Studied by 33 peopleDescribe Viruses.
replicate independently from the host cell, but require a host to be able to replicate.
acellular ( have DNA or RNA, nucleic acid)
10-2300 nm in size
What is a protein coat and what is it's function?
a capsid (composed of capsomeres) , it protects the virus while outside of a host and initiates the infectious process when a suitable host is encountered.
What is the difference between positive sense and negative sense?
in positive sense the RNA genome and mRNA are both positive with a DNA complement, while in negative sense the RNA genome is - and mRNA is + making them compliments of one another.
What is helical symmentry and give an example?
covers nucleic acids with capsomeres influenza virus, measles virus, mumps virus, rabies virus, and Ebola virus
What is Icosahedral symmetry? ex?
20 faces and 12 vertices, most efficient way to enclose space. human papillomavirus, rhinovirus, hepatitis B virus, and herpesviruses
What is binal symmetry? ex?
bacteriophages; which possess icosahedral head and helical tail.
What makes animal viruses different from other viruses?
They are mostly enveloped. Outer, flexible layer, and proteins protect from surfaces.
Describe the steps of viral replication.
attachment (adsorption of phage virion, this is not random and requires a receptor)
Penetration of viral nucleic acid ( injection, genome penetrates)
synthesis of viral nucleic acid and protein ( some animal viruses do endocytosis into the cell)
assembly and packaging of new viruses.
cell lysis and release of new virions.
What is a bacteriophage ?
most are naked, very diverse and structurallly complex, most are DOUBLE STRANDED DNA!
what are virulent bacteriophages and what is their life cycle ?
aka Lytic: these phages replicate and lyse the host cell. T4 bacteriophages: attachment- penetration- transcription- biosynthesis- maturation- lysis
what are temperate bacteriophages and what is their life cycle ?
aka Lysogenic: these bacteriophages remain in the host WITHOUT destroying the host. Integrates viral genome into host genome in a relationship called lysogeny. Lambda: becomes a non-infectious phage called a prophage
How does lysogeny and the lytic cycle possible induce lysogens?
This can be induced by a stressor to convert to the lytic cycle, such as exposure to UV light or chemical mutagens that cause DNA Damage.
Animal virus infection: describe and give an example. VIRULENT
kills the host cell ex. rhinovirus
Animal virus infection: describe and give an example. LATENT
virus stops reproducing and remains dormant for sometime. during latency, syptoms, antivirus-antibodies, and viruses are not detectable . ex. HSV in children, cold sores in adults, varicella-zoster
Animal virus infection: describe and give an example. PERSISTENT
the virus is almost always detectable, clinical symptoms are mild or constant for long periods of time ex. hepatitis B or HIV
How can a virus cause cancer?
these viruses are capable of inserting the onca gene on animal chromosomes. A proto-oncogene is a tumor suppressor gene that a virus can interfere with and turn it off.
What is a cancer causing virus called?
oncoviruses
What is the replication process of retroviruses.
An RNA virus is a retrovirus that uses reverse transcriptase to convert RNA to DNA. Reverse transcriptase binds to retrovirus RNA and makes viral DNA. new viral DNA and integrase enter the nucleus, and the integrase cuts host DNA and attaches the viral DNA. transcription takes place and copies the viral RNA produced. ribosomes translate the viral RNA and make viral proteins such as integrases and capsids, and assembly can occur.
what is an example of a retrovirus
HIV
Describe the structure of SARS-CoV-2
enveloped with club shaped spikes, positive sense, single stranded RNA genome. helical capsid symmetry
What disease does SARS-CoV-2 cause?
a respiratory infection is caused
How is SARS-CoV-2 transmitted?
person to person via direct contact, droplets, or asymptomatic carriers.
SARS-CoV-2 infection, replication, and release.
the spike proteins attach to the host receptor via endocytosis or fusion with the cell membrane; new virions are released from the host cell by exocytosis.
Describe the DNA in prokaryotic cells.
plasmids are extrachromosomal DNA that is usually small, enclosed circular DNA pieces that exist and replicate independently and contain few non-essential genes.
Chromosomes consist of 4 base pairs (AT, CG)
Define Gene
DNA segment that codes for a polypeptide, rRNA, or tRNA ex. hisC = HisC Protein
Define Genotype
specific set of genes an organism possesses ( the nucleotide sequence)
define phenotype
set of observable characteristics ex. brown vs blue eyes
define Wild-type strain
strain isolated from nature
define mutation
stable, heritable change in nucleotide sequence. genotype is altered, may or may not have an effect on phenotype of an organism
Describe Forward Mutations
wild-type to mutant form ( ex. prototroph to auxotroph ( a nutritional mutant) )
Describe Reverse Mutation
mutant phenotype to wild type phenotype (auxotroph to prototroph)
What is a revertant?
same-site revertants, second-site revertants (compensatory mutations)
What is a prototroph?
a microorganism that can synthesize all it's required nutrients
what is an auxotrph
a nutritional mutant that cannot synthesize all of it's required nutrients. ( it cannot grow in minimal media, especially if specific nutrients are not provided)
What is the difference between screening and selection?
screening detects mutants via observation while selection uses environmental conditions to favor growth of a particular organism based on the corresponding genotype
How does the replica plating technique work?
by inoculating plates with a numbered scheme while retaining a master plate, the technique allows for the isolation of auxotrophic mutants by plating colonies on selective media and complete media. the complete media will grow all organisms and the selective media will grow all but the mutants ( negative selection)
this allows you to compare plates and see which colonies are growing on both plates and which are only growing on the complete plate.
