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Administrative Challenges and Academic Integrity in Higher Education

• Faculty-Student Interaction Models: In some departments, students meet with faculty once a month to discuss laboratory plans. This serves as a quality control mechanism to ensure students learn specific faculty goals, though it adds administrative burden. The current department does not follow this model, which alleviates faculty workload but potentially disconnects students from core learning objectives.

• Grading and Accreditation: There is a notable difference between campus sectors. Some use coordinators to vet exam questions for accreditation purposes.

• The Major Field Test Controversy:

  • Implementation: The test was created by administrators approximately $10$ years ago but was not strictly enforced until about $5$ years ago.

  • Graduation Holds: Students (seniors) face holds on their accounts and graduation if they do not take the test, as recorded on Degree Works.

  • The Disconnection Issue: Administration uses "bean counters" to compare course grades with Major Field Test scores. A systemic problem exists where students receiving As in classes often score no higher than a $70$ on the test.

  • Accreditation Risks: Organizations like SACS may view this discrepancy as evidence of grade inflation or a lack of institutional integrity.

  • Ethical Violations: An example of academic malpractice occurred where a faculty member offered extra points on a final exam in exchange for canned food donations. This was identified as unethical and grounds for termination, subsequently halted.

Laboratory Proficiency: Serial Dilutions and Pipetting

• Technical Skills Gap: Faculty reporting from external labs indicates that newly hired technicians often require retraining on basic skills like pipetting. While everyone pipettes differently, there is a perceived decline in foundational scientific literacy.

• Serial Dilutions: This is considered a critical skill for all biomedical sciences, not just microbiology. It is often "brushed off" in general classes.

• Diauxic Growth Observations: In lab settings, serial dilutions allow for the visualization of bacterial growth phases, or "dioxy effects," when comparing different carbon sources.

Molecular Genetics: The Mechanism of Bacterial DNA Replication

• DNA Helicases: These enzymes recognize the origin of replication, denoted as the $oriC$. Their primary function is to "open up" the DNA by separating the hydrogen bonds between strands, acting as a molecular zipper.

• DNA Polymerase III: This is the primary enzyme for synthesizing new DNA strands.

  • Requirement: It requires a primer to provide a free $3'$ hydroxyl (OH) group to attach incoming nucleotides.

  • Directionality: Synthesis always proceeds in the $5'$ to $3'$ direction.

• Primase: This enzyme provides the necessary primer by synthesizing short strands of RNA.

• Leading vs. Lagging Strands:

  • Leading Strand: Synthesized continuously as the replication fork moves.

  • Lagging Strand: Due to the anti-parallel nature of DNA and the $5'$ to $3'$ synthesis requirement, the lagging strand is made in "okidaki fragments."

• DNA Polymerase I: This enzyme is responsible for removing RNA primers and replacing them with DNA nucleotides.

• DNA Ligase: Required to join the fragments together into a continuous strand.

• Topoisomerases: Enzymes that alleviate the physical stress and supercoiling caused by the unwinding of the DNA double helix.

• Single-Stranded Binding Proteins (SSBPs): Essential for stabilizing the separated strands, though involving over $30$ different proteins and significant consumption of ATP energy.

Antimicrobial Pharmacology: Inhibition of Replication and Synthesis

• Quinolones and Fluoroquinolones (e.g., Ciprofloxacin, Gentamicin):

  • Mechanism: These drugs bind to topoisomerases to prevent DNA replication by inducing stress and potential DNA breakage through supercoiling.

  • Secondary Mechanism: In gram-positives, they can prevent the separation of chromosomes at the end of replication.

  • Requirement for Activity: These drugs only work on actively replicating cells. Bacteria in a "viable but not culturable" state or sister cells may survive treatment.

• Resistance: Bacteria like Pseudomonas can develop resistance via a single nucleotide base change that alters the conformation of the topoisomerase, preventing antibiotic binding.

• Clinical Risk: Broad-spectrum antibiotics like Cipro can destroy the host microbiota, leading to secondary infections like CDAD.

• Protein Synthesis Inhibitors:

  • Tetracyclines (e.g., Doxycycline): Interfere with the ribosomal machinery.

  • Erythromycin: Another protein synthesis inhibitor.

  • Chloramfetacol: Used as a last resort due to high nephrotoxicity.

Polymerase Chain Reaction (PCR): Mechanism and Applications

• Concept: PCR is a laboratory "analogue" to DNA replication, simplified by using heat instead of a complex suite of enzymes like helicases or SSBPs.

• History: Carrie Mullis is credited with the Peltier thermocycle design in the late 1980s, though the original work was done by a female researcher in Montana studying extremophiles in hot springs.

• Standard Cycle (Repeated $30$ to $40$ times):

  1. Denaturation: Heating to $95-98$ degrees to separate DNA strands by breaking hydrogen bonds.

  2. Annealing: Cooling to allow specific primers to bind to the template DNA.

  3. Extension: Raising temperature to approximately $72$ degrees, where a thermal stable polymerase (derived from hot-spring bacteria) synthesizes the new DNA.

