Studied by 38 people
What are the common cell morphologies?
coccus and bacillus or round and rod
What are the 3 most common prokaryotic cell arrangements?
Diplo = double
Strepto = chain
Staphylo = bunch of graphs, clusters of cocci
Define Plasmid
small, circular, extrachromosomal piece of double-stranded DNA that are not essential for life.
Explain the function of R plasmids to bacteria.
R-plasmids function is to carry antibiotic resistance to genes.
Describe the structure of a bacterial ribosome.
A 30S subunit is composed of 16S rRNA and a 50S subunit is composed of 23S and 5S rRNA.
Contrast G(+) and G(-) bacteria.
G(+) has a single, thick layer of peptidoglycan and contains, Teichoic acid, Lipoteichoic acid, and exoenzymes.
G(-) has a double, thin layer of peptidoglycan and outer membrane, and contains Braun’s lipoprotein, Porin, and LPS
Compare G(+) and G(-) bacteria.
Both have peptidoglycan
Compare the structure/ function of pili (fimbriae) and flagella.
function is motility
Contrast the structure/ function of pili (fimbriae) and flagella.
flagella have a larger structure, the flagellar movements are swarming, swimming, and spirochete motility, while pili (fimbriae) movements are twitching and gliding.
Discuss why endospores are of particular importance in food microbiology.
Endospores can be a source of food contamination or health risks. For example, C. botulinum can form spores and is commonly found in canned foods; that’s why canned food undergoes high temperature and pressure processes to kill the spores.
What is a species?
a group of strains sharing most of the same properties and that is different from another group of strains.
What’s a strain?
a population descended from one pure culture, it’s like a subunit.
What is the relevance of Streptomycetes?
they produce many natural products used in antibiotics and are found in culturable soil bacteria.
What type of positive and negative effects does the bacteria in order Rhizobiales have on plants?
it has fix nitrogen that plants can use, but can produce tumors on plants
What is a capsid?
a protein coat that encloses and protects the nucleic acid and is made of proteins called protomers.
What is an enveloped virus?
a full complete virion that has a lipid layer outside the capsid
What is a naked virus?
a full complete virion: nucleic acid, and a capsid
Explain the basic molecular events that take place during attachment.
molecules on the outside of the virus (ligands) interact with molecules on the outside of the cell (receptors)
Explain the basic molecular events that take place during Entry.
The viral genome is injected into the cytoplasm or the entire nucleocapsid enters the host cells: enveloped viruses fuse to the host cell membranes and release nucleocapsids followed by the uncoating step where the capsid is degraded, and the genome is released. Naked viruses enter by endocytosis, nucleocapsid enters the endosome, where it is uncoated, and the viral genome is released.
Explain the basic molecular events that take place during Synthesis.
The virus uses the host cells machinery for the synthesis of viral nucleic acids and the viral proteins, early protein and late proteins.
Explain the basic molecular events that take place during Assembly.
New nucleocapsids are made, and can be assembled in the cytoplasm, nucleus, or virus factories.
Explain the basic molecular events that take place during Release.
Some viruses lyse their host cells for release, lysosome, and holin, viruses are released by budding, which can create viral envelopes, or some viruses aren’t released to the environment, but to the new host cells.
What is the lytic cycle?
A bacteriophage immediately begins replicating upon entering a bacterial host, assembles new virions, and destroys the bacterial cell to release these virions.
What is the lysogenic cycle?
Phage injects its DNA into the cytoplasm, the phage then integrates into the hosts chromosome, then Prophage DNA is copied when the cells divide.
What is the theoretical maximum number of ATP generated by glycolysis, Krebs Cycle, and ETC
Glycolysis produces 2 ATP, Kreb Cycle can produce 2 ATP and the ETC can produce 28-32.
Why does aerobic respiration yield less ATP in bacteria than in eukaryotes?
The bacteria cycle yields less ATP because energy is used to power flagella. Also, the process is shorter and has different carriers than eukaryotic cells
Name two examples of how microbes can be used in bioremediation.
sewage treatment and to degrade or contain oil spills
Define halophile.
salt loving
Define mesophile and thermophile.
mesophiles are medium-loving temperatures like 37 degrees Celsius. Thermophiles are heat-loving temperatures like 65 degrees Celsius.
Define acidophile.
Acidophile is acid-loving with a pH less than 7.
What are the different phases of bacterial growth in a lab and how is nutrient availability related to the different phases?
First is the lag phase: cells are stressed and don’t divide but make materials, second is the exponential phase where lots of nutrients are used to supply the rapid cell division. Third is the stationary phase where cells stop dividing to conserve energy as nutrients deplete. Lastly, the death phase where cells run out of nutrients, and they drown in their own waste and die.
