BIOL 2460 Exam 3

4 basic steps of bacterial reproduction

1. growth of cell size & increase in cell components

2. replication of DNA

3. division of the cytoplasm (cytokineses)

4. septum formation and division of daughter cells

generation time

time takes to double population

E. coli generation time

20 minutes

B. subtilis generation time

120 min

S. aureus generation time

30 min.

M.tuberculosis generation time

15-20 hrs

closed cultures have ___ resources

infinite

culture density

the number of cells per unit volume

lag phase

inoculum cells added and adjust to culture medium; no change in population

log/exponential phase

binary fission occurs; cell replication > cell death

stationary phase

resources become depleted; cell replication = cell death

death phase

endospores can form cell replication < cell death

ways to measure growth

microscopic cell count, flourescent staining for alive & dead cells, coulter count, viable cell count, optical density

direct microscopic cell count

cells are counted under a microscope

fluorescence staining

cells are counted under a microscope or flow cytometer

- red stains binds to damaged cells to indicate dead cells

Coulter counter

detects electrical resistance change due to cell denisty

- does not differentiate live/dead

viable plate counts

count of viable cells; samples are diluted and grown on solid media

results expressed in ___ ___ ___ per volume (CFU/ml)

colony forming units

membrane filtration technique

known vol. filtered through a membrane; membrane plated and colonies counted

most probable number (MPN)

statistical method used when counts are very low (<30 CFU/ml)

- water and food testing

biofilm formation

micro ecosystem of one or more species that can provide protection

forms mainly in liquid environment

biofilm structure

clusters of microbes in a matrix

extracellular polymeric substances

secreted by organisms in the biolfilm

hydrated polysaccharide gel with other macromolecules and channels

biofilm formation step 1

attachment of planktonic cells to a substrate

biofilm formation step 2

attachment becomes irreversible; cells become sessile

biofilm formation step 3

growth & division on substrate

biofilm formation step 4

production of extracellular polymeric substance (EPS)

biofilm formation step 5

attachment of secondary colonizers & dispersion of microbes to new location

biofilm formation is formed through ____ ____, or cell to cell communication

quorum sensing

normal biota in lungs is good or bad?

good

plaque formation on teeth is good or bad?

bad

main factors that affect growth

oxygen levels

pH

temperature

osmotic pressure

barometric pressure

is o2 always needed or tolerated?

no, many environments do not have 02

optimal oxygen concentration

ideal concentration of O2

minimum permissive oxygen concentration

The lowest concentration of oxygen that allows growth

maximum permissive oxygen concentration

The highest tolerated concentration of oxygen

obligate

must have

facultative

can do both

aerotolerant

tolerant

aerobe

prefers O2

anaerobe

prefers others than O2

fluid thioglycolate medium

low percentage agar tube has a gradient of oxygen

aerotolerance

determined by location of growth

anerobic jars or anaerobic chambers _____ o2

remove

example of obligate aerobes

micrococcus luteus

example of obligate anaerobe

bacteroides spp.

example of facultative anaerobe

Staphylococcus aureus

example of aerotolerant anaerobe

Lactobacillus

example of microaerophiles

Campylobacter jejuni

optimal growth pH

most favorable pH for growth

minimum growth pH

lowest pH for growth

maximum growth pH

highest pH for growth

mesophiles temp

20-45 C

psychrotrophs temp

4-20 C

psychrophiles temp

<0 C

Thermophiles temp

50-80

hyperthermophiles temp

80 to >121

halophiles

salt loving, oceans

halotolerant

tolerant high salt, salt marshes where high solutes aren't present all the time

barophiles

require high atmospheric pressure

photoautotrophs

cyanobacteria and green sulfurs

enriched media

contains growth factors, vitamins, and other essentials to promote growth

fastidious organisms

cannot make certain nutrients

chemically defined medium

complete chemical composition known

complex medium

contains extracts and digests of yeasts, meat, or plants; exact composition not known

selective media

inhibit unwanted, promote growth of organism of interest

enrichment culture

promote growth of desired organism; only represents a fraction present

differential media

distinguish colonies of bacteria by color change

sterilization

removal/killing of ALL microbes

Disinfection/Antisepsis

inactivation of microbes

sanitation/degerming

decreasing microbial load

example of BSL-1

nonpathogenic E.coli and B. subtilis

BSL-1

very little risk, sink for hand washing & door to close off lab, agents that do not cause infection in healthy adults.

BSL-2

pose moderate risk, restrictive access, PPE, self closing doors, eyewash station, autoclave or other sterilization method,

example of BSL-2

S.aureus & salmonella spp.

viruses like hepatitis, mumps and measels

BSL-3

potential to cause lethal infections by inhalation, bsl-2 plus respirator, bio safety cabinets, hands free wash sink, two sets of doors, directional air flow

example of bsl-3

M. tuberculosis & B. anthracis

west nile virus and HIV

BSL-4

most dangerous & fatal, bsl-3 plus full biohazard suit, change clothing on entry, shower on exit, decontaminate all material on exit, lab must have own air supply

example of bsl-4

ebola and marburg viruses

critical

must be sterile, items used inside the body

example of critical

sterile tissue, bloodstream, surgical instruments, catheters, IV fluids

semicritical

do not require high level sterilization, items might contact non-sterile tissue but do not penetrate tissue

example of semicritical

GI endoscope, respiratory therapy equipment

noncritical

do not require sterilization, items contact but do not penetrate

examples of noncritical

stethoscope, bed linens, blood pressure cuffs

complete killing or removal of all microbes from ____

fomite ( inanimate objects )

Methods of sterilization

heat, pressure, chemicals, filtration

___ _____ is used to prevent sterile environment from becoming contaminated

aseptic technique

disinfectant

inactivation/ kill of mircobes on fomites

antiseptic

acts on microbes but not organisms/tissue

examples of antiseptics

hydrogen peroxide and rubbing alcohol

sanitation

reduce microbial load on fomite

what is sanitation usually done with?

heat or chemicals

degerming

reduce microbial load on living tissue

what is an example of degerming

washing hands, wiping with paper towel

-cides

kill

-static

stop growth

degree of control can be observed with

microbial death curve

factors that affect success of control

length of exposure, concentration of agent, population level

decimal reduction time

how much time it takes to kill 90% of population