Biol 241 Test 1 (topics 1-4)

What is Microbiology?

• microbiology is the study of microbes

• microbial life is too small to be seen with the naked eye

• interactions with humans, food, and the environment

• independent, unicellular, adaptable, efficient (microbes)

What are microbes?

• microorganisms

  • prokaryotes (bacteria and archaea)

  • eukaryotes - have nuclear envelope

  • living as they can carry out cell functions (metabolism, growth, etc)

• viruses - acellular, unable to perform metabolism

  • not living “organisms”

What are the sizes of microorganisms?

• variable

• bacteria are typically 0.5-5μm in length

• small eukaryotic cells are usually >5μm in length

• 10-100μm

• Thiomargarita Magnifica is an exception (1 cm)

How is the T. magnifica cell size possible?

• bacteria rely on diffusion to exchange nutrients and waste with the environment, putting an upper limit on cell size

• smaller cell = <SA:V, more efficient

• T.magnifica has a large vacuole that pushes the cell contents to the cell wall, effectively lowering the cell volume

Typical Prokaryotic cell: Structure of E. coli

• no membrane bound organelles

• In the cytoplasm there is:

  • nuceloid

  • stew of macromolecules

  • inclusion bodies

    • granules for C storage, sulfur globules, gas vesicles, carboxysomes, megnetosomes

Sulfur Globules

• stores sulfur, allows for metabolic activities

Gas Vesicles

• contributes to buoyancy

Carboxysomes

• store inorganic compounds + C fixation

Magntosomes

• stores iron, allows for orientation in a specific direction

Nucleoid

• mass of DNA coated with proteins/RNA molecules

Typical prokaryotic cell: the cytoskeleton

• Dynamic protein filaments that organize cell structure, growth, and division

• Key proteins: FtsZ (tubulin-like), MreB and ParM (actin-like)

• Functions: Maintains cell shape, directs cell wall synthesis, and positions chromosomes/plasmids

• Dynamics: filaments continuously assemble and disassemble

• Role in division: forms the Z-ring and ensures proper DNA segregation

Typical prokaryotic cell: Bacterial Cell Envelope

• Components: Plasma membrane, cell wall (peptidoglycan), and sometimes an outer membrane

• plasma membrane: phospholipid bilayer with proteins; functions in transport, signalling, and energy production

• Cell wall: peptidoglycan, maintains cell shape and prevents osmotic lysis

• Gram-positive: Thick peptidoglycan layer

• Gra,-negative: Thin peptidoglycan later + outer membrane containing LPS and porins

• Outer membrane function: selective barrier that increases environmental and antibiotic resistance

Typical prokaryotic cell: variations in bacterial morphology

• several distinct categories of shapes:

• spherical → coccoid

• rod → bacillary form

• curved → vibrio

• spiral → form

What is Archaea?

• Prokaryotes that lack a membrane-bound nucleus

• originally classified as bacteria (“Archaebacteria”)

• identified as a separate domain by Carl Woese via RNA analysis

• Distinct from bacteria in membrane composition, genetics, and metabolism

• often found in extreme environments

• one of the 3 domains of life: Archaea, bacteria, eukarya

Archaeal Morphology

• rods, spheres, spirals

• irregular shapes

• square/rectangular shapes

Structural Features of Archaea

• similar to bacteria as it is 0.5 - 5 μm in size, contain singular, circular chromosomes, lack a membrane-bound nucleus, has a cell wall, some cytoskeletal proteins

• similar to eukaryotes: DNA complexed with histones, many DNA replication enzymes similar to Eukaryotes, some cytoskeletal proteins

• Unique to Archaea: plasma membrane structure

Archaeal cell wall

• some archaea lack a cell wall

• differ from bacterial cell walls

• Many archaea have pseudomurein instead of peptidoglycan (PGN).

• Pseudomurein contains different sugars and β(1→3) linkages.

• As a result, resistant to lysozyme and many antibiotics that target bacterial cell walls.

Archaeal Histones

• proteins that package DNA into structural units.

• Archaea have histone proteins similar to eukaryotes.

• Archaeal DNA wrapping is different from eukaryotic nucleosomes and forms simpler structures.

• Functions: DNA compaction, protection, and regulation of gene expression.

Bacterial Flagella

• grows from the tip

Archaeal Flagella

• grows from the base

Characteristics of Prokaryotes Simplified

• Nucleoid (no nucleus)

• Single circular chromosome

• No membrane-bound organelles

• Divide by binary fission

• Usually unicellular and smaller

Characteristics of Eukaryotes Simplified

• Nucleus with nuclear envelope

• Multiple linear chromosomes

• Membrane-bound organelles present

• Divide by mitosis/meiosis

• Can be unicellular or multicellular; usually larger

Shared by all cells (bacteria, archaea, and eukaryotes)

• Plasma membrane

• Cytoplasm

• DNA

• Ribosomes

• Macromolecules: lipids, carbohydrates, proteins, nucleic acids.

Eukaryotic Cells and Organisms

• defined by a membrane-bound nucleus

• usually larger and more complex than prokaryotes/archaea

• contain membrane-bound organelles for specialized functions

• may have a cell wall (cellulose in plants, chitin in fungi)

• have a complex cytoskeleton (microfilaments, microtubules, intermediate filaments)

Eukaryotic Cell: Nucleus

• spatial separation of genetic material

  • transcription occurs in nucleus and translation occurs in cytoplasm

• sounded by a double membrane (nuclear envelope)

• Function: stores and protects DNA

• key idea: spatial separation creates a stepwise order (transcription first, then translation)

• part of the central dogma of molecular biology

Eukaryotic Cells: Flagella

• different from bacteria and archaea

• extensions of the cytoskeleton and are covered by the cell membrane

Eukaryotic cell: cell wall

• some eukaryal cells only create