Lecture 1: Basic Microbiology & Bacterial Taxonomy

Question 1

What is the definition of Microbiology?

Answer 1

the study of organisms called microorganisms (microbes) that are too small to be perceived clearly by the unaided human eye

Question 2

Microbes include:

Answer 2

some metazoan animals, protozoa, many algae, and fungi, bacteria, and viruses

Question 3

Why are microbes probably the most significant life form sharing the planet with humans?

Answer 3

because they are ubiquitous in nature, capable of utilizing any available food source, including humans whose defenses may be compromised

Question 4

Infection

Answer 4

the invasion of the body by a harmful microbe resulting in a disease

Question 5

Disease

Answer 5

a disorder with a specific cause and recognizable signs and symptoms

Question 6

Pathogen

Answer 6

any microbe that has the capacity to cause disease

Question 7

Koch’s Postulates

Answer 7

1) pathogen found in diseased organisms, but not healthy
2) able to isolate pathogen from diseased host and grow on culture
3) pathogen from pure culture must cause disease in inoculated healthy animal
4) able to isolate pathogen from inoculated animal

Question 8

Exceptions to Koch’s Postulates

Answer 8

• some microbes have unique culture requirements or do not grow on cultured media (ie Treponema pallidum, Mycobacterium leprae, rickettssial and viral pathogens)
• some pathogens do not show distinct symptoms *some diseases involve several pathogens

Question 9

3 Major microbe categories

Answer 9

Viruses
Prokaryotes (bacteria, mycoplasmas, rikettsiae, and chlamydiae)
Eukaryotes (fungi, protozoans, and multicellular parasites)

Question 10

Prions

Answer 10

noncellular infectious proteins, also inherited form

Question 11

Characteristics of Prions

Answer 11

• long incubation time
• characteristic spongiform changes associated with neuronal loss and failure to induce inflammatory response
• prion proteins modify the folding of normal human cellular proteins (cellular proteins or PrP^c) into additional prions (PrP^sc)

Question 12

Human Prion Diseases

Answer 12

Creutzfeldt-Jakob disease (CJD)
Variant Creutzfeldt-Jakob disease (vCJD)
Kuru

Question 13

Animal Prion Diseases

Answer 13

Mad Cow Disease (bovine spongiform encephalopathy)
Chronic Wasting Disease (CWD)
Scrapie

Question 14

Viruses

- classification
- size
- cellular or noncellular?
- structure
- examples

Answer 14

VIRUSES ARE OBLIGATE INTRACELLULAR PARASITES
*smallest and simplest of all microbes (except for prions and viroids)
*NONCELLULAR
*DNA or RNA (not both) enclosed by a protein coat
*may or may not have a lipoprotein envelope
EX: HIV, SARS, Viral Hepatitis (A,B,C,D,E) H1N1

Question 15

Viral attachment

Answer 15

attachment proteins on capsid or envelope determine specificity of infection

Question 16

Viral reproduction

Answer 16

dependent on host cell

Question 17

Prokaryotes

 - Def
 - Nucleic Acid
 - Organisms

Answer 17

• Unicellular organisms with no clearly defined nuclear membrane
• Nucleic acid not complexed with histones, no chromosomes
• Bacteria, mycoplasmas, chlamydiae, rickettsiae

Question 18

Eukaryotes

- Def
- Nuclear material (arrangement)
- size

Answer 18

• uni- and multicellular organisms with well defined nuclear membranes and organelles
• nuclear material (nucleic acid plus histones) is arranged in chromosomes
• usually larger than prokaryotic cells

Question 19

Fungi

- Prok. or Euk.?
- Cell wall composition
- Major Sterol in membranes
- 4 Types

Answer 19

Eukaryotes
*Cell walls containing chitin, glucans, and mannans
*Membranes with ergosterol as major sterol
Include:
-Yeasts (Unicellular)
-Filamentous molds (Mycelia)
-Dimorphic fungi (can grow like yeast or mold)
-Saprophytes (utilize organic matter for energy e.g. mushrooms)

Question 20

Parasite

- Def
- Animal parasite characteristics

Answer 20

• an organism that lives in or on another organism (host) and causes damage to the host
• animal parasites are euk. organisms with no cell walls, single celled to large organisms, multicellular worms

Question 21

Classification of bacteria is based on what?

Answer 21

1) Morphological differences
2) Biochemical/metabolic differences
3) Immunololgic characteristics
4) Genetic characteristics

Question 22

2 common stains for identification of bacteria

Answer 22

Gram stain

Acid fast stain

Question 23

Questions to ask when identifying bacteria

Answer 23

1) Gram + or Gram -
2) Morphology (rod, coccus, spiral, pleomorphic)
3) Cells occur singly or in chains
4) Size of cells

Question 24

Gram Stain components

Answer 24

1) Crystal Violet -primary stain
2) Iodine -mordant
3) Alcohol -decolorizer
4) Safranin -counter stain

Question 25

Cell Wall - functions - components

Answer 25

semirigid cell wall outside the cell membrane - maintains shape - prevents cell from bursting - porous * Peptidoglycan -molecules of N-acetyl glucosamine alternate with N-acetyl muramic acid

Question 26

Gram (+) Amino Acids Gram (-) Amino Acids

Answer 26

G(+): L-Alanine, D-Glutamic Acid, L-LYSINE, D-Alanine G(-): L-Alanine, D-Glutamic Acid, L-DIAMINOPIMELLIC ACID, D-Alanine

