Lecture 13: Intro to Microbiology

Question 1

what is microbiology

Answer 1

the study of microbes or microorganisms

Question 2

what are microbes

Answer 2

Microbes are living & nonliving things; small enough that they can be seen only with a microscope
-Living microbes are also cellular. E.g., eubacteria, archaea, algae, protozoa, fungi
-Nonliving microbes are also called acellular microbes or infectious particles. E.g., viruses, viroids, prions

Question 3

how big are microbes

Answer 3

-viruses: 10-300nm (0.01-0.3mm)
-Eubacteria: 1-3nm
-Protists: 5-2000nm
-Yeast: 3-5nm

Question 4

what is the visualization of microbes

Answer 4

-larger microbes= light scope
-smaller particulate (viruses)= electron microscope

Question 5

why study microbes

Answer 5

They are important!
-Pathogens cause disease. Infectious diseases occur when microbes colonize your body
-Microbial intoxication – when you ingest toxins from microbes
-Nonpathogenic microbes – comprise our indigenous microflora
-Opportunistic pathogens – are not usually pathogenic, become so when given the opportunity. E.g., E. coli in your gut; E. coli in a wound.
-Ecological Benefits – photosynthesis; decomposers; nitrogen-fixers; mycorrhizae; plankton; food chain; biotechnology; source of antibiotics; foods & chemicals- wine, cheese, yogurt, bread, ethanol, acetic acid,…

Question 6

what are prions

Answer 6

Prions are infectious proteins; very difficult to kill
-Cause other proteins to spontaneous turn into a prion protein
-Spread by consuming material that contains the prions
-Creutzfeldt-Jakob disease, mad cow disease, scrapie
-Prion protein PrP, in brain has normal (functional) structure: Can be induced to become abnormal (nonfunctional) by the abnormal structure

Question 7

what are viroids

Answer 7

-Short, naked ssRNA molecules that cause a number of plant diseases
-ssRNA causes errors in cell regulation, leading to problems in development & growth
-No animal diseases known at this time

Question 8

what is a virus

Answer 8

-Minuscule, acellular, infectious agents (smaller than a ribosome)
-Can’t replicate without a host → obligate parasite
-Someone or something is going to get sick
-Contains several hundred genes that allow it to enslave a parasite
-Genetic material – (May be DNA or RNA; never both) –dsDNA, ssDNA, dsRNA, ssRNA
-The genetic material is protected by a protein coat

Question 9

describe a virus outside the cell

Answer 9

-Outside cell (extracellular state) – the complete viral particle → Virion
-Genetic material surrounded by capsid (envelope) → nucleocapsid
-Protection, and recognizing and infecting a cell

Question 10

describe a virus inside the cell

Answer 10

Inside a cell (intracellular state) → Virus
-Uncoated (capsid removed), thus, possess genetic material only

Question 11

how are viruses non-living

Answer 11

-No metabolic pathway
-Neither grow nor respond to the environment
-Cannot reproduce independently (recruit the cell’s metabolic pathways to increase their numbers)
-No cytoplasmic membrane, cytosol, or organelles

Question 12

describe the viral capsid (protein coat)

Answer 12

-Contains host & viral proteins
-Contain capsomere subunits: Consist of single or multiple protein types, Nucleocapsid – intact capsid and the nucleic acid inside
-Protect the nucleic acid; and serves as means of attachment to host cells
-Confers fragility – more fragile than naked viruses
-Usually gives shape to the virion: Helical, polyhedral, complex

Question 13

review slide 11 on viral shapes

Question 14

what are the different classes of animal viruses

Answer 14

1. double-stranded DNA (dsDNA)
2. single-stranded DNA (ssDNA)
3. double-stranded RNA (dsRNA)
4. single-stradned RNA (ssRNA); serves as mRNA
5. ssRNA; template for mRNA synthesis
6. ssRNA; template for DNA synthesis

Question 15

describe bacteriophage- viral reproductive cycle

Answer 15

-Bacteriophage or phage – a virus that infect bacteria
-Have 2 possible life cycles–lytic and lysogenic cycles
-virus using only the lytic cycle are usually virulent; Kills its host within hr of infection
-Virus using both → temperate or lysogenic. Kills host (as above), or ‘hide’ inside the bacteria in an inactive form for generations, and, only upon activation, kill its host
-Both cycles are similar, except there is an extra step in lysogenic
-Viral genetic material is incorporated into bacterial chromosome → prophage
DNA

Question 16

what are the five stages of the lytic reproductive cycle (bacteriophage)

