Basic Microbiology Notes

Zacharias Jansen

built the first compound microscope

Robert Hooke

built the first USABLE compound microscope

Antoni van Leeuwenhoek

“wee animalcules!”

spontaneous generation theory

states that life emerges from non-living matter; vital force required

biogenesis theory

states that life begets life

francisco redi

he conducted a series of experiments using meat in jars to show that maggots did not spontaneously arise from decaying flesh but rather came from eggs laid by flies

john needham

conducted experiments where he boiled meat broth in flasks, sealed them, and observed microbial growth, claiming it represented spontaneous generation

lazzaro spallanzani

conducted experiments that showed boiling broth and sealing it in flasks prevented microbial growth, disproving the theory of spontaneous generation

Schulze

passed air through strong acids

Schwann

passed air through red-hot tubes

Schroder and Dusch

filtered air through sterile cotton wool

Louis Pasteur

placed nutrient solution in flasks; created flasks with long, curved necks, boiled the solutions, let flasks exposed to air

John Tyndall

demonstrated that dust carries microorganisms

John Tyndall

provided evidence for the existence of exceptionally heat-resistant forms of bacteria

Ferdinand Cohn

discovered the existence of heat-resistant bacterial endospores

Germ Theory of Disease

states that diseases are caused by specific agents called germs

Ignaz Semmelweis

asepsis in obsterical wards to prevent thte transmission of childbirth fever from patient to patient

Ignaz Semmelweis

policy for all attending physicians to wash their hands with chloride of lime between patients

Joseph Lister

Father of Antiseptic Surgery

Joseph Lister

provided indirect evidence for the importance of microorganisms in causing human diseases

Joseph Lister

used phenol of carbolic acid in surgical dressing, heat-sterilized surgical instruments

Robert Koch

established the relationship between Bacillus anthracis and anthrax

• solid culture media

• aseptic technique

• pure culture maintenance

• petri plate

Koch’s work led to the development of:

• Causative agents of several human diseases do not cause disease in any known experimental animals

• Some microbes are obligate intracellular parasites and are very challenging to grow on artificial media

• Some diseases have variable signs and symptoms between patients

• Some diseases may be caused by a variety of microbes

• Some pathogens cause several different diseases

• Certain pathogens cause disease in humans only

what are the limitations of Koch’s postulates?

• chlamydia

• viruses

examples of microbes that are obligate intracellular parasites

tetanus

example of diseases that have variable signs and symptoms

• pneumonia

• nephritis

examples of diseases that may be caused by a variety of microbes

S. pyrogenes

examples of pathogens that cause several different diseases

HIV

example of pathogen that cause disease in human only

Edward Jenner

father of immunology

Edward Jenner

used a vaccination procedure to protect individuals from smallpox

Pasteur and his co-workers

developed vaccines for chicken cholera, anthrax, and rabies

Pasteur and his co-workers

discovered that incubation of cultures for long intervals between transfers caused pathogens to lose their ability to cause disease

Pasteur and his co-workers

discovered that growing pathogen in an abnormal host weakens

Charles Chamberland

developed porcelain bacterial filter used to isolate first viruses studied

Paul Ehrlich

developed 606^th compound SALVARSAN (inorganic compound used to treat syphilis)

SALVARSAN

inorganic compound used to treat syphilis discovered by Paul Ehrlich

Alexander Fleming

discovered miracle drug penicillin from Penicillium

Louis Pasteur

discovered that fermentations were the result of microbial activity

Louis Pasteur

developed the process of pasteurization to preserve wine

Eduard Buchner

discovered cell-free fermentation (extract from yeast cells)

Martinus Beijerinck

studied microorganisms in and around plants, and in soil

Martinus Beijerinck

discovered enrichment cultures and selective media

Sergei Winogradsky

discovered chemolithotrophy and biogeochemical cycles

light microscope

electron microscopes

two major types of microscoeps

• simple

• compound

two types of light microscopes

light microscopes

microscopes that use light waves and mirrors

simple

light microscope with short focal length, only 1 lens, and 300x magnification

compound or complex

light microscope with two set of lens and 1000x magnification

electron microscopes

microscopes that use electron beams and magnetic fields, for objects smaller than 0.2 mm in diameter, in vacuum

