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MCS > TBL 4 - INTRO TO MICROORGANISM > Flashcards

TBL 4 - INTRO TO MICROORGANISM Flashcards

1
Q

What is microbiology and what are the exceptions to this definition?

A

Microbiology study of very small living things which is seen by the naked eye
Expectation to this are fungi/protozoa which are very large and obvious

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2
Q

Who is known as the father of microbiology?

A

Antione van Leeuwenhoek - farther of microbiology - first record of microorganism after he produced microscope

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3
Q

What are the 3 domain system of carl woese?

A

1) Bacteria: unicellular prokaryotes with cell wall containing peptidoglycan
2) Archaea: unicellular prokaryotes with no peptidoglycan in cell wall
3) Eukaryote: Protista, fungi, plantae, animalia

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4
Q

What is the difference between bacteria and eukaryotic cell?

A

Bacteria has a simple internal structure without membrane enclose organelles compared to eukaryotic cells which has membrane enclosed organelles.

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5
Q

What is the structures and functions of bacteria?

9 STRUCTUE/FUNCTIONS

A

Cell membrane: Selective permeability
Cell wall: Support and protection
Ribosomes: Protein synthesis
Inclusion bodies: Storage of Carbon, phosphorus and other substances
Nucleoid: Genetic material
Capsules and slime layer: Resistance and adherence
Flagella: Motility
Endospore: Survival in harsh conditions
Pili/fimbriae: Various roles

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6
Q

What do cell walls surround and the exception to this?

A

Rigid cell wall surrounds all bacteria cells except mycoplasmas gives cell its shape and rigidity.

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7
Q

What is peptidoglycan vital for?

A

Rigid layer of peptidoglycan (murein) vital for bacterial cell survival.

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8
Q

What does the cell wall protect the cell from?

A

Cell wall protects cell from mechanical disruption and from being burst by osmotic pressure, maintaining high conc of solutes inside cell.
Useful for identification cus gram stained

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9
Q

Where are peptidoglycan found?

A

Peptidoglycan found in gram +/gram - bacteria gives cell wall strength.

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10
Q

What are the 2 alternating sugar derivatives in peptidoglycan and what bonds are used to link them?

A

Consists of linear glycan chain of 2 alternating sugar derivatives: N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) which is linked by B1:4 glycosidic bonds.

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11
Q

What are glycosidic bonds?

A

Glycosidic bonds are strong but will not give rigidity in all directions so glycan chains are cross linked with tetrapeptide amino acid side chains.

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12
Q

What are the amino acids that alternate between L- and D- amino acids that are connected to NAM (4 things)?

A

L alanine
D glutamic acid
Lysine or diaminopimelic acid
D alanine

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13
Q

What happens when tetrapeptides cross link and connect to peptidoglycan sheets?

A

Cross-links between other tetrapeptides connect the peptidoglycan sheets to form a 3D rigid matrix which forms a peptidoglycan sac
Shape of cell determined by length of peptidoglycan chains and the manner and extent of cross linking

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14
Q

What are the features of gram + bacteria (2 things)?

A
  • Thick cell wall provides greater protection from enviro stresses
  • 20 layers of peptidoglycan (up to 90% cell wall) and teichoic acid
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15
Q

What are the features of gram - bacteria (2 things)?

A
  • Thin cell wall (10% cell wall) also has periplasm and outer membrane
  • Multi-layered and complex
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16
Q

What type of acid is found in gram + cell wall only?

A

Teichoic acids found in gram + cell walls only.

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17
Q

What are the 2 acidic polysaccharides in gram + cell wall?

A

Acidic polysaccharides are either polymers of glycerol phosphate or ribitol phosphate.
Some covalently linked to the NAM residues of peptidoglycan or lipids in plasma membrane.

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18
Q

What is the function of teichoic acid?

A

Up to 50% of gram + wall may be teichoic acid important as they anchor wall to cell. Some protrude out of peptidoglycan layer and provide an overall negative charge which helps bacterium evade phagocytosis.