Answer 16

1. attachment: the T4 phage uses its tail fibers to bind to specific receptor sites on the outer surface of an E. coli cell
2. entry of phage DNA and degradation of host DNA: the sheath of the tail contracts, injecting the phage DNA into the cell and leaving an empty capsid outside, the cell’s DNA is hydrolyzed
3. biosynthesis of viral genomes and proteins: the phage DNA directs production of phage proteins and copies of the page genome by host enzymes, using components within the cell
4. assembly: three seperate sets of proteins self-assemble to form phage heads, tails, and tail fibers. the phage genome is packaged inside the capsid as the head forms
5. release: the phage directs production of an enzyme that damages the bacterial cell wall, allowing fluid to enter. the cell swells and finally bursts, releasing 100 to 200 phage particles

Question 17

review slide 15 (lysogenic life cycle of bacteriophage

Question 18

describe the steps in animal viruses

Answer 18

Similar to Phage:
1. Recognition/binding – leads to specificity
2. Entire virus enters cell, via phagocytosis
3. Genetic info is uncoated, & can either remain latent or immediately proceed
to step 4
4. Eventually, viral-protein and nucleic acid biosynthesis occurs
5. Virus assembly
6. Viral release – can destroy cell, or leave by budding (enveloped viruses). Inclusion bodies (incomplete virus bits) may remain behind in cells: Useful for diagnosis of e.g., AIDS, rabies, smallpox, herpes, poliomyelitis

Question 19

what are latent animal viruses

Answer 19

resides in the body for a period and then resurfaces
-those in the herpesvirus family are good examples of latent viruses: cold sores, shignles/ chicken pox, genital herpes

Question 20

what are oncogenic viruses (animal viruses)

Answer 20

cause cancer
-Epstein-Barr: mononucleosis (kissing disease), & 3 types of cancer: nasopharyngeal carcinoma, Burkitt’s lymphoma, and B-cell lymphoma
-Human papillomavirus – cervical, penile, anal
-Herpes virus – Kaposi sarcoma
-Hepatitis B/C viruses – hepatocellular (liver) carcinoma
Antiviral medications attempt to block steps in viral lifecycle

Question 21

what are prokaryotes

Answer 21

-Prokaryotes come in three shapes
-They are unicellular or colonial
-They are usually 1-5 mm
-Domains:
 Archaea
 Bacteria
 Eukarya

Question 22

describe the bacterial cell wall

Answer 22

-Consists of polysaccharides and proteins (primarily peptidoglycan)
-Gram-positive – Thick layer of peptidoglycan outside of PM; presence of teichoic and lipoteichoic acid; absorbs lots of crystal violet → appears dark purple when stained
-Gram-negative – Thin layer of peptidoglycan outside of PM, Has outer membrane; Lipopolysaccharide (endotoxins). Appears pink or red when stained

Question 23

describe gram-negative cells

Answer 23

-Lipopolysaccharides (lipid A, endotoxins) – in outer membrane responsible for sickness
-Cause septic shock (fever, low BP, rapid HR, hyperventilation, organ failure)
-Exotoxins are produced by bacteria, cause toxic shock (fever, low BP, rash, vomiting, organ failure)
-Presence of extra membrane → Gm –ve bacteria take up less antibiotics

Question 24

what are the different type of toxins (bacterial cell wall)

Answer 24

-Different types of toxins, classified by their effect:
-Neurotoxins: NS
-Exfoliative toxins: cause skin to slough off in layers
-Enterotoxins: cause vomiting/diarrhea
-Mycoplasmas are a group of eubacteria that lack cell walls. E.g., Mycoplasma pneumoniae

Question 25

list some other bacterial cell structures

Answer 25

-Glycocalyx capsule: sticking
-Glycocalyx slime layer: to glide
-Glycocalyx: made of protein or polysaccharide; Can protect from WBC phagocytosis
-Fimbriae and pili: sticking
-Sex pili: transfer of genetic material (plasmid DNA)

Question 26

describe bacterial cell motility

Answer 26

-Use flagella
-Consists of three parts:
 Basal apparatus
 Hook
 Filament
-Exhibit taxis → chemotaxis

Question 27

what are the different types of bacterial flagellar arrangement

Answer 27

1. peritrichous bacterium
2. amphitrichous bacterium
3. lophotrichous bacterium
4. monotrichous bacterium

Question 28

how do bacteria reproduce

Answer 28

reproduce by: binary fission, snapping division, and budding

Question 29

describe binary fission

Answer 29

1. cell replicates its DNA; both molecules are attached to the cytoplasmic membrane
2. the cytoplasmic membrane elongates, separating DNA molecules
3. cross call forms; membrane invaginates
4. cross wall forms completely
5. daughter cells may seperate

Question 30

describe budding

Answer 30

dna, which is attached to the cytoplasmic membrane is replicated. cell elongates to form a bud; the expnading cytoplasmic membrane carries one attached DNA molecule into the bud -> young bud-> daughter cell

