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Theme 2.1 Microbiology > Introduction to Microbes > Flashcards

Introduction to Microbes Flashcards

1
Q

What is microbiology?

A

Study of microscopic living forms

BUT SOME ARE VERY LARGE

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2
Q

Which are the medically important micro-organisms?

A

Virus
Bacteria
Fungi
Parasites

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3
Q

Prokaryotes and Eukaryotes

A

Prokaryotes – Bacteria

Eukaryotes – fungi, parasites

Virus – don’t fit in

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4
Q

What are the differences between Eukaryotes and Prokaryotes?

A

Eukaryotic cells contain a nucleus with a nuclear membrane enclosing multiple chromosomes.

Prokaryotic cells have a single chromosome that is not enclosed in a nuclear membrane.

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5
Q

The cell wall of prokaryotes vs eukaryotes

A

PRO: Contains peptidoglycan, lipids, and proteins

EUK: Absent
When present contains chitin or cellulose

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6
Q

The nuclear membrane, chromosomes, and ploidy of prokaryotes vs eukaryotes.

A

PRO: Absent (nuclear membrane)

Single, closed, circular, dsDNA (chromosomes)

Haploid (ploidy)

EUK:
Present nuclear membrane

Multiple, linear, chromosomes

Diploid, haploid

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7
Q

The motility in prokaryotes vs eukaryotes.

A

PRO: has a simple flagella

EUK: has a complex flagella

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8
Q

Which ribosome is found in Prokaryotes?

A

70S

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9
Q

Which ribosome is present in Eukaryotes?

A

80S

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10
Q

These are absent in Prokaryotes:

A

Mitochondria
Golgi complex
Endoplasmic reticulum

But they are present in Eukaryotes

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11
Q

These are present in Eukaryotes:

A

Mitochondria
Golgi complex
Endoplasmic reticulum

But they are absent in Prokaryotes

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12
Q

So, what is commonly present in PROS and EUK?

A

Cytoplasmic membrane.

in PRO it has phospholipids with no sterols with some exceptions

in EUK it has both phospholipids and sterols

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13
Q

Where is energy generated in PROKARYOTES?

A

Cytoplasmic membrane-associated

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14
Q

Where is energy generated in EUKARYOTES?

A

mitochondria

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15
Q

Sexual reproduction in PROKARYOTES?

A

Absent

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16
Q

Sexual reproduction in EUKARYOTES?

A

Present may alternate with asexual reproduction

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17
Q

How is the recombination and gene exchange done in PROKARYOTES?

A

Chromosomal or plasmid gene exchange via transformation, transduction or conjugation

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18
Q

How is the recombination and gene exchange done in EUKARYOTES?

A

Diploid zygote formed from haploid germ cells; meiosis results in genetic recombination

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19
Q

What are viruses essentially?

A

Strict intracellular parasites of other living cells

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20
Q

What organisms do viruses affect?

A

Mammals, plants, even bacteria!! (bacteriophages)

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21
Q

Give a description of VIRUSES characteristics

A

> Biologically active, replicate
Either DNA/RNA –never both!
Protein coat over the nucleic acid
Sometimes lipid surface membrane from the cell they infect

> Viruses use their own genes to replicate but they direct the infected cell to make the component parts (other structures that they need?)

> The infected cell may die due to lysis

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22
Q

Give a description of BACTERIA

A

Have a cell wall, cytoplasmic membrane
Cytoplasm only contains ribosomes & single DS DNA
NO organelles
NO nucleus
Free living
Binary fission in artificial media-grow within a day

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23
Q

What is the size range for BACTERIA?

A

0,1 - 10um

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24
Q

What are the shapes of BACTERIA?

