Comparing Bacteria and Archaea By: Matthew Myles, Tatiana Baldwin, Sophia Kopyna and Jacob McLennan
What are Archaea and Bacteria? Bacteria and archaea are two of the three domains in the three domain-system put forth by Carl Woese. Though archaea and bacteria are both unicellular prokaryotic cells, they have different ribosomal RNAs (rRNAs).
Common Structures: Bacteria & Archaea Bacteria and archaea have common organization as they are both prokaryotic cells. Similar structures include: • Plasma membrane • Cell wall (composition varies) • Flagella (used for motion) • A localized nucleoid • Fimbriae and pili that aid in attachment to surfaces, conjugation, and transformation
Internal Structure of Bacteria • The cell walls are composed of peptidoglycan - amino acids and sugars that give bacteria structural support. • Only certain bacteria have endospores - dormant thick-walled spores that are resistant to heat and chemicals. • Capsules and slime layers are materials composed in layers outside the cell wall. • S-layers are the outermost wall in certain bacteria.
Internal Structure of Archaea • Cell walls don’t contain peptidoglycan. • Archaea have three RNA polymerases (enzymes that produce primary transcript RNA) like eukaryotes, but bacteria have only one. • No archaea possess endospores.
External Shape: Bacteria and Archaea COCCI (singular Coccus) - ball shaped prokaryotes BACILLI (singular Bacillus) - rod shaped prokaryotes Spiral shaped forms are also present in both bacteria and archaea. Bacteria and archaea can also be pleomorphic (many shaped)
External Shape: Bacteria Only bacteria are shaped as: • Cubes • Pyramids • Rods with star shaped cross section
External Shape: Archaea Only archaea are shaped as: • Plates • Rectangular rods
Comparing Nutrition Some archaea and bacteria are heterotrophic and can obtain nutrients from other organisms, organic and inorganic compounds and solar energy. Some bacteria are autotrophic and can undergo photosynthesis to obtain food. Archaea cannot undergo photosynthesis but can still use solar energy as a source of metabolic energy.
Respiration - Bacteria and Archaea Aerobic respiration • glucose is oxidized to produce ATP, and CO2 as a by-product (ie. cellular respiration) • occurs in the cytoplasm Anaerobic respiration • glucose is broken down by compounds other than oxygen (NH3, SO4) to produce ATP (by-products include methane for archaea)
Extremophile Vs. Mesophile Extremophiles and mesophiles can be found in both bacterial and archeal domains. EXTREMOPHILES -live in habitats categorized by extreme conditions MESOPHILES -live in moderate environments (most bacteria are mesophiles)
Classifying Extremophiles METHANOGENS - Organisms living in places with little oxygen (eg. swamps or the intestinal tracts of animals). They are able to survive off of the methane they produce. ACIDOPHILES - Organisms that thrive in acidic environments with pH levels less than 5. ALKALIPHILES - Organisms that thrive in pH levels more than 9. THERMOPHILES - Organisms that thrive in high temperatures. HALOPHILES - Organisms that thrive in water with a salt concentration typically above 20%.
Endospores: • Hard, wall like structures that protect the DNA • Allows certain types of bacteria to become highly resistant to high temperatures, drying out, freezing, radiation, and toxic chemicals • Have only been found in bacteria
How Are Bacteria Further Classified? • The Gram Stain, a method developed in the 19th century, classifies bacteria into two distinct categories. • There are Gram-positive and Gram-negative bacteria.
How Are Bacteria Further Classified? Gram-negative bacteria • Groups of bacteria that are larger in number and variety of species. When they they are dyed, they are stained pink due to their thin cell wall. Gram-positive bacteria • Contain less diverse species than the gram-negative group. When they they are dyed, they are stained purple due to their thick cell wall.
Reproduction of Bacteria and Archaea • Bacteria and Archaea only have one chromosome • They reproduce asexually through a process called binary fission • The only ways for genetic variation are through random mutation and conjugation
Binary Fission • The single chromosome of a bacteria or archaea duplicates • The cell grows and elongates • As the cell elongates the two chromosome segregates • The septum (partition between the cells) forms • Cytokinesis occurs and two smaller and genetically identical cells form
Conjugation cont. • The pilus from the F+ connects to receptors on the outside of the F- recipient cell. • Cleavage enzyme cuts the plasmid and allows for transfer of the DNA • The strand of DNA sent from one cell to the other • a full plasmid is synthesized and both cells are now donor cells
Plasmids • Loops of DNA separate from the chromosome • Are circular and double stranded • Are in both bacteria and archaea • Can replicate independently from the chromosome in a cell and are therefore useful in gene cloning
Life Cycle of Bacteria/ Archaea The Bacteria/ Archaea life cycle consists of 4 stages. The lag phase, the log or exponential phase, the stationary phase and the death phase.
The Lag Phase • bacteria/Archaea does not grow. • adjusts to their environment and metabolize (produces vitamins and amino acids needed for division.) • begin to make copies of their DNA. • more nutrients that the environment supplies, the shorter the lag phase is.
Log phase, Stationary phase, Death • log or exponential phase the Bacteria/ Archaea multiplies rapidly. • stationary phase the Bacteria/ Archaea growth slows down to almost no growth due to accumulating waste and lack of space. • death phase the bacteria/ Archaea loses all ability to reproduce, which is when the bacteria dies.
Bacteria and Human Health Bacteria cause food to spoil- • The metabolism of anaerobic bacteria produces toxic products that have the ability to cause human nausea or possibly death • Are not dangerous unless they are in a contained area with food for a period of a time in anaerobic condition)
Bacteria and Human Health • Exotoxins are poisons released by live bacteria • Endotoxins are poisons released when the bacteria die • Food must be under a hot temperature above the boiling point of water under high pressure
Bacteria and Human Health • through contaminated water • through contaminated food • through sexual contact • through the air, when infected people sneeze or cough • through contact with animals • bacteria moving from one part of the body, where they are harmless, to another part, where they cause illness
Archaea and Biotechnology • Biotechnology depends on enzymes for DNA analysis and diagnosing disease • Most enzymes break down and cease functioning as a result of extreme environments, but archaea and their enzymes do not.
Review external structure internal structure nutrition extremophiles binary fission conjugation human health biotechnology respiration Life cycle
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