BIOL 303 - Exam 1

What does it mean that microbes are essential to human life?

• play defense

• boost immune system

• protect us from allergies and auto immune diseases

• make nutrients available

• detoxify

Old friends hypothesis

• early exposure to certain microbes helps the immune system distinguish between friendly and harmful microbes

• Ex. H. pylori

leaf cutter ants

• have crypts that house antifungal bacteria protecting their food

1918 influenza pandemic

• novel influenza strain

• 675,000 americans infected

• 20-40 mil worldwide

polio

• vaccine was introduced and thus the vaccination assistance act led to its elimination in the USA

smallpox virus

• 10mil deaths in 4,000 years

• intense global vaccination program started in 1967 - eradicated in 1980

• no known cases since 1977

Edward Jenner

• developed first ‘vaccine’ for smallpox

the plague

• 1/3 of the European population died

• control host - rodents

• antibiotics made available

2 leading causes of death in infectious diseases

• respiratory infections and diarrheal diseases

factors associated with emerging disease

• changing lifestyles

• decline of vaccinations

• pathogens become resistant

• increased travel and immigration

Changing lifestyle with emerging disease

• urban sprawl into undeveloped areas

• e. more contact with disease vectors (ticks and lyme disease)

vaccine decline

• diseases have been eradicated from the US but are reappearing with declining vaccine rates

• lack of firsthand knowledge is causing this

herd immunity

• protection occurring when enough of a population is immune

pathogens become resistant

• antimicrobial medications

• vaccines become less effective with variants and mutations

increased travel and immigration

• diseases eliminated from developed countries exist in many parts of the world and thus can be spread quickly with travel

Why do microbes ‘run the world’

they make up most of earth’s biomass and diversity

key functions of the human microbiome

• stimulating immune development

• detoxifying harmful compounds

• defending against pathogens

symbiotic microbes protect leaf-cutter ants primarily by

producing antifungal compounds

Why would changing lifestyles increase emerging disease risk

urban sprawl increases encounters between humans, wildlife reservoirs and vectors

Why did the 1918 influenza pandemic cause such a dramatic mortality spike despite existing health departments

the influenza strain was novel, so human populations lacked immunity

Robert hooke

• built first compound microscope

• coined term ‘cell’

Antoni van Leeuwenhoek

• first glimpses of single celled microbes

• “wee animalcules” and “cavorting beasties”

• considered the father of microbiology

biogenesis

• living organisms arise from preexisting life

spontaneous generation (abiogenesis)

• living organisms arise from nonliving matter

aristotle

• suggested maggots spontaneously generate from rotting meat

Jean-Baptiste van Helmont

• suggested mice spontaneously generate from wheat and vital force (sweat)

Francisco Redi

• maggots did not appear in a jar with meat in it that was covered in gauze but did in the open jar with meat

John Needham

• flasks with broth boiled and sealed with a cork grew microorganisms

• problems: wasn’t boiled long enough to kill bacteria and air could get in through the cork

Lazzaro Spallanzani

• boiled broth longer and sealed glass

• proved microbes came from the air

Louis Pateur

• father of modern microbiology

• showed air contains microorganisms

• disproved spontaneous generation with a swan necked flask

Tyndall

found broths made from hay had heat-resistant microbes

Ferdinand Cohn

• discovered endospores

• explained difference between broths with sugar or yeast and not hay

Historical View of microorganisms

• diseases due to supernatural forces or imbalances of the body

Joseph Lister

• developed antiseptic surgery system

• used carbolic acid to clean wounds and air in the operating room

• proved indirectly that microorganisms cause disease

Robert Koch

• established cause of anthrax

• demonstrated importance of epidemiology

• established cause of TB

• developed Koch’s postulates to establish link between some microorganisms and the disease it causes

Edward Jenner

• 1st vaccination

• used safer, related pathogen to induce immunity

Louis Pasteur

• developed first vaccines based on weakened microbe strains

Immunization

• stimulation of the immune system by deliberately inoculating the body with a foreign material

How much of the microbial species can be cultured

less than 1%

3 domain system for microorganisms

• bacteria

• archaea

• eukarya

prokaryotes

• no membrane-bound nucleus

eukaryotes

• have membrane-bound nucleus and organelle

bacteria

• single-celled prokaryotes

• DNA in nucleoid (no membrane-bound nucleus)

