ex 3 lec 1

Chemoheterotrophs and Media Growth

• Chemoheterotroph Definition: Organisms that require organic carbon for energy and biosynthesis.

  • Must have an organic carbon source to grow.

• Media Types and Growth:

  • Medium A: No organic carbon source; only autotrophs could grow here (e.g., photoautotrophs, chemoautotrophs).
  • Medium B and Medium C: Both contain organic carbon sources.
  • Medium B: Complex medium.
  • Medium C: Defined medium.
  • Chemoheterotrophs can grow in Medium B and C.

Exam Discussion and Performance

• Exam 1 Curve:

  • Average score approximately 70, but subject to change with online exams.
  • Previous curve increase due to poor exam scores associated with procrastination, especially after spring break.

• Midterm Logistics:

  • The instructor had concerns about the depth of material covered and overall test difficulty.

Classification and Biotechnology Overview

• Classification Systems:

  • Old classification: Five kingdom system by Whitaker: Animals, Plants, Protists, Fungi, Monera (bacteria).
  • Modern classification: Domains of life include Bacteria and Archaea identified by Carl Woese, leading to a shift in classification.

• Molecular Biology Techniques:

  • Biotechnology, including PCR and next-gen sequencing, plays a significant role in microbial diagnosis and classification.
  • Molecular Phylogeny: Understanding evolutionary relationships through DNA and RNA sequencing.

Ribosomal RNA and Classification

• 16S rRNA Gene: Essential for identifying evolutionary relationships among prokaryotes due to low mutation rates.

  • Used as a phylogenetic marker.

• Comparison of Ribosomes:

  • Prokaryotic Ribosomes: 70S with 30S and 50S subunits; fewer polypeptides (52).
  • Eukaryotic Ribosomes: 80S with larger subunits; more complex structure with additional RNA species (up to 80 polypeptides).

Advances in Taxonomy

• Continuous Evolution: Taxonomy remains dynamic, constantly updated as new information arises (e.g., through advances in sequencing technology).
• Determinative Bacteriology:
  • Classical methods remain important for identifying organisms despite advancements.
  • Bergey's Manual: Traditional reference for bacterial classification still referenced in microbiology.

Modern Identification Techniques

• High Throughput Technology:
  • Shift towards DNA sequencing and microarray technology for rapid organism identification.
  • Next-Generation Sequencing (NGS): Allows sequencing of entire microbial communities; transforming microbial identification.
• PCR Technology: Rapid genetic amplification for clinical samples, replacing culture-based methods.
  • Use of microarray technology to analyze genetic markers.

Serology and Other Tests

• Serology: Antibody-based testing that is complementary to genetic tests. Examples include ELISA assays and rapid tests (e.g., pregnancy tests, strep throat tests).
• Interferon Gamma Release Assays: Modern tuberculosis tests that offer faster results than traditional methods.

Mass Spectrometry in Microbiology

• MALDI-TOF Mass Spectrometry: Fingerprint-like analysis for microorganism identification, especially beneficial for fungi.
  • Uses a unique characteristic pattern of organisms, offering confirmatory results against contamination.

Conclusion

• Study Forward: Next class will cover bacterial diversity.
• Preparation Reminder: Importance of understanding both historical and current methodologies in microbiological testing and classification as both are relevant in clinical practice.