Intro to Microbio

Question 1

What decreased the death rate in the 20th century?

Answer 1

Implementation of public health departments - most people were getting sick from people throwing their garbage on the streets and allowing animals to decompose on the streets.
So public sanitation and vaccines.

Question 2

What are the relative size of the different infectious agents?

Answer 2

• virus is the smallest and simplest, non-living infections
• bacteria are the smaller independently living cells
• virus

Question 3

Which genus of bacteria is predominately food in various location of the body?

Answer 3

skin - propionibacteria
mouth - lots of streptococci
oropharynx - neisseria
stomach and small bowl = helicobacter pylori
colon - bacterioides
nose - staphylococcus
nasopharynx - pneumococci
vagina (during childbirth years) - lactobacillus
vagina (prepub and post menopause) - c. albicans and diphtheroids

Question 4

What’s symbiotic?

Answer 4

benefits the host - like gut bacteria that participate in digestion

Question 5

What are commensals?

Answer 5

neutral relationship to the host (oral streptococci)

Question 6

What is parasitic?

Answer 6

harm to host (tape worms)

Question 7

What is a resident?

Answer 7

an established niche at a particular body site (bacteria found in the particular body site)

Question 8

What are transients?

Answer 8

acquired from the environment and establish themselves briefly (inhibited by resident bacteria or by host immune system) -> inhibited by commensals relationship

Question 9

What is a carrier state?

Answer 9

a potentially pathogenic organism becomes a resident (streptococcus mutant)

Question 10

What are opportunistic infections?

Answer 10

when microbes invade a normally sterile location (urinary tract, bladder, abdominal cavity, accessory sinuses) or an area where there are reduced host defenses. Also can occur when an immunologic response opens the way for invasion by flora.

Question 11

What is the exclusionary effect?

Answer 11

Competition between normal flora and potential invaders. Normal flora can overpower invaders most of the time. When antibiotics take out the normal flora, you lose the competitive advantage.

Question 12

What is priming the immune system?

Answer 12

presence of microbiota is important for the development for our immune system.

Question 13

What is differential media?

Answer 13

distinguishes between closely related species of bacteria based on characteristics on the media (color change, colony morphology)…what it looks like on the plate
ex) blood agar

Question 14

What is selective media?

Answer 14

is used to isolate specific groups of bacteria
- an example of this is the notes media inhibits the growth of one type of bacteria and permits the other - selects for gm + bacteria
(so if you want all gram + bacteria, you put a chemical in that kills only gram neg.)

Question 15

What is the cytopathic effective?

Answer 15

a test that checks for viral infections which exhibit morphological changes to the cells host tissues

Question 16

What are immunological tests?

Answer 16

are tests that check for antibody against a virus in the blood. These include precipitation reaction tests (where the antibody and antigen form a precipitate) and hemagglutation (where red blood cells cross link if theres a reaction)

Question 17

What is nuclei acid detection?

Answer 17

target DNA is bound to a membrane and complementary DNA primers attached to a color producing enzyme are reacted with a membrane. A positive test is indicated by a color producing enzyme or a product formed in the sample.

Question 18

What are gram stains?

Answer 18

This stains ribonucleic proteins inside cells (Gm + is purple, Gm - is pink)

• crystal violet is the primary stain - everything gets stained purple at first, then the wash step removes the stain from gram negative because of their thing cell wall (stains gram + bacteria purple)
• safranin red is the counterstain (stains gram neg bacteria red)

Question 19

What is acid fast staining?

Answer 19

this stains the mycolic acid (part of a special cell wall) of acid fast bacteria

• carbol fusión red stains acid fast bacteria red
• methylene blue stains non-acid fast bacteria blue

Question 20

What are the basic shapes of bacteria?

Answer 20

spheres (cocci)
rods (bacilli) - can be straight or bent
spirals (spirilla)
-vibro - comma shaped
-spirochete - corkscrew

Question 21

What are the common components and structures of all bacteria cells and how do they differ from eukaryotic cells.

Answer 21

all bacterial cells have:

• nucleiod-chromosal DNA
• cytosol (including polyribosomes, proteins ,carbs, inclusion bodies)
  
  • densely packed with ribosomes
  • cytoskeleton provides shape to the cell
• plasma membrane (made of phospholipids and proteins)
• cell wall

bacteria are different than eukaryotic cells because they don’t have organelles like mitochondria, nucleus, Golgi, ER

Question 22

What are the structures found in SOME bacteria (like spores) and what are their functions?

