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Microbiology – Alcamo Lecture: Bacterial Structures -Not all bacteria have all structures.

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Presentation on theme: "Microbiology – Alcamo Lecture: Bacterial Structures -Not all bacteria have all structures."— Presentation transcript:

1 Microbiology – Alcamo Lecture: Bacterial Structures -Not all bacteria have all structures

2 Shapes of Bacteria 3 Different Shapes:

3 Bacilli Rod shaped Most occur singly, but some form long chains called Streptobacilli Examples: –Typhoid fever –Anthrax –Diptheria

4 Cocci Usually sphere shaped but can be oval Diplococci – cocci that remain in pairs –Examples – Gonorrhea, Menengitis Streptococci – cocci in chains –Examples - Strep throat, Tooth decay Staphylococcus – irregular grape-like cluster of cells –Examples – Food poisoning, staph skin infections

5 Spiral Bacteria Vibrios – curved rods - look like a comma –Example - Cholera Spirilla – corkscrew shape with flagella –Example – Rat Bite fever Spirochetes – corkscrew shape but no flagella –Example - syphilis

6 Flagella Used by some bacteria to achieve motion Made of long rigid strands of protein called flagellin Protein strands are permanently coiled Permits the flagellum to rotate and propel the bacterium forward

7 Flagella Complicated structure: Filament attached to hook-like shaft which is inserted through cell wall and attached to cell membrane

8 Flagella Monotrichous Lophotrichous Amphitrichous Peritrichous

9 Axial Filament Only spirochete One flagella attached at both ends of flexible spiral MO Motion effected by cell spinning around filament

10 Pili Look like short flagella but have nothing to do with motion Very tiny protein “Hairs” that enable MO to stick to surfaces - like “Velcro”

11 Pili Pili aid in transfer of genetic material between bacteria Pili anchor bacteria to surfaces like living tissue Can enhance MO’s disease effect Example - gonorrhea

12 Capsule Some bacteria secrete a layer of polysaccharides and proteins that stick to its surface Sticky and gelatinous Serves as a buffer between the bacteria and its environment –Protects bacteria against dehydration –Protects bacteria against host’s immune system


14 Glycocalyx Some bacteria produce a Slime Layer Complex sugar, made inside cell wall secreted as liquid, polymerizes to jelly like substance Cavities – S. mutans attaches itself to teeth by using the sugar a person eats – creates an acid that breaks down tooth enamel

15 Cell Wall All bacteria have a cell wall except mycoplasmas Semi-rigid structure, protects, gives shape Amount of chemical “Peptidoglycan” determines characteristics of cell wall If a lot: Thick, G+ stain reaction, sensitive to penicillin and lysozyme in tears, saliva, mucous


17 If small: thinner, G- stain reaction, not sensitive to penicillin or lysozyme If MO is pathogenic, disease more difficult to cure

18 Cell Membrane Boundary layer of the cell inside of cell wall Contains Cytoplasm, controls molecular traffic in and out of the cell Triple layer structure, 60% proteins, 38% lipids (phospholipid bilayer), 2% sugars Antimicrobials (detergents, alcohol, some antibiotics) dissolve cell membrane

19 cell membrane animation

20 Cytoplasm Gelatinous mass of proteins carbohydrates lipids nucleic acids salts ions water

21 Important Structures in Cytoplasm Ribosomes – protein synthesis Inclusion Bodies – globules of starch or lipids – store nutrients Bacterial Chromosome – closed loop of DNA without a membrane or proteins (nucleoid region) Plasmids – smaller, separate molecules of DNA – few genes but do give bacteria drug resistance (R genes)

22 Endospores Some Gram + bacteria produce highly resistant structures - spores –Bacteria grow, mature and reproduce as vegetative cells –Then the bacterial chromosome replicates and the cell membrane grows in to seal off a developing spore –Next, thick layers of peptidoglycan form to protect the cell –Finally, the cell wall of the vegetative cell disintegrates and the spore is released


24 Endospores Very resistant to poor environmental conditions: –Extreme temperatures – boiling water –Chemicals – 70% alcohol –Spores have even been recovered alive from an Egyptian mummy’s intestines Examples of spore formers – anthrax, botulism, tetanus


26 “Sporulation” is spore formation - DNA + some cytoplasm wrapped in spore case formed by cell membrane “Germination” occurs when good environmental conditions return – vegetative cell

27 Kingdom Classification

28 Archaeobacteria Have existed on earth longer than any other living organism They are different from eubacteria: –No peptidoglycan in cell wall –Different lipids in cell membrane –Different ribosomal RNA –Now archaeobacteria and eubacteria are classified as different kingdoms

29 Archaeobacteria 3 Types: –Methanogens – rods that live in anaerobic conditions and produce methane gas – common in marshes and the guts of cows and humans –Thermoacidophiles – resistance to acid and high temperatures – live in hot springs and ocean vents –Extreme Halophiles – thrive in high salt environments (Great Salt Lake)

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