intro to microbiology and major themes

what is microbiology

the study of organisms too small ot be seen without magnification

what are examples of microorganisms

Bacteria, viruses, single-celled eukaryotes

which microorganisms can be visible to the naked eye?

fungi and algae

what are some multicellular microbes

Myxobacteria and slime molds

what defines microbiology?

Techniques incl. culture media, biochemistry, and molecular/genetic techniques

what common structures do all cells share?

cytoplasmic membrane, cytoplasm, and ribosomes

how is genetic information stores in cells?

As DNA, organised into genes forming a genome

what do chromosomes carry

essential genes

what do plasmids carry

Non-essential genes

what are the 3 categories of midroorganisms?

Eukaryotes, prokaryotes, and viruses.

what are the distinguishing features of eukaryotes?

• membrane bound nucleus

• membrane bound organelles

• complex internal organization

• division by mitosis and meiosis

what are the 2 major groups of eukaryotic microbes?

Protists, fungi

what are protists?

these are any eukaryotes that are not plants, animals or fungi

they have 3 main groups: protozoa (animal like), algae (photosynthetic) and slime and water molds (filamentous)

what are fungi?

these are unicellular (yeasts), filamentous (molds), or multi-cellular (mushrooms)

what are the distinguishing features of prokaryotes?

• no membrane bound nucleus

• generally smaller

• divide by binary fission

what are the two major groups of prokaryotes?

Bacteria and archaea

How do bacteira differ from archaea

they are genetically and biochemically distinct

what is unique about archaea?

they are always non-pathogenic

distinguishing features of viruses?

• Acellular infectious particles

• obligate parasites

what does LUCA stand for

Last Universal Common Ancestor

when did the first anaerobic life appear?

between 3.8-3.9 bya

What did photosynthetic bacteria do?


Oxygenated the Earth about 2 billion years ago

When did the first plants and animals appear?


about 0.5 bya

what is the significance of SSU rRNA genes?

help classify organisms based on evolution

What ribosomes do prokaryotes have?

70S

What ribosomes do eukaryotes have

80S

why are rRNA genes important in classification?

they change slowly over time

what is the first step in sequencing rRNA genes

DNA is collected from a pure culture

What techniques is used to amplify the SSU rRNA gene?

PCR

what is done after amplifying the SSU rRNA gene

the gene is sequenced

what is a phylogenetic tree

A graphic representation of evolutionary distance

What domains of life are based on the rRNA sequence

Bacteria, archaea, eukarya

what does the Asgard superphylum represent

The closet relative of eukarya

What is the phylogenetic species concept?

A group of strains with a recent common ancestor

What is required for species of bacteria and archaea?

Greater than 97% sequence similarity

Who was the first to describe microbes?

Robert Hooke

What did Robert Hooke use to observe microbes?

A compound microscope

What was the magnification capability of Hooke’s microscope

30X

What did Hooke observe with his microscope?

cells in cork and bread mold

who built microscopes that magnified specimens by 50-300X

Antoni Van Leeuwenhoek

What did Leeuwenhoek call single celled microorganisms

Animalcules

What did Louis Pasteur Study?

Wine and beer production

What process did Pasteur discover related to yeast

Fermentation

What is a colony in microbiology

A mass of cells from one single cell

How can colonies be used in microbiology

To create a pure culture

What are the techniques for isolating pure cultures?

spread and pour plate

What is the purpose of diluting a sample before plating

to allow separate cells to grow

what is the formula for calculating titre?

titre=# colonies/ (volume)(dilution)

how is titre expressed

in cfu/ml

what is the countable range of colonies on a plate

30-300 colonies

what is the purpose of a bright-field microscope

To make specimens visible against surroundings

Dark specimen against bright background

What are the two sets of lenses in a microscope

objective and ocular lens

formula for calculation

magnification = objective * ocular

what is the maximum magnification achievable with a light microscope

about 2000X

def. of magnification

ability to make an image larger

def. of resolution

ability to distinguish 2 objects as separate

how does wavelength affect resolution?

as wavelength decreases, resolution improves

limit of resolution for a light microscope?

about 0.2 micrometer

what is the purpose of staining in microscopy

to improve contrast for better visibility

common examples of stains used in microscopy

methylene blue, safranin, crystal violet

two types of simple staining

• basic dye- positively charged chromophore will attach negatively charged molecules on cell surface

• acidic dye- negatively charged chromophore will stain b/g not the cell

gram stain process

gram positive cells after staining

purple

gram negative cells after staining

red/pink- this is the counterstain

what does the acid-fast stain detect

mycolic acid in mycobacterium cell walls

colour of mycobacterium cells after acid fast stain

pink- fuschia

colour do other cell walls appear on the slide after an acid fast stain

blue

colour of endospores after staining

green

colour of cells after endospore stain

pink

purpose of phase contrast microscopy

improve contrast w/o using stains

dark field

bright specimen against dark b/g

how does dark field microscopy illuminate specimens

with a hollow cone of light

what is fluorescnece microscopy used for

to visulaize specimens the fluoresce

resolution of confocal scanning laser microscoopy

0.1 micrmeter

main advantage of differential interference contrast microscopy

gives 3D apperance to structures

what do electron microscopes use to image cells

electrons instead of photons

resolution of transmission electron microscopy (TEM)

0.2 nm

what must the specimens be for transmission electron microscopy

very thin (20-60nm)

what is required to visualise unstained cells in TEM

staining with lead or uranium

what is the purpose of a scanning electron microscopy (SEM)

produce a 3D image of a specimen’s surface

coccus

roughly spherical

Bacillus

rod shaped

spirillum

spiral shaped

example of spirochete

Treponema pallidum

example of filamentous bacteria

streptomyces griseus

example of budding and appendages bacteria

caulobacter crescentus

characteristic arrangements of prokaryotic cells

• staphylococci- grape like clusters

• anabaena - long chains

• micrococcus and deinococcus - tetrads

size range for prokaryotes

0.2 µm to >700 µm in diameter

size range for eukaryotic cells

10 to >200 µm in diameter

advantages of small cells

higher surface area relative to volume

what is the advantage of high s/v ratio?

greater nutrient exchange

average size of E.coli

~ 1.0 x 3.0 μm

average size of mycoplasma genitalium

~ 0.3 μm

What is the size of Epulopiscium fishelsonii?

~ 80 x 600 μm

what is the significance of being small for cells

supports faster growth and evolutionary change

What is the lower limit of cell size for cellular oranisms

Unlikely to be < 0.15 μm

where are small cells commonly found?

in open oceans and pathogenic bacteria

what is the function of the cytoplasmic membrane

separates the cell from the environment

what is the cytoplasm made of

aq. mixture of macromolecules, ions, proteins

what si the role of ribosomes in cells

site of protein synthesis