lesson four Flashcards
endotoxin
- part of the cell structure-anchored in outer membrane
- lipid molecule
- released from the cell when the cell dies and disintegrates
exotoxin
- produced by the bacterial cells, not a part of the cell strucuture
- released from cell in many ways, damages other cells
- protein
- three functional types: enterotoxin, neurotoxin and cytotoxin
bacterial metabolism
sum total of all chemical reactions within an organism
- catabolic: release energy
anabolic: store energy
- catabolism: chemical reactions that release energy, breakdown of organic compounds
anabolism
chemical reactions that require energy, building of complex organinc molecules from simpler compounds (stores ATP)
reaction rates
temperature dependent,
higher the temp, higher the reaction rate
- drawback: high temperature may kill cells (denaturation of proteins)
enzymes
Large protein molecules (biological catalysts)
* Make chemical reactions happen 100,000,000 X faster
* Substrate specific (what they work on)
* Have suffix “ase”
* May need cofactors – e.g. metal ions like zinc, magnesium
* Recyclable, unchanged during reaction
what cellular controls affect function of enzymes
- temp
- pH
- saturation
- salt concentration
- inhibitors (mercury, silver)
energy production
- most microbes use carbohydrates as number 1 source for production of energy
- glucose the most common nutrient source
Two processes by which glucose is used
a. cellular respiration (aerobic, anaerobic)
b. fermentation
both processes need ATP to run
energy sources other than glucose
- lipids: broken down by lipases
protiens: broken down by proteases
physchrophiles
-5 to +15 C
pyschrotrophs
20-30 C (listeria)
mesophiles
25-45 C
thermophiles
45-70 C
hyperthermophiles
70-110 C
Listeria monocytogenes
- gram +, non-spore forming
- facultatively anaerobic, motile
- wide temp range: 3-42 C
- wide pH range: 5.5-9.5
- grow in high concentrations of salt (10%)
listeria growth/survival
- survives in low temp, high acidity and salt concentrations
listeria habitat
- soil, animal intestine through contaminated feed
listeria symptoms in animals
CNS infections, goats, cattle (circling disease)
listeria symptoms in man
- food borne disease
- CNS infections/death
- abortion
how listeria causes disease
ingestion of contaminated food
- invasion of bacteria through gastric epithelial cells
- gene ActA codes for this protein- an “invasin”
- grows in macrophages, destroys the phagolysosome with listerolysin
- intracellular and extracellular growth
listeria clinical infection
meningitis, encephalitis, septicemia
-incubation period may be as long as 2 months
-elderly and immunocompromised at risk
mortality of CNS infections 20-50%
pregnant women can cause abortion or stillbirth
listeria transmission
- fecal-oral
- foods implicated as a vehicle of infections: coleslaw, soft unpasteurized cheeses, turkey wieners, cold cuts, mushrooms and prepackaged salads, milk
listeria epidemiology
- hard to track because of long incubation period
- responsible for 1700 cases of invasive disease
fatal in about 1/3 of cases even with antibiotics
listeria treatment
antibiotics for treatment but you have to diagnose the infection in time
physical factors: pH
5-8 usual activity zone for human pathogens
physical factors: osmotic pressure
- isotonic solution is balenced
- hypotonic: cell swells
- hypertonic: cell shrinks, plasmolysis
gaseous requirements for growth
- strict aerobe: needs oxygen
- facultative anaerobe: can be exposed to some oxygen
- strict anaerobe: no oxygen
- aerotolerant anaerobe: can have oxygen or not
- microaerophile: small amounts of oxygen
chemical factors
- sources of C,N,O,S,P and trace elements
- sources of organic growth factors (yeast extract in artificial media, cysteine or other amino acids)
environmental factors: intracellular
- evade WBC
- need antibiotics that penetrate host cell membranes
- some cannot be grown on artificial media
- may be dependent on host cell for energy
bacterial reproduction
binary fission
bacterial generation time
- dependent on media and growth conditions
- aerobic bacteria usually grow faster than anaerobic (higher productions of ATP)
bacterial growth kinetics
lag phase, log phase, stationary phase, death phase
biofilms
- bacteria like to live in communities
dynamic: bacteria are not stuck, they can leave the biofilm and start a new focus of infection - slimy matrix with polysaccharides, proteins, DNA, bacteria
- antibiotics ineffective against biofilms
how to grow bacteria in the lab
- nutrient material
- agar: complex polysaccharide from algae for solid culture
- bacteria grow in “colonies” – piles of bacteria where the original bacteria was placed on the surface of the agar filled plate
hemolysis
breakdown of blood cells in agar plates
- used for presumptive bacterial identification of streptococcus species
Alpha
partial breakdown of RBC (greening) around and under colony
Beta
total breakdown (clearing) of RBC around and under colony
gamma
no breakdown of RBC around or under colony
complex media
used for growing human pathogens
differential media
ingredients in media allow us to tentatively identify bacteria into major groups
