General Microbiology - BIOL 336 AO Quiz

General Microbiology

• BIOL 336 AO, Spring 2025 course taught by Dr. Purple
• Office: MANS 334
• Email: [email protected]

The Microbial World

• Microorganisms (microbes) are life forms too small to be seen by the human eye
• Diverse in form and function
• Major fraction of Earth's biomass
• Many are single-celled, some form complex structures, and some are multicellular
• Live in microbial communities

Studying Microbes

• Microscopy is used to view individual microbes
• Culture involves growing cells in or on nutrient mediums
• A medium is a liquid or solid mixture containing all required nutrients, that promotes growth to form visible colonies

Microbial Colonies

• A microbial colony is a visible cluster of microorganisms viewed with the naked eye
• Colonies form from individual bacteria growing in a medium

Microbes as Model Organisms

• All cells are composed of the same elements
• Cells replicate DNA

Prokaryotic vs. Eukaryotic Cells

• Prokaryotes include bacteria and archaea
• Lack membrane-enclosed organelles and nuclei
• Eukaryotes include plant, animal, fungi, protists, and algae
• Possess membrane-enclosed organelles and a nucleus

Elements of Microbial Structure

• All cells share cytoplasmic (cell) membranes, cytoplasm, ribosomes, and may have a cell wall

Genes, Genomes, Nucleus, and Nucleoid

• Genome: A cell's full set of genes
• Prokaryotic DNA is generally single, circular chromosomes aggregating into the nucleoid region
• Can also have plasmids (extrachromosomal DNA) conferring special properties like antibiotic resistance
• Prokaryotic DNA is compact (0.5-10 million base pairs)
• Eukaryotic DNA is linear and contained within the nucleus, much larger (up to billions of base pairs)

Microbial Cell Activities

• Metabolism: Cells take up nutrients, modify them and expel wastes
• Growth: Nutrients are converted into new cell materials.
• Differentiation: Some cells form new structures such as spores
• Communication: Cells interact through chemical signals
• Evolution: Cells develop new traits.
• Genetic exchange: Cells transfer genes.

Microorganisms and the Biosphere

• Earth is 4.6 billion years old
• First cells appeared 3.8-4.3 billion years ago
• The atmosphere was initially anoxic (no oxygen)
• Early lifeforms used anaerobic metabolisms and were photosynthetic (anoxic)
• Plants and animals appeared approximately 0.5 billion years ago

Domains and Extremophiles

• Domains are distinct lineages of microbial cells
• Extremophiles live in extreme habitats (hot springs, glaciers)
• Microbial metabolic activities change habitats and affect other organisms

The Impact of Microorganisms on Human Society

• Microorganisms as disease agents
• Control of infectious diseases over the last century
• Bacterial and viral pathogens
• Negative impacts of microbes on food: food spoilage and foodborne disease
• Positive impacts of microbes on food: improving food safety and preservation (dairy products, cheeses, yogurt, buttermilks, sauerkraut, kimchi, pickles, chocolate, coffee, leavened breads, beer)
• Microbes and industry, including biofilms (growth on surfaces like pipes, tanks, implanted medical devices) and industrial microbiology (growth to make low-cost products like antibiotics, enzymes). Biotechnology involving genetically engineered microbes that produce high-value products.
• Bioterrorism: Microbes have been used as weapons in the past.

Microbiology History

• Antony van Leeuwenhoek: Invented magnifying glasses to view animalcules
• Robert Hooke: Described microscopical mushrooms (common bread mold)
• Louis Pasteur: Disproved spontaneous generation
• Robert Koch: Demonstrated link between microbes and infectious diseases, discovered causative agents for anthrax, tuberculosis and cholera.

Microscopy

• Light Microscopy: Light passes through the specimen
• Bright-field microscope, Fluorescent microscopy
• Electron Microscopy: Has high resolving power that allows viewing smaller details
• Transmission Electron Microscopy (TEM): Beam of electrons pass through the sample
• Scanning Electron Microscopy (SEM): Beam of electrons scan the sample's surface

Improving Contrast in Light Microscopy

• Staining increases contrast in light microscopy
• Differential stains distinguish different cell types (e.g., Gram stain)
• Phase-contrast microscopy improves image contrast of unstained, live cells

Imaging Cells in Three Dimensions

• Confocal scanning laser microscopy (CSLM) allows for creating 3D images of a specimen by focusing a laser on single layers.

Postulates

• Koch's Postulates are experimental steps confirming the causative link between a suspected pathogen and a disease

Woese and the Tree of Life

• Carl Woese recognized rRNA sequences for phylogenetic relationships
• Named the new group Archaea
• Phylogenetic trees depict evolutionary histories, showing three domains (Bacteria, Archaea, Eukarya)

Introduction to Microbial Life

• Bacteria: Prokaryotes, single cells, diverse, vary in size and shape
• Archaea: Prokaryotes, less morphological diversity, often associated with extreme environments
• Eukarya: Plant, animal, fungi, algae, protozoa, diverse in size and structure.
• Viruses: Obligate parasites, do not carry out metabolism, vary dramatically in composition