Microbio exam 3

Binary Fission

most common form of bacterial reproduction

steps of binary fission

1) Growth of cell size and increase in cell components
2) Replication of DNA
3) Division of the cytoplasm (cytokinesis)
4) septum formation and division of daughter cells

Z ring assembly

FtsZ assembles Z ring to form divisome

Generation Time

time it takes to double a population

Lag Phase

intense activity preparing for population growth, but no increase in population

log/exponential phase

Phase of growth during which cells grow and multiply at the maximum rate.

Stationary Phase

there is a plateau in the numbers

Death/decline phase

exponential decrease in number of living bacterial cells

Measuring Growth

Quantifying populations size is important for determining infection, contamination of water or food supply, etc.

Direct Microscopic Cell Count

-Cells are counted under a microscope
-Known volume is transferred to a calibrated slide (Petroff-Hausser chamber) and cells are manually counted)
-Cannot distinguish between live vs dead

Fluorescence Staining

-cells are counted under a microscope or flow cytometer
-red stain binds to damaged cells to indicate dead cells

Viable Plate Counts

Count of viable cells; samples are diluted and grown on solid media
- results expressed in colony forming units per vol

Membrane Filtration Technique

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

Most Probable Number

A statistical method of measuring bacterial growth used when samples contain too few organisms to give reliable measures by the plate count method

Alternate Patterns of Growth

some divide unsymmetrically or fragmentation

Biofilm Formation

micro ecosystem of one or more species that can provide protection

Biofilm structure

clusters of microbes in a matrix

Extracellular Polymeric Substance

recreated by organisms in the biofilm
- hydrated polysaccharide gel with other macromolecules and channels

Steps of Biofilm Formation

attachment, colonization, development, active dispersal

Respiration Terminology

oxygen requirements can be used to group microbes

Obligate Aerobes

have to have oxygen
- Micrococcus Luteus

Obligate anaerobes

can not grow in the presence of O2
- Bacteriodes spp

facultative anaerobes

can live with or without oxygen but prefer oxygen
- Staphylococcus spp

aerotolerant anaerobes

can deal with oxygen but don't have any use for it
- lactobacillus spp

Microaerophiles

"goldilocks" only want a little amount of oxygen
- campylobacter spp

Fluid Thigolycolate Medium (FTM)

Low percentage agar tube that has a gradient of oxygen

Aerotolerance

is determined by location of growth

pH Requirement

PH can effect efficacy of macromolecules; most vulnerable are proteins
-microbes can prefer acidic (

Optimal Growth pH

most favorable pH for growth

Minimal growth pH

lowest pH for growth

Maximum growth pH

highest pH for growth.

Neutrophiles

pH of around 7

Acidophiles

ph < 5.5

Alkaliphiles

pH of around 8-10.5

Mesophiles

20-45 C

Psychrotrophs

4-20 C

Psychrophiles

< 0 C

Thermophiles

50-80 C

Hyperthermophiles

80- 110 C some survive at 121 C

Halophiles

salt/soulte lovers; found in oceans

Halotolerant

tolerate high salt; salt marshes where high solutes aren't present all the time

Barophiles

required high atmospheric pressure
- found at the bottom of ocean
- largely uncultivable; not much known
- also can be thermo or hyperthermophiles

Photoautotrophs

cyanobacteria and green sulfurs

Photoheterotrophs

purple nonsulfers

Enriched Media

contains growth factors, vitamins, and other essential nutrients to promote the growth of fastidious organisms

Fastidious Organisms

Can not make certain nutrients

Chemically defined medium

complete chemically composition known

Complex Medium

Contains extracts and digest of yeasts, meats or plants; exact composition not known

Selective Media

inhibit unwanted, promote growth of organism of interest

Enrichment Cultures

promote growth of desired organism; only represents a fraction present

Differential Media

Distinguish colonies of bacteria by color change

Main Goal

reduce microbial load and reduce infection or contamination

Biological Safety Levels

Levels of cleanliness assigned to labs
- CDC, NIH, WHO established the 4 levels

BSL-1

very little risk
- sink for handwashing and door to close off lab
- agents that do not cause infection in healthy adults
-nonpathogenic E.coli and B.subtillis

BSL-2

pose moderate risk; restrictive access

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
•Indigenous or "exotic" pathogens
•M. tuberculosis, B. anthracis

•West Nile Virus, HIV

BSL-4

•Most dangerous; often 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
•"Exotic" pathogens; Ebola and Marburg viruses
•(only 13 in USA)

critical

must be sterile; items used inside the body (ie. sterile tissue or bloodstream)
-ex: surgical instruments, catheters, IV fluids

Semicrtical

do not require high-level sterilization; totems might contact non-sterile tissue (e.g. gut) but not penetrate tissue.
ex: GI endoscope, respiratory therapy equipment

Noncritical

Do not require sterilization; items contact but do not penetrate intact skin

ex: stethoscopes, bed linens, blood pressure cuffs

Sterilization

complete killing or removal of all microbes from famine --> inanimate objects

Methods of sterilization

heat, filtration, pressure, chemical (sterilants)

ascetic technique

used to prevent sterile environment from being contaminated

Disinfectant

inactivation/kill of microbes on frites

ex: vinegar and bleach

- some microbes may not be inactivated disinfection does not equal sterile

Antiseptic

acts on microbes but not organism/tissue

ex: hydrogen peroxide, rubbing alcohol

-decreasing of microbial load (amt of microbes)

Sanitization

reduce microbial load on fomite

- usually with heat or chemical

degerming

reduce microbial load on living tissue

- usually mechanical- washing hands, wiping with paper towel

- may be used in combination with disinfectant to maximize microbial reduction

- cides

to kill

- static

stop growth

microbial death curve

measures of percentage of kill

decimal reduction time

how much time it takes to kill 90% of population

heat sterilization

oldest and most common

- alters membranes and or denatures proteins

thermal death point

lowest temp that will kill in 10 minutes

thermal death time

length of time to kill at a certain temperature

dry heat

aka incineration; direct application of high heat (>250 C)

- Bunsen burner

- bacteria incinerator

moist heat

application of high temp liquid/vapor

- beneficial b/c penetrates cells better than dry ex: autoclave

autoclave

raise temp of temp water above boiling point ( ~ 121 C) by raising pressure to 15 psi

- kills viruses and endospores

gravity

uses steam to push out air

prevacuum

vacuums out air first

- require periodic QC to check functionality:

autoclave tape, spore tests, disc tubes, recorders

refrigerating and freezing

usually not sterilization method but static

- slows metabolism but will grow when temps are raised

- ultra low temps (- 80 C) can be used for preservation

pressure sterilization

high pressure used in food industry

- hyperbaric chambers can be used to treat infections