BIOL 2051 Lab Midterm

What makes up the Latin binomial name of an organism?

Genus name and species name

What is mandatory to wear during lab?

gloves and safety glasses

Complex medium

composed of digests of chemically undefined substances such as yeast and meat extracts or digests

Defined medium

a precise chemical composition is known

Broth

liquid medium

What is in solid medias?

agar

Plates

Solid media in petri dishes

Deeps

test tubes containing solid medium solidified in an upright position (anaerobic growth)

Slants

test tubes containing solid medium solidified at an angle (maintenance of stock cultures pf microorganisms)

Selective medium

a nutrient medium designed to favor growth of certain microbes and to inhibit undesirable competitors

Differential medium

provides a visible indication of a physiological characteristic of a microorganism

Phenyl ethyl alcohol agar (PEA)

selective only (gram positive organisms)

Mannitol salt agar (MSA)

both selective and differential (salt-tolerant and manitol fermentors change color)

Eosin methyl blue agar (EMB)

both selective and differential (gram negative bacteria and lactose fermenters take up dye)

Sterilization

the killing or removal of all living organisms and their viruses from a growth medium

Autoclave

a sealed device that allows the entrance of steam under pressure (121C/15 psi for 15 min - 1 hour)

Dry heat sterilization

direct flaming, kills by oxidation

Hot-air sterilization

items such as glassware sterilized by being placed in an oven at 170C for 2 hours

Filtration

a device with pores too small for the passage of microorganisms but large enough for passage of gases and liquids

Gas chemo-sterilizers

toxic gas (ex. ethylene oxide) is released in a sealed chamber for 2 hours

Cold-sterilization

sterilization that does not require heat (ex. ethylene oxide)

Electromagnetic radiation

microwaves, UV radiation, x-rays, gamma rays, and electrons

Ultraviolet radiation

causes damage to the DNA (thymine dimers), leading to the death of exposed organisms; can only sterilize exposed surfaces

Ionizing radiation

ions and other reactive molecules are produced and these reactive molecules can degrade or alter biopolymers such as DNA and proteins

What do microorganisms growing on solid culture medium form?

colonies

Colony morphology

the shape of the colony, the form of the colony margin, and the elevation and pigmentation of the colony

Contaminant

an unwanted organism which has been accidentally introduced into the culture

Molds are made of branching, intertwined, threadlike ________ forming a network called _________ that can grow beyond the colony observed on the agar surace.

hyphae; mycelium

What do you do with a plate with mold/fungal contamination?

leave the lid on the plate to prevent the release of spores into the air

What is the colony morphology of a microorganism dependent on?

the medium it is growing on

What in a medium affects colony morphology?

the amount of nutrients present; will affect size, shape, and color

Whole colony shape

round, irregular, rhizoid

Margin shape

smooth, lobate, filamentous

Elevation

convex, umbonate, flat

Optical properties

opaque, semi-translucent, translucent

Surface characteristics

dull, shiny, wrinkled, concentric, pigmentation

Aseptic technique

a procedure performed under sterile conditions

What type of sterilization is used in aseptic technique?

dry heat sterilization

What is a common way to isolate and maintain a microbial culture?

a streak plate

What portion of cells are you pulling into each quadrant?

approx. 10%

What is the purpose of a steak plate?

to dilute the number of cells in each quadrant so that by the final quadrant the cells can grow as an isolated colony

Inoculation

to introduce bacteria into a sterile growth medium

Confluent growth

bacteria that has been allowed to continuously grow

Pure culture

a culture containing a single kind of organism

Colony

a population of cells which arise from a single cell growing on a solid medium

How is a pure culture determined?

colony morphology and cellular morphology/structure through staining (simple or gram stain)

Subculturing

the transfer of a colony to a new plate to maintain cultures

What percent of cells are water by weight?

