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HDID-test 2-blevins > Lecture 31 - Bacterial Growth and Physiology > Flashcards

Lecture 31 - Bacterial Growth and Physiology Flashcards

1
Q

Steps of Prokaryotic Cell Division

A
  • replication of the bacterial chromosome is initiated at the cytoplasmic membrane
  • the process triggers cell division
  • each daughter chromosome is anchored to a different portion of the membrane
  • binary fission
  • as the membrane grows, the daughter chromosomes are pulled apart
  • a septum (S) grows from opposite sides toward the center of the cell and divides that daughter bacteria into two cells
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2
Q

Cell Division (Complete) Requires …..

A
  • transpeptidases (like PBP -Penicillin Binding Proteins
  • along with other enzymes
  • incomplete cleavage yields linked chains (Streptococcus) or clusters (Staphylococcus)
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3
Q

Energy Sources

A

Phototroph - energy from light (the sun)

Chemotroph - energy from oxidation of organic/inorganic compounds

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4
Q

Electron Sources

A

Lithotrophs - reduced inorganic molecules

Organotrophs - organic molecules

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5
Q

Carbon Sources

A

Autotrophs - CO2 is principal bio-synthetic carbon source

Heterotrophs - reduced, preformed, organic molecules from other organisms

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6
Q

Obligate Aerobes

A
  • require oxygen (terminal electron acceptor)

- die without oxygen

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7
Q

Obligate Anaerobes

A
  • oxygen kills these

- they obtain energy (ATP) from fermentation

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8
Q

Facultative Anaerobes

A
  • capable of fermentation in presence of lack of oxygen
  • but still prefer oxygen
  • KEY = can switch btwn respiration and fermentation
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9
Q

Microaerophiles

A
  • can withstand very low levels of oxygen

- pneumococcus & strep pnuemonae

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10
Q

Why is oxygen toxic to anaerobes?

A
  • lack of SOD - super oxide dismutase
  • lack of catalase or peroxidase to decompose H2O2

**both super-oxide and H2O2 are toxic to bacteria

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11
Q

Thermophillic

A
  • optimum temp (55-75 C)
  • minimum temp (35-40 C)
  • thermaphillus aquaticus (Yellowstone)
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12
Q

Mespophilic

A
  • optimum temp (30-45 C)
  • minimum temp (10-15 C)
  • these inhabit humans often (pathogenic bugs)
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13
Q

Psychrophilic

A
  • Facultative (similar to mesophiles, but can grow slowly near 0 C)
  • obligate (optimum temp 15-18 C), killed above 20 C
  • in lakes in Antarctica
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14
Q

Typical Bacterial Growth Curve

A
  • lag phase
  • exponential phase
  • stationary phase
  • decline
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15
Q

Lag Phase

A
  • grow is slow at first
  • happens while bacteria get acclimated to food/nutrients of new habitat
  • biochem activity is high
  • bacteria store nutrients, synthesize enzymes & prepare for binary fission
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16
Q

Log Phase

A
  • once you have the metabolic machinery running
  • bacteria start multiplying exponentially
  • do this until nutrients run out
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17
Q

Stationary Phase

A
  • more bacteria competing for dwindling nutrients

- replicative growth stops and the number of bacteria stabilizes

18
Q

Decline Phase

A

-toxic waste products build up and the bugs may begin to die

19
Q

Generation Time (Doubling Time)

A
  • the generation time is the time interval required for the cells (or population of cells) to double in number
  • g = t/h

t- time interval (min, hr), n - number of generations (# times cell population doubles during time interval)

20
Q

How to quantify Doubling Time?

