mic 206 midterm

water, energy source, carbon source, nitrogen, minerals, & vitamins

6 nutrients needs for microbes to grow

chemotrophs

break chemical bonds to derive energy

phototrophs

energy derived from sunlight via photosynthetic pigments

heterotrophs

obtain organic carbon (carbohydrates, fats, proteins, DNA, amino acids)

autotrophs

obtain carbon by fixing CO2

where is sterilization of media preparation performed?

in an autoclave

why is sterilization of media preparation performed in an autoclave?

because it kills all microbes

aseptic technique

A procedure performed under sterile conditions.

complex media

exact chemical composition is unknown; wide range of growth

defined media

exact chemical composition is known; usually composed of pure chemicals off the shelf; narrow range of growth

selective medium

has a component(s) added to it which will inhibit or prevent growth of certain types or species of bacteria and/or promote the growth of desired species

differential medium

a component(s) is added that allows a researcher to distinguish between different types of bacteria based on some observable trait (color) in their pattern of growth on the medium

pure culture

contains only one species or strain

quadrant streak

a technique, in order to obtain isolated colonies

isolated colony

the idea that one bacterial cell will divide into a visible colony

bacterial colony

a visible group of bacteria growing on a solid medium

colony growth from single bacteria cell

1 →2 →4 →8 →16 →32 →64 →128 →256

purpose of quadrant streak

to isolate colonies to generate a pure culture for identification

Colony Morphology: Elevation

raised, convex, flat, umbonate, , plateau. raised spreading edge, flat raised margin, growth into media

colony morphology: margin

smooth entire, rhizoid, irregular (erose), lobate, flamentous

colony morphology: shape

round, irregular, punctiform (tiny, pinpoint)

colony morphology: texture

moist, mucoid, dry

colony morphology: pigment production

opaque, translucent, shiny, dull

name 5 subcategories of colony morphology

shape, margin, elevation, texture, pigment production

name 4 environmental growth factors discussed in lab

oxygen, temperature, osmotic pressure, pH

Obligate (strict) anaerobes

Microorganism for which oxygen is lethal; requires complete absence of oxygen.

obligate (strict) aerobes

Microorganisms that require oxygen to grow and survive.

facultative anaerobes

can live with or without oxygen

Microaerophilic

prefers less oxygen than the levels found in the atmosphere (10%)

aerotolerant anaerobes

do not utilize oxygen but can survive and grow in its presence

anaerobic jar important components

gas pack, palladium pellets, indicator strips

indicator strips methylene blue

blue: presence of O2

clear: absence of O2

indicator strips resazurin

pink: presence of O2

clear: absence of O2

anaerobic jar gas pack

Packet that contains sodium borohydride, sodium bicarbonate, and citric acid

generates H2 and CO2

anerobic jar palladium pellets

convert H2 and O2 to H2O

candle jar

lowers O2 levels ; great for microaerophiles

fluid thyoglycollate medium

-can determine the growth characteristics of a microorganism based on its oxygen requirements

-The reducing agent thioglycolic acid creates an anaerobic environment deeper in the tube, allowing anaerobic bacteria in the absence of oxygen.

-Methylene blue/Resazurinis a REDOX indicator that turns pink in the presence of oxygen and colorless when the oxygen is absent.

why are environmental conditions important for enzymes?

-Each microbe has an optimum condition for growth and a range in which less growth is possible.

-Physiological processes within microbes are governed by protein catalysts known as enzymes to run all biochemical reactions in the cell.

-Outside of the optimum condition, the activity of the enzyme will be lower, thus lowering the growth of the microbe.

what happens to enzymes outside of optimum conditions?

proteins will misfold causing cell death

thermal energy

plays a crucial role in the movement of molecules, structure, and function of a cell's proteins and membranes

Psycophiles

-5C-20C

mesophiles

20C-40C

thermophiles

40C-80C

extreme thermophiles

80C-121C

osmotic pressure

the force water exerts on the semi-permeable membrane (plasma membrane) surrounding the cell. This force is due to a difference in solute concentration on one side of the membrane compared to the other side, thus resulting in water movement

isotonic environment

• Solute concentration is the same on the inside as out

• Equal movement of solute and water

hypotonic environment (most environments)

• High Solute inside the cell

• Water will move into the cell and solute moves out

• Results in cell swelling

hypertonic environment

• High Solute OUTSIDE the cell

• Water will move out of the cell and solute moves in

• Results in plasmolysis and cell death

• Preserve food

• Halophiles

microscopic counts

• One, two, three...

• Impractical,inaccurate

standard plate count

make serial dilutions to reduce number of microbes to a countable number

optical density

uses light scattering to determine size of a microbial population

absorbance is the same as

optical density

OD 600

wavelength of spectrophotometer

are there units for OD?

no

pH

measure of hydrogen ion (H+) concentration or the degree to which a substance is acidic or basic.

acidophiles

grow in acidic environments below 5.5

alkaliphiles

grow optimally at pH above 8.5

neutrophiles

organisms that prefer pH levels between 5.5 and 8.5

thymine dimer

When UV hits a pair of thymine, they abnormally bond into a covalent bond between the two thymine molecules

exposure to UV radiation pathway to cell death

exposure to UV radiation, formation of thymine dimers, mutations, cell death

effects of low UV to thymine dimers

no damage

serial dilution factor

total dilution from tube to tube

plating factor

volume transferred from the tube to plate

total dilution

(serial dilution factor of the tube to be plated) + (plating factor)

CFU

colony forming unit

Original cell density formula

(colonies counted) / (volume put onto the plate)(dilution factor of the broth)

antibiotics

Low molecular weight compounds made by microbes or chemically synthesized, which inhibit or kill other microorganisms.

sterilants

destroy all microorganisms

sanitizers

agents used to lower the levels of bacterial cells

Bacteriostatic

an agent that inhibits the growth of bacteria

Bactericidal

an agent that kills bacterial cells

zone of inhibition

area around a disk where no growth has occurred due to the agent in the disk

four classes of antibiotics

-cell wall synthesis inhibitors (beta-lactam antibiotics)

-protein synthesis inhibitors

-RNA synthesis inhibitors

-DNA synthesis inhibitors

Spectrum of Antibiotic Activity

describes the range of types of microorganisms it can kill or inhibit

tetracylines

broad spectrum antibiotics

Amoxicillin

extended spectrum antibiotics; penicillin derivative

polymyxins

narrow spectrum antibiotics

penicillin is effective against Gram- _________ bacteria

positive

Kirby-Bauer Test

antibiotic sensitivity testing is used to determine the susceptibility of bacteria to various antibiotics

Kirby-Bauer method

Uses Mueller-Hinton agar because it is a non-selective, non-differential medium and allows the antibiotic to diffuse from the disk into the media easily.

disinfectants

substances that are applied to non-living objects to destroy microorganisms that are living on the objects

antiseptics

antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection