Bacteria: Chapter 18 & 27 - Black Death & Cell Structure

• Chapter 18 and 27 focus on bacteria

The Black Death

• In the 1350s, the Black Death resulted in the death of 1/3 of Europe, or 25 million people.

Bubonic Plague

• The mortality rate is 30-75%.

Pneumonic Plague

• The mortality rate is 90-95%.

Septicemic Plague

• This form results in disseminated intravascular coagulation (DIC).
• The mortality rate is almost 100%.

Origin

• The first prokaryotes appeared 3.5-4 billion years ago.
• Chemoautotroph's likely predated heterotrophs.
• The oldest fossils include stromatolites, layered rocks formed from prokaryote activities up to 3.5 billion years ago.

Domains

• Archaea and Eukarya are more closely related.
• Bacteria evolved later than Archaea.
• Archaea can thrive in extreme environments
  • Halophiles
  • Thermophiles
  • Methanogens

Bacteria Cell Structure

• Cell wall protects the cell and prevents cell lysis in hypotonic environments.
  • Includes peptidoglycan in bacteria, but not archaea; archaea cell walls have other polymers.
• Capsule is sticky and used for attachment, defense, and prevents drying.
• Pili are used for attachment and DNA transfer during conjugation, becoming a conjugation tube.
• Fimbriae are tiny, hair-like extensions.
• Plasma membrane is semi-permeable.
• Ribosomes have different protein and RNA content than eukaryotes.
• Nucleoid is the “DNA area” that is double stranded.
  • Undergoes semi-conservative replication.
• Plasmid is circular DNA that carries non-essential genes and can be exchanged.
• Flagellum is used for locomotion and rotates; does not whip back and forth.
• Endospore consists of a chromosome and plasmid surrounded by a thick, dormant wall.

Anthrax

Gram Staining

• Used to identify bacteria with violet dye, and rinsed with alcohol and with red dye.
• Gram-positive bacteria have abundant peptidoglycan in their cell walls.
  • Stain violet/blue.
• Gram-negative bacteria possess less peptidoglycan and contain lipopolysaccharides in their outer membrane, making them more resistant to antibiotics.
  • Stain red.

Respiration Requirements

• Obligate aerobes require O₂.
• Obligate anaerobes is poisoned by O₂
• Facultative anaerobes use O₂ when it is present.

Bacterial Shapes

• Coccus can be diplococcus, streptococcus, or staphylococcus.
• Bacillus can be strepto bacillus.
• Example: Spirilla

Reproduction

• Binary Fission occurs.
  • Transformation, transduction, and conjugation.
• Transformation happens when bacteria absorb DNA from their surroundings, altering their genotype.
• Lysed bacteria release DNA fragments.
• Transduction involves imperfect virus assembly, leading to DNA transfer between bacteria through viral infection.
  • Bacterial DNA is inserted into a new host.
  • Recombinant bacteria results from phage coats.
• Conjugation involves the transfer of genetic material between bacteria

Plasmids

• F plasmids and R plasmids.
• Ability to conjugate and to become antibiotic resistant.

Beta Lactam Antibiotics

• Beta lactam antibiotics block cell wall synthesis: Penicillins.

Mechanisms of Antimicrobial Resistance

• Antibiotic inactivation or modification of bacteria to develop enzymes that destroy and inactivate antimicrobials.