Introduction and Microbial Diversity

Definition of Microorganisms

  • Microorganisms include:

    • Prokaryotes: Bacteria and Archaea

    • Protozoans: Unicellular eukaryotic organisms

    • Fungi: Eukaryotic organisms (molds and yeasts)

    • Non-living Infectious Agents:

    • Viruses: Non-cellular infectious agents

    • Viroids: Infectious agents affecting plants

    • Prions: Infectious proteins causing neurodegenerative diseases

Names of Microorganisms

  • Proper naming is critical:

    • Escherichia coli: Written full name first time; thereafter, abbreviated to E. coli.

    • Formatting: Italics for typed names, full form must be written out the first time in the document.

Roles and Uses of Microorganisms

  • Microbial Roles:

    • Cleaning & Recycling: Used in bioremediation and waste treatment.

    • Agriculture and Food: Utilized widely in food production (e.g., bread, yogurt, kefir).

    • Biomedical Research: Contributions to scientific discoveries and medical advancements.

    • Biofuel Production: Engaging microbes for sustainable energy sources.

    • Bodily Microbiomes: Integral parts of human health and digestion.

    • Ecological Niches: Maintain ecosystem balance; microbes inhabit diverse environments.

    • Diseases: Notably, archaea are not known to cause diseases in humans.

3 Domains of Life

  • Archaea: Prokaryotic organisms, often extremophiles.

  • Bacteria: Prokaryotic organisms.

  • Eukaryotes: Organisms with complex cells (includes fungi, protozoa, animals, plants).

Comparison: Eukaryotes vs Prokaryotes

Feature

Eukaryotes

Prokaryotes

Nucleus

Present (membrane-bound)

Absent

Organelles

Membrane-bound

Absent

Size

10 to 100 μm in diameter

0.1 to 5 μm in diameter

Thiomargarita magnifica

  • A bacterium found in Guadeloupe that can grow up to ~1 cm in length, consisting of membrane-bound compartments for DNA packaging.

Properties of Archaea and Bacteria

Property

Archaea

Bacteria

Cell Wall Composition

No peptidoglycan

Peptidoglycan present

Cell Membrane Composition

Ether-linked lipids

Ester-linked lipids

Protein Synthesis Initiation

Methionine

Formylmethionine (fMet)

Pathogenicity

No known human pathogens

Many known human pathogens

Archaea - Extremophiles

  • Thermophiles: Survive at high temperatures (> 45 °C).

  • Halophiles: Live in highly saline environments (≥ 9% NaCl).

  • Alkaliphiles: Thrive in alkaline pH environments (8.5 - 11).

  • Acidophiles: Survive in highly acidic conditions (≤ pH 5.0).

  • Barophiles: Adapted to high hydrostatic pressure.

Thermophiles

  • Organisms function improperly below 45 °C (113 °F) and are found in environments such as compost and biotechnology applications.

Hyperthermophiles

  • Optimal growth temperature > 80 °C (176 °F).

Halophiles and Bioplastics

  • Tolerant to saline (sea level) environments and can be harnessed for producing bioplastics.

Alkaliphiles

  • Capable of acidifying their cytosol in alkaline environments.

Acidophiles

  • One example, Picrophilus torridus, can thrive in a pH of 0.5 (equivalent to ~1.2 molar sulfuric acid).

Other Types of Microorganisms

  • Psychrophiles: Thrive in cold temperatures -20 °C.

  • Mesophiles: Optimal growth from 20 °C to 45 °C (68 °F to 113 °F) - includes human pathogens.

  • Piezophiles: Optimized for high-pressure environments.

Methanogens

  • Anaerobic archaea producing methane through methanogenesis; found in the digestive system of ruminants (e.g. cattle) aiding in cellulose digestion.

Bacteria

  • Notable examples include:

    • Escherichia coli

    • Staphylococcus aureus

    • Streptococcus pyogenes

Protozoa

  • Eukaryotes that can be unicellular or colonial, heterotrophic, and lacking cell walls.

  • Examples include various parasitic protozoa (e.g., Plasmodium | malaria).

Disease-Causing Protozoa

  • Malaria: Caused by the Plasmodium genus; life cycle involves complex stages within human and mosquito hosts.

  • Toxoplasmosis: Caused by Toxoplasma gondii.

Fungi

  • Distinctive features of fungi include:

    • Cell walls made of chitin

    • No motile cells

    • Ergosterol in cell membranes

Fungi Characteristics

  • Microscopic forms include yeasts and molds, with both being saprophytic (decaying organic matter) and some being parasitic.

Fungi in Symbiosis

  • Mycorrhizae: Fungi forming symbiotic relationships with plant roots.

  • Lichens: Composites of fungi and algae/cyanobacteria, providing nutrients mutually.

Fungal Significance

  • Decomposers returning nutrients to the ecosystem.

  • Contributions to food production (e.g., bread, alcohol).

  • Medical significance - some fungi produce antibiotics (e.g., Penicillium species).

Parasitic Fungi

  • Cause diseases in hosts; notable examples include dermatophytes, Candida albicans, and Aspergillus niger.

Before Next Class

  1. Thoroughly read the syllabus.

  2. Complete the discussion board assignment (due Thursday, September 4th by midnight).

  3. Review/Preview chapters 11-13 of the textbook.