This document summarizes the structure of bacteria. It describes that bacteria are typically 0.5-2.0 um in size, much smaller than human red blood cells. Bacteria come in different shapes including coccus, bacillus, spirillum, and spirochete. The structures of bacteria include a cell wall, cell membrane, flagella, pili, capsule, cytoplasm, and some can form spores. The cell wall composition differs between gram-positive and gram-negative bacteria.

1. STRUCTURE OF BACTERIA
 DR SAIMA TARIQ

2. Size of Bacteria
 Average bacteria 0.5 ‐ 2.0 um in diam.
 RBC is 7.5 um in diam.
 SurfaceArea ~12 um^2
 Volume is ~4 um
 Surface Area toVolume is 3:1
 Typical Eukaryote Cell SA/Vol is 0.3:1
 Food enters through SA, quickly reaches all partsof
bacteria
 Eukaroytes need structures & organelles

3. Shapes of Bacteria
 Coccus
 Chain = Streptoccus
 Cluster = Staphylococcus
 Bacillus
 Chain = Streptobacillus
 Coccobacillus
 Vibrio = curved
 Spirillum
 Spirochete
 Square
 Star

9. Bacterial Structures
 Flagella
 Pili
 Capsule
 Plasma Membrane
 Cytoplasm
 Cell Wall
 Lipopolysaccharides
 TeichoicAcids
 Inclusions
 Spores

10.  Motility ‐ movement
Fla
Sg
wa
e
rm
llia
ng occurswith some bacteria
 Spread across Petri Dish
 Proteus species most evident
 Arrangement basis forclassification
 Monotrichous; 1 flagella
 Lophotrichous; tuftatone end
 Amphitrichous; both ends
 Peritrichous; all around bacteria
 Observe Picture in Micro Lab.

12. Mono- or Lophotrichorus

14. Pili
 Short protein appendages
 smallerthan flagella
 Adhere bacteria tosurfaces
 E. coli has numerous types
 K88, K99, F41, etc.
 Antibodies towill block adherance
 F‐pilus; used in conjugation
 Exchangeof genetic information
 Flotation; increase boyancy
 Pellicle (scum on water)
 Moreoxygen on surface

15. F‐Pilus for Conjugation

16. Capsule or Slime Layer
 Glycocalyx ‐ Polysaccharide on external surface
 Adhere bacteria tosurface
 S. mutans and enamel of teeth
 Prevents Phagocytosis
 Complementcan’t penetrate sugars

17. Cytoplasm
 80% Water {20% Salts‐Proteins)
 Osmotic Shock important
 DNA iscircular, Haploid
 Advantages of 1N DNA over 2N DNA
 Moreefficient; grows quicker
 Mutations allow adaptation toenvironment quicker
 Plasmids; extracircular DNA
 Antibiotic Resistance
 Noorganelles (Mitochondria, Golgi, etc.)

18. Cell Membrane
 Bilayer Phospholipid
 Watercan penetrate
 Flexible
 Notstrong, ruptureseasily
 Osmotic Pressure created bycytoplasm

22. Cell Wall
 Peptido‐glycan Polymer (aminoacids + sugars)
 Unique to bacteria
 Sugars; NAG & NAM
 N‐acetylglucosamine
 N‐acetymuramicacid
 D form of Aminoacids used not L form
 Hard to break down D form
 Aminoacidscross link NAG & NAM

29. Cell Wall Summary
 Determine shapeof bacteria
 Strength prevents osmotic rupture
 20‐40% of bacteria
 Unique to bacteria
 Someantibiotics effect directly
 Penicillin

30. Video Clip on Cell Wall

31. Teichoic Acids
 Gram + only
 Glycerol, Phosphates, & Ribitol
 Attachment for Phages

33. Lipopolysaccharide (LPS)
 Endotoxin or Pyrogen
 Fevercausing
 Toxin nomenclature
 Endo‐ partof bacteria
 Exo‐ excreted intoenvironment
 Structure
 Lipid A
 Polysaccharide
 O Antigenof E. coli, Salmonella
 G‐ bacteria only
 Alcohol/Acetone removes

36. LPS (cont’d)
 Functions
 Toxic; kills mice, pigs, humans
 G‐ septicemia; deathdue to LPS
 Pyrogen; causes fever
 DPTvaccination always causes fevers
 Adjuvant; stimulates immunity
 Heat Resistant; hard toremove
 Detection (all topical & IV products)
 Rabbits (measure fever)
 Horseshoecrab (Amoebocytes Lyse in presenceof LPS)

37. LPS (cont’d.)
 Appearance of Colonies
 Mucoid = Smooth (lots of LPS orcapsule)
 Dry = Rough (little LPS orcapsule)
 O Antigen of Salmonella and E. coli
 2,000 different O Ags of Salmonella
 100’sdifferent O Ags of E. coli
 E. coli O157
 O Ags differ in Sugars, not Lipid A

38.  Resistant structure
End
 H
oes
atp
, iro
rad
rie
atis
on, cold
 Boiling >1 hrstill viable
 Takes timeand energy to makespores
 Location important inclassification
 Central, Subterminal, Terminal
 Bacillus stearothermophilus ‐spores
 Used forqualitycontrol of heatsterilization
equipment
 Bacillusanthracis ‐ spores
 Used in biological warfare

41. G+ vs. G‐
 G+
 Thickercell wall
 Teichoic Acids
 G‐
 Endotoxin ‐ LPS
 Which are moresensitive to Penicllin?
 Alcohol/Acetone affects which more?