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B6W2L3 Bacterial cell biology
Terms in this set (66)
Prevalence of helicobacter pylori
40% of people worldwide
What are the symptoms of helicobacter pylori infection?
-gastric and duodenal ulcers
-class 1 carcinogen
How large is the genome sequence of Helicobacter pylori?
What problems occur with drug-resistant bacterial infections?
-increasing antibiotic resistance
-difficult to treat
-increased morbidity and mortality
What is the prevalence of extensively drug resistant tuberculosis?
Global spread, except for Greenland and a few countries in latin America and Africa
What is the evolution of drug resistant tuberculosis?
-TB > MDR TB (1990) > XDR TB (2006) > TDR TB (2009)
-difficult to treat and pressing problem in developing countries
What is the survival rate of XDR TB and HIV coinfection?
60 days from time of diagnosis
What is the prevalence of tuberculosis?
-1/3 infected worldwide
-leading cause of morbidity and mortality in developing countries
How fast is the rate of spread of tuberculosis?
A carrier can infect 10-15 people each year via infected respiratory droplets
-drug resistant TB found in 1990s
-resistant to 1st-line drugs such as isoniazid and rifampin
-drug resistant TB found in 2006
-resistant to 1st-line drugs (isoniazid and rifampin) and 2nd line therapeutics (FQ and AMK/KM/CP)
What are the implications of drug resistant bacteria?
can no longer blindly rely on antibiotics to cure infectious disease
-drug resistant TB found in 2009
-resistant to both 1st line and 2nd line drugs
What drugs are used to treat TB?
Size of E. coli
How do bacteria replicate?
Where do bacteria live?
Soil, aquatic, other organisms
What parts of the human body contain normal flora?
How many bacteria are in the normal flora of the gut?
-10^11 bacteria/mL in the proximal colon
-500-1000 different species
-1 kg of bacteria in large intestine
-totality of microbe in an environment (normal flora)
-Different parts of body have different compositions of bacteria
How many bacteria normal coexist inside humans?
-2,600 species of bacteria, only 80 pathogenic
-10:1 bacteria: human cells
-3,300,000 bacterial genes vs. 20,000 human genes
-humans are extensively colonized
How do normal human flora affect the human body?
-nutrition and vitamin synthesis (vitamin K)
-impacts gut architecture
-exclude pathogens to competition
-may cause disease: IBD, endocarditis, acne
-may have a role in obesity > lean vs. obese have different bacterial profiles
When do we acquire bacteria?
-vaginal microbiota changes before delivery > inoculation of infant microbiota
-from birth, everything you touch > contributes to microbiota
What are 3 types of relationships that bacteria can have with humans?
-commensal (no harm or benefit)
What categories of relationships do normal microbiota have with humans?
-usually commensal or symbiotic
-some, such as S. aureus, S. epidermidis, E. faecalis, and S. pneumonia, can turn pathogenic
-presence of possibly pathogenic bacteria during disease doesn't mean it's the culprit
How many types of bacteria in dental plaque?
-commonly cause periodontal disease
-can get into bloodstream and cause endocarditis
6 factors of bacterial pathogenesis
-attachment and surface colonization
-always multifactorial, many virulence factors
What are virulence factors?
Secreted molecules (toxins) or cell surface molecules (adhesins) that contribute to pathogenesis of bacteria/viruses/etc
-can also include strain, group, serotypes, etc.
What is the procedure for a gram stain?
-stain with crystal violet
-add potassium iodide to fix dye
-decolorize with alcohol (affects only gram negative bacteria)
-counterstain with safranin (red)
-gram + bacteria appear dark blue/purple (crystal violet + potassium iodide)
-gram (-) bacteria appear pink/red (safranin)
Structure of anthrax
-gram-positive rod shaped bacilli
-causes rapidly progressing fulminant disease
outer collection of membranes in bacteria
What are the 3 targets of antibiotics?
-ribosomes and protein synthesis
Goal in designing antibiotics
-want selective toxicity against bacteria
-avoid resistance, bacteria can't mutate to protect against antibiotic and retain normal function
What is the structure of gram negative bacteria?
Cytoplasmic membrane > thin peptidoglycan cell wall > thick outer membrane
What is the structure of the genetic material of bacteria?