A
  • the pour plate
  • serial dilution method
  • plate after dilution
  • look at CFU’s (colony forming units)
  • can finally see population and count them, then backtrack to determine original population
21
Q

Aspesis

A

-the state of being free of microorganisms

22
Q

Sterilization

A

-inactivation or elimination of ALL viable organism and their spores

23
Q

Disinfection

A

-process of removing or killing MOST of the microorganisms on or in a material

24
Q

Sanitization

A

-a cleaning process which REDUCES pathogen levels to produce a healthy clean environment

25
Q

Germicide

A
  • substance that kills vegetative bacteria (bacteria that can divide) and SOME spores
  • attain disinfection but not sterilization
26
Q

Disinfectant

A
  • substance used on non-living objects to render them non-infectious
  • kills vegetative bacteria, fungi, viruses, but NO SPORES
27
Q

Antiseptic

A
  • substance used to prevent multiplication of microorganism when applied to living systems
  • antiseptic is BACTERIOSTATIC in action but not necessarily bactericidal
28
Q

Physical Sterilization/Disinfection

A
  • Autoclave
  • Hot Air Sterilization
  • Radiation (Gamma, Beta, X-ray sterilization)
  • Filtration Disinfection
  • Radiation (UV light)
29
Q

Autoclave

A
  • 15 lbs/sq inch pressure at 120C for 15-20 mins
  • sterilizes with moisture, microorganisms destroyed at lower temp than dry heat
  • method of choice if material is compatible
  • fast, least toxic, cheap, large spectrum
30
Q

Hot Air Sterilization

A
  • 160C for 1-4 hours

- sterilizes and used on materials that would be damaged by moist heat (gauze, dressings, powders)

31
Q

Filtration Disinfection

A

-via

32
Q

Radiation

A

-used on materials that would be destroyed by heat (petri dishes, gloves, syringes)

  • UV = Thymine Dimers (disinfects, but poor penetration)
  • Ionizing (gamma, beta, X-rays) = breaks DNA backbone and sterilizes
33
Q

Chemical Sterilization/Disinfection

A
  • Ethylene Oxide (C2H4O)
  • Alcohols
  • Halogens
34
Q

Ethylene Oxide (C2H4O)

A
  • sterilizes powerful alkylating agent
  • carcinogenic & explosive
  • used as low-temp sterilization for heat-labile materials & delicate instruments
35
Q

Alcohols

A
  • 60-90% ethyl and isopropyl
  • disrupts cellular membranes, solubilization of lipids, denatures prot. by acting as S-H functional group
  • problem = evaporate rapidly (need extended contact times)
  • ineffective against spores
36
Q

Halogens

A
  • Chlorine = 1:10 - good as disinfectant, but must be made fresh daily
  • Iodine = good as disinfectant and antiseptic
  • method of action - oxidizes microbial proteins
37
Q

Disinfecting the Skin

A
  • alcohol scrub better than soap and water
  • NEED SOAP for C.difficile
  • use of chlorohexidine alcohol for skin antisepsis, not povidone-iodine for surgical = significant reductions in hospital acquired infections
38
Q

Biofilm

A

-microbes that are:

  • attached to hydrated surface
  • embedded in polysaccharide slime
  • behave as community
  • demonstrate antibiotic resistance and resistance clearance by the host immune system
  • removed from the biofilm, the bacteria is sensitive to the antibiotic

-think splinters, teeth, knee replacement, etc.

39
Q

Biofilm Diseases

A
  • CF
  • endocarditis
  • osteomyelitis
  • chronic UTI
  • prostatitis
  • otitis media
  • dental infections
  • endophthalmitis
  • serious skin infections
  • indwelling medical device
40
Q

Significance of Biofilms

A
  • 65-80% of all infections are biofilm related
  • biofilm infection resolution = cut it out
  • antimicrobial agents dont work (100-1000x more resistant)
  • host immune response dont work

-$90 billion, 17 million infections/yr, 550,000 deaths/yr in United States alone

41
Q

Why are biofilms resistant to bacteria?

A
  • biofilms reduce antibiotic penetration
  • cells within a biofilm are very slow growing (DNA and protein synthesis inhibitors not effective)
  • cells within a biofilm express many stress response genes that resist antibiotic action
42
Q

Implications of Biofilms to Infectious Disease

A
  • inaccurate MIC/MBC (min inhibitory/bactericidal conc) prediction of bacterial populations
  • inaccurate CFU determination from clinical samples (ex. UTI)
  • viable but not cultureable
  • missing the nidus of infection

HDID-test 2-blevins (3 decks)

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