What are the various fates of donor dna during horizontal gene transfer?
donor dna can become integrated into the DNA of the host cells genome by use of a plasmid and replicate alongside the host genome. (plasmid)=reproduction=stable recombinants or Donor dna cannot self replicate and the host restricts plasmid recombination and their are no stable recombinants formed.
What is homologous recombination in bacteria?
this is the reciprocal exchange of DNA base pairs that makes the same nucleotide sequence. DNA strand is nicked, and the single strand binding protein and RecA protein complex is formed. The recipient DNA is invaded, and crossover leads to exchange which is then ligated to, two recombinant DNA molecules.
How do you detect recombinants?
plate tryptophan-negative cells and observe no growth on selective media lacking tryptophan. Then add the DNA from tryptophan-positive cells to an agar plate lacking tryptophan and observe growth.
Describe the process of transformation
uptake of naked DNA by a competent cell followed by incorporation of dna into the recipient cells genome.
what is cell competence?
refers to the cells ability to take up foreign ( extracellular) dna from it's surrounding environment.
what is generalized transduction?
dna from any portion of the host genome is packaged inside the virion
what is specialized transduction?
dna from a specific region of the host chromosome is integrated directly into the virus genome.
Describe the process of bacterial conjugation.
the bacteria connect via sex pilus. a single strand of DNA enters teh f- cells and both cell synthesize the complementary strand.
what is the significance of RecA?
dna repair protein that catalyzes the DNA strand exchange reaction in homologous recombination
what is the significance of F+?
cells that contain the fertility plasmid
what is the significance of F-?
cells that do not contain the fertility plasmid
what is the significance of Tra?
transfer genes that encode the proteins for bacterial conjugation
what is the significance of Ori?
origin of replication in bacterial conjugation
Describe PCR
PCR (polymerase chain reaction) synthesizes large quantities of a DNA fragment
what is PCR used for?
diagnostic microbiology forensics paternity testing gene cloning
What are the three steps of PCR and what is required for each.
Denaturing: target DNA denatured with heat
Annealing : primers bind to target DNA
Extension: copies of target DNA synthesized
How do you make a recombinant plasmic using the three steps in molecular cloning?
isolation and fragmentation of source DNA
insertion of DNA fragments into cloning vector
introduction of cloned DNA into host organism
describe how restriction enzymes work
proteins created by bacteria that can cleave DNA at specific sites. used in cloning to cut the desired DNA sequences
describe how plasmid vectors work
can be used as a vector to carry cloned DNA into another bacteria
describe how DNA ligase work
an enzyme that joins DNA strands. can be used in cloning to form recombinant molecules.
describe bacterial plasmids
contain bacterial DNA and genetic material nonessential within their bacterial hosts, this is because they are not required for bacteria to function. however they can sometimes confer natural advantages for host.
how to bacterial plasmids work with horizontal gene transfer?
transfer advantages from one bacterium to another through horizontal gene transfer. this allows genes which confer advantages in one bacterium to be spread throughout a population.
how are bacterial plasmids used as cloning vectors?
the genes present within them can be switched with genes that want to be transferred in cloning.
What are the characteristics of plasmids that makes them useful in cloning?
easy to purify small selectable markers unique cloning sites
Be able to read a plasmid map!
map provided!
know the locations of normal microbiota and its role in maintaining good health.
diagram provided!
Describe the characteristics of bacteria found on the skin.
Three microenvironments: dry skin, moist skin, and sebaceous skin. skin has resident (staph and strep) and transient. the microflora on the skin are influenced by environmental factors and host factors such as age, weather, personal hygeine, and hormones. body odor is caused by gram-positive bacteria that produce volatile fatty acids the bacterium propionibacterium acnes causes zits
Describe the characteristics of bacteria found in the mouth.
microbes colonize on teeth and gums ( biofilm) streptococcus spp. are faculative and obligate anaerobes (depending on the location of the mouth) microbes in the mouth can cause ddental cavities, gingivitis, and periodontal disease
Describe the characteristics of bacteria found in the stomach.
most microbes are killed by the acidic condition. some may survive if they pass through the stomach.
Describe the characteristics of bacteria found in the intestines.