-circular bacterial chromosome
-no nuclear membrane
-stored in supercoiled form
enzyme that unwinds supercoiled DNA
-enzyme that supercoils DNA
-important for DNA replication, transcription, etc.
How large is the E. coli genome?
-1 mm in length if physically stretched out
What is the mechanism of action of quinolones?
inhibit DNA gyrase and topoisomerase 4 > prevent supercoiling
What are 2 quinolones?
What is the structure of gram positive bacteria?
Cytoplasmic membrane (phospholipid bilayer) > thick, extensive peptidoglycan cell wall
What are some important proteins in peptidoglycan?
-lipoteichoic acid (LTA)
-teichoic acid (TA)
What is the function of the cytoplasmic membrane of bacteria?
-e- transport and ATP synthesis
-transport of nutrient, etc
What is the function of peptidoglycan?
-Protect cytoplasmic membrane (from osmotic lysis, etc)
-responsible for cell shape
-Gm(+) restricts diffusion
-some resistance to antibodies in Gm (+) bacteria
What is the structure of peptidoglycan?
-repeated disaccharide unit linked by peptide cross bridges
-repeating glycan chain of N-Acetyl-glucosamine and N-acetyl-muramic acid, b1,4 linkage
-linked to tetrapeptide (A-E-DAP/K-A)
-DAP(-)/K(+) have free amines that can link to COOH on the tail A of another chain (peptide cross bridge)
-transpeptidases can also called penicillin binding proteins
What is the effect of lysozymes on peptidoglycan?
-Cleaves the B1,4 linkages in the glycan chains
-important in mucosal defense against bacterial colonization
Cross-linking in peptidoglycan
-tetrapeptide of A-E-DAP-A attached to N-acetyl-muramic-acid
-the enzyme transpeptidase can attach DAP to an alanine on another tetrapeptide
What is the mechanism of B-lactams?
-inhibit transpeptidases that catalyze peptide cross bridges between glycan chains
-prevent building of cell wall > bacteriostatic mechanism
What is the structure of the outer membrane of gram negative bacteria?
-contains trimeric porins for nutrient/Abx transport
-inner layer of phospholipids
-outer layer of lipopolysaccharides
What do porins have to do with antibiotics?
-able to uptake small molecules, including Abx
-can acquire mutations to prevent passage of Abx > resistance
What is the structure of lipopolysaccharides (LPS)?
-conserved lipid A base embedded in outer membrane
-moderately conserved core polysaccharide
-O antigen (sugar) repeats
-O antigen very variable and result in different serotypes
-2 glucosamine molecules (often phosphorylated) linked to long-chain fatty acids
-recognized by immune system as PAMPS for Gm (-) bacteria
What are examples of PAMPS?
Lipid A, TA, LTA, CW, etc
What are PAMPS?
-pathogen associated molecular patterns
-conserved moieties on prokaryotes (and viruses) that are recognized by our immune system as pathogenic
-recognized by toll-like receptors, etc
-activate innate immunity
What are the dangers of high levels of PAMPS?
at high levels, can overstimulate immunity > fever, hypotension, DIC, shock, death
What are the characteristics of bacillus anthracis spores?
-highly resistant to heat, dessication, freezing, radiation, etc
What are bacterial capsules?
-extracellular globs of polysaccharide around bacteria
-found on both gram (+)/(-) bacteria
-often confers antiphagocytic virulence factors
-impact immunity and vaccination
Structure of bacterial pili
-thin, hair-like appendages
-composed of polymerized piliin
Function of bacterial pili
-adherence and attachment to host
-determines tissue tropism
-sex pili for DNA transfer
Secretion systems in bacteria
transfer peptides from inside a cell to outside
-type 3 secretion system
-composed of a cytoplasmic basal body with an ATPase, a transmembrane shaft, and a protruding needle
-needle inserts pore/penetrates eukaryotic plasma membrane to allow for release of a bacterial "effector" into cytoplasm of host cells
-found on salmonella, E. coli
-avoids antibodies, immune evasion
What secretion system is used by cholera?
Cholera uses a type 2 secretion system (T2SS) to release cholera toxin
space between plasma/outer membrane and peptidoglycan in bacteria
What is the selective advantage of a pathogen causing disease?
-disperse organism to environment to amplify
-sometimes evolutionary accident of bacteria
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