Week 3: Microbiology Flashcards
What are the main differences between prokaryotes and eukaryotes?
- Prokaryotes: single circular chromosome, no nucleus, plasmids, cellular respiration on PM, sex or attachment pili
- Eukaryotes: paired linear chromosomes, nucleus, cellular respiration in mitochondria, no pili
What is the mesosome in bacteria?
where chromosomal DNA attaches to the plasma membrane for bacterial division
What are the 2 subunits in peptidoglycan and which one has variability?
- NAM and NAG
- NAM can have different amino acids attached
What does penicillin inhibit in peptidoglycan?
crosslinking between polysaccharide chains
How are the results of gram stain determined?
purple = gram positive pink = gram negative
What is special about Mycoplasma?
smallest free living organism
- no cell wall (hard to treat with antibiotics)
- membranes contain sterols
What is special about Mycobacteria?
- acid fast bacteria
- small amounts of peptidoglycan
- large amounts glycolipids (mycolic acids make cell wall impermeable)
- Mostly cause respiratory disease
What is in the core of endospores?
calcium dipicolinate
Why to bacteria form spores?
resistant to: heat, dessication, chemical damage, dehydration
-allow survival in nutrient limited conditions
What are the basic characteristics viriods?
- very small single stranded circles of DNA
- cause disease in plants
What is the main component of: spore wall spore coat cortex core
- spore wall: peptidoglycan
- spore coat: keratin like proteins
- cortex: thickest part, peptidoglycan with fewer links
- core: calcium dipicolinate and nucleic acid for later growth
What species make endospores?
-Bacillus and Clostridium
What are basic characteristics of viruses?
-viral envelope, nucleocapsid/ capsid (protects nucleic acids), capsomere (subunit of capsid structure). polyhedral/ helical
What are the basic characteristics of prions?
- no nucleic acid
- resistant to heat
- inactivated by detergents
- causative agent is prion protein (PrP ^sc)
- same sequence as functional protein but folded differently (not degraded)
What are enveloped viruses vs naked capsid viruses?
enveloped = acquire membrane from host
naked capsid = nucleic material with coat or capsid
What are the 3 main types of fungi?
yeasts (single cell, reproduce by budding), molds (grow as filamentous hyphae, cross walls called septae, masses of hyphae are mycelia), and mushrooms
What is the generation time?
the amount of time for number of cells to double
-doubling time
What are the phases in the growth curve?
- lag phase = bacteria adapt to new nutrient rich environment
- log phase = exponential growth, bacteria double every generation time
- stationary phase = nutrients are exhausted
- death phase = not all bacteria have this state, they begin to die
How do you determine the amount of bacteria in liquid sample?
dilution x colonies on plate = CFU/mL
What are the differences between fermentation, respiration, and photosynthesis?
- fermentation- form ATP not coupled to electron transport
- Respiration: formation of ATP by oxidative phosphorylation where ATP is formed during electron transport
- photosynthesis: ATP formed by reduction of oxidant via light energy
How are fermentation products formed?
lactate formed to regenerate NAD+ to be reused in glycolysis
What is a heterotroph?
type of nutritional requirement that requires pre-formed organic compounds like sugars, amino acids, and vitamins
How do bacteria take up nutrients (3 ways)?
- carrier mediated diffusion (facilitated, not energy dependent
- Phosphorylation-linked transport, energy dependent
- Active transport- energy dependent, protons pumped out causing flux, uses symport
What does positive polarity vs negative polarity mean for virus structure?
Single stranded RNA genomes can have same (positive) or complimentary (negative) polarity as viral mRNA.
-positive polarity can be translated right away
What enzyme changes superoxide to hydrogen peroxide?
superoxide dismutase
What is the viral attachment protein (VAP)?
-on capsid of naked virus, interacts with the cell
enveloped viruses have specific glycoproteins that act as VAPs
What is the difference between differential and selective media?
- differential media: supplies nutrients and indicators for visual determination of which organisms are present
- selective media: selects AGAINST growth of particular bacteria by addition of dyes, acid/base, salts, or antibiotics
What are the 3 temperature classifications?
- psychrophiles- low temps
- mesophiles- most, medium temps
- thermophiles- high temps
What are the 3 classification categories for human viral pathogens?
- virion structure
- nucleic acid characteristics
- replication strategy
What are the 2 possible types of capsids?
- cylindrical (helical form)
- cubic shape (icosahedron form)
What 3 things are part of the viral envelope?
lipids, proteins, and glycoproteins
Which are more hardy, enveloped or naked viruses?
naked viruses, enveloped viruses are disrupted by non-moist environments
What 3 factors influence host range?
virus ability to 1) enter a cell, 2) find appropriate cellular machinery, and 3) exit the cell
What determines productive vs nonproductive viral infection?
production = infection yields new infectious viruses non-productive = infection occurs when viral genetic material persists in cell (latent state) but no infectious viruses formed
What are the 6 phases of viral multiplication?
1) attachment
2) penetration
3) uncoating
4) virus component synthesis
5) assembly
6) release
What are cytopathic effects (CPE)?
morphological changes to host cell from synthesizing viral proteins
ex) cell rounding, cell fusion, etc
What are viroporins?
- small, hydrophobic virus encoded proteins that oligomerize at host cell membranes
- involved in envelope virus budding and non enveloped virus cellular lysis
- cytopathogenic effects: formation of hydrophilic pores and alterations of calcium and H+ gradients
What are the parts in the one step growth cycle?