Question 31

describe bacterial survival

Answer 31

endospores:
-Produced by Gram-positive bacteria Bacillus and Clostridium
-Defensive strategy against unfavorable conditions
-Each vegetative cell transforms into one endospore
-Each endospore germinates to form one vegetative cell
-Concern to food processors, health care professionals, and governments

Question 32

what are the three steps in bacterial gene transfer

Answer 32

transofrmation. conjugation, transduction

Question 33

describe transformation

Answer 33

-Bacteria take up foreign DNA from the environment
-Incorporate it into their own genome
-Humans use this ability to put foreign DNA in bacteria e.g., the gene for human insulin is produced by bacteria now

Question 34

describe transduction

Answer 34

-involves “mistakes” made by a temperate virus in the lysogenic cycle
-virus takes some extra [bacterial] DNA with it to the next bacteria it will infect

Question 35

describe conjugation

Answer 35

-One cell sends over a copy of a plasmid to another cell through a sex pilus
-To do this, bacteria must contain a F (fertility) factor

Question 36

what is the significance of sharing DNA between bacteria

Answer 36

-It occurs between different species of bacteria
-Plasmids can contain multiple antibiotic resistance genes (R-factors) & result in the formation of superbugs!

Question 37

what are the major nutritional modes for bacteria

Answer 37

-Autotroph: photoautotroph & chemoautotroph
-Heterotroph: photoheterotroph & chemoheterotroph

Question 38

describe bacterial oxygen requirements

Answer 38

-Obligate Aerobes: need O2 or die
-Facultative aerobes: can deal with O2 but prefer it to be absent
-Obligate anaerobes: die in the presence of O2
-Facultative anaerobes: can live without O2, but prefer to have it
-Aerobes can detoxify O2 by reducing it to something less toxic (water) during respiration
-Anaerobes can’t: they reduce NO3- (to NO2-) or SO42- (to S or H2S/S2-), etc.
during respiration
-Most bacteria in/on our bodies are anaerobic! (Thus, the NO2- in urine if
bladder infection…)

Question 39

what are symboises

Answer 39

-Ecological relationships that occur b/w different species that live in
direct contact
-Some spp. are obligate parasites (chlamydias, rickettsias)

Question 40

review slide 32

Question 41

describe microbes and disease

Answer 41

For disease to occur, several conditions must be met:
-Pathogen must land in/on correct tissue & encounter receptor sites that it recognizes
-Pathogen must be able to reproduce (microbial antagonism by indigenous microflora outcompete or produce antimicrobial compounds)
-Microbe must escape/survive external & internal defenses (all 3 lines of defense: physical/chemical barriers, innate defense, acquired immunity)

Question 42

what are the stages of an infectious disease

Answer 42

-incubation period (no signs or symptoms)
-prodromal period (vague, general symptoms)
-illness (most severe signs and symptoms)
-decline (declining signs and symptoms)
-convalescence (no signs or symptoms)

Question 43

what are eukaryotic microbes

Answer 43

Eukaryotic cells have a nucleus & other organelles
-WRT disease:
-Algae – rarely cause problems: exception is intoxication (red tide &
contaminated shellfish)
-Protists – cause many serious diseases: malaria, sleeping sickness, amebic
dysentery, Chagas’ disease, diarrhea, giardiasis, meningo-encephalitis,
pneumonia, toxoplasmosis…
-Many are vectored by insects
-Fungi: cause some intoxications, but can also colonize persons:
cryptococcosis, histoplasmosis, meningitis, pneumonia, thrush, ringworm, yeast vaginitis
-Some larger eukaryotes also cause disease - nematodes; flukes & cestodes
(Platyhelminthes)

Question 44

describe fungi

Answer 44

-Chemoheterotrophic; cell walls typically composed of chitin
-Lack chlorophyll→ non photosynthetic
-More closely related to animals than plants

Question 45

what is the significance of fungi

Answer 45

-Decompose dead organisms and recycle their nutrients
-Help plants absorb water and minerals
-Used for food, in religious ceremonies, and in manufacture of foods and
beverages
-Produce antibiotics and other drugs
-Serve as important research tools
~30% produce mycoses → cause diseases of plants, animals, and humans
-Can spoil fruit, pickles, jams, and jellies
-Reproduction is by asexual and sexually

Question 46

describe prokaryotes

Answer 46

-Typically considered ‘bacteria’
-Lack nucleus, organelles,
microtubules
-Chromosomes: 1 strand DNA (no protein), circular; plasmids
-Lack cilia, flagella are simpler in structure
-Chemically & structurally complicated cell walls including peptidoglycan

Question 47

describe eukaryotes

Answer 47

-Consist of plant, animal, fungi, algae, or protozoan cells (algae + protozoa= protist)
-Have nucleus, organelles,
microtubules
-Chromosomes: 1+ strand of DNA and proteins, linear
-Can have flagella or cilia
-Simple cell walls (when present), e.g., cellulose