• Logarithmic Amplification: Each cycle doubles the DNA, allowing visualization on a gel or sequencing.

• Bioinformatics (In Silico): Experiments should be mapped out digitally before using expensive reagents ($4$ dollars a cup for sequencing at Geneliz).

• Microbiome Research: Use of "degenerate primers" (G, T, or C) allows amplification of unknown gut bacteria, though it cannot distinguish between residents and transients.

The Central Dogma: Transcription and the Lac Operon

• Central Dogma: The flow of information from DNA to RNA to Protein.

• Transcription: RNA polymerase synthesizes mRNA, tRNA, or rRNA de novo (without a primer).

• Operons (Prokaryotes): Multiple genes organized under a single regulatory sequence.

• The Lac Operon Example:

  • Structure: Includes $lacZ$ (beta-galactosidase), $lacY$, and $lacA$.

  • Dioxic Effect: E. Coli prefers glucose and will only utilize lactose after glucose is exhausted, resulting in two lag phases in a growth curve.

  • Biotechnology (Blue/White Screening): Scientists use iBTG and exgal; if $lacZ$ is intact, colonies turn blue. Successful cloning (inserting a gene like insulin into $lacZ$) results in white colonies.

• Coupling: In bacteria, transcription and translation occur simultaneously in the cytoplasm because there is no nuclear membrane.

Translation: Ribosomes and Codons

• Codons: Nucleotides are read in triplets. One codon equals one amino acid.

• Ribosome Binding Site (RBS): Also known as the Simon Delgado, Shain Belgorod, or Shandel Gagne/Shange El Gardo sequence. It is a purine-rich region upstream of the AUG start codon that sets the "reading frame."

• The Translation Process:

  • tRNA: Contains an anticodon that hydrogen bonds to the mRNA codon to deliver amino acids.

  • Ribosomal Sites:

    1. A site (Acceptor): Where the incoming tRNA enters.

    2. P site (Polymerization): Where peptide linkages are formed between amino acids.

    3. E site (Exit): Where spent tRNAs leave.

• Codon Bias: Different organisms (e.g., Malaria vs. Pseudomonas) prefer specific codons for the same amino acid based on their GC or AT genome richness.

Viral Biology: Bacteriophages and Animal Viruses

• Bacteriophages (Phage): Bacterial viruses that look like spaceships and inject nucleic acid while leaving the capsid outside.

  • Lytic Cycle: Causes immediate lysis and death of the bacterial cell, forming "plaques."

  • Lysogenic Cycle: The viral DNA (prophage) integrates into the bacterial chromosome and replicates with it.

  • Transduction: Errors in the lysogenic-to-lytic transition can transfer bacterial genes, leading to new pathogens (e.g., shiga toxin in $E. coli O157:H7$).

  • Therapeutic Phage: Undergraduates in the "fire program" (Graham Hatfield/Bill Jacobs) discovered phages to treat Mycobacterium avium in Cystic Fibrosis patients.

• Animal Viruses: Classified by the Baltimore scheme (e.g., dsDNA like pox/herpes, ssRNA).

  • Structure: Always have a capsid; some have an envelope (phospholipid bilayer) stolen from the previous host cell.

  • Entry: Animal viruses enter the cell entirely (capsid and all) via endocytosis or fusion.

  • Viral Outcomes:

    • Acute: Rapid cell death (e.g., rhinovirus).

    • Persistent: Slow, chronic replication.

    • Latent: Hiding in the host (e.g., herpes, HPV).

    • Transformation: Approximately $30\%$ of human cancers are oncogenic/viral in origin (e.g., HPV, HTLP 3).

Questions & Discussion

• Q: Where was your English Composition professor?

  • A: Students reported taking English Comp at community colleges or noted that professors are rarely seen grading essays in large universities; usually, it's a student or TA.

• Q: What are the stipulations for the Major Field Test?

  • A: The main threat is a "graduation hold" on the account, preventing students from finishing their degree regardless of class grades.

• Q: Have you done serial dilutions in lab?

  • A: One student performed them in a Biochem lab with Dr. Altura. After finishing a short $30$-minute PCR lab, they used large graduated cylinders ($200\,mL$) to practice dilutions.

• Q: Does the PCR extension time change for longer chains?

  • A: Yes. The generic rule of thumb is that for every kilobase ($kb$) of DNA, you need one minute of extension time.

• Q: If a man has HPV but it is hidden, can the vaccine make it go away?

  • A: Studies in women suggest the HPV vaccine can act as a treatment, but its efficacy as a therapeutic in men is currently a subject of debate and ongoing research.", "title": "Comprehensive Study Guide: Microbiology, Molecular Genetics, and Virology"}