Explain how activators and repressors proteins exert control over gene expression.
Activator proteins ACTIVATE transcription by binding to the DNA which is a positive control. They are activated by inducers and inactivated by inhibitors.
Repressor proteins bind DNA to turn transcription OFF, which is a negative control. It is activated by corepressors and inactivates by inducers.
Explain what happens to regulate the lac operon when lactose is present/absent
If there’s no lactose to take into the cell then these genes (LacZ, LacY, and LacA) are off. Lac repressor proteins bind to DNA to cut off transcription, and the repressor proteins regulate this.
If there is lactose, transcription is ON. An inducer binds to the lac repressor which turns on transcription, which stops the blocking of the enzyme. The inducer changes the shape of the lac repressor which makes it unbind from the lactose.
Define conjugation.
the transfer of DNA by direct cell-to-cell contact (it is similar to sexual reproduction).
Define transduction.
the transfer of genes between bacterial cells by viruses
Define transformation.
the uptake of free DNA from the environment (usually plasmid or linear DNA).
Define biofilm.
a community of microbes encased in a sticky matrix and associated with a surface.
Define quorum sensing.
bacteria monitor their own population density by sensing the level of signal molecules released by these bacteria.
How do biofilms form?
First bacteria needs to attach itself to a surface. Once there is enough of them, the bacteria attach together and secrete EPS, forming a matrix. The bacteria then replicates into a mature biofilm secreting a polysaccharide matrix and pieces of biofilm can detach and colonize new surfaces.
Describe the structure and function of a CRISPR/Cas system in bacteria.
CRISPR is a Clustered, Regularly Interspaced Short Palindromic Repeats, which is a series of repeats and spacers in a bacterial genome. The nucleotide spacers are different because they are derived from viral genomes. The newest viral infections are at the beginning of the system, while the oldest are at the end. The repeats are all identical to each other.
Outline the events of the adaptation and interferences stages of CRISPR/Cas system function.
Adaption is when the virus infects a bacterial cell for the FIRST time and is incorporated into the spacers. Interference is when a virus infects a cell a SECOND time making CRISPR mRNA, and Cas proteins cut the mRNA into crRNAs, and these crRNAs guide degradation machinery to viral DNA/RNA. It is essentially waiting to kill the bacteria.
Where did the CRISPR/Cas9 system originate from and how it was adapted to edit genomes in eukaryotic organisms, including humans
Cas9 is a DNA endonuclease that is guided by RNA. Guide RNAs target Cas9 to a location where it cuts DNA in a precise spot allowing for deletion, insertion, or modification of the DNA. It is essentially a “find and replace” for genes, which can be used in eukaryotic organisms or humans to add or remove genes of choice.
What are the 3 modes of action of common antibacterial drugs?
The first mode is it can disrupt cell wall synthesis in gram-positive bacteria. B-lactams (penicillin) bind to transpeptidase and prevent peptide cross-linking in the peptidoglycan cell wall.
The second mode is it can inhibit protein synthesis (transcription). Tetracyclines bind to A site of ribosome which stops the making of amino acids. Macrolides then bind to the P site, it stops the transfer of peptides from A site to P site which stops elongation.
The last mode of action is it can inhibit nucleic acid synthesis (transduction). Rifamycin binds to the beta subunit of bacterial RNA polymerase preventing mRNA synthesis.
Define drug inactivation
chemical modification can make enzymes that inactivate the antibiotic.
Define R-Plasmid.
plasmid with 1 or more resistance gene; resistance plasmids
Compare inherent and acquired antibiotic resistance
Inherent resistance is when a bacterium is resistant because it lacks the target of an antibiotic. Acquired resistance is a change in the bacterial genome that converts it from sensitive to resistant.
What are the 3 common mechanisms of acquired antibiotic resistance?
On a genetic level, the bacteria can modify the antibiotic’s target by mutating the gene that makes the target unrecognizable. The second is drug inactivation, where the bacteria can make enzymes that inactivate the antibiotic. The third is Efflux pumps where the gene pumps the antibiotic/drug out of the bacterial cell. which can lead to multi-drug resistance.
How can antibiotic resistance be transferred from those that have it to those that do not?
Horizontal gene transfer and conjugation allow the transfer of immunity genes. These genes are often transferred on plasmids (R-plasmids).
List Koch’s Postulates and apply them to an experimental scenario.
suspected pathogens are found in every case of disease not found in healthy individuals.
Need to be able to isolate and grow in a pure culture.
need to be able to inoculate the culture and test it on a subject.
Must be able to re-isolate the pathogen from the new host and must be identical to the pathogen from postulate. 2.
