Bacteria and Archaea: The Prokaryotic Domains Ch. 26

What are the three shapes of prokaryotes?

1. Cocci (Spherical) 2. Bacilli (Rod-Shaped) 3. Spirochete (Spiral-Shaped)

What was Robert Koch's criteria for determining if a bacterium was pathogenic?

1. The organism must always be found in the individual with the disease. 2. The organism must be taken form the hose and grown in pure culture. 3. A sample of the culture must produce disease if injected into a healthy individual. 4. The newly infected individual must yield a new pure culture of the same organism.

What are some of the shared characteristics of Archaea?

Archaea lack peptidoglycan cells walls and have very distinctive lipids in their cell membranes. These are linked by ether linkages. No other organism possess this type of lipid.

What are synapomorphies?

A synapomorphy is a common property shown by two or more groups of organisms, that can be traced back to the most recent ancestor that both the groups evolved from. However, this character may not be shown by other closely-related groups, because some of them may have evolved further, or lost the character altogether.

What are the three categorizations for living things?

Achaea, Bacteria (Prokaryotes), and Eukarya.

What are actinobacteria?

Actinobacteria or high-GC Gram-positive bacteria develop an elaborately branched system of filaments, some with chains of spores at the tips. This group includes the pathogen Mycobacterium tuberculosis (tuberculosis). However, one of our most potent antibiotics comes form this group. Streptomycin is produced by the actinobacteria Streptomyces. Most currently used antibiotics come form actinobacteria.

Can bacteria exist in a group?

All of the different shapes may aggregate to form chains or plates of cells. Advanced associations may result in filaments that are encased in a protective sheath.

Why do Archaea and Bacteria not share the synapomorphies of Eukarya (organelles, nuclei, cytoskeleton, etc)?

All organisms that posses these Eukarya synapomorphies are descended form the common ancestor of Eukarya, while the absence of these features in Archaea and Bacteria is a retained characteristic inherited from the common ancestor of all life on earth (a prokaryote).

From what did all the three domains derive?

All three domains arose form a common ancestor possessing a circular chromosome and machinery for transcription and translation of DNA code to protein.

What are bacterial flagella? How does it compare to the eukaryotes' flagellum?

Bacterial flagella are whiplike and are composed of a single protein called flagellin. In contrast, the flagellum of eukaryotes is complex.

When did the divergence from the prokaryote common ancestor begin?

Billions of Years Ago.

What was the role of cyanobacteria in the early earth?

Cyanobacteria, using photosynthesis, enriched the atmosphere with oxygen. Oxygen levels become too high for many existing organisms; many others evolved to those niches, and new organisms arose.

Why can the cell wall of prokaryotes be useful for research?

Cell wall composition is one of many ways of differentiating bacteria and archaea. Cell wall structure within the bacteria also serves as a diagnostic characteristic among different bacteria. This difference is used in the Gram staining technique.

What are chemoheterotrophs?

Chemoheterotrophs obtain energy and carbon consuming organic molecules.

What are chemolithotrophs?

Chemolithotrophs oxidize inorganic substances for energy. Some chemolithotrophs fix carbon dioxide into carbohydrate. Others fix nitrite or ammonia, hydrogen gas, hydrogen sulfide, and other materials.

What are chlamydias?

Chlamydias are the smallest bacteria and exist only as parasites. They have a two stage life cycle and are responsible for several human disease.

Briefly Describe Cyanobacteria

Cyanobacteria undergo photosynthesis similar to eukaryotic photosynthesizers. They contribute to the current oxygen-rich environment. These organisms frequently exist in colonies with distinct divisions of labor. Some cells are vegetative and photosynthesize. Others form resting stages called spores that can withstand harsh environmental conditions. Still others, called heterocyst, fix nitrogen.

What are obligate aerobes?

Obligate aerobes require oxygen and cannot survive in the absence of it.

What are obligate anaerobes?

Obligate anaerobes are oxygen-sensitive and can only survive in oxygen-poor conditions.

Although all organisms have similarities, what similarities indicate evolutionary relationships?

Only derived similarities (synapomorphies) indicate evolutionary relationships.

What are the synapomorphies of Eukarya?

Eukarya have nuclei, membrane - enclosed organelles, and cytoskeletons.

What are Facultative Anaerobes?

Facultative Anaerobes can shift between aerobic and anaerobic modes of respiration. Some facultative anaerobes do not respire aerobically but are not harmed by oxygen-rich atmosphere as obligate anaerobes are.

What must be true for a bacterium to be pathogenic?

In order to be pathogenic, an organism must be able to reach a new hose, invade the host, evade the host's defenses, multiply, and infect a new host. Relatively few organisms can do this.

What are korarchaeota?

Korarchaeota are archaea known only from DNA isolated from hot springs.

What is true for pathogenic bacteria?

Only a small minority of bacteria are pathogenic. Bacteria cause diseases because they produce toxins that are harmful to host tissues. Endotoxins are released when bacterial cells burst, but are rarely fatal. Exotoxins are secreted by bacteria and may be fatal.

Why do rRNA sequences not provide clear data for bacteria?

Lateral gene transfer - genetic transfer between species - makes these data hard to understand.

What are chrearchaeota?

Live in hot, acidic environments and are thermophilic and acidophilic. They require temperatures above 55°C and can survive in an environment with a pH as low as 0.9 while maintaining an internal pH of 7.

How do prokaryotes move?

Many prokaryotes are mobile and move by gliding, rolling, regulating gas vesicles, or flagella.

What type of groups are the Archaea, Bacteria, and Eukarya?

