micro week 1

microbio 5 key concepts

-emergence and evolution of microorganisms

-microbial genetics

-microbial ecology and diversity

-microbes and pathogenicity

-applications of microbes and microbiology

microbes

generally <1mm, but some macroscopic

organisms are simple in their construction + lack differentiated tissuses

cellular microbes

fungi, protists, bacteria, archaea

ex. yeast, algae, e.coli, methanogens

acellular microbes

viruses (NOT ALIVE!), viroids, satellites, prions

ex. nucleic acid, rna, nucleic acid in protein shell, protein

carl woese

led to recognition of “archaebacteria” a ‘third kingdom’ of life, and redrawing of the phylogenic taxonomic tree

ribosomal rna genes (16s ribosomal RNA)

domain bacteria

-usually single celled

-most have cell wall with peptidoglycan

-lack membrane bound nucleus

-can be found in extreme environments (our bodies)

-both disease causing + non-disease causing exist

domain archaea

-distinguished from bacteria by unique rna sequences

-have unique membrane lipids

unusual metabolic characteristics

many live in extreme environments (extremophiles)

-do not directly cause disease in humans

domain eukarya

membrane-enclosed nucleus

larger and more morphologically complex

-protists + fungi

protists

unicellular, generally larger than bacteria + archaea

protozoa- animal like metabolism

algae - photosynthetic

fungi

unicellular (yeast)

or multicellular (molds and mushrooms)

origins of life

life first identified on earth 3.5-3.8 billion years ago

-carbon dating/fossils/molecular fossiles - hopanes

cyanobacteria changing environment to bring o2\

PROKARYOTES FIRST ON EARTH!

oxygen revolution

caused the extinction of some prokaryotes

-oxidation of glucose (energy boost created eukaryotes, etc)

others adapted using