bacterial structure(2)

8/8/2019 Bacterial Structure(2)

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Size of Bacteriay Average bacteria 0.5 - 2.0 um in diam.

y RBC is 7.5 um in diam.

y Surface Area ~12 um

y Volume is ~4 um

y Surface Area to Volume is 3:1

y Typical Eukaryote Cell SA/ Vol is 0.3:1

y Food enters through SA, quickly reaches all parts of bacteria

y Eukaryotes need structures & organelles


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Size of Bacteriay Average bacteria 0.5 - 2.0 um in diam.

y RBC is 7.5 um in diam.

y Surface Area ~12 um

y Volume is ~4 um

y Surface Area to Volume is 3:1

y Typical Eukaryote Cell SA/ Vol is 0.3:1

y Food enters through SA, quickly reaches all parts of bacteria

y Eukaryotes need structures & organelles


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Shapes of Bacteriay

Coccus

y Chain = Streptoccus

y Cluster = Staphylococcus

y Bacillus

y Chain = Streptobacillus

y Coccobacillus

y Vibrio = curved

y Spirillum

y Spirochete

y Square

y Star


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Square shaped


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Grouping of BacteriaGrouping of Bacteria

y Diplo- Groups of two

y Strepto- chains

y Staphylo- Grape like clusters


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Bacterial Structures

y Flagella

y Pili

y Capsule

y Plasma Membraney Cytoplasm

y Cell Wall

y Lipopolysaccharides

y Teichoic Acids

y Inclusions

y Spores


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Flagella

y Motility - movement

y Swarming occurs with some bacteria

y Spread across Petri Dish

y Proteus species most evident

y Arrangement basis for classification

y Monotrichous; 1 flagella

y Lophotrichous; tuft at one end

y Amphitrichous; both ends

y Peritrichous; all around bacteria


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Piliy Short protein appendagesy smaller than flagella

y Adhere bacteria to surfaces

y E. coli has numerous typesy K88, K99, F41, etc.

y Antibodies will block adherance

y F-pilus; used in conjugation

y Exchange of genetic information

y Flotation; increase boyancy

y Pellicle (scum on water)

y More oxygen on surface


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Capsule or Slime Layery Glycocalyx - Polysaccharide

on external surface

yAdhere bacteria to surfacey enamel of teeth

y Prevents Phagocytosis

y Complement cant penetrate

sugars


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Cytoplasm

y 80% Water {20% Salts-Proteins)

y Osmotic Shock important

y DNA is circular, Haploid

y Advantages of 1NDNA over 2NDNA

y More efficient; grows quicker

y Mutations allow adaptation to

environment quicker

y Plasmids; extra circularDNA

y Antibiotic Resistance

y No organelles (Mitochondria, Golgi, etc.)


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Cell Membraney Bilayer Phospholipid

y Water can penetrate

y Flexible

y Not strong, ruptures easily


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Chapter 4

Functions of the cytoplasmic membrane


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Cell Wally Peptido-glycan Polymer (amino acids + sugars)

y Unique to bacteria

y Sugars; NAG & NAM

y N-acetylglucosamine

y N-acetymuramic acid

y D form of Amino acids used not L form

y Hard to break down D form

y Amino acids cross linkNAG & NAM


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Teichoic Acidsy Gram + only

yGlycerol, Phosphates, & Ribitol

y Attachment for Phages


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Lipopolysaccharide (LPS)y Endotoxin or Pyrogen

y Fever causing

y Toxin nomenclature

y Endo- part of bacteriay Exo- excreted into environment

y Structure

y Lipid A

y Polysaccharidey O Antigen of E. coli, Salmonella

y G- bacteria only

y Alcohol/Acetone removes


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LP

S (contd)y Functionsy Toxic; kills mice, pigs, humans

y G- septicemia; death due to LPS

y Pyrogen; causes fever

y DPT vaccination always causes fevers

y Adjuvant; stimulates immunity

y Heat Resistant; hard to remove

y Detection (all topical & IV products)

y Rabbits (measure fever)

y

Horse shoe crab (Amoebocytes Lyse in presence of LPS)


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LPS (contd.)y Appearance of Colonies

y Mucoid = Smooth (lots of LPS or capsule)

y Dry = Rough (little LPS or capsule)

y O Antigen of Salmonella and E. coli

y2,000 different O Ags of Salmonella

y 100s different O Ags of E. coli

y O Ags differ in Sugars, not Lipid A


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Endospores

y Resistant structure

y Heat, irradiation, cold

y Boiling >1 hr still viable

y Takes time and energy to make spores

y Location important in classification

y Central, Subterminal, Terminal

y Bacillus stearothermophilus -spores

y Used for quality control of heat sterilization equipment

y Bacillus anthracis - spores

y Used in biological warfare


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G+ vs. G-y G+

y Thicker cell wall

y

Teichoic Acids

y G-

y Endotoxin - LPS

yWhich are more sensitive to Penicllin?

yAlcohol/Acetone affects which more?


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Prokaryotes vs. Eukaryotesy Cell Wall

y

Teichoic Acidsy LPS

y Endospores

y Circular DNA

y Plasmids


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Eukaryote Cell Structure

bacterial structure(2)

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