A 
Cocci- round
Bacilli – rod-like
Cocco-bacilli-very short rods
Spirochaetes – spiral
Curved
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25
What are the different possible arrangements of BACTERIA?
Bacteria can be arranged in: >Clusters >Chains >Coryneform(chinese letters)
26
Describe the Capsule found in BACTERIA
- Hydrophilic gel - Almost all bacteria - Not readily stained - Slime - Capsule- discreet layer - Smooth,mucoid colonies on agar - Polysaccharide
27
What is the function of the capsule in Bacteria?
Functions: 1. Protection 2. Interferes with phagocytosis (ingestion by neutrophils) 3. Aid colonization-attach to surfaces 4. Not necessary for survival
28
What is the cell wall?
``` Internal to capsule ALL bacteria (except cell wall-less Chlamydia, mycoplasma) ```
29
What are the functions of cell wall in bacteria?
Function: 1. Rigidity & shape 2. Protection from bursting & mechanical disruption 3. Barrier from toxins 4. Anti-phagocytosis
30
The main structural component of the cell wall is a ‘---------’, a mixed polymer of hexose sugars and amino acids.
PEPTIDOGLYCAN
31
Peptidoglycan/Murein – only in prokaryotes | Describe its components and bonds.
1. NAGA (N-acetyl-glucosamine) 2. NAMA (N-acetyl-muramic acid) 3. Alternating units 1:4 linkages 4. Lysozyme can break this bond - Tetrapeptide side chains –alternating L- & D- amino acids - Cross bridges – sheets –peptide bonds - 3rd aa to 4th(terminal)
32
What are the Penicillin-binding proteins?
= Penicillin-binding proteins(PBP) – transpeptidases/co-peptidases are enzymes that export new polymers from the cell & link them to the inner aspect of the cell wall (ANTIBIOTICS!!) **addition Penicillin-binding proteins are a group of proteins that are characterized by their affinity for and binding of penicillin. They are a normal constituent of many bacteria; the name just reflects the way by which the protein was discovered
33
What do Autosylins do?
Autolysins remove old Peptidoglycan
34
Bacteria are classified according to their cell wall as:
gram-positive or gram-negative.
35
Describe the GRAM POSITIVE BACTERIA.
The peptidoglycan forms a thick layer external to the cell membrane There is Techoic acid – polymers of ribitol/glycerol from PG or cell membrane Stabilize cell wall, antigenic, adherence Cell wall structures eg M protein, S layer, C polysaccharide
36
Examples of Gram-positive bacteria
A. Streptococci = Gram pos in chains [ Strep pyogenes ] or in pairs [ Strep pneumoniae ] B. Staphylococci =Gram pos in clusters : Staph aureus or Staph epidermidis ** C. Neisseria =Gram neg cocci in pairs: Neisseria meningitidis or N. gonorrhoeae
37
GRAM POSITIVE SPORE-FORMING BACILLI
BACILLUS : FACULTATIVE ANAEROBIC CLOSTRIDIA: OBLIGATE ANAEROBES
38
GRAM POSITIVE NON-SPORE FORMING BACILLI
CORYNEBACTERIUM Listeria
39
Describe the GRAM-NEGATIVE BACTERIA.
- The Peptidoglycan layer is thin(single layer) - overlaid by an outer membrane, anchored to lipoprotein molecules in the peptidoglycan layer - Outer membrane proteins – attachment - Porins- pores through which small hydrophilic solutes can pass - Periplasmic space bet. CM & OM
40
FACULTATIVE ANAEROBES/ AEROBES. | ** Enterobacteria
ENTEROBACTERIA-found in the gastrointestinal tract ``` >Escherichia [ E. coli ] >Klebsiella >Proteus >Salmonella >Shigella ```
41
What are Pseudomonas in gram neg?
PSEUDOMONAS - Found in moist environments in hospital - Green pigment-dressings!!
42
Lipopolysaccharide - in gram-negative bacteria
- core polysaccharide - lipid A - O-sp polysaccharide side chains - major surface antigenic determinants in gram-neg bacteria (gnb)
43
Describe the endotoxin activity- gram neg bacteria
- extremely toxic to man - Even minute amount - endotoxic shock (fever & shock)/gram-negative shock
44
Compare and contrast between Gram-positive and Gram-negative bacteria.
Gram-positive: 1. Thick cell wall 2. Lipoteichoic acids transversing wall and anchored in the membrane 3. Lipid bilayer plasma membrane with integral proteins Gram-negative bacteria: 1. Thin cell wall 2. Lipid bilayer with integral proteins 3. Porins through the outer membrane 4. Polysaccharide (O antigen) on the outer membrane 5. Lipid A 6. Between the Inner membrane and the Peptidoglycan there is a periplasmic space
45
What is the gram-stain?
Crystal violet (purple) Iodine (black) Decolouriser Safranin/carbol fucshin (pink) ** A Gram stain is a test that checks for bacteria at the site of a suspected infection.
46
A method of gram stain.
1. Crystal violet which serves as the primary stain 2. A weak solution of iodine - bind dye. 3. The cell is then treated with an organic decolorizer, such as equal parts of 95% ethyl alcohol and acetone. 4. Some bacterial species because of the chemical nature of their cell walls will retain the crystal violet and appear purple under the microscope and are called gram-positive 5. Other bacteria are decolorized and pick up the safranin counter stain and appear pink-red microscopically and are called gram-negative
47
How do we get a presumptive identification in gram stain?
