Unit IV: Bacteria Flashcards
Structural Features of Bacteria (5)
Cell Wall (peptidoglycan)
Capsule (polysaccharides, increased virulence)
Glycocalyx (biofilms for adherence, protection)
Flagella (H antigens)
Pili
Different Membrane Compositions
Gram Positive: thicker peptidoglycan layer without a second cell wall, teichoic and lipoteichoic acids
Gram Negative: thin peptidoglycan w/ second lipid bilayer including lipopolysaccharides
Peptidoglycan
n-acetylglucosamine and n-acteylmuramic acid subunits w/ varying sidechains
Can be cross-linked or covalently linked to phospholipids
Lipopolysaccharides
Lipid A, core polysaccharide, O side chian
Teichoic Acid
covalently linked to peptidoglycan and extend beyond layer, involved in adherence
4 phases of bacterial growth phase
Lagging Phase: adjustment phase of new enzyme production.
Exponential phase: maximal cell division for resources available, growth proportional to # of cells (constant doubling time
Stationary Phase: essential nutrients consumed, toxic metabolites produced, growth slows
Death Phase: number of viable bacteria decreases via autolysis
5 Classifications of Bacteria
Aerobes: require oxygen, cannot ferment
Anaerobes: ferment and are killed in oxygen
Indifferent: ferment w/ or w/o oxygen
Facultative: respires w/ O2, ferments w/o
Microaerobic: grow best at low O2, but can grow w/o
Heterotrphic vs autotrophic
Heterotrophs require any form of carbon, Autotrophs require CO2 as source of carbon
Fermentation
use organic compounds as electron donors and acceptors with no net oxidation of substrates in both aerobic and anaerobic conditions
Respiration
ATP generated through electron transport with O2 as final electron acceptor.
Energy currencies
Higher cells generate energy currency in the form of ATP and electrochemical gradients.
Currency can also include electron holders (NADPH)
Antimicrobial targets (4)
Cell wall, inner and outer plasma membranes, protein synthesis, nucelic acid synthesis
3 Sources of Bacterial Genetic Diversity
Spontaneous Mutation
Recombination
Acquisition of New DNA
Spontaneous Mutation
PMs, insertions, or deletions
Very rare but can give growth advantage
(ABX resistance Pseudomonas/Myco and Strep Pyogenes invasiveness)
Recombination
site-specific or homologous recombination
occurs w/in an organism or between organisms
Includes phase variation through promoter changes
Acquisition of New DNA
Incorporation of free DNA into chromosome or plasmid
Transposons, bacteriophage, plasmid acquisition, pathogenicity islands
Transformation
Naked DNA from lysing cells taken up by bacteria in correct growth phase in correct environment
Most common between similar species
Tranduction
gene transfer via bacteriophage, bacterial DNA taken up by bacteriophage and injected into new bacterium
Conjugation
F plasmid contains information for conjugation (replication, sex pilus, conjugative transfer, integration), DNA replicated into recipient cell and then incorporated into plasmid or genome
Temperate Phage
Cause lysogenic response in addition to lytic response. Creates prophage that suppresses viral gene expression via repressor protein until it experiences stress.
Lysogenic Conversion
Prophage in lysogenic phase obtains new phenotype
Microbial Toxins
macromolecular products that alter cell structure or function. Manifest as symptoms of disease or contribute to pathogenesis w/o specific signs
Include bacterial proteins and LPS of gram negatives
Steps to determine toxin is pathogenic
Toxin causes same symptoms as bacteria
Antitoxin prevents symptoms
Virulence corresponds to amount of toxin
Nontoxigenic mutants are a-virulent
Mechanisms of action for microbial toxins (5)
Facilitating Spread of Microbes Damage Cellular Membrane Stimulating Cytokine Production Inhibiting Protein Synthesis Modifying Intracellular Signaling