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Bellas Microbiology Exam II With 100% Verified
Solutions | Updated & Verified | 2024
Prokaryote Characteristics - ✔✔- No membrane surrounding their DNA; no nucleus
- Lack organelles - internal membrane-bound structures
- Small; ~1.0 μm in diameter (RBC ~10 μm)
- Simple structure Prokaryote Types - ✔✔Bacteria & Archaea Prokaryote External Structures (3) - ✔✔Glycocalyces, Flagella and Fimbrae & Pilli Gycocalyx - ✔✔"Sugar cage" - Polysaccharides
- Capsule & Slime Layer Capsule - ✔✔Hard glycocalyx with consistent structure around prokaryote Slime Layer - ✔✔Inconsistent outsider layer loosely attached to cell surface; water soluble; protects cells form druing out; sticky layer that allows prokaryotes to attache to surfaces Flagella - ✔✔Long, whiplike structures that extend beyond surface of cell and is responsible for movement
Flagella Structure - ✔✔- Composed of filament, hook, and basal body
- Flagellin protein (filament) arranged in chains and forms helix around hollow core
- Base of filament inserts into hook Flagella Function - ✔✔- Rotation propels bacterium through environment
- Rotation can be clockwise or counterclockwise; quickly reversible
- Prokaryotes move in response to stimuli (taxis) Runs - ✔✔movement of cell in singel direction for some time; increase with favorable stimuli - chemotaxis or phototaxis Tumbles - ✔✔- abrupt, random, changes in direction; increase with unfavorable stimuli: negative chemotaxis - away fr chemical or negative phototaxis - away fr sunlight
- no steering mechanism Fimbrae & Pili - ✔✔Nonmotile extensions of prokaryotes Fimbrae - ✔✔- Sticky, proteinaceous, bristlelike projections
- Used by bacteria to adhere to one another, to hosts, and to substances in environment
- May be hundreds per cell and are shorter than flagella
- Serve an import function in biofilms
- Have a outer membrane composed of phospholipids, channel proteins (porins), and lipopolysaccharide (LPS) --> this part is extremely toxic Lipopolysaccharide (LPS) - ✔✔- Union of lipid with sugar
- Also known as endotoxin (lipopolysaccharide)
- Lipid portion known as lipid A (extremely poisonous)
- Released from dead cells when cell wall disintegrates
- May trigger fever, vasodilation, inflammation, shock, and blood clotting
- Can be released when antimicrobial drugs kill bacteria Archael Cell Walls - ✔✔- Do not have peptidoglycan
- Cell walls contain variety of specialized polysaccharides and proteins Prokaryotic Cytoplasmic Membrane - ✔✔Phospholipid Bilayer --> lipids and associated proteins Prokaryotic Membrane Function - ✔✔- Controls passage of substances into and out of the cell; selectively permeable
- Functions in energy production - bacteria need ATP, but bacteria has no mitochondria, therefore, ATP produced by cytoplasmic membrane
- Harvests light energy in photosynthetic prokaryotes --> no chloroplasts, therefore occurs w/in plasma membrane Control across membrane - ✔✔- Naturally impermeable to most substances - middle is pure lipid, so no polar materials can pass thru
- Proteins allow substances to cross membrane
- Occurs by passive or active processes Passive Processes - ✔✔- Diffusion - nonpolar molecules
- Facilitated Diffusion- proteins assist as nonspecific channel protein for polar molecules (shielded from lipid environment)
- Osmosis (water movement) -->Isotonic (same salt) Solution - no change -->Hypertonic (high salt) Solution - shrivels as water moves out of cell -->Hypotonic Solution - swell and burs as water moves in. Active Processes - ✔✔- Active Transport - utilizes carrier proteins and expends ATP -->Uniport - one substance moves one way (one in) -->Antiport - one moves in while another moves out --> Symporti - two move the same way (often coupled; both in)
- Group Translocation - substance chemically modified during transport; doesn't utilize ATP -->Maintains a concentration gradient and electrical gradient; collectively known as electrochemical gradient - Chemicals concentrated on one side of the membrane or the other; Voltage exists across the membrane Prokaryotic Cytoplasm - ✔✔- Cytosol - liquid portion of cytoplasm
- Inclusions - may include reserve deposits of chemicals
- Ribosomes - sites of protein synthesis