Question 27

Teichoic Acid - G(+) or G(-) - Def - 2 Classes - Functions

Answer 27

Gram (+) only -polyol phosphate polymers with either ribitol or glycerol linked by phosphodiester bonds Classes: (1) Lipotechoic acids (2) Wall techoic acid Functions: (a) binds and regulates movement of cations in and out of the cell (b) provides wall's antigenic specificity (c) may also assume a role in cell growth, preventing extensive wall breakdown and possible cell lysis

Question 28

Outer Membrane - G(+) or G(-) - function - contents

Answer 28

Primarily in Gram (-) -bilayer membrane -controls transport of certain proteins from the environment Contents: -surface antigens and receptors present -Lipopolysaccharide (LPS) -consists of: a) O-antigen polysaccharides (antigenic) O for outer b) water soluble core polysaccharide c) Lipid A

Question 29

Lipid A

Answer 29

responsible for toxic properties | Gram (-) Endotoxin

Question 30

Gram (+) vs. Gram (-) | -Envelope

Answer 30

``` Gram (+) -2 Layers 1) Peptidoglycan (open, netlike) 2) Cytoplasmic membrane (hydrophobic) Gram (-) -3 Layers 1) Outer membrane (hydrophobic) 2) Peptidoglycan (open, netlike) 3) Inner membrane (hydrophobic) ```

Question 31

Gram (+) vs. Gram (-) | -Unique features

Answer 31

Gram (+) -Teichoic Acids -helps in the attachment to human cells (along with pili and specific virulence factors) Gram (-) - Outer membrane and endotoxin - Pili - Specific Virulence Factors

Question 32

Gram (+) vs. Gram (-) | -Antigens & Proteins

Answer 32

Gram (+) - Surface antigens- Teichoic acids - Surface specific proteins * M-protein (Streptococcus (fimbria)) * Tuberculin (M. tuberculosis) * A-protein (S. aureous) Gram (-) - O antigens (polysaccharide of LPS) - Outer membrane proteins - Fimbria and pili

Question 33

Gram (+) vs. Gram (-) | -Capsules and Flagella

Answer 33

Gram (+) - Capsular material (except S. pyogenes hyaluronic acid capsule) - Flagella Gram (-) - Capsular material - Flagella

Question 34

Gram (+) vs. Gram (-) | -Peptidoglycan

Answer 34

Gram (+) -thick layer, highly cross linked by pentaglycine bridges Gram (-) -thin layer, not highly cross linked

Question 35

Gram (+) vs. Gram (-) | -Susceptibility to lysozyme and beta lactam drugs

Answer 35

Gram (+) -more susceptible Gram (-) -less susceptible

Question 36

Gram (+) vs. Gram (-) | -Major trigger of inflammation

Answer 36

Gram (+) -peptidoglycan-teichoic acids Gram (-) -endotoxins

Question 37

4 major shapes of bacteria

Answer 37

1) Cocci: spherical 2) Bacilli: rods (short bacilli are cocco-bacilli) 3) Spiral forms: comma, S, or spiral shaped 4) Pleomorphic: lacking a distinct shape (like jello)

Question 38

Gram (+) Bacteria

Answer 38

6 classic: 2 cocci, and 4 bacilli - Streptococcus - Staphylococcus - Bacillus (spores) - Clostridium (spores) - Corynebacterium - Listeria

Question 39

Gram (-) Bacteria

Answer 39

Cocci - Neisseria Spiral - Spirochetes -rest are G(-) rods or pleomorphic

Question 40

Acid Fast Stain

Answer 40

1) Corbol Fuschin with heat 2) Alcohol 3) Methylene blue *acid fast =red, non acid fast =blue Mycobacterium ->acid fast Nocardia ->partially acid fast All bacteria except Legionella micadadei ->non-acid fast

Question 41

Non Gram Staining Bacteria

Answer 41

Mycoplasma -permanently lack peptidoglycan *Diagnosis -largely clinical. 65% patients produce cryoagglutinins (agglutinate RBC's in cold) -suggestive, not specific Ureaplasma -does not have a cell wall

Question 42

Poorly Gram staining or poorly visible bacteria

Answer 42

* Mycobacteria -waxy cell wall, does not take stain * Rickettsiae and Chlamydiae -stain color not visible (too small to be visualized) * Spirochetes -Treponema pallidum (syphilis) and Borrelia burgdorferi (Lyme disease) detected by dark field microscopy

Question 43

Obligate Aerobes

Answer 43

-require Oxygen for growth at atmospheric oxygen levels (21%) -no fermentive pathways -generally produce superoxide dismutase (eg Pseudomonoas, M.tuberculosis, Bacillus)

Question 44

Microaerophiles

Answer 44

-require oxygen for growth, but concentration of oxygen must be below atmospheric level (<21%) (eg Campylobacter, Helicobacter)

Question 45

Facultative Aerobes

Answer 45

-organisms will use oxygen if it is present but can grow by anaerobic respiration or fermentation in the absence of oxygen (eg most human pathogens, Streptococci, Enterobacteria) -Aka Facultative anaerobes

Question 46

Aerotolerant Anaerobes

Answer 46

-organisms can grow in the presence of oxygen by they cannot use it (eg Streptococcus spp.)

Question 47

Obligate Anaerobes

Answer 47

-organism cannot grow in presence of oxygen -utilize fermentive pathways (eg Actinomyces, Bacteriodes, Clostridium) (^ABC of anaerobiosis)