Monophyletic Groups: A group composed of a collection of organisms, including the most recent common ancestor of all those organisms and all the descendants of that most recent common ancestor. A monophyletic taxon is also called a clade. Examples : Mammalia, Aves (birds), angiosperms, insects, etc.

What are firmicutes?

Most, but not all, firmicutes are low-GC Gram-positive. They produce endospores that are capable of surviving in extremely harsh conditions. Many medically important bacteria fall within this group, including Clostridium botulinum (botulism), Staphylococcus (many skin infections, and Bicillis anthracis, causative agent of anthrax. Another subgroup, mycoplasmas, may represent the smallest life form.

What is true about the mutation of prokaryotes?

Mutations are important in prokaryotic variation. Because prokaryotes have single circular DNA pieces, mutations cannot be masked and are passed on through fission. This is in contrast to diploid organisms in which mutations plays a small role in genetic variation.

What are nanoarchaeota?

Nanoarchaeota, obtained from a deep-sea hydrothermal vent, is minute and lives attached to cells of Ignicoccus, or crenarchaeota.

Do prokaryotes have membrane-enclosed organelles (MEO)?

No, they do not.

What are photoautotrophs?

Photoautotrophs are photosynthetic and convert light energy to chemical energy. Some photoautotrophs use chlorophyll a and give off oxygen as by-products. Others use bacteriochlorophyll and produce sulfur as a by-product.

What are photoheterotrophs?

Photoheterotrophs use light energy but also require outside carbon sources.

Give a brief description of Prokaryotes.

Prokaryotes are prolific and are most numerous of all organisms. Because they are single celled (there are a few exceptions) and very small, they generally escape human notice. They play an extremely important roles in the biospheres, for instance nutrient cycling. They can also metabolize many substances that eukaryotes.

How quickly do prokaryotes evolve? What are the characteristics of this speed?

Prokaryotes evolve comparatively rapidly because of rapid reproduction, persistent mutation, and selection. Mutations leading to antibiotic resistance are of extreme and can occur in a matter of just a few years.

Do prokaryotes have a cytoskeleton? What results from this?

Prokaryotes lack a cytoskeleton; therefore, true mitosis does not occur. Prokaryotes go through an asexual process called fission after replicating their DNA.

Are prokaryotes mutualistic?

Prokaryotes live in many mutualistic associations. Many of your digestive processes rely on bacteria that inhabit your intestine.

How do Prokaryotes reproduce?

Prokaryotes reproduce asexually but may exchange genetic information through transformation, conjugation, and transduction.

What is the use of ribosomal RNA in research?

Ribosomal RNA gives us information about relationships among organisms. It is useful for this purpose because it is evolutionarily ancient, is found in al organisms, has the same function in all organisms, and is highly conserved (it evolves slowly). Scientist compare signature sequences to make evolutionary inferences.

What is the relationship between antibiotics + peptidoglycan-containing cell wall?

Some antibiotics work by interfering with the synthesis of peptidoglycan-containing cell walls. Eukaryotic cells are not harmed because their cell walls lack this material.

How can bacteria use nitrogen ° sulfur compounds?

Some bacteria carry out respiratory electron transport using nitrogen or sulfur compounds as electron acceptors. These organisms are extremely important in nutrient cycling.

What are Euryachaeota?

Some members of Euryarchaeota produce methane gas and are obligate anaerobes. These organisms are prevalent in the guts of herbivores. Others live near volcanic vents. Another group of Euryarhcaeota live in extremely salty conditions and are referred to as halophiles.

What are spirochetes?

Spirochetes are corkscrew-shaped prokaryotes characterized by the presence of axial filaments that run through their periplasmic space. Many spirochetes are parasites of humans.

What is the physiology of the prokaryotes' cell wall?

The cell wall of prokaryotes is thick and rigid and composed of peptidoglycans (bacteria) or protein (achaea). This cell wall is very different form that of plant and fungal cell walls.

Although Bacteria can be subdivided into a series of monophyletic groups, scientist don't agree on what?

The composition (membership) of these groups is not considered to be the same by all scientist.

Which two principle domains are closely related?

The domain Archaea is more closely related to Eukarya than to the Bacteria.

What are proteobacteria?

The five groups of proteobacteria represent the largest number of known species. This group is believed to be the origin of the eukaryotic mitochondria. The early ancestor of this group was probably a photoautotroph, but today, the group encompasses multiple metabolic schemes. Included among the proteobacteria are E.coli, and nitrogen-fixing Rhizobium, and many human pathogens.

What is role do bacteria play in the nitrogen cycle?

The nitrogen cycle depends on nitrification by bacteria. Nitrifying bacteria use nitrogen to make ATP, which is used to fix carbon dioxide into glucose and other food molecules. Through this process, unusable nitrogen sources are converted into biologically available nitrogen sources.

Since prokaryotes do not have MEO, what can be said about DNA replication + respiration?

The organization + replication of DNA proceeds differently in prokaryotes than it does in eukaryotes. Also, the processes of cellular respiration and photosynthesis are carried out differently and rely on infoldings of the cell cell membrane.

What can be said about the shared characteristics of Eukarya + Archaea?

Though they are members of two different domains, Archaea and Bacteria have several structural similarities that are indicative of evolutionary adaptation to similar environments.

How have we discovered the unique features of Archaea + Bacteria?

Unique and distinguishing features of Archaea + Bacteria have been discovered through biochemistry and genetic studies.

What is the Gram Staining technique?

Whether a cell is Gram-negative or Gram-positive relates to the amount of peptidoglycan in the cell wall. 1. Gram-positive cells stain purple and have thick layer of peptidoglycan. 2. Gram-negative cells do not retain stan and appear red due to the think layer of peptidoglycan, and the otter lipopolysaccharide layer.