Appunti VERIFICATO
BIOLOGIA DEI MICRORGANISMI
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- **Microorganisms Overview:**
- Defined by their microscopic size, primarily unicellular.
- Classified into prokaryotic (bacteria, archaea) and eukaryotic (fungi, algae, protozoa).
- Viruses are obligate intracellular parasites, not considered living cells.
- Historical context: Pasteur disproved spontaneous generation; Koch's postulates defined disease causality; Woese's three-domain classification.
- **Bacterial Cell Structure:**
- **External Structures:** Capsules (adhesion, anti-opsonization), Fimbriae/Pili (adhesion, conjugation), Flagella (motility, chemotaxis).
- **Cell Wall:** Composed of peptidoglycan (NAM, NAG). Gram-positive bacteria have a thick peptidoglycan layer with teichoic acids; Gram-negative bacteria have a thinner peptidoglycan layer, an outer membrane with LPS (Lipid A, polysaccharides), and porins. Mycoplasmas lack cell walls. Archaea have diverse cell wall types, some with pseudopeptidoglycan.
- **Cytoplasmic Membrane:** Lipid bilayer (phospholipids, no cholesterol in bacteria, some opanoids), proteins. Functions include permeability, energy generation, and chemotaxis.
- **Internal Structures:** Nucleoid (bacterial chromosome), Plasmids (extrachromosomal DNA, carry advantageous genes), Ribosomes (protein synthesis), Inclusions (storage for energy, gas vacuoles for buoyancy, magnetosomes for orientation).
- **Viral Biology:**
- **Structure:** Virions consist of genetic material (DNA or RNA, single or double-stranded, linear or circular) encased in a protein capsid (helical or icosahedral symmetry). Some viruses also have an outer lipid envelope.
- **Replication Cycle:** Involves adsorption, penetration, uncoating, genome replication, protein synthesis, assembly, and release (via lysis or budding).
- **Baltimore Classification:** Groups viruses based on their nucleic acid type and replication strategy to produce mRNA.
- **Bacteriophages:** Engage in lytic cycles (host cell destruction) or lysogenic cycles (phage DNA integration into host chromosome). They are mediators of transduction.
- **Microbial Metabolism & Ecology:**
- **Carbon Sources:** Autotrophs (CO2), Heterotrophs (organic compounds).
- **Energy Sources:** Chemotrophs (chemical oxidation), Phototrophs (light).
- **Oxygen Requirements:** Aerobes, Anaerobes, Facultative anaerobes, Microaerophiles, Aerotolerant.
- **Environmental Factors:** Temperature (psychrophiles, mesophiles, thermophiles, hyperthermophiles), pH, and pressure (barotolerant, barophilic) influence growth.
- **Microbial Growth & Identification:**
- **Growth Curve:** Lag, exponential (log), stationary, and death phases describe population dynamics.
- **Culture Media:** Liquid (broths) or solid (agar); minimal or complex; enriched, selective, or differential for specific purposes.
- **Identification Techniques:** Gram staining, Ziehl-Nielsen staining, FAME analysis, DNA-DNA hybridization, 16S rRNA sequencing, and metagenomics.
- **Microbial Interactions & Pathogenesis:**
- **Interactions:** Include synergy, competition, commensalism, mutualism, and parasitism.
- **Virulence Factors:** Adhesins, enzymes, and toxins (exotoxins: cytotoxic, neurotoxic, enterotoxic; endotoxins: LPS Lipid A in Gram-negatives) contribute to pathogenicity.
- **Antimicrobial Strategies:** Sterilization (complete removal), disinfection (partial removal of pathogens). Antibiotics exert selective toxicity by targeting unique microbial processes.
- **Antibiotic Resistance:** Can be natural or acquired through mutation or horizontal gene transfer (transformation, conjugation via plasmids, transduction via phages). Mechanisms include target modification, enzymatic inactivation, efflux pumps, and reduced permeability.
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