Microbiology Exam 1 Review

Cheatsheet Content

### Microbes in Our Lives - **Impact:** Disease, food production (fermentation), decomposition, nutrient cycling, biotechnology (insulin production), bioremediation. ### Major Groups & Domains - **Domains:** - **Bacteria:** Prokaryotic, peptidoglycan cell walls, diverse metabolism. - **Archaea:** Prokaryotic, no peptidoglycan, extremophiles. - **Eukarya:** Eukaryotic, includes Fungi, Protozoa, Algae, Multicellular Parasites. - **Microbial Groups:** - **Bacteria:** Unicellular prokaryotes. - **Archaea:** Unicellular prokaryotes, often in extreme environments. - **Fungi:** Eukaryotes (yeasts, molds), chitin cell walls, decomposers. - **Protozoa:** Unicellular eukaryotes, motile, diverse nutrition. - **Algae:** Eukaryotes, photosynthetic, diverse forms. - **Viruses:** Acellular, obligate intracellular parasites (DNA or RNA core, protein coat). - **Multicellular Animal Parasites:** Eukaryotes (helminths), not strictly microorganisms but relevant clinically. ### History of Microbiology - **Van Leeuwenhoek:** First to observe "animalcules" (microbes) with microscopes. - **Spontaneous Generation vs. Biogenesis:** - **Spontaneous Generation:** Life arises from non-living matter. - **Biogenesis:** Living cells arise only from pre-existing living cells. - **Pasteur:** - Disproved spontaneous generation with swan-neck flask experiments. - Fermentation (microbes cause spoilage). - Pasteurization (heating to kill spoilage microbes). - Vaccines (rabies, anthrax). - **Lister:** Pioneered antiseptic surgery (phenol to sterilize instruments and wounds). - **Koch's Postulates:** Criteria to establish that a specific microbe causes a specific disease. 1. Microbe present in all disease cases, absent in healthy. 2. Isolate microbe and grow in pure culture. 3. Introduce pure culture into healthy host, cause disease. 4. Re-isolate same microbe from now-diseased host. - **Jenner:** Developed first vaccine (smallpox) using cowpox. - **Winogradsky & Beijerinck:** Pioneered environmental microbiology, discovered chemolithotrophy and nitrogen fixation. - **Germ Theory of Disease:** Microorganisms cause infectious diseases. ### Acellular Infectious Agents - **Viruses:** DNA or RNA core, protein coat (capsid), replicate only inside living host cells. - **Viroids:** Short pieces of naked RNA, typically plant pathogens. - **Prions:** Infectious proteins, cause neurological diseases (e.g., mad cow disease). ### Bacterial Cell Shapes & Arrangements - **Shapes:** - **Coccus:** Spherical (e.g., Staphylococcus, Streptococcus). - **Bacillus:** Rod-shaped (e.g., E. coli, Bacillus). - **Spirillum:** Spiral, rigid (e.g., Spirillum minus). - **Spirochete:** Spiral, flexible (e.g., Treponema pallidum). - **Vibrio:** Comma-shaped (e.g., Vibrio cholerae). - **Arrangements:** - **Diplo-:** Pairs (diplococci, diplobacilli). - **Strepto-:** Chains (streptococci, streptobacilli). - **Staphylo-:** Grape-like clusters (staphylococci). - **Tetrads:** Groups of four. - **Sarcinae:** Cube-like groups of eight. ### Bacterial External Structures - **Glycocalyx:** Outer viscous layer (capsule or slime layer). - **Function:** Adherence, protection against phagocytosis, desiccation. - **Flagella:** Long, filamentous appendages for motility. - **Structure:** Filament, hook, basal body. - **Types:** Monotrichous (one), Amphitrichous (at both ends), Lophotrichous (tuft at one end), Peritrichous (all over surface). - **Chemotaxis:** Movement towards or away from chemical stimuli (runs and tumbles). - **Axial Filaments (Endoflagella):** Found in spirochetes, internal flagella wrapped around cell body, causing corkscrew motion. - **Fimbriae:** Short, hair-like appendages for adherence to surfaces and other cells. - **Pili:** Longer than fimbriae, involved in twitching motility and DNA transfer (conjugation, sex pilus). ### Bacterial Cell Wall - **Peptidoglycan (Murein):** Primary component of bacterial cell walls. - **Structure:** Polymer of alternating NAG (N-acetylglucosamine) and NAM (N-acetylmuramic acid) disaccharide units, cross-linked by polypeptides. - **Gram-Positive Cell Wall:** - Thick layer of peptidoglycan. - Contains teichoic acids and lipoteichoic acids. - **Gram Stain:** Retains crystal violet-iodine complex, appears purple. - **Gram-Negative Cell Wall:** - Thin layer of peptidoglycan. - Outer membrane (lipopolysaccharide - LPS, lipoproteins, phospholipids). - LPS contains Lipid A (endotoxin). - Periplasmic space between plasma membrane and outer membrane. - **Gram Stain:** Does not retain crystal violet, decolorizes, takes up safranin counterstain, appears pink/red. - **Archaea Cell Wall:** Lacks peptidoglycan; may have pseudomurein (pseudopeptidoglycan) or S-layers (surface-layer proteins). ### Prokaryotic Plasma Membrane - **Structure:** Phospholipid bilayer with embedded proteins (fluid mosaic model). - **Chemistry:** Primarily phospholipids and proteins, no sterols (except Mycoplasma). - **Functions:** - Selective permeability (regulates passage of substances). - Site of ATP production (electron transport chain). - Nutrient processing. - Enzyme activity. ### Bacterial Internal Structures - **Nuclear Area (Nucleoid):** Contains the bacterial chromosome (circular DNA). No nuclear envelope. - **Ribosomes:** Sites of protein synthesis (70S in prokaryotes). - **Plasmids:** Small, circular, extrachromosomal DNA molecules; carry non-essential genes (e.g., antibiotic resistance). - **Inclusions:** Reserve deposits of various substances (e.g., metachromatic granules, polysaccharide granules, lipid inclusions, magnetosomes). - **Endospores:** Dormant, highly resistant structures formed by some Gram-positive bacteria (e.g., Bacillus, Clostridium) during nutrient depletion. - **Sporulation:** Process of endospore formation. - **Germination:** Return of endospore to vegetative (active) state. - **Function:** Survival under adverse conditions, not reproduction. ### Microbial Nutrition - **Macronutrients:** Required in large amounts (C, H, O, N, P, S, K, Mg, Ca, Fe). - **Micronutrients (Trace Elements):** Required in small amounts (e.g., Zn, Mo, Mn, Cu). - **Transport Mechanisms:** - **Simple Diffusion:** Movement of molecules from high to low concentration, no energy, no carrier. - **Osmosis:** Movement of water across a selectively permeable membrane. - **Facilitated Diffusion:** Movement from high to low concentration, requires carrier proteins, no energy. - **Active Transport:** Movement against concentration gradient, requires energy (ATP), requires carrier proteins. - **Group Translocation:** Substance is chemically altered during transport across the membrane, requires energy. - **Culture Media:** - **Chemically Defined Media:** Exact chemical composition is known. - **Complex Media:** Exact chemical composition varies (e.g., yeast extract, peptone). - **Selective Media:** Suppresses growth of unwanted microbes and encourages growth of desired ones. - **Differential Media:** Distinguishes between different types of microbes based on their growth characteristics. - **Enrichment Media:** Favors the growth of a particular (fastidious) microorganism that is present in small numbers.