in other cells. Major cause blindness.3. Spirochetes-Spiraled shaped with internal like flagellum. Caused syphilis and Lyme disease.4. Cyanobacteria-does type I photosynthesis generating oxygen. Some cells specialized (heterocysts) for fixing nitrogen5. Gram-positive bacteria-Metabolic diverse group. Some obligate parasites, some secrete antibiotics.

Domain Archaea-Supergroups can live in extreme environments and more normal environments. More closely related to eukaryotes than other prokaryote

1. Extreme halophiles can tolerates saline enviroments. Tolerance from slightly saline to over 9% saline (Marine enviroments is 3.5% saline).

2. Exterme thermophiles can tolerate very hot environments. Proteins are very stable at this temperature and DNA remains as a double helix. One strain of Geogemma barossii can tolerate temperature of over 121o C.

3. Methanogens- use CO2 to oxidize H2 to make methane gas. Obligate anaerobes. Found under ice, swamps, guts of cattle, and termites.

4. Moderate environment-many prokaryotes from the Domain Archaea are live in moderate environments.

Prokaryotes in the environmentSymbiotic relationships-Mutualistic- Ex-certain bacteria in your gut are important to the digestive system and the bacteria benefit by the food that is provided to them.Commensalistic-Ex There a many bacteria living on the surface of the skin. They do not harm or provide any benefit to the epidermal cells. The epidermal cells provide oils, food and a habitat to liveParasitic-Ex-Some prokaryotes are pathogens (cause disease). Many bacterial diseases can be treated with antibiotics which are compounds that destroy prokaryotic cells but not eukaryotic cells. Usually the disease is caused by either an exotoxin (made and secreted by the prokaryote) or endotoxin (made by the prokaryote and only released if the prokaryote dies). Botulism is caused by an exotoxin made by Clostridium botulinum and typhoid fever is caused by an endotoxin made by Salmonella typhi.

What is the source of the nitrogen used by prokaryotic cells that can do nitrogen fixation?A)  the air in the form of N2 B) the soil in the form of nitrates C) the water in the form of ammonia D) the soil in the form of nitrates

ANS: AThe source of the nitrogen for nitrogen fixation comes from the N2 in the atmosphere. It is reduced to ammonia and then later oxidized to either nitrates or nitrates. Plants can use the ammonia, nitrates and nitrites as a source for nitrogen.

Prokaryotes are the most dominant organisms on this earth. Without them, life as we know it would not exist. They are important in-decomposers-nutrient recycling-nitrogen fixation-food industry-symbiosis-medicine-producers in food chains.

This chart compares and contrast three different domains. It is based on the sequencing of the rRNA found in the small ribosomal subunit. The Archaea prokaryotes are more closely related to eukaryotes than to the Bacteria prokaryotes.

There are certain bacteria that live in the digestive system and have the ability to make vitamin D. The digestive system provides nutrients for the bacteria. This relationship could most precisely be classified as A) symbiotic B) parasitic C) commensalistic D) mutualistic

 

ANS: DMutualism is the most precise answer because both organisms benefit. It is a form of symbiosis but mutualism is the most precise. Commensalism and parasitism is a form of symbiosis.

Which of the following would not be a classification for a cell that has the ability to take in carbon dioxide and reduce it to methane gas?A) prokaryote B) bacteria C) methanogen D) Archaea

ANS: BMethanogens belong in the domain Archaea and the domain Bacteria. Cells in both of these domains are prokaryotes.