Microbial World and You Quiz

Microbial World and You

• Binomial Nomenclature: A naming system that gives each organism a two-part Latin name, e.g., Escherichia coli (E. coli).
• Hierarchy of Classification: Kingdom, Phylum, Class, Order, Family, Genus, Species, organizes organisms into categories.
• Taxonomy: The science that classifies organisms, provides universal names, and places them in categories.

Types of Microbes

• Bacteria: Single-celled, prokaryotic organisms with peptidoglycan cell walls. Some are motile by flagella.
• Archaea: Prokaryotic; distinct from bacteria, often found in extreme environments.
• Fungi: Eukaryotic organisms; yeasts (unicellular) and molds (multicellular) that decompose organic material.
• Protozoa: Single-celled eukaryotes, that often move by pseudopods, cilia, or flagella.
• Algae: Photosynthetic eukaryotes, vital for aquatic food chains and oxygen production.
• Viruses: Acellular, obligate intracellular parasites, made of nucleic acids (DNA or RNA) enclosed in a protein coat.
• Multicellular Animal Parasites: Helminths (worms), which affect human health.

Classification of Microbes

• Domains:
• Bacteria: Unicellular prokaryotes with peptidoglycan walls.
• Archaea: Prokaryotes lacking peptidoglycan. Often extremophiles.
• Eukarya: Includes protists, fungi, plants, and animals.

Spontaneous Generation Debate

• Proponents believed life arose from nonliving matter.
• Opponents argued for biogenesis, that life arises only from preexisting life.

Pasteur's S-neck Flask Experiment

• Demonstrated that microbes, not air, cause contamination. Contained sterile broth that remained free of microbes.

Koch's Postulates

• Establishes a causal relationship between a microbe and a specific disease:
• The pathogen must always be present in cases of the disease.
• The pathogen must be isolated and grown in a pure culture.
• The cultured pathogen must cause the disease in a healthy host.

Observing Microorganisms Through a Microscope

• Compound Light Microscope: Uses visible light; magnifies up to ~1000x.
• Phase-Contrast Microscope: Enhances contrast in transparent specimens without staining.
• Fluorescence Microscope: Uses UV light for viewing fluorescently labeled structures.
• Electron Microscope:
• Transmission Electron Microscope (TEM): High-resolution internal structures.
• Scanning Electron Microscope (SEM): 3D images of surface structures.
• Resolution and Magnification: Resolution depends on light wavelength and lens; magnification is objective lens × ocular lens.

Preparing Smears for Staining

• Specimens are spread thinly on a slide, air-dried, heat-fixed, then stained to visualize structures.

Types of Stains

• Simple Stain: Uses a single dye for visualization.
• Differential Stain: Highlights differences. Examples include Gram stain (distinguishes Gram-positive and Gram-negative bacteria).
• Special Stains: Visualize specific structures (e.g., endospore, capsule stains).

Prokaryotic and Eukaryotic Cells Functional Anatomy

• Prokaryotic Cells: Have cell walls, plasma membranes, ribosomes, nucleoid, pili, flagella, and sometimes capsules and endospores.

Microbial Metabolism

• Enzymes: Facilitate metabolic reactions. Composed of apoenzymes (protein portion) and cofactors/coenzymes (non-protein helpers).
• Factors Affecting Enzyme Activity: Temperature, pH, substrate concentration, and inhibitors (competitive and non-competitive).
• ATP Generation: Substrate-level phosphorylation and oxidative phosphorylation.

Key Pathways

• Glycolysis, Krebs Cycle, Electron Transport Chain, and Fermentation.

Microbial Growth Requirements

• Physical: Temperature, pH, osmotic pressure, and specific chemical factors (carbon, nitrogen, sulfur, trace elements).
• Types of Media: Selective media, differential media, enrichment media.

Control of Microbial Growth

• Microbial Death Rate: The permanent loss of reproductive ability in a population.
• Actions of Microbial Control Agents: Alter membrane permeability, denature proteins, or damage DNA/RNA.
• Physical Methods of Microbial Control: Heat, filtration, radiation, or desiccation.

Microbial Genetics

• DNA Replication: Prokaryotic: initiation, elongation, termination, and steps involved in eukaryotic DNA replication.
• Transcription: DNA to mRNA using RNA polymerase.
• Translation: mRNA to polypeptides using ribosomes.

Biotechnology

• Recombinant DNA (rDNA): Combining DNA from different sources to create genetic modifications.

Cloning Methods

• Restriction Enzymes : cut DNA at specific sequences. PCR : amplifies specific DNA sequences.
• Gel Electrophoresis: Separates DNA fragments by size.
• Southern Blotting: Transfers DNA from gel to membrane for detection.
• DNA Structure : Double helix, antiparallel strands, and base pairing (A-T, G-C).
• DNA Replication: Semi-conservative process involving helicase, DNA polymerase, etc.

Classification of Microorganisms

• Domains: Bacteria, Archaea, Eukarya.
• Biochemical Tests: Identify metabolic characteristics.
• Serology: Detects antigens or antibodies (e.g., ELISA, Western blotting).
• DNA Fingerprinting: Compares DNA patterns for identification.
• Cladograms: Visual representations of evolutionary relationships.

Chemotherapy

• Spectrum of activity: Broad or narrow spectrum.
• Mode of action: Inhibit cell wall synthesis, disrupt cell membranes, inhibit protein synthesis, inhibit nucleic acid synthesis, or antimetabolites.

Prokaryotes

• Proteobacteria: Largest bacterial phylum. Includes important examples like Escherichia coli, Rhizobium, Rickettsia, Burkholderia, Neisseria, and Pseudomonas.
• Other bacterial classes, like Spirochetes,Bacteroidetes, and Fungi & Protozoa.

Viruses

• Structure: Nucleic acid (DNA or RNA), protein capsid, sometimes an envelope.
• Growth: Viral multiplication requires a host cell.
• Types: Lytic cycle, and lysogenic cycle (prophage).
• SARS-CoV-2: Details about COVID-19, its effects, and pathogenesis, including how it infects cells and replicates itself.

Epidemiology

• Classifying infectious diseases: Acute, chronic, latent, communicable, non-communicable.
• Development of disease: Incubation, prodromal, illness, decline, and convalescence.
• Transmission: Direct or indirect contact, vector-borne, fomites.
• Vectors: Biological, mechanical.
• Nosocomial infections: Hospital-acquired infections.

Pathogenicity

• Adherence: Microbes attaching via adhesins (e.g., fimbriae).
• ID50: Infectious dose necessary to infect 50% of the population, related to pathogen's virulence or ability to cause disease.
• Exotoxins: Secreted proteins; trigger inflammation and have specific targets (e.g., neurotoxins, enterotoxins).
• Endotoxins: Lipid A components of the outer membrane of Gram-negative bacteria that trigger inflammation.
• Parenteral Route: Pathogens that bypass barriers (injections, wounds)