Eubacteria And Archaea Flashcards
Eubacteria Key Characteristics
→ Prokaryotic → Unicellular → Cell walls made of Peptidoglycan → Reproduce asexually via binary fission → Reproduce sexually via conjugation → can be Autotrophic or Heterotrophic
Bacteria: Friend or Foe?
Harmless are called nonpathogenic and and harmful are called pathogenic.
Non-pathogenic (Friend)
→ Bacteria involved in the production of yogurt and other fermented milk products
→ Gut Flora: Perform a number of functions in the digestive track
→ Act as decomposers
→ Bioremediation: remove toxins for toxic waste
→ Botox (Reduces muscle contractions in the skin)
Pathogenic (Foe)
→ Bacteria causes Tooth Decay
→ Foodborne illness ( E.coli and Salmonella )
→ Diseases (Tetanus, Diphtheria)
Bacterial Structure as a Prokaryote (General)
→ They are prokaryotic. So they lack membrane organelles like... ↪ Nucleus ↪ Vacuole ↪ Mitochondria ↪ Chloroplasts
→ However they still have
↪ Ribosomes (However they have a smaller and lighter version called 70s Ribosomes while eukaryotes have 80s ribosomes)
↪ Cytoplasm
↪ DNA ( In the form of a DNA region called the Nucleoid and sometimes plasmids for conjugation )
↪ Cell Membrane
Bacteria Structures that are not found in Eukaryotes.
Nucleoid - DNA region that houses loose DNA in the cytoplasm
Cell wall - Only some bacteria have a cell well to give rigidity and added protection. Unlike plant cells however, this wall is made from peptidoglycan and not cellulose.
Capsule - The Capsule is only found in some bacteria and it provides added protection against the environment, antibodies and White blood cells. The capsule is made of polysaccharides ( monosaccharides [ The most basic unit of a sugar/carbohydrate: CH2O ] linked with glycosidic bonds [ A bond between a carbohydrate group and something else ] ).
↪ The capsule is anti-phagocytic, so it limits the ability of phagocytes to engulf bacteria
↪ Can help bacteria adhere to a host cell
Pili - These are protrusions on the cell wall that allow bacteria to attach to surfaces and play an important part in conjugation.
↪ Some of these pili are longer than the other, these are called sex pili as they help in conjugation
↪ Made of a protein called Pilin
Flagellum - Makes bacteria motile/mobile
Classifying Bacteria
There are a series of prefixes that help classify bacteria → Mono - one/single → Diplo - two/double → Strepto - Chain → Staphylo - Cluster
There are structures of bacteria to look out for... → Coccus - Sphere like bacteria → Bacillus - Rod like bacteria → Spirillum - Spiral in shape → Helix - Helical or wavy in shape
Bacterial Reproduction (Asexual) - Vertical Gene Transfer
The bacteria undergoes the process of Binary Fission (not mitosis in meiosis which are processes for Eukaryotes).
Bacteria have one chromosome (All the loose DNA amounts to one chromosome)
1) The cell replicates its one Chromosome, making it into two chromosomes and plasmids. The cell also grows in size
2) The cytoplasmic membrane elongates so that the two chromosomes are separated. Where the plasmids go are random (This contributes to genetic diversity)
3) A cell wall starts to grow in the middle of the cell thanks to the FtsZ proteins forming a ring at the midpoint between the two chromosomes that starts the formation of said cell wall. The cell wall being formed is called the Septum
4) Cross wall form completely and cell splits into two daughter cells
→ Bacteria can rapidly multiply. In the right conditions it only takes 20 minutes.
↪ This rate of reproduction is found in bacteria that cause food poisoning, throat infection, in sewage plants and compost heaps
Bacterial Reproduction ( Sexual ) - Horizontal Gene Transfer
→ Much less common than Asexual reproduction
→ Uses Conjugation
Conjugation:
1) Donor cell attaches to the recipient cell via a conjugation pilus (Donor is called F+ cell and recipient is called F- cell)
↪ F is the fertility factor. Since one cell has a fertile plasmid called the F plasmid, it is F+ and since the other does not have this, it is F-
2) The pilus brings the cells together and the bacteria contact one another
3) One strand of the plasmid DNA is transferred to the recipient
4) The recipient synthesizes a complementary strand to complete the plasmid DNA and become a F+ cell
Genetic Variation in Bacteria
→ In transformation, a bacterium takes up a piece of DNA floating in its environment.
→ In transduction, DNA is accidentally moved from one bacterium to another by a virus (Bacteriophages for Bacteria and other viruses for archaea). Sometimes when viruses reproduce in a bacteria, they get the Bacteria’s DNA.
→ In conjugation, DNA is transferred between bacteria through a tube between cells.
→ Transposable elements are chunks of DNA that “jump” from one place to another. They can move bacterial genes that give bacteria antibiotic resistance or make them disease-causing.
Bacterial Diseases
→ Bacteria are responsible for many diseases that range in severity like cholera, lyme disease, pertussis, etc..
→ Some cause disease by producing and releasing toxins like
↪ e.g. botulism - the bacteria grows on poorly preserved food. The botulism toxin causes muscle paralysis that can be fatal
→ Others cause disease by releasing a toxin after the cell dies
↪ e.g. E. coli strain O157:H7 - causes severe food poisoning
Bacterial Diseases - Treatment
→ Bacterial infections are treated with antibiotics
↪ Like penicillin, amoxicillin or tetracycline
→ Many antibodies attack the cell wall of the bacteria and destroy (bacteria is nothing without its cell wall)
→ Many antibiotics are natural substances that are produced by bacteria themselves or other organisms
↪ Bacteria often compete with each other for resources, so through evolution they have developed mechanisms that produce chemicals to kill bacteria that they get in contact with. Humans can uses these toxins to treat bacterial infections.
Antibiotic Resistance
→ The overuse of antibiotics can lead to the bacteria evolving antibiotic resistance through natural selection
There are two types of Antibiotics
Broad-Spectrum - Kill man bacterial species
Narrow-Spectrum - Kill one/some species
→ Scientists are always in a race to stay ahead of bacterial mutations
Kingdom: Archaea
→ Little known about them
→ Eubacteria and Archaea used to be classified together as the Kingdom, Monera
However there were differences
→ Archaea cell wall doesn’t contain peptidoglycan
→ Cell membrane structure is different
→ Method of protein synthesis differ (little is known about this)
→ RNA molecules are different ( There are specific non coding RNA molecules that important to code for the traits that help archaea live in extreme environments )
Key characteristics of Archaea
→ Prokaryotic
→ Non-pathogenic (there has not been one archaea found that is pathogenic)
→ Cell wall composed of unique proteins (made of various polysaccharides and glycoconjugates [ Carbohydrates that are covalently linking to biological molecules like amino acids ] )
→ Reproduce asexually by binary fission and sexually by conjugation
→ Tend to live in extreme environment (called extremophiles)
Examples of the categories of Archaea.
Thermophiles 🡪 live in extreme heat (e.g. hot springs, thermal vents deep in the oceans)
Halophiles 🡪 live in high salt environments (e.g. in the Dead Sea)
Psychrophiles 🡪 live in extreme cold (e.g. Antarctic/Ocean, deep in cold oceans)
Acidophiles 🡪 live in highly acidic environments
Archaea Classification
→ Archaea is classified into its own domain due to difference in the ribosomal RNA
→ Archaea is more closely related to Eukarya then Bacteria
↪ They contains histone proteins in DNA like those in Eukarya
