final exam study questions

transformation

uptake and incorporation of free (naked) DNA from the environment into a bacterial cell’s genome

transduction

transfer of bacterial DNA from one cell to another via a bacteriophage (virus that infects bacteria)

conjugation

direct transfer of genetic material (usualy plasmid DNA) from one bacterial cell to another through cell-to-cell contact via synthesis of a conugative pilus

CRISPR

family of DNA sequences in the genomes of prokaryotic organisms such as bacteria and archaea. these sequences are derived from DNA fragments of bacteriaphage that had previously infected the prokaryote. detect and destroy DNA from similar bacteriophages during infections

CRISPR-CAS9 technology

gene-editing technology involving a guide RNA to match a desired target gene and Cas9 (CRISPR-associated protein 9)- an endonucease that causes dsDNA to break, allowing modifications to the genome

possibilities of using CRISPR-Cas9 technology in science

geneticists and researchers can edit parts of the genome by removing, adding, or altering sections of the DNA sequence and directly address genetic diseases.

pathogenicity island

a large distinct segment of bacterial DNA acquired through horizantal gene transfer that contains clusters of genes responsible for virulence, such as toxins, secretion systems, or adhesion factors

examples of a pathogenicity island

pathogenic systems encoded within pathogenicity islands include- TIIISS of Salmonella, TIIISS of O157:H7, or TIVSS of Helicobacter

why do bacteria control cell division in response to environmental changes

it is a survival strategy to adapt to different conditions, such as resource availability, stress response, quorum sensing, and biofilm formation. this is a critical adaptive mechanism allowing them to survive and thrive in diverse habitats. by adjusting their growth and division rates, bacteria can optimize their fitness and ensure survival in fluctuating environmental conditions

what is quorum sensing

cell-to-cell communication system in bacteria where gene expression is regulated based on population density using small signaling molecules (autoinducers)

autoinducer role in quorum sensing

control the population density once a threshold concentration is reached, they trigger changes in gene expression that lead to coordinated responses such as biofilm formation, virulence factor production, motility, and sporulation

bacterial chemical signaling

process by which bacteria release and detect small molecules (signals) to coordinate behavior such as biofilm formation, virulence, and bioluminescence

how can quorum sensing or bacterial chemical signaling influence infectious diseases

regulates the virulence of pathogenic bacteria. for example, many pathogenic bacteria use quorum sensing to regulate the expression of virulence factors that allow them to colonize host tissues, evade the host immune system, and cause disease, such as Pseudomonas aeruginosa, Salmonella enterica serovar Typhimurium, uropathogenic E. coli, and other enteropathogenic E. coli strains

primary reason why bacillus species sporulate

it is a crucial survival mechanism utilized by certain bacteria, particularly Bacillus and Clostridium, to withstand harsh environmental conditions and ensure long-term survival.

may contribute to environmental resiliance, long-term survival, dispersal, infectious diseases, and biotechnological applications of these speices

compare sporulation of bacillus subtilis with cell divison.

during sporulation, two cells with different fates are produced, a prespore and mother cell while in cell division or binary fission, two identical cells are formed

what event begins the process of sporulation

amino acid starvation and activation of Spo0A are essential mechanisms that start the process

sporulation

formation of highly resistant endospores in certain bacteria (e.g. bacillus, clostridium) in response to stress conditions like nutrient starvation

cell division in e.coli

binary fission which results in identical daughter cells

cell division in caulobacter crescentus

asymmetric cell division producing two distinct cells: a motile swarmer cell and a stalked/sessile cell. CtrA is the master regulator of cell fate in C. crescentus

what effect does the λ repressor ahve on the gene expression of λ phage genes?

turns off the expression of all phage genes except its own gene

what causes the activation of Cro?

DNA damage causes activation of the protease activity of RecA that cleaves the λ repressor.

what is the Cro primary function

in bacteriophage λ, Cro promotes the lytic cycle by repressing the transcription of the λ repressor

what role does MinCDE play in cell division

selection of the division site at the center (midcell) of the cel to ensure a proper cell division, generating two identical bacterial daughter cells

what are the advantages of the bacteria living in a biofilm versus planktonic solution

biofilm bacteria are less susceptible to antibiotics, immune system surveillance, biocides, environmental stresses, and other threats

step-by-step process of biofilm formation

bacteria transition from a free-floating (planktonic) state to a surface-associated, multicellular community.

following these steps:

1. Initial attachment of free-swimming bacterial cells to a surface using pili or adhesions.

2. Bacteria irreversibly adhere and secrete extracellular polymeric substances (EPS) .

3. Microcolony formation in monolayers occurs when the cells divide and form clusters encased in EPS, creating mircrocolonies that will mature into biofilm.

4. Microcolonies develop into a complex structured biofilm with water channels for nutrient flow (mushroom-like forms).

5. Some bacteria detach from the biofilm to colonize new surfaces, continuing the cycle

what is c-di-GMP

an intracellular signaling molecule that contributes to the decision to form a biofilm. the opposing activities of diguanylate cyclase and cyclic nucleotide phosphodisterase regulate the cytoplasmic concentration of c-di-GMP

how important is the gut microbiota against bactieral pathogen infection

protects the host by competing with pathogens for nutrients and attachment sites, producing antimicrobial substances that inhibit pathogen growth, and stimulating and regulating the host immune system. additionally, the gut microbiota also helps maintain normal gut physiological functions such as digestion, pH regulation, etc.

what are two-component systems in bacteria

widespread signaling pathways commonly found in bacteria, enabling them to sense and respond to environmental changes. its two components are sensor histidine kinase and response regulator

sensor histidine kinase (HK)-

transmembrane protein in the bacterial cell membrain with an extracellular domain that senses specific envrionmental signals like pH, temp, nutrients and a cytoplasmic domain with kinase activity. when sensor domain detects a stimulus, it undergoes a conformational change that activates the kinase activity of the cytopasmic domain. the activated kinase domain autophosphorylates a converted histidine residue. the phosphoryl group from activated histidine kinase is transferred to a conserved aspartate residue on response regulator, leading to phosphorylation

response regulator (RR)

transcription factors that regulate gene expression in response to environmental signals. phsophroylation of the RR alters its conformation and/or DNA-binding affinity, allowing it to bind to specific DNA sequences (promoters) and modulate the expression of target genes

examples of two-component systems in bacteria

PhoPQ in Salmonella, ENvZ/OmpR in E.coli, QseBC in E.coli