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19
Q

What type of gel like substance is formed from peptidoglycan and what is its function?

A

Some peptidoglycan forms a single-layered sheet around cell and the rest, with minimal cross-linking forms gel-like substance which is called periplasmic gel.
Sac gives cell its shape/integrity even with reduced peptidoglycan.

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20
Q

What does the periplasm contain?

A

Periplasm contains various proteins including enzymes with hydrolytic functions, antibiotic-inactivating enzymes and binding proteins with roles in chemotaxis and active transport of solutes into the cell.

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21
Q

What is the function of the outer membrane?

A

Outer membrane external to its periplasm. Function including creation of periplasm and provision of outer surface with a strong negative charge - helps evade phagocytosis and action of complement. Acts as a permeability barrier against host lysosome, bile salts, digestive enzymes and many antibiotics.

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22
Q

What does the inner and outer membrane contain?

A

Outer membrane inner layer consists of ordinary phospholipids whereas outer membrane consists of lipopolysaccharide (LPS)

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23
Q

What is LPS and what can it cause?

A

LPS is toxic to humans and other animals referred to as an endotoxin
Minute amounts of LPS can produce fever and shock ( gram - shock/endotoxic shock)

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24
Q

What are the 3 things that LPS contain?

A

1) lipid A: a phospholipid containing glucosamine (toxic component) rather than glycerol
2) Core polysaccharide: Contains some unusual carbohydrate residues e.g. Salmonella contains keto deoxycortone, heptoses, glucose, galactose & N-acetylglucosamine (NAG))
3) O-antigen polysaccharide: major surface antigen of Gram –ves galactose, glucose, rhamnose & mannose (hexoses) & unusual dideoxy sugars e.g. abequose, colitose, paratose or tyvelose

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25
Q

What can the LPS in the outer membrane act as?

A

LPS in the outer membrane acts a barrier that blocks the passage of most organic molecules into the cell and therefore Gram negatives must make provision for the rapid entry of nutrients.

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26
Q

What are the proteins that form pores in the outer membrane?

A

Special proteins form pores through the outer membrane called porins. These channels allow hydrophilic molecules of low MW to diffuse into the periplasm

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27
Q

What is the cell membrane made up of?

A

Made up of phospholipid bilayer with integrated membrane proteins.

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28
Q

How do you give rigidity to the phospholipid bilayer?

A
  • To give some rigidity the phospholipid bilayer in eukaryotes contain sterols whereas bacterial cells contain hopanoids.
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29
Q

What is the function of the cell membrane?

A

The cell membrane acts as a selective permeability barrier. It plays an important part in regulating the movement of substances in and outside of the cell. For example, hydrophilic and charged molecules cannot pass thorough the hydrophobic phospholipid bilayer, so movement is regulated through various membrane channels or mechanisms. The cell membrane regulates essential nutrients uptake by active transport mechanisms.

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30
Q

What does a bacterial cell surround themselves with?

A

Bacterial cell surround themselves with hydrophilic gel

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31
Q

What is the different between a true capsule and slime layer?

A

True capsule: Material defined in shape
Slime layer: Material is amorphous in appearance

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32
Q

How can bacteria form biofilms?

A

Capsules assist in colonisation by assisting cell to attach to surfaces and allow bacteria to form biofilms.

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33
Q

Does a prokaryotic cell contain a nucleus?

A

Prokaryotic cells do not have a true nucleus.

34
Q

What happens during prokaryotic DNA?

A

Prokaryotic DNA is extensively folded/condensed into nucleoid structure which does not have a nuclear membrane.
Single circular chromosome consisting of double-stranded DNA which encodes all genes required for essential cell functions. Extra-chromosomal genetic exist called plasmids.

35
Q

Which has smaller ribosomes prokaryotes or eukaryotes?

A

Prokaryotes smaller then eukaryote equivalent (70s vs 80s)

36
Q

What are the 2 subunits that prokaryotic ribosomes consist of?