Plant Cell Walls Composition - ✔✔Cellulose Fungal Cell Walls - ✔✔Cellulose, chitin &/or glucomannan Algal Cell Walls - ✔✔Cellulose, agar, cargeenan, cilicates, algin, calcium carbonate or combination of these Eukaryotic Cell Membranes - ✔✔- All eukaryotic cells have cell membrane
- Is a fluid mosaic of phospholipids and proteins
- Contains steroid lipids to help maintain fluidity - stabilize membranes
- Controls movement into and out of cell - use diffusion, facilitated diffusion, osmosis, and active transport -->Endocytosis; phagocytosis if solid substance and pinocytosis if liquid substance (not all eukaryotes) --> Exocytosis enables substances to be exported from cell removes waste Microbe Nutrients - Based on - ✔✔- Source of Carbon
- Chemical or Light use as a source of energy Definitions as Source of Carbon - ✔✔Autotrophs vs. Heterotrophs Autotrophs - ✔✔Uses an inorganic carbon source (not hooked up to carbon)
Heterotrophs - ✔✔catabolizing reduced organic molecules (proteins, carbohydrates, amino acids and fatty acids) Definitions as Chemical or Light Use - ✔✔Chemotrophs (acquire energy from redox reactions involving inorganic/organic chemicals vs. Phototrophs (use light as energy source) Four Basic Groups of Organisms - ✔✔- Photoautotrophs
- Chemoautotrophs
- Photoheterotrophs
- Chemoheterotrophs Four Toxic Forms of Oxygen - ✔✔- Singlet Oxygen
- Superoxide Radicals
- Peroxide Anion
- Hydroxyl Radical
-->Aerobes also use antioxidants such as vitamins C and E to protect against toxic oxygen products Singlet Oxygen - ✔✔- molecular oxygen with electrons boosted to higher energy state; when electrons move back to stable state, release excess energy
- occurs during photosynthesis so phototropic organisms have carotenoids that remove the excess energy of singlet oxygen
Aerobes - ✔✔undergo aerobic respiration Anaerobes - ✔✔do not use aerobic metabolism Facultative Anaerobes - ✔✔can maintain life via fermentation or anaerobic respiration or by aerobic respiration- if give O2 will use it; will switch to fermentation in absence of O Aerotolerant anaerobes - ✔✔do not use aerobic metabolism but have some enzymes that detoxify oxygen's poisonous forms
- O2 doesn't hurt/help Microaerophiles - ✔✔aerobes that require oxygen levels from 2-10% and have a limited ability to detoxify hydrogen peroxide and superoxide radicals - small amounts of O2 (air has ~20% O2) Nitrogen Requirements - ✔✔- Anabolism often ceases due to insufficient nitrogen needed for proteins and nucleotides
- Nitrogen acquired from organic and inorganic nutrients; also, all cells recycle nitrogen from amino acids and nucleotides
- The reduction of nitrogen gas to ammonia (nitrogen fixation) by certain bacteria is essential to life on Earth because nitrogen is made available in a usable form Other Chemical Requirementso - ✔✔- Phosphorus - required for phospholipid membranes, DNA, RNA, ATP and some proteins
- Sulfur structure - component of sulf-containing amino acids, disulfide bonds critical to tertiary structure of proteins and in vitamins (thiamin and biotin)
- Trace elements - usually found in sufficient quantities in tap water (magnesium, iron, etc.) Physical Requirements for Growth - ✔✔Temperature (ideal), pH (ideal), osmolarity Neutrophiles - ✔✔most bacteria --> grow best in a narrow range around neutral pH (6.5-7.5) Acidophiles - ✔✔fungi & bacteria that grow best in acidic habitats --> acidic waste products can help preserve foods by preventing further microbial growth Alkalinophiles - ✔✔live in alkaline soils and water up to pH 11.5 (basic) Hydrostatic Pressure - ✔✔- Water exerts pressure in proportion to its depth -- or very add'l 10m of depth, water pressure increases 1 atm
- Organisms that live under extreme pressure are barophiles Culturing Microorganisms - ✔✔Inoculum instroduced into medium (broth or solid) Obtaining Pure Cultures - ✔✔Cultures composed of cells arising from a single progenitor --> termed a CFU Two Common Isolation Techniques - ✔✔Streak Plates & Pour Plates
Stationary - ✔✔nutrient depletion accumulation of wastes (chemostat) - runs out of food or waste products produced suppresses growth Death - ✔✔Cells die faster than produced Methods for Measuring Microbial Growth - ✔✔Direct Vs. Indirect Direct Method - ✔✔Standard Plate count, Viable Plate counts, Membrane Filtration, Microscopic counts, Electronic counters, Most Probable Number Standard Plate Count - ✔✔count bacteria on plate Viable Plate Count - ✔✔when bacteria is too concentrated, take series of solutions (serial solutions) and based on dilution compute calculation to determine # Membrane Filtration - ✔✔when bacteria is too dilute, filter sample and culture from membrane Microscopic Counts - ✔✔utilizes slides with grids; calculate knowing precise volume of fluid w/in slides; can't distinguish b/t dead & live cells Indirect Method - ✔✔Metabolic Activity, Dry Weight, Turbidity
Metabolic Activity - ✔✔may know that bacteria produces vit K, then measure how much Vit K produced Dry Weight - ✔✔weigh organism; more weight more bacteria Turbidity - ✔✔cloudiness; use spectrophotometer to read cloudiness; sends light thru sample and measures % light that passes through; quick and efficient Symbiosis - ✔✔to live together Symbiotic relationships - ✔✔the relationship b/t microorganisim & host Types of Symbotic Relationships - ✔✔Mutualism, Commensalism, Parasitism Mutalism - ✔✔beneficial - Microbe & Infected Organism both benefit (ex. Bacteria in colon) Commensalism - ✔✔beneficial - Microbe & Infected Organism both benefit (ex. Bacteria in colon) Parasitsim - ✔✔Microbe benefits, infected organism is harmed—causes disease (tuberculosis bacter in human lung) Types of Normal Microbiota (2) - ✔✔Resident & Transient Resident Microbiota - ✔✔- Part of normal microbiota throughout life (always there)
- Found on viruses (attachment proteins) and many bacteria (adhesins)
- Surface lipoproteins or glycoproteins, called ligands, that bind host cell receptors
- Interaction of ligand with host receptor can determine specificity for host cells
- Ability to change or block the ligand or its receptor can prevent infection
- Inability to make attachment proteins or adhesins renders the microorganisms avirulent Manifestations of Disease - ✔✔Symptoms, Signs, Syndrome Symptoms - ✔✔subjective characteristics of disease felt only by the patient Signs - ✔✔objective manifestations of disease that can be observed or measured by others Syndrome - ✔✔group of symptoms and signs that characterize a disease or abnormal condition Asymptomatic (clinical) Infections - ✔✔infections lack symptoms but may still have signs of infection --> "I feel fine", but may have a disease Exceptions to Koch's Postulates - ✔✔- Using Koch's postulates is not feasible in all cases -->Some pathogens can't be cultured in the laboratory -->Some diseases are caused by a combination of pathogens and other cofactors -->Ethical considerations prevent applying postulates to pathogens requiring a human host Difficulties in satisfying Koch's postulates -->Diseases that can be caused by >1 pathogen
-->Pathogens that are ignored as potential causes of disease Virulence Factors of Infectious Disease - ✔✔Pathogenicity & Virulence Pathogenicity - ✔✔ability of a microorganism to cause disease (can make mildly/deathly sick) Virulence - ✔✔- degree of pathogenicity - virulence factors contribute to an organisms virulence -->Adhesion factors -->Extracellular enzymes -->Toxins -->Antiphagocytic factors Extracellular Enzymes - ✔✔- Enzymes secreted by the pathogen
- Dissolve structural chemicals in the body
- Help pathogen maintain infection, invade further, and avoid body defenses Toxins - ✔✔- Chemicals produced by the pathogen
- Harm tissues or trigger host immune responses that cause damage
- Toxemia refers to toxins in the bloodstream that are carried beyond the site of infection
- In blood, circulating in body - systemic effects Two Types of Toxins - ✔✔Exotoxins (made by body) & Endotoxins (part of bacteria)
Incidence - ✔✔number of new cases of a disease in a given area during a given period of time Prevalence - ✔✔number of total cases of a disease in a given area during a given period of time Nosocomial Infectons - ✔✔Infections acquired while in a health care facility Types of nosocomial infections - ✔✔- Exogenous- pathogen acquired from the health care environment
- Endogenous- pathogen arise from normal microbiota due to factors within the health care setting
- Iatrogenic - results from modern medical procedures