- eclipse period- time between infection and increase in total virions per cell
- latent period- time between infection and released virions accumulating (2nd increase on graph)
- early protein is for replication of AAs then shut off
- late proteins are structural proteins of virus
Where do most RNA viruses replicate? exceptions?
in cytoplasm (except orthomyxoviruses like influenza and retro viruses)
Which DNA virus remains in the cytoplasm and how?
poxviruses (have enzymes with them)
Which DNA viruses (3 families) have doubles stranded DNA genome?
- adenoviruses
- herpesviruses
- papovaviruses
What type of DNA and replication does hepadnaviruses (Hepatits B) undergo?
- partially double stranded DNA genome
- replicate DNA in nucleus via RNA intermediate
- involves RND- dep DNA polymerase (reverse transcriptase)
- can transform cells
What kinds of DNA viruses have a single strand of DNA as genome?
parvoviruses (some strains need helper virus to replicate)
How do cytoplasmic DNA viruses replicate?
Poxviruses, have double stranded DNA genome
- provide their own mRNA and DNA
- synthesize own envelope
What cancer does the virus family papovavirdae, virus HPV cause?
Genital tumors (cervical, vulvar, penile) squamous cell carcinoma
What cancer does virus family Herpesviridae, virus EBV Virus cause?
Nasopharyngeal carcinoma, African Burkitt’s lymphoma, B-cell lymphoma
What cancer does virus family Herpesviridae, virus Herpes simplex type 2 cause?
cervical carcinoma
What cancer does virus family Hepadnaviridae, virus Hepatitis B virus cause?
Hepatocellular carcinoma
What cancer does virus family retroviridae, cancer HTL virus cause?
Adult T cell leukemia
What 2 genes can be targeted to cause cancers?
p53 (turns on p21 which phosphorylates the master break)
pRB (when complexed with inactive transcription factors, acts as master break)
What are the 6 general classes of cellular oncogenes?
- nonreceptor protein tyrosine kinases
- receptor protein tyrosine kinases
- serine/threonine protein kinases
- growth factors
- membrane associated G proteins
- nuclear transcription factors
What are 2 tumor suppressor genes?
retinoblastoma (RB)
p53 gene
What are the main characteristics of Adenoviruses?
- vary in oncogenic potential
- transform rodent cells (no human tumors)
- E1a binds p110^Rb (represses cell proliferation)
- E1b binds p53 (represses cell proliferation)
What are the main characteristics of Papillomaviruses?
- majority of cervical, penile, and vulvar cancers contain HPV DNA
- E6 binds p53
- E7 binds p110^Rb
What are the main characteristics of Herpesviruses?
- EBV (estine bar virus)
- viral genome is episomes (ouside chromosomes)
- need 3 genes for transformation (LMP 1 and LMP 2a and b)
- large virus, 16 cellular genes
What are the main characteristics of Hepadnaviruses?
- 75-85% primary human hepatocellular carcinoma cells have hep B (HBV) genes
- X protein interacts with p53
- has reverse transcriptase
What are the 3 transformation mechanisms for viruses?
- introduction of oncogenes
- insertional activation or promoter insertion
- transcriptional activation
What are characteristics of Retroviridae?
- helical nucleoprotein complex inside icosahedral capsid which is enveloped
- reverse transcription
- as DNA genome integrates into host genome
- cause tumors
- HIV-1 causes AIDS
What are the 3 subfamilies of retroviruses?
- Lentiviruses (HIV)
- Spuma viruses
- onco viruses (types B,C, and D
What type of retrovirus is naturally occurring in humans?
Endogenous type C viruses
-viral information is a constant part of genetic constitution
How many viruses or bacteria do you need to be sick?
- viruses need a lot in body to cause disease
- bacteria can have toxins, so may not need many
What are the 3 mechanisms that bacteria cause disease?
- direct
- indirect (natural immune response)
- indirect via adaptive immune response (hypersensitivity)
What is virulence?
quantitative measure of pathogenicities measured by number of bacteria required to cause disease
What are virulence factors?
properties of a bacteria which assist in causing disease (pili, capsules, toxins, etc)
What are the 6 bacterial virulence factors?
- pili
- capsules (stop phagocytosis)
- glycocalyx
- endotoxin
- biofilms
- bacterial secretion systems
What are the 4 main portals of entry?
respiratory tract (most common), GI tract, skin, genital tract
what does complement do in bacteria?
necessary for cell to be lysed
What are exotoxins?
polypeptides secreted by bacteria
- toxoids (when treated with formaldehyde or heat for protective vaccines)
- AB subunits (B binds and A is toxic)
- genetically coded in bacterial chromosome
What is endotoxin?
- part of gram negative cell wall (lipid A of LPS) is toxic when being broken down by body
- causes fever and shock
What is the difference between innate and acquired immunity?
- innate: macrophages endocytose and complement causes lysis
- acquired: antibodies form to specific antigens, and cytotoxic T cells kill what antibody binds to
What is active vs passive immunity?
- active: given specific antigens to stimulate development of immunity to protect from disease (ex: MMR, HPV, rubella, Varicella)
- passive: give antigen to protect from disease (ex: Hep A, polio, rabies, cholera)
How do bacteria avoid innate immune response?
- avoid contact with phagocytes
- inhibition of engulfment (capsid and biofilm)
- survival within phagocyte (escape, adapt, or modify phagosomal compartment)
How do bacteria avoid acquired immune response?
- antigenic variation
- immunological disguise (bind antibodies to hide)