• rigid cell wall containing peptidoglycan

• multiply via binary fission

• many use flagella to move

Archaea

• cell walls lack peptidoglycan

• many are extremophiles

• otherwise like bacteria

Eukarya

• protists

• larger than bacteria and archaea

• unicellular or multicellular

• fungi

Fungi

• energy from degrading organic materials

Algae

• single-celled or multicellular

• photosynthetic

• many have flagella

• cell walls

Protozoa

• ingest organic compounds - predators

• no rigid cell wall

• flagella and cilia

• many human diseases

Acellular Infectious Agents

• don’t have a normal cellular structure and are not alive (can’t reproduce without host)

• microbe, not microorganism

Viruses

• nucleic acid packaged in protein cost

• obligate intracellular parasite

• infect loving cells (host)

Viroids

• short close circular piece of RNA

• no protective protein coat

• cause plant diseases

Satellites

• nucleic acids in capsid and need a helper virus to replicate

Prions

• infectious proteins

• misfolded versions of normal cellular proteins found in cells (high conc in neurons)

• cause neurodegenerative diseases

Light microscopy

• magnifies 1,000X

• magnification

• resolution

• contrast

magnification

• apparent increase in size

total magnification

• ocular x objective

parfocal

stays in focus when its focal length or magnification is changed

resolution

• ability to clearly make out two objects very close together

resolving power

• minimum distance between two objects that can still be viewed as two objects

what does resolution depend on

• quality of the lens and wavelength usdd

what is the maximum resolving power of most bright field microscopes

0.2 micrometers

why is immersion oil used

• to displace air between the lens and the specimen

• prevents light refraction

• has a similar refractive index as glass

contrast

• how easily cells can be seen

dark-field microscopy

• only light scattered by specimen enters objective lens

• used to observe living, unstained preperations

phase-contrast microscopy

• darker microbe against lighter background

light waves

• light passes through specimen

phase plate

special plate in the objective lens manipulating light waves

interference

• converts invisible phase shifts into visible brightness differences when light waves recombine

result

• living, unstained cells stand out

Fluorescence microscopy

• uses light emitted from specimen

• light absorbed by excitation/emission wavelengths

• UV/blue light

what does fluorescent microscopy allow

visualization of cells attached to surfaces

Confocal microscopy

• uses laser bean to illuminate a fluorescently labeled specimen

• pinhole aperture to block light

• precise localization

what type of microscopy replaces visible light with electrons

electron microscopy

what type of microscope transmits electrons through specimen and highlights intracellular structures

transmission electron microscope

what type of microscope highlights surface structures

scanning electron microscope

what type of microscopy scans probes over sample surfaces and builds topography of the specimen

atomic force microscopy

what tracks the cantilever’s deflection

laser

what does AFM resolution depend on

the shape of its probe

what is lateral resolution limited by

probe tip width

what does vertical resolution rely on

cantilever deflection

what type of preparation involves a drop of liquid specimen

wet mount

what type of preparation involves drying and fixing the specimen before viewing

smear

what does fixation do for a slide

• preserves structures

• kills organisms

• attaches organisms to slide

what type of fixation is routinely used with bacteria and archaea

heat fixation

what type of fixation is routinely used with larger, more delicate microorganisms

chemical fixation

why is chemical fixation used with large, more delicate organisms

protects structures and morphology

what does staining do for a slide

provides contrast (increasing visibility)

what is a salt consisting of positive and negative ions, where one is colored

a stain

what charge is the chromophore in a basic dye

positive

what charge is the chromophore in an acidic dye

negative

what layers does the negatively charged acidic dye highlight

layers external to cell wall

what are some common basic dyes

• methylene blue

• crystal violet

• safranin

• malachite green

what are some common acidic dyes

• nigrosin

• india ink

what type of stain makes all cells one color

simple stain

what is the size, shape and arrangement of bacteria

morphology

what type of staining distinguishes one cell type from another

differential staining

differential staining is also used to detect presence or absence of what

structures (endospores, capsules, flagella)

What type of staining separates into gram negative and positive

gram staining

what determines whether something is gram negative or positive

peptidoglycan layer

is this cell gram negative or positive before and after decolorizer

gram positive