Answer 22

• Flagella or flagellum - motility (gm + and gm -)
• fimbriae (pili) - small hairlike (fimbriae), thicker and longer than fimbriae may be used to transfer DNA (pili) for attachment (gm + and gm -)
• capsule (slime layer) - made of carbs, involved in immune system evasion, can be a nutrient source (gm + and gm-)
• outer membrane (gm -)
• spores (endospores) - help survive hard conditions (gm +)
• periplasm - space between membrane layers (gm -)

Question 23

What’s the difference between Gm - and Gm ) bacterial cells walls?

Answer 23

Gm neg:
- two membranes and one layer of peptidoglycan (thin) in between
- impermeable outer membrane that has porins (allow diffusion of nutrients and excludes harmful stuff)
- periplasm space - between the two membrane layers and contains lots of important proteins and enzymes needed for survival
- LPS present on outer membrane - has 3 parts
1) O antigen polysaccharide side chain
2) core polysaccharide (similar between species)
3) lipid A (toxin) - if Bacteria is destroyed, these get released into hose and can cause sickness even after the bacteria is dead
Gm pos:
- has a thick (multilayered) peptidoglycan and teichoic acids ( a polymer of glycerol phosphate - function can be for attachment or secretion)

Question 24

What are the peptidoglycan structural differences in gm +/- ?

Answer 24

• peptidoglycan is a glycan backbone made up of alternating sugars - NAG and NAM
• NAMS are interconnected by a tetrapeptide side chain linked to pentaglycine interbridge
• Gram - uses a DAP, instead of lysine, to connect these two sides

Question 25

What is LPS and what are the various components and functions of this molecule? What types of bacteria has this?

Answer 25

Lipopolysaccharides (LPS) also known as lipoglycans and endotoxins are large molecules consisting of a lipid and polysaccharide composed of O-antigen, outer core, an inner core joined by a covalent bond; they are found in the outer membrane of gram neg bacteria and elicit strong immune responses in animals.

• the neg charge given by LPS protects the cell from phagocytosis
• the lipid A (toxin) has a glucosamine instead of the normal glycerol found in its outer membrane

Question 26

What are obligate aerobes?

Answer 26

respiration only. require O2 to grow. So have a lot of catalase and superoxide dismutase

Question 27

What are obligate anaerobes?

Answer 27

fermentation only. can not grow when O2 is present

Question 28

What are facultative aerobes?

Answer 28

contains genes for fermentation and respiration. Can grow with/ or without oxygen but grow faster and much more efficiently with oxygen.

Question 29

What are aerotolerant anaerobes?

Answer 29

anaerobic metabolism - fermentation, but can tolerate oxygen.

Question 30

Fermentation and Respiration and Catabolism

Answer 30

• respiration provides more energy than fermentation
• fermentation uses substrate level phosphorylation, Respiration uses oxidative phosphorylation
• which statement best describes biosynthetic reactions?- precursor metabolites are used to make nucleotides
• catabolism is the breakdown of sugar or an energy source into smaller molecules

Question 31

What are the basics of bacterial chromosomal replication?

Answer 31

1) bacterial chromosome is circular
2) steps of chromosomal replication are as follows:
a) initiation - depends on growth rate (the faster the initiation, the higher growth rate)
b) elongation
c) termination
3) DNA replication is bidirectional - goes in both directions around the circular plasmid
4) DNA replication is semiconservative - each new DNA has one new and old strand

Question 32

What are mutations?

Answer 32

• are spontaneous

- changes to DNA sequence = occur once in every million cells for any one gene (haploid)

Question 33

What is base substitution?

Answer 33

when a nucleotide is changed. If not affect on protein sequence (silent) but could effect expression

Question 34

What is insertion?

Answer 34

insertion of nucleotide results in frameshift and dysfunctional protein

Question 35

What is deletion?

Answer 35

deletion of nucleotide results in frameshift and dysfunctional protein

Question 36

What is nonsense?

Answer 36

base pair change results in stop codon, results in truncated protein

Question 37

What is missense?

Answer 37

base pairs change results in different amino acid -> dysfunctional protein or could confer antibiotic resistance

Question 38

What is duplication?

Answer 38

when DNA sequence is abnormally copied -> may result in abnormal protein function or frameshift

Question 39

What is silent mutation?

Answer 39

a base pair change that doesn’t change the amino acid sequence.

Question 40

What’s Natural Transformation?

Answer 40

ability to take up DNA from the environment - this is mediated by quorum sensing

Question 41

What is conjugation?

Answer 41

the transfer of plasmid DNA through the use of sex pills - plasmid DNA gets degraded and recombines with chromosome

Question 42

What is transduction?

Answer 42

bacteriophage (virus) “accidentally” injecting bacterial DNA into host bacterial cell (can continue through either the lytic cycle or the lysogenic cycle)

Question 43

What are transposable elements?

Answer 43

DNA that can insert or excise itself from the chromosome or plasmid into recipient DNA. Larger transposons carry genes for antibody resistance or virulence genes.