A

Prokaryotic ribosomes are made from protein and RNA and consist of 2 subunits:
1) 30S subunit - 16s rRNA and 21 protein
2) 5S and 23S rRNA and 34 proteins

37
Q

What is the sedimentation coefficient of prokaryotic ribosomes?

A

When joined, prokaryotic ribosome has a sedimentation coefficient of 70S as opposed to 80S due to tertiary structure.

38
Q

What is the function of inclusion granules and what are volutin granules?

A

Are carbohydrates, lipids, proteins or inorganic substances
Serve as useful energy and nutrient reserves.
Volutin granules consist of high energy phosphate reserves

39
Q

What is the function of flagellum?

A

Provides swimming movement for motile bacteria and enable bacteria to reach their environmental niche.

40
Q

Flagella distributed around cell differently What does monotrichous mean?

A

Monotrichous - one hair

41
Q

Flagella distributed around cell differently What does lophotrichous mean?

A

Lophotrichous - tuft of hair

42
Q

Flagella distributed around cell differently
What does Amphitrichous mean?

A

Amphitrichous - hair on both sides

43
Q

Flagella distributed around cell differently
What does Peritrichous mean?

A

Peritrichous - around the cell

44
Q

What is chemotaxis?

A

Chemotaxis: motile response to certain chemicals - bacteria attracted to useful substances or repelled from toxic substances.

45
Q

What is phototaxis?

A

Phototaxis: motile response to light

46
Q

What is aerotaxis?

A

Aerotaxis: motile response to O2

47
Q

What is magnetotaxis?

A

Magnetotaxis: motile response to magnetic fields which is useful behaviour for sourcing ferrous metals

48
Q

What does flagellar filaments consist of?

A

Flagellar filaments consist of polymerised molecules of single protein called flagellin which only found in bacteria.
Protein forms H-antigen of bacterium which used for serological identification of bacterial strains

49
Q

What are the structure of pilis?

A

Molecular hair-like projections found of surface of cells composed of molecules of protein called pili.
Pilli arranged to form tube with minute, hollow core.

50
Q

What is the function of common pili?

A

Common pili cover surface of cell, act as adhesions allowing bacteria to colonise surfaces and cells.

51
Q

What are sex pili?

A

Sex pili involved in exchange of genetic material between mating bacteria.

52
Q

What are endospores?

A

Small, metabolically inert cells with thick cell walls formed by some gram + bacteria in adverse conditions.

53
Q

What are spores and what are they resistant to?

A

Spores oval or round cells within vegetative cells.
Spores resistant to high temp, irradiation, strong acids, disinfectants - enable cells to survive in extreme enviros.
Spores show no signs of life - cryptobiotic or dormant

54
Q

Who developed gram stain?

A

Developed by Dr Christian Gram 1884

55
Q

What 2 groups are bacteria divided into?

A

Divides bacteria into 2 groups: Gram + (purple cells)/Gram - (pink cells)
Stained cells visualised under light microscope.

56
Q

The gram stain extracts iodine/crystal violet from which bacteria? And what colour is stained?

A

Gram stain extracts iodine/crystal violet complexes with ethanol or ethanol/acetone mixtures. Iodine/crystal violet complexes retained in peptidoglycan in gram + cell wall, stained purple.

57
Q

What colour is stained in gram - cell wall and what is the stain called?

A

Complexes extracted from gram - cell wall, stained pink with counter-stain safranin.

58
Q

What are the 4 stages in peptidoglycan synthesis?

A

1) Bacterial enzymes called autolysins break the glycosidic bonds between the peptidoglycan monomers and break the peptide cross-bridges
2) Peptidoglycan monomers are then synthesized in the cytosol and carried across the cytoplasmic membrane by bactoprenols
3) Transglycosidase enzymes insert and link new peptidoglycan monomers into the breaks in the growing peptidoglycan chains
4) Transpeptidase enzymes reform the peptide cross-links between the rows and layers of peptidoglycan to make the wall strong

59
Q

What is binary fission?