You can take two organisms one with a disease and one that is completely healthy. You take a sample of the pathogen from the diseased animal and then you can isolate and grow it in pure culture. Then take the now cultured agent and inject it into the healthy (susceptible) organism, which kills it, and then take the causative agent from the now dead organism and re-isolate it to see if it is identical to the pathogen from the first diseased organism.
Define host
a larger organism that supports the growth and survival of a pathogen
Define pathogen
an organism that causes disease
Define reservoir
the natural location for which a pathogen normally resides; it can be living or nonliving and can be a source of infection.
Define vector
organisms that promote the spread of the disease from one host to another. An example of this can be a tick
Define virulence and virulence factor
Virulence is how harmful a microorganism is and virulence factors are what make a pathogen more harmful.
What are the four stages of an infectious disease?
The first stage of an infectious disease is the incubation period, which is the time between exposure to a pathogen and the development of symptoms. The second stage is the prodromal stage where the signs or symptoms that are developed are now appearing but not specific enough to diagnose, in this stage, you’re more likely to be contagious. The third stage is the illness period where the characteristics of the symptoms are most severe, which then triggers the immune response. After that the convalescence period occurs and your symptoms begin to disappear.
What do infectious and lethal doses mean and how do they relate to disease transmission?
An infectious dose is the number of microorganisms required to cause disease in 50% of hosts. The higher the infectious dose the less it’s virulent (less harmful) and the lower the infectious dose, the more virulent it is (more harmful), which means that it can be transmitted rapidly by using people as vectors.
A lethal dose is the number of microorganisms required to be lethal (kill) to 50% of hosts. The higher the lethal dosage the lower the toxicity and the lower the lethal dosage the higher the toxicity.
What are 3 ways virulence factors can make microbes more harmful to their respective host?
Virulence factors can: help pathogens adhere to and colonize host cells making them more successful at making the host sick; they can help improve resistance to immune responses by modifying the cell wall components to avoid detection, mainly the antigens (sugars on the outside of the bacteria), and they can help pathogens invade other tissues by invading the host cell, rearranging the cytoskeleton of the host cell to take in bacteria, disrupt attachments between cells, which blocks phagosome killing.
Define mutualism
a relationship where both organisms benefits: they are obligatory meaning that organism A can’t survive without organism B and vice versa
Define commensalism
A relationship were one organism benefits and the other doesn’t care: organism A can live off of organism B without it being harmed.
Define amensalism
a relationship where one species causes harm to another without any benefit to itself
Define core microbiome
species present in 95% or more of individuals, a large number of very few species.
Define dysbiosis
the disruption of normal microflora
What is the importance of the human microbiome in maintaining homeostasis?
A human microbiome is all the microbes associated with a healthy human host. The microbes that are in our body benefit from the nutrients, pH, and temperature, in our gut environment; as a result, we get a more metabolic diverse gut microbiome and protection against gut pathogens that are trying to invade
Describe several factors that influence the diversity and stability of a human’s microbiome.
Different environments such as the Skin, Nose, and Mouth, and Gut can influence the diversity and stability of a human microbiome.
Name one factor that may cause dysbiosis
It can be caused by eliminating essential bacteria from the core microbiome
Which part of the body has the largest community of microbes?
large intestine (colon)
The number of microorganisms required to cause a clinical disease in 50% of inoculated hosts is called the _____.
infectious dose 50
Virulence factors are products, mainly proteins, that increase the pathogenicity of microorganisms. What mechanisms do virulence factors use to do this?
Improving a pathogen's ability to adhere to host cells and Increasing efficiency of pathogen invasion of other tissues
The natural environment in which a pathogen normally resides is called a _____.
Reservoir
Which of the following statements regarding the human microbiome is correct?
Taking antibiotics can dramatically alter the gut microbiome
Which type of skin contains the largest diversity of microorganisms?
dry
The human mouth can be a difficult place for bacteria to grow because _____.
There is constant exposure to mechanical stress.
A gram-positive bacterium is treated with endopeptidase, an enzyme that cleaves peptide bonds. Will endopeptidase affect the integrity of this bacterium’s cell wall?
Endopeptidase will affect the cell wall by cleaving the peptide bonds that cross=-link peptidoglycan helices together
Members of _____ cause diarrheal illness cholera in humans and “scale rot” in some species of fish.
order vibrionales
During the nitrogen cycle bacteria take nitrogen gas (N2) out of the atmosphere and convert it into organic nitrogen via ___ and, ultimately, bacteria return N2 to the atmosphere via ____.
Nitrogen fixation and Denitrification
What are the molecular events in the bacterial cell cycle?
Period of growth results in the doubling of cellular components, the chromosome is replicated, chromosomes move toward poles; the cell elongates and the Z-ring forms at the center of the cell.
Note 
Flashcard (40)