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27 Cards in this Set
- Front
- Back
What are autotrophs?
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Use non-living carbon and energy sources: the vast majority
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Saprophytes
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putrefactive. Live off nitrogenous waste: include some potential pathogens
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Name 3 type of symbiont relationships.
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interact with plants & animals
i) Commensal - normal flora ii) Mutualistic - mutually beneficial iii) Parasitic - disease producing (= the minority) |
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Give 3 points about identifying the appearance of bacteria.
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1. Identification starts with a knowledge of colony appearance on plates and growth requirements
2. Then morphology + Gram stain on individual cells in a smear (see practical manual) 3. Bacteria are either Gram positive or Gram negative (are some exceptions) |
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List the structures of an dealised bacterium (8)
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1. Cell Wall.
2. Capsule. 3. Flagella. 4. Mesosome 5. Sexpilus 6. Fimbriae/pili 7. Cytoplasmic membrane surrounding the protoplast. 8. Nucleus. |
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What is the function of the cell wall? Give an example of a bacterium that does not posses the cell membrane.
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Cell walls give shape, and protect from osmotic pressure and the external environment.
Mycoplasma |
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Which layer can the peptidoglycan be found in the gram positive and gram negative bacterium?
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Top on the +ve and middle in the -ve.
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What is peptidoglycan consists of?
What is the difference between gram +ve and -ve ? |
Consist of N-acetylglucosamine (G) and N-acetylmuramic acid (M), with L and D amino acids and lysine or diaminopimelic acid.
Gram positives have many such layers, whilst Gram negatives only have 1 or 2 such layers. |
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Why does the gram positive bacteria stain blue?
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The thick layers of peptidoglycan holds the stain,
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What is the effect of lysosome on the cell wall.
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A natural antibacterial agent also works by breaking down the chains of G and M that make up the peptidoglycan.
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What extra layer does the gram negative bacteria have?
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Cells are surrounded by an outer membrane of lipopolysaccharide
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The space between the layers of peptidoglycan and the cell membrane is called the .............. .............. ?
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periplasmic space
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What are the 3 major regions of the LPS?
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O Polysaccharide
Core polysaccharide Lipid A |
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O Polysaccharide
Describe 3 points. |
>may be branched : mny different combinations
>antigenic : generates specific immune response >highly species specific: gives serotype to bacteria. |
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What is important about lipid A?
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Lipid A
toxic internal, hence protected (Fatty acids + N-acetylglucosamine |
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Give 3 points of the capsule.
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1. Outer polysaccharide layer around some bacteria
2. - can convey resistance to phagocystosis (eg Bacillus anthracis) 3. Tight, or loose and slimy |
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What is the Glycocalyx?
Why is it important? |
A slimy outer layer in some bacteria.
Involved in adhesion, clumping & biofilm formation BIOFILMS e.g. Catheters, lungs |
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Why are biofilms a major problem?
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They reduce penetration of antibiotics and disinfectants and provide the bacteria living in such communities with physical protection and other advantages.
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What are Pilus or Fimbria ?
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surface structures
rod-like protrusions polypeptide subunits >Extremely important in attachment of mucosal pathogens (therefore used in vaccines) |
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What is the function of a sex pilus?
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- a single rod like structure protruding from the surface
- involved in transfer of DNA between bacterial cells (conjugative plasmids) |
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Briefly give two points about the flagella,
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>Organs of motility, possessed by many bacteria.
>Require energy: driven by a rotary engine at the anchoring point in the inner cell membrane - pumps protons |
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Define monotrichous
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one polar flagellum at one cell end
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Lophotrichous
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several at one end
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Amphitrichous
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several at both ends
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Petrichous
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many all over the cell surface
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Name 2 genera that produces spores.
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-Bacillus
- Clostridium |
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Give 4 significance of spores.
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1. Microbial ecology (allows long term survival in the environment)
2. Food (contamination by spores and subsequent spoilage or food poisoning) 3. Sterilisation (difficult to acheive because of their resistance to nature. 4. Epidemiology (resevoirs in the soil). |