microlab midterms

streaking method

simplest method for bacterial isolation

> involves bacterial sample mixed with melted agar medium

size of microbial colonies

<1mm - 3cm

color of microbial colonies

absolutely white

various degrees of pigmentation

texture of microbial colonies

determined by touching the colony with a needle

smooth texture

buttery

dry texture

granular

mucoid texture

slimy

appearance of microbial colonies are judged by the manner in which the

colony refracts light

appearances (5)

• clear

• glistening

• dense

• opaque

• translucent

form

shape of colony

• circular

• irregular

• filamentous

• rhizoid

elevation (4)

degree where colony growth is raised

• flat

• raised

• convex

• umbonate

margin (5)

shape of edge / margin of colony

• entire

• undulate

• fusiform

• curled

• lobate

bacteria grow in collections of cells on agar called

colonies

can be an aid in identification of microorganisms

colony morphology

method of transferring growing organisms from a pure culture to a sterile medium

inoculum

method of preventing UNWANTED microorganisms from gaining access to pure culture (gate)

aseptic technique

purposeful intro of bacteria into a sterile growth medium

inoculation

how to know if the material is sterile

when it has no living organisms present

presence of unwanted microorganisms

contamination

practices that prevent contamination of growth media

aseptic techniques

basic bacterial reqs in nutrition

• water

• carbon

• nitrogen

streaking method

most widely used method for isolating pure culture

spreading method

mixed culture or microorganisms is not diluted in melted agar medium

> diluted in a series of tubes containing water or saline

used to dissolve materials to be transported across cytoplasmic membrane

water

required for construction of all organic molecules & source of energy

carbon

photoautotrophs

energy source: use radiant energy or light

chemotrophs

source of energy: microbes use chemical compunds:

• iron

• sulfur

autotrophs

sole source of energy: use inorganic carbon (co2)

heterotrophs

source of energy: use organic substances

obligate

source of energy: living form that strictly requires host

nitrogen

obtained from inorganic source & organic source

> many organisms use nitrogen gas by nitrogen fixation to produce ammonia

inorganic source

nitrogen gas (n2)

nitrate (no3)

nitrite (no2)

ammonia (nh3)

required in small amounts

iron

sulfur

phosphorus

optimal growth temperature

temp range at which the highest rate of reproduction occurs

psychrophiles otr:

5-30ºc

mesophiles otr:

30-60ºc

thermophiles otr:

45-90ºc

most bacteria are pathogens that require

37ºc

temp: psychrophiles

some will exist below 0ºc if liquid’s available

• oceans

• ref

• freezers

temperature: mesophiles

most human flora & pathogens

temperature: thermophiles

• hot springs

• effluents from laundromat

• deep ocean thermal vents

oxygen

required for aerobic respiration & energy production

oxygen: obligate aerobic

grow only when oxygen is available

oxygen: obligate anaerobic

grow in the absence of oxygen

oxygen: facultative anaerobe

require oxygen but exhibit maximal growth rates at reduced oxygen concentrations

halophiles

bacteria that specifically require NaCl for growth

moderates

grow best at 3% NaCl solution

> many ocean dwelling bacteria

extreme

grow well at NaCl concentrations > 15% salt lakes, pickle barrels

in salinity, halophiles growing within salt lakes often

turn the water pink

• Great Salt Lake, Utah

in salinity, staphy are salt tolerant up to

concentrations of 10% NaCl

• grown on surface of skin

bacterial pH reqs

microbes have different optimum pH reqs

acidophiles

some bacteria can grow in acid substrates

neutrophiles

most microbes prefer a pH near neutrality

alkalinophiles

microbes grow in very alkaline substrates

osmotic pressure

exerted on plasma m. due to solute concentrations of a solution

osmotolerant

bacteria able to grow in solutions w high solute concentration

hydrostatic pressure

exerted by the weight of water

barotolerant

bacteria able to grow at deep ocean depths

photosynthetic microorganisms

require light at min. lvls of intensity & proper wavelengths

• exposure to light causes death of some

• some bacteria will produce pigments, protecting them from exposure to lethal effects of light

ultraviolet radiation is harmful to

dna of bacteria

• causes abnormalities in cell growth & division

oxygen: microaerophiles

microbes that utilize low oxygen tension

serial dilution method

developed by joseph lister

> known for isolation & culturing of bacteria

> isolation technique, specific microorganism isolated form mixed culture

Biological Safety Levels

series of protection relegated to autoclave-related activities

> individual safeguards designed to protect lab personnel

BSL-1

lowest biosafety lab

> microbes not known to consistently cause disease in immunocompetent adult humans

risk lvl: minimal

BSL-2

microbes pose moderate potential hazard to ppl

> personnel are expected to take greater care

risk lvl: moderate

BSL-3

yellow fever, west nile virus

bacteria: yersinia pestis

agents: indigenous/exotic microbes that may cause serious or potentially lethal disease via inhalation

risk lvl: serious

BSL-4

pose a high risk of aerosol-transmitted lab infections & life threatening disease

e.g. Ebola & Margburg viruses

risk lvl: high

Centers for Disease Control & Prevention (CDC)

sets BSL lab lvls