• focal length

• resolving power and limit of resolution

• refractive index/index of refraction

• numerical aperture (NA)

• working distance

principles of microscopy and important features of objectives

• bright field (BF)

• phase-contrast (PC)

• dark field (DF)

• fluorescence (FL)

• differential interference contrast (DIC)

different types of light microscopes

bright field (BF)

microscopic object is brightly lit, objects under study are darker, gross morphology

phase-contrast (PC)

detailed examination of internal structure, principle is based on variations in the refractive index

dark field (DF)

microscopic field is dark, objects under study are luminious

dark field (DF)

used for specimens that are invisible in ordinary LM, cannot be stained by standard methods, distorted by staining

fluorescence (FL)

naturally fluorescent substances or stained with fluorochromes

DAPI (4',6-diamidino-2-phenylindole)

examples of fluorochrome

differential interference contrast (DIC)

principle is based on variations in the refractive indices

no diffraction halo associated with phase-contrast

advantage of differential interference contrast (DIC)

three-dimensional structure may not represent reality

disadvantage of differential interference contrast (DIC)

brightly lit

in bright field, the microscopic field is [brightly lit/dark]

darker

in bright field, objects under study are [luminous/darker]

gross morphology

bright field is used to study [internal structure/gross morphology]

internal structure

phase-contrast is used for detailed examination of [internal structure/gross morphology]

dark

in dark field, the microscopic field is [brightly lit/dark]

luminous

in dark field, objects under study are [luminous/dark]

• phase-contrast

• differential interference contrast

two microscopes that are based on differences in refractive index

phase-contrast

[phase-contrast/differential interference contrast] exhibits diffraction halo

• Transmission Electron Microscope

• Scanning Electron Microscope

different types of electron microscopes

transmission electron microscope (TEM)

used to examine viruses, ultrastructures in thin sections of the cells

scanning electron microscope (SEM)

used to examine surface features of viruses and cells; reveals a 3D image

scanning electron microscope (SEM)

[TEM/SEM] reveals a 3D image

transmission electron microscope

[TEM/SEM] ultrastructures in thin sections of cells

scanning electron microscope

[TEM/SEM] surface features of viruses and cells

• electron beam

• vacuum

two reasons why living things can’t survive in an electron microscope

fixation and dehydration

important for preparing samples for both TEM and SEM

ultramicrotome

used to cut the specimen into 100 mm or thinner in TEM

transmission electron microscope (TEM)

[TEM/SEM] uses heavy metals to increase the level of contrast in the final image

scanning electron microscope (SEM)

[TEM/SEM] not cut into ultra thin sections

scanning electron microscope (SEM)

[TEM/SEM] coated with a thin layer of metal (usually gold or gold-palladium)

• osmic acid

• permanganate

• lead

• uranium

• gold

• gold-palladium

• silver

• lanthanum

examples of electron microscope stains

• natural state

• accurate morphology, cell arrangement, and dynamic life processes

• short period preparation

• fewer artifacts

advantages of examining microorganisms in live state

• movement makes it difficult to observe

• observed as soon as they are prepared

• details cannot be seen

• light-sensitive organisms

disadvantages of observing microorganisms in their living or natural state

• wet mount

• hanging drop technique

methods to observe microorganisms in living or natural state

• good contrast

• preserved slides

• killed specimens

advantages of stained preparations

• complicated and tedious

• expensive

• possible distortion

disadvantages of stained preparations of microorganisms

• smear preparation

• fixation

• staining

three basic steps of stained preparations

methylene blue

example of basic or positively charged dye

nigrosin

example of acidic or negatively charged dye

negative

charge of bacterial cell wall

• positive staining

• negative staining

• differential staining

different types of stains

• gram staining

• acid-fast staining

• structural staining

examples of differential staining

pure culture

a culture which contains a single species of microorganism

cultivation

increasing the population of microorganisms by providing their nutritional and physical requirements

nutrients

extracellular substances which provide the cell with materials for building protoplasm and for energy generation

culture medium

any nutrient material for growth, cultivation, and maintenance of microorganisms in the laboratory

culture medium

any nutrient material to study microbial action on some constituents of the medium

• liquid (broth)

• semi-solid

• solid

types of culture media according to physical state

• synthetic

• complex

types of culture media according to chemical composition