BIO 120 EXAM #1

what is microbiology?

study of microorganisms like bacteria, viruses, fungi, and protozoa

why is microbiology important?

microorganisms can cause disease but also benefit food, medicine, nutrients, and ecosystems

what is pasteurization?

heating to reduce harmful microorganisms

does pasteurization kill every microorganism?

no, reduces harmful microorganisms but does not sterilize

what is a common example of pasteurization?

heating milk to reduce harmful bacteria

what is germ theory of disease?

microorganisms can cause specific diseases

what are koch's postulates used for?

show that a specific microorganism causes a specific disease

what is koch's first postulate?

microorganism found in diseased but not healthy individuals

what is koch's second postulate?

microorganism must be isolated and grown in pure culture

what is koch's third postulate?

isolated microorganism cause the same disease in a healthy host

what is koch's fourth postulate?

same microorganism isolated again from the infected host

what is the basic idea behind koch's postulates?

find the microorganism, isolate it, show it causes the disease, find it again

what is magnification?

how much larger an object appears

what is resolution?

ability to see two close objects as separate and clear

which is more important for seeing details, magnification or resolution?

resolution

can you have high magnification but poor resolution?

yes the image can be very large but still blurry

easy way to remember magnification vs. resolution?

magnification means bigger but resolution means clearer

what does a bright-field microscope do?

uses visible light to view specimens usually with stains

what does a specimen usually look like with bright-field microscopy?

a darker specimen against a bright background

what is bright-field microscopy commonly used for?

viewing stained bacteria and cells

what does a dark-field microscope show?

bright specimens against a dark background

when is dark-field microscopy useful?

for viewing thin organisms that are difficult to stain like spirochetes

easy way to remember dark-field?

dark background means bright organism

what is phase-contrast microscopy used for?

viewing living unstained cells

why is phase-contrast useful?

increases contrast to see living cells without staining

what does a fluorescence microscope use?

UV/short-wavelength light and fluorescent substances

what does a fluorescent specimen look like?

bright/glowing against a darker background

why is fluorescence microscopy useful?

identifies specific microorganisms or structures using fluorescent dyes/antibodies

what does SEM stand for?

scanning electron microscope

what does an SEM show?

the surface/exterior of a specimen

what kind of image does an SEM produce?

detailed 3D-looking image of the surface

how do you remember SEM?

s means surface

what does TEM stand for?

transmission electron microscope

what does a TEM show?

inside of a specimen at high magnification

what kind of image does a TEM produce?

highly detailed 2D image

how do you remember TEM?

t means through

what is a simple stain?

one dye to make bacteria easier to see

what can you learn from a simple stain?

shape, size, and arrangement of cells

what is a differential stain?

uses multiple reagents to distinguish different types of cells/structures

what is the purpose of a gram stain?

separates bacteria into gram-positive and gram-negative based on their cell wall

what color are gram-positive bacteria?

purple

what color are gram-negative bacteria?

pink/red

why are gram-positive bacteria purple?

thick peptidoglycan cell wall retains the crystal violet-iodine

why are gram-negative bacteria pink/red?

thin peptidoglycan loses crystal violet after decolorization and takes up pink/red counterstain

what does gram-positive mean structurally?

thick peptidoglycan and no outer membrane

what does gram-negative mean structurally?

thin peptidoglycan and an outer membrane

what are the four main steps of the gram stain?

crystal violet to iodine to alcohol/acetone to safranin

what is crystal violet?

primary stain in the gram stain

what does iodine do in the gram stain?

mordant that helps crystal violet stay in the cell

what does alcohol/acetone do?

decolorizer that removes crystal violet from gram-negative

what does safranin do?

counterstain that makes gram-negative cells pink/red

gram positive equals?

purple + thick peptidoglycan

gram negative equals?

pink + thin peptidoglycan + outer membrane

what is an acid-fast stain used for?

identifies bacteria with waxy mycolic acid rich cell walls

what important genus is identified with an acid-fast stain?

mycobacterium

why are acid-fast bacteria difficult to stain?

waxy cell wall makes stains hard to enter and leave

what color are acid-fast bacteria?

usually red/pink

what is an endospore stain used for?

detecting endospores in certain bacteria

what is an endospore?

highly resistant survival structure made by some bacteria

are endospores used for reproduction?

no, they help bacteria survive harsh conditions

what are two important endospore-forming genera?

bacillus and clostridium

what is a capsule?

gelatinous layer around some bacterial cells

what does a capsule help a bacterium do?

avoid phagocytosis and attach to surfaces

why is a capsule stain useful?

shows a clear area around the cell since it’s difficult to stain

is capsule staining an example of negative staining?

yes

what is a flagellar stain used for?

makes flagella visible under a microscope

why do bacterial flagella need a special stain?

flagella are too thin/small to see clearly with a standard light microscope

what does bacillus mean?

rod-shaped bacterium

what is a diplobacillus?

two rod-shaped bacteria together

what is a streptobacillus?

rod-shaped bacteria in chains

what does coccus mean?

spherical/round shaped bacterium

what are diplococci?

cocci arranged in pairs

what are staphylococci?

cocci arranged in clusters

what are streptococci?

cocci arranged in chains

diplo

pairs

staphylo

clusters

strepto

chains

what is a vibrio?

curved comma shaped bacterium

what is a spirillum?

rigid spiral shaped bacterium

what is a spirochete?

long, thin, flexible spiral shaped bacterium

what is the difference between spirillum and spirochete?

spirilla are more rigid while spirochetes are long and flexible

what does selectively permeable mean?

membrane allows some substances through but blocks others

what is the bacterial plasma membrane used for?

controls what enters and leaves the cell and helps with energy production

where does much of a prokaryote's energy production occur?

plasma membrane

where is the bacterial chromosome located?

nucleoid region of the cytoplasm

is the bacterial chromosome inside a nucleus?

no

what is the typical shape of a bacterial chromosome?

circular dna

Plasmids

what is a plasmid?

small usually circular piece of DNA separate from the bacterial chromosome

Plasmids

what can plasmids contain?

extra genes that provide useful traits like antibiotic resistance

what are fimbriae?

short hair like structures that help bacteria attach to surfaces or host cells

what are pili?

hair like structures used for attachment, genetic transfer, and movement

what is a sex pilus used for?

genetic transfer between bacteria

what are three functions associated with pili/fimbriae on your study guide?

attachment, genetic transfer, and motility

what is the cytoplasm?

material inside the cell membrane where many cellular reactions occur

what can be found in bacterial cytoplasm?

ribosomes, DNA, enzymes, water, and other cellular components

what is the main function of bacterial flagella?

motility/movement

what is a bacterial "run"?

relatively straight movement in one direction

what is a bacterial "tumble"?

change in direction

why do bacteria use run-and-tumble movement?

to move toward favorable conditions and away from unfavorable conditions

how are bacterial flagella different from eukaryotic flagella?

bacterial flagella rotate like propellers while eukaryotic flagella bend and have a 9 + 2 pattern