The gram-stained reaction in conjunction with the types, e.g. cocci and bacilli, as well as the arrangement of the bacterial cells is then used to make a presumptive identification.
48
Describe the cell membrane of BACTERIA.
- Encloses cytoplasm - Phospholipid bilayer - Rich in proteins - No sterols - Contains enzymes for respiration, PG & lipid synthesis, etc - Bacterial chromosome attached to it - Mesosomes – increase surface area
49
The cytoplasm of bacteria is:
amorphous gel with enzymes, ions, granules, plasmids, ribosomes Many ribosomes- faster growth rate 70S(50 S + 30 S)
50
What ribosome is found in BACTERIA (and its little parts)
The Bacteria has Many ribosomes- faster growth rate 70S(50 S + 30 S)
51
What is the nucleoid?
Nucleoid: Single chromosome 4000 genes-ds DNA Coiled-1000 times length of cell!
52
What is the Plasmid?
``` Plasmids: Extrachromosomal DNA Small circular 1 type/>1 type Genes code for enzymes that protect cell from toxins eg abt ```
53
The Flagella in the Bacteria. Components and function
- For motility - Flagellin - Filament,hook, basal body - From cytoplasm - Peritrichous/lophotrichous/monotrichous
54
The Fimbria in bacteria. Components and function.
- Non-flagellar hair-like projections on the surface - Adhesion – virulence eg neiserria - Sex pili in gram negatives - fimbrillin
55
Describe the spores in bacteria.
- Resting/dormant stage - For survival - Bacillus/Clostridia - Spherical/oval in bacteria - Location, size, shape - Doesn’t stain - Need sterilization temp. to kill
56
What is Mycology?
Study of fungi * *FUNGI IS: 1. Free-living 2. Widely found in nature 3. Slow-growing
57
What are dimorphic fungi?
Yeast/mould/both (dimorphic fungi) **DIMORPHIC MEANS A COMBINATION OF BOTH BEING YEAST AND MOULD Many fungi that infect man are dimorphic: 1. Yeast at body temperature 2. Mould at room temperature
58
Describe Fungi by growth
Filamentous: Growing as multi nucleate, branching hyphae, forming a mycelium Yeasts: Growing as ovoid or spherical single cells multiply by budding and division
59
Yeast
eg Candida albicans, Cryptococcus neoformans
60
Mould
eg Aspergillus
61
Describe the Structure of Fungi (nucleus and cytoplasm)
>Eukaryotic- nucleus, nuclear membrane, nucleolus, linear chromosomes >Organelles >Cytoplasmic membrane contains ergosterol & not cholesterol like human cells >BUT have a rigid cell wall – different structure from bacteria
62
Fungi have an external cell wall comprising:
Rigid external cell wall comprising: - Glucan- form fibrils to strengthen - Mannan – mannose-based polymers - Chitin- poly-NAGA. Similar to crab shell
63
Describe the Structure of Fungi (Size and extensions)
``` Size varies (2-4um) yeast to visible with naked eye eg mushrooms Bud extends from yeast cell, constricts-new cell (blastoconidia) Hyphae – tube-like extensions - mould Aerial hyphae – “fluffy”. Bear reproductive structures Vegetative- portion grows into medium/soil ```
64
What is mycelium?
intertwined mass of hyphae
65
What is septa?
Septa-cross-walls that divide hyphae into subunits
66
What is conidia?
Conidia arise from from hyphae/ from conidiophore (stalk-like)
67
FUNGAL REPRODUCTION
- Haploid usually - Diploid during sexual reproduction - Asexual - Multiply by budding- mitosis - conidia - Sexual – produce spores - meiosis
68
Fungal pathogens can be classified on the basis of :
1. their growth forms, or | 2. the type of infection they cause.
69
What are protozoa?
Single-celled Free-living/parasites Mostly tropical & sup-tropical countries Their structure:- 2 - >100um Nucleus & cytoplasm Shape/size/distribution of these – distinguishing Endoplasm – food vacuoles Ectoplasm – locomotion eg flagella/pseudopodia
70
What are helminths?
Macroscopic Multi-cellular worms <1mm – 1m!
71
What are the types of fungal infections?
Three types of infection(mycoses) are recognized: 1. Superficial mycoses where the fungus grows at the body surface on skin or hair. 2. Cutaneous and subcutaneous mycoses where nails and deeper layers of the skin are involved. 3. Systemic or deep mycoses with involvement of internal organs.
72
What are the four classes of Protozoa?
1. Rhizpods(amoebae)eg Entamoeba histolytica 2. Ciliates 3. Flagellates eg Trichomonas spp 4. Sporozoa eg malaria(Plasmodium falciparam
73
Protozoa infect tissue and body organs as:
1. Intracellular parasites in a wide variety of cells (red cells, macrophages, epithelial cells, brain, muscle). 2. Extracellular parasites in the blood, intestine, or urogenital system.
74
What are Helminths?
PARASITIC WORMS
75
What are the types of Parasitic worms that we have?
1. Tapeworms(Cestodes)- flat 2. Flukes(Trematodes) – leaf-shape 3. Roundworms(nematodes) - Tapeworms & flukes-flattened bodies with suckers/hooks - Roundworms – long, cylindrical bodies
76
What is the general body structure of Helminths?
1. Complex body structure 2. Nervous/reproductive/alimentary systems 3. No circulatory system 4. Suckers/hooks/teeth/plates for attachment at anterior 5. Body has tough cuticle ** sizes: Larval stages (100-200um) Adult stage cm to metres

Theme 2.1 Microbiology (10 decks)

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