BIO 175- General Microbiology

1
BIO 175- General Microbiology

• Chapter 4- Functional Anatomy of Prokaryotic and
  Eukaryotic Cells

2
Prokaryotes Vs. Eukaryotes

• Prokaryotes
• DNA not surrounded by membrane (no nucleus)
• DNA not associated with histones
• No membrane surrounded organelles
• Cell walls contain peptidoglycan (99.9 of
  prokaryotes)
• Divide by binary fission
• Examples bacteria, archaea

3
Prokaryotes vs. Eukaryotes contd.

• Eukaryotes
• DNA in true membrane-enclosed nucleus
• DNA associated with histones
• Have membrane-enclosed organelles such as
  mitochondria, Golgi complex, etc.
• May or may not have a cell wall, but it is not
  made of peptidoglycan when present.
• Cell division usually by mitosis
• Examples plants, animals, fungi, protozoa

4
Size, Shape and Arrangement of Bacterial Cells

• Size most range from 0.2-2.0µm
• Basic Shapes coccus (sphere), bacillus (rod),
  spiral
• Arrangement prefixes diplo-, strepto-, staphylo-
• Tetrads-
• Sarcinae-

5
Arrangements of cocci
6
Arrangements of bacilli
7
Types of spiral-shaped bacteria
8
The prokaryotic cell
9
Structures external to the cell wall

• Glycocalyx- sugar coat
• Sticky polymer made of polysaccharides (sugars),
  polypeptides (proteins), or both
• Composition varies with species
• Capsule- highly organized, firmly attached
  glycocalyx
• Slime layer- unorganized, loosely attached
  glycocalyx
• Functions of the glycocalyx

10
Structures external to the cell wall

• Flagella
• Whip-like appendages used for locomotion
• NOT the same structurally as eukaryotic flagella
• Atrichous
• Monotrichous
• Lophotrichous
• Amphitrichous
• Peritrichous

11
Four arrangements of bacterial flagella
12
Motility

• Ability of an organism to move by itself
• Taxis movement of a bacterium toward or away
  from a stimulus
• Examples phototaxis, chemotaxis
• Positive/negative taxis

13
Fimbriae and Pili

• fimbriae- hair-like appendages shorter than
  flagella, used for attachment
• Pili- longer than fimbriae, used by some bacteria
  to transfer DNA (also known as conjugation or sex
  pili)

14
The bacterial cell wall

• Major function- protect bacterium from rupturing
  as it takes on water
• Clinical importance- site of action of some
  antibiotics, contributes to some species ability
  to cause disease
• Composed of peptidoglycan

15
Peptidoglycan

• Consists of cross linked disaccharides and
  polypeptides
• Penicillin disrupts linking of peptidoglycan
  rows, weakening cell and causing lysis

16
Gram-positive vs. Gram-negative cell walls

• Gram thick, rigid structure composed of many
  layers of peptidoglycan, contain teichoic acids
• Gram- thin layer of peptidoglycan, surrounded by
  an outer membrane made of lipopolysaccharides
  including Lipid A

17
Gram-positive Cell Wall
18
Gram-negative Cell Wall
19
Structures Internal to the Cell Wall

• Plasma membrane
• Consists of a phospholipids and proteins
• Arrangement of phospholipid bilayer
• Proteins can be integral, peripheral, or
  transmembrane
• Glycoproteins-
• Glycolipids-
• Fluid mosaic model-

20
Functions of Plasma Membrane

• Selective permeability-
• Contains enzymes important in nutrient breakdown
  ATP production
• Some bacteria have photosynthetic pigments in
  infoldings of the membrane called thylakoids

21
Movement of substances across the membrane

• Passive processes-no energy required
• Simple diffusion-
• Facilitated diffusion-
• Osmosis-

22
Simple Diffusion
23
Facilitated Diffusion
24
Osmotic Pressure

• Pressure needed to prevent the movement of water
  across a semi-permeable membrane
• Isotonic solution equal concentration of solutes
  outside and inside the membrane, no net movement
  of water
• Hypotonic solution lower conc. of solutes
  outside the membrane, water moves into the cell
• Hypertonic solution higher conc. of solutes
  outside the membrane, water moves out of cell

25
(No Transcript)
26
Movement of Substances Across Plasma Membrane

• Active Processes-energy required
• Active transport-
• Group translocation-
• Both processes allow the cell to accumulate
  substances that are in low concentrations in the
  environment

27
Cytoplasm

• 80 water
• Contains enzymes, carbohydrates, lipids, ions,
  many low m.w. compounds
• Major structures- nuclear area, ribosomes,
  inclusions

28
Nuclear Area

• AKA nucleoid- is not a nucleus because it has no
  surrounding membrane
• Contains bacterial chromosome- a single,
  circular, double strand DNA molecule
• Plasmids- small circular bacterial DNA not
  attached to the chromosome, usually contain 5-100
  genes

29
The Bacterial Chromosome
30
Ribosomes

• Found in all cells- prokaryotic and eukaryotic
• 10,000 to a cell
• Composed of 2 subunits
• Made of protein and rRNA
• Site of protein synthesis- links amino acids
  found in cytoplasm to form proteins

31
Inclusions

• Reserve deposits of many different material in
  cytoplasm
• Amounts/types of inclusions vary with species
• Volutin granules-
• Polysaccharide granules-
• Sulfur granules-
• Carboxysomes-
• Gas vacuoles-
• Magnetosomes-

32
Endospores

• When the going gets tough
• Certain Gram-positive bacteria such as Bacillus
  and Clostridium form endospores
• A highly resistant dormant cell that can
  germinate into a growing cell when conditions
  improve
• Can withstand heat, dehydration, and many
  chemicals
• Can last for millions of years!

33
Formation of endospores by sporulation