90%

What does staining cells do?

makes them more visible by providing contrast

Round shaped cellular morphology

cocci

Cocci in pairs

diplococci

Cocci in chains

streptococci

Cocci in groups of four

tetrads

Cocci in grapelike clusters

staphylococci

Rod-shaped cellular morphology

bacilli

Bacilli that remain attached after division

diplobacilli

Bacilli in chains

streptobacilli

Short oval cells

coccobacilli

Branched bacillus

filamentous

Spiral cellular morphology (helical shape)

spirilla

Incomplete spiral (curved rods)

vibrios

Spiral with an axial rod

spirochete

Spiral with irregular or variable shape

pleomorphic

Prosthecate cells

organisms that produce prosthecae, cellular appendages that increase cell surface area which helps transport nutrients into the cell

What do simple/direct stains use?

an aqueous or alcohol solution of a single basic dye

What is the difference between direct and indirect staining?

direct colors the microorganism while indirect colors the background

What is a gram stain?

a differential stain

Differential stains

use a combination of dyes to demonstrate a chemical or structural component of a cell

Gram positive cells

many layers of peptidoglycan, contain teichoic acids

Gram negative cells

few layers of peptidoglycan surrounded by an outer membrane (LPS)

Endospore

a specialized dormant structure that is commonly produced by certain gram-positive rods

When do endospores form?

when essential nutrients are depleted or when water is unavailable

Why are endospores important in the food industry?

they can survive heating, freezing, desiccation treatment by chemicals, and radiation; underprocessing of foods can be dangerous

Vegetative cell

a cell that can grow and divide under optimal conditions

Cryptobiotic state

no metabolic activities are occurring (ex. endospores)

Sporulation

to convert vegetative cells into a single endospore

Spore septum

the first stage of endospore formation, replicated chromosome and a small amount of cytoplasm are isolated

Forespore

a double-layered plasma membrane surrounding genetic material

Cortex

a peptidoglycan laid down between the two plasma membranes

Spore coat

formed by spore proteins around the outside of the structure, responsible for the resistance of the endospore to harsh chemicals

What are the three positions endospores may be located in?

central, terminal, subterminal

What protects the endospore DNA from damage?

small acid-soluble proteins and dipicolinic acid (found in the core along with DNA, RNA, ribosomes, and enzymes)

Outgrowth

process of returning a endospore back into a vegetative state (synthesis of DNA, RNA, and bacterial proteins)

Germination

a rapid process where endospore characteristics are no longer needed (dipicolinic acids are released)

What is different about the process of staining a endospore?

heat is used to force the primary stain into the endospores

What are the traits of mycobacterium?

aerobic, non-endospore forming, nonmotile, rod-shaped bacteria

Mycolic acids

a unique lipid component possessed by acid-fast positive bacteria, a group of complex branched-chain hydroxy lipids complexed to the peptidoglycan of the mycobacterial cell wall

What makes acid-fast cells difficult to stain?

mycolic acids

Why are Mycobacterium cells called acid-fast?

they resist decolorization

What is the colony morphology of Mycobacterium?

compact, wrinkled

Why is Mycobacterium’s colony morphology wrinkled?

the cell wall is hydrophobic, explains why the cell is slow growing since nutrients are impermeable

What makes Mycobacterium difficult to disperse in aqueous solutions?

surface lipids

What is used to disperse Mycobacterium cells instead of water?

egg albumin (has a high protein content)

Carbolfushsin

basic fuchsin dye and phenol

How does the dye penetrate a acid-fast stain?

phenol and heating (penetrates into the lipid of the cell)

What does a capsule consist of?

layers of polysaccharide or polypeptide-containing material which surround the cell wall of bacteria

When and why are capsules formed?

they are formed only by genetically capable bacteria in the presence of excess nutrients

Is a capsule a survival structure

it can be since it is a reserve energy store

What is the principle component of a capsule?

water (prevents dessiccation)

What are other functions of a capsule?

attachment (sticky)