Basic Bacteriology Flashcards
targets of antibiotics that prokaryotes have that eukaryotes don’t
ribosomes & cell wall
pathogen associated molecular patterns
highly conserved motifs in the cell wall of bacteria, recognized by Pathogen Recognition Receptors
*can be targeted with antibiotics
bacterial cell wall
*chemical composition: peptidoglycan is a sugar backbone with peptide side chains, cross-linked by transpeptidase
-composed largely of NAG and NAM sugars, connected by beta-glycosidic bonds
-CROSS-LINKED by amino acids (L and D symmetry) to form SHEETS of peptidoglycan layers
*function: netlike structure gives rigid support, protects against osmotic pressure damage
gram positive cell wall
* THICK peptidoglycan layer above cytoplasmic membrane
-traps and binds gram stain (PURPLE means gram positive)
-small molecules can diffuse
*rich in techoic acid and LIPOTECHOIC acid, vital to cell survival
liPOteichoic acids = gram POsitive
techoic acid & lipotechoic acid
unique to gram POSITIVE cell wall
-help to anchor the cell wall
liPOtechoic acid = gram POsitive
gram negative cell wall
*THIN
*3 layers:
1. thin outer membrane, rich in LPS and porin molecules
2. periplasmic space (a pool for enzymes such as beta-lactamases)
3. cytoplasmic membrane
periplasmic space
*unique to gram negative
*contains thin peptidoglycan and a pool for enzymes (like beta lactamases)
LPS in the gram neg outer membrane
3 covalently linked components:
1. outer carbohydrate chains of 1-50 oligosaccharide units
2. core polysaccharide that is water soluble
3. lipid A (ENDOTOXIN) - stimulates TLR4 receptors when bacteria lyse
gram staining exceptions
- Treponema, Leptospira: spirochetes, too thin to be visualized
- Mycobacteria: acid-fast organisms; cell wall has high lipid content (mycolic acid)
- Mycoplasma, Ureaplasma: no cell wall
- Legionella, Rickettsia, Chlamydia, Bartonella, Anaplasma, Ehrlichia: primarily intracellular
mnemonic: These Little Microbes May Unfortunately Lack Real Color But Are Everywhere
classification of bacteria based on shape/morphology
-coccus
-coccobacillus
-vibrio (comma-shaped)
-bacillus (rod)
-spirochetes
obligate aerobes
-need oxygen
-use glycolysis, Krebs cycle, and ETC
-have enzymes to handle ROS
facultative anaerobes
-prefer oxygen, but can use anaerobic fermentation as an alternative energy source
-have enzymes to handle ROS
obligate ANaerobes
-lack enzymes needed to handle oxygen
-use anaerobic fermentation that produces gas such as gangrene
superoxide dismutase
dispose superoxide radical to hydrogen peroxide
catalase-positive organisms
*catalase degrades hydrogen peroxide (H2O2) to water and bubbles of O2
people with CGD (NADPH oxidase deficiency) have recurrent infections with catalase-positive organisms
catalase test: strep vs. staph
*staph is catalase (+)
*strep is catalase (-)
enzyme deficiency in chronic granulomatous disease (CGD)
*lack of NADPH oxidase
*patients susceptible to catalase (+) organisms
spores
*ONLY GRAM POSITIVE bacteria
-metabolically dormant
-thick protective covering composed of multiple membranes, peptidoglycan mesh, keratin-like protein, and outer exporium
-resistant to heat, cold, drying, and chemical agents
examples of spore-forming species
Bacillus and Clostridium
recall: ONLY GRAM + microbes can form spores
- Bacillus: B anthracis (anthrax); B cereus (food poisoning)
- Clostridium: C botulinum (botulism), C difficile, C perfringes, C tetani
obligate intracellular organisms
-cannot live outside host
-steal ATP
facultative intracellular organisms
-invade host and resist lysosome when it is advantageous
-evade host defenses
-ex: listeria monocytogenes
coagulase
*converts fibrinogen to fibrin (to cause coagulation)
*bacteria use clotting to evade host immune defenses
*often used to differentiate types of Staph
*cloudy/clot at the bottom = positive
urease
*converts urea to ammonia and CO2, raising pH
*organisms grown in buffered broth with pH indicators as a test
*PINK = POSITIVE; yellow = negative
virulence factors
-molecules and structures that enhance bacterial effectiveness
-improve entry into host and formation of colonies
-aid in host immune system evasion or immunosuppression
-assist bacteria in acquiring nutrients