-largest microbial population in the body. -the large intestines can have up to 10^12 microbes/ g of wet weight. -microbes present are obligate anaerobes. -colonic bacteria produce essential vitamins such as B12 and K plus gas. -bacteria make up 1/3 of fecal matter.
bacteria in intestines are replaced rapidly due to high growth rate. -the gut-brain axis is what can happen in your brain based on your gut microflora.
Describe the characteristics of bacteria found in the respiratory tract.
Nasopharynx may contain low numbers of potentially pathogenic microbes. -In the lower respiratory tract, there is NO normal microflora, only particles smaller than 10 micrometers.
microbes can be removed by a continuous stream of mucus generated by goblet cells, ciliated epithelial cells, phagocytosis by alveolar macrophages, and lysozyme in mucus.
Describe the characteristics of bacteria found in the urogential tract.
the kidneys, ureter, and bladder may harbor residential microbes ( but should be FREE of microbes)
distal portions of the urethra (opening to the environment) may have few microbes found.
main causes of urinary tract infections
female genital tract has a complex microbiota that is constantly in a state of flux due to the menstrual cycle.
Name an example of bacteria found on the skin.
step, staph, propionibacterium acnes
Name an example of bacteria found in the mouth.
streptococcus spp.
Name an example of bacteria found in the stomach
heliobacter pylori (stomach ulcers)
Name an example of bacteria found in the intestines
small: enterococcus faecalis, lactobacilli large: bacteriodes, clostridium
Name an example of bacteria found in the respiratory tract.
staphylococi, streptococci
Name an example of bacteria found in the urogenital tract.
E.coli and lactobacillus acidophilus (predominates in vagina)
Describe the conditions of the skin.
mechanically strong barrier, slightly acidic pH,
high concentrations of NaCl,
many areas are low in moisture and contain inhibitory substances such as lysozymes
Describe the conditions of the mouth
moist, warm, nutrient rich environment.
saliva in mouth contains antimicrobial enzymes such as lysozyme and lactoperoxidase
Describe the conditions of the stomach.
most microbes are killed by the acidic conditions pH of 2
Describe the conditions of the intestines.
increasing pH and number of bacteria as you move down the intestines. the large intestine (colon) has the largest microbial population of the body . large intestines can have up to 10^12 microbes/g of wet weight
Describe the conditions of the respiratory tract.
microbes can be removed by a continuous stream of mucus generated by goblet cells, ciliated epithelial cells, phagocytosis by alveolar macrophages, and lysozyme in mucus.
Describe the conditions of the Urogenital tract
female genital tract has an acidic pH
Difference between infection and disease?
infection: occurs when a foreign invader enters the body and begins to colonize and replicate within the host tissue. disease: occurs as a result of infection if the infection continues and inflicts damage upon tissues or throughout the system of its host
How can normal microbiota cause infection and sometimes disease?
normal microbiota can be opportunistic pathogens. this means that these bacteria can produce disease under certain conditions but will not cause disease in normal conditions. this usually occurs from normal microbiota traveling to another location of the body in which they are not native.
Describe the course of an infectious disease and what factors will influence the outcome.
exposure to pathogens
adherence to skin or mucosa
invasion through epithelium
multiplication: growth and production of virulence factors and toxins. this can diverge into one of two things
toxicity: toxin effects are local or systemic
invasiveness: further growth at origin and distant sites both result in tissue or systemic damage
related to disease transmission define: direct
transmission from infected host to a susceptible host (carrier transmits disease directly)
related to disease transmission define: indirect
transmission from infected host to susceptible host through indirect contact. can be fecal-oral, airborne, or fomites (particles left on inanimate surfaces)
related to disease transmission define: vector
something that can be used to carry a disease
related to disease transmission define: reservoirs
animate or inanimate location in which an infectious agent thrives and may infect a host
related to disease transmission define: zoonosis
disease that primary occurs in animals, but it is transmitted to humans occasionally
what is common source infectious disease pattern?
rapid rise to peak of infection, moderately rapid decline
what is propogated infectious disease pattern?
(host to host) slow, progressive rise and gradual decline
describe the immune system
main function is to recognize foreign invaders in the body and deal with them. this is done through the use of a variety of cells and other defensive mechanisms.
define immunity
ability to resist a particular disease or infection
innate immune response
generalized natural response
specific immune response
specific to invader, stimulated by memory cells recognizing the invader and dealing with it accordingly
innate immunity:
1st line of defense
lacks immunological memory, general response to foreign invader
phagocytes: cells that ingest, kill and digest microbial pathogens
Adaptive immunity
2nd line of defense
recognized antigens from pathogens (specific)
has immunological memory: memory T and B cells
cell mediated response:
memory T cells: memory for T cells (attack invaders inside cell) a
antibody mediated response:
plasma cells are differentiated B cell that creates antibodies
memory B cells (produce antibodies and attack invaders outside of cells. )
how does an person acquire immunity?
naturally, artificially, actively or passively
natural immunity is acquired through...
normal life experiences as a human actively: previous infections passively: maternal antibodies
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