Structure of Bacteria
Dr.Ghada YounisChapter 4
Size of BacteriaAverage bacteria 0.5 - 2.0 um in diam. RBC is 7.5 um in diam. Surface Area ~12 um 2 Volume is ~4 um Surface Area to Volume is 3:1 Typical Eukaryote Cell SA/Vol is 0.3:1 Food enters through SA, quickly reaches all parts of bacteria Eukaroytes need structures & organelles
Chapter 4
Shapes of BacteriaCoccus Chain = Streptoccus Cluster = Staphylococcus Bacillus Chain = Streptobacillus Coccobacillus Vibrio = curved Spirillum Spirochete Square Star
Chapter 4
Chapter 4Chapter 4
Chapter 4
Chapter 4Chapter 4
Bacterial StructuresFlagella Pili Capsule Plasma Membrane Cytoplasm Cell Wall Lipopolysaccharides Teichoic Acids Inclusions Spores
Chapter 4
FlagellaMotility - movement Swarming occurs with some bacteria Spread across Petri Dish Proteus species most evident Arrangement basis for classification Monotrichous; 1 flagella Lophotrichous; tuft at one end Amphitrichous; both ends Peritrichous; all around bacteria Observe Picture in Micro Lab.
Chapter 4
Chapter 4
Chapter 4Pili
Short protein appendages smaller than flagella Adhere bacteria to surfaces E. coli has numerous types K88, K99, F41, etc. Antibodies to Pili will block adherence F-pilus; used in conjugation Exchange of genetic information
Chapter 4
F-Pilus for ConjugationChapter 4
Capsule or Slime LayerGlycocalyx - Polysaccharide on external surfaceAdhere bacteria to surfaceS. mutans and enamel of teethPrevents PhagocytosisComplement can’t penetrate sugars
Chapter 4
Cytoplasm80% Water {20% Salts-Proteins) Osmotic Shock important DNA is circular, Haploid Advantages of 1N DNA over 2N DNA More efficient; grows quicker Mutations allow adaptation to environment quicker Plasmids; extra circular DNA Antibiotic Resistance No organelles (Mitochondria, Golgi, etc.)
Chapter 4
Cell Membrane
Bilayer Phospholipid Water can penetrate Flexible Not strong, ruptures easily Osmotic Pressure created by cytoplasm
Chapter 4
Chapter 4Chapter 4
Cell WallPeptido-glycan Polymer (amino acids + sugars) Unique to bacteria Sugars; NAG & NAM N-acetylglucosamine N-acetymuramic acid D form of Amino acids used not L form Hard to break down D form Amino acids cross link NAG & NAM
Chapter 4
Chapter 4Chapter 4
Chapter 4
Cell Wall SummaryDetermine shape of bacteria Strength prevents osmotic rupture 20-40% of bacteria Unique to bacteria Some antibiotics effect directly Penicillin
Chapter 4
Teichoic AcidsGram + only Glycerol, Phosphates, & Ribitol Attachment for Phages
Chapter 4
Chapter 4Lipopolysaccharide (LPS)
Endotoxin or Pyrogen Fever causing Structure Lipid A Polysaccharide O Antigen of E. coli, Salmonella G- bacteria only Alcohol/Acetone removes
Chapter 4
Chapter 4
Chapter 4LPS (cont’d) Functions Toxic; kills mice, pigs, humans G- septicemia; death due to LPS Pyrogen; causes fever DPT vaccination always causes fevers Heat Resistant; hard to remove
Chapter 4
LPS (cont’d.) Appearance of ColoniesMucoid = Smooth (lots of LPS or capsule)Dry = Rough (little LPS or capsule)O Antigen of Salmonella and E. coli2,000 different O Ags of Salmonella100’s different O Ags of E. coliE. coli O157O Ags differ in Sugars, not Lipid AChapter 4
EndosporesResistant structure Heat, irradiation, cold Boiling >1 hr still viable Takes time and energy to make spores Location important in classification Central, Subterminal, Terminal Bacillus stearothermophilus -spores Used for quality control of heat sterilization equipment Bacillus anthracis - spores Used in biological warfare
Chapter 4
Chapter 4Chapter 4
G+ vs. G-G+ Thicker cell wall Teichoic Acids G- Endotoxin - LPS Which are more sensitive to Penicllin? Alcohol/Acetone affects which more?