A

Bacteria replicate by binary fission, a process by which one bacterium splits into two. Therefore, bacteria increase their numbers by geometric progression whereby their population doubles every generation time.

60
Q

What is generation time?

A

Generation time is the time it takes for a population of bacteria to double in number

61
Q

What happens during the lag phase?

A

Lag phase: After inoculation into liquid medium, cell do not multiply during lag phase. The cells at this stage are increasing in metabolic activity due to synthesis of enzymes proteins, DNA and there may be an increase in cell size. etc.

62
Q

What happens during log phase?

A

Log phase: At this stage the cell population doubles at regular intervals or grows exponentially depending upon the growth conditions (culture medium, temperature etc).

63
Q

What happens during the stationary phase?

A

Stationary Phase: When the exponential phase or log phase ceases, cells enter stationary phase in which there is no net increase or decrease in cell number.

64
Q

What happens during the death phase?

A

Death Phase: During this phase the number of viable cells decreases exponentially.

65
Q

What are plasmids?

A

Plasmids are important “vehicles” for the communication of genetic information between bacteria.

66
Q

Why are plasmids important in medical microbiology?

A

The study of plasmids is important to medical microbiology because plasmids can encode genes for antibiotic resistance or virulence factors.

67
Q

What is horizontal gene transfer?

A

Horizontal gene transfer (HGT) is the movement of genetic information between organisms, a process that includes the spread of antibiotic resistance genes among bacteria (except for those from parent to offspring), fuelling pathogen evolution.

68
Q

What is conjugation?

A

Conjugation is the process by which one bacterium transfers genetic material to another through direct contact.
During conjugation, one bacterium serves as the donor of the genetic material, and the other serves as the recipient.
The donor bacterium carries a DNA sequence called the fertility factor, or F-factor.

69
Q

What is the transformation process?

A

Bacterial transformation is a process of horizontal gene transfer by which some bacteria take up foreign genetic material (naked DNA) from the environment.

70
Q

What is the transduction process?

A

Transduction is the process by which a virus transfers genetic material from one bacterium to another. Viruses called bacteriophages are able to infect bacterial cells and use them as hosts to make more viruses.

71
Q

What is the veriduction process?

A

Transduction and vesiduction refer to the transfer of bacterial DNA (red DNA strand) by bacteriophages (C) or extracellular vesicles (EVs, D).

72
Q

How many cells do the human body have?

A

human body has approximately 1 x 10^13 human cells.

73
Q

What does colonisation do?

A

colonization is often the first stage in the development of disease and therefore the colonization protect the body from infection. These beneficial aspects above are the basis of probiotics, where certain foods such as live yoghurts contain “friendly” bacteria which colonize the gut and impart health benefits.

74
Q

What is a pathogen and what types of host are there?

A

A pathogen is an organism capable of causing disease in a host.
The host can be humans, animals, plants and even other microorganisms.

75
Q

What does microbial pathogens cause?

A

Microbial pathogens cause a range of infections in humans which vary in severity from being a nuisance (the patient may recover without treatment) such as sore throats, food poisoning or skin infections, to those which are deadly (small chance of recovery without treatment), such as TB, plague, anthrax, MRSA, Cl. difficile colitis.

76
Q

What is the definition of spoilage?

A

Spoilage adversely affects the aroma, texture, appearance and safety of food.
approximately one third of all the food produced in the world is wasted due to spoilage.

77
Q

What is an example of putrefaction?

A

putrefaction – meat decomposition

78
Q

What is an example of souring?

A

souring – milk, fruit juices

79
Q

What is an example of rotting?

A

rotting – fruit and vegetables

80
Q

What is an example of rancidity?

A

rancidity – butter spoilage

81
Q

What is an example of mouldy?

A

mouldy – fungal growth on food

82
Q

What is an example of slimy?

A

slimy – bacterial surface growth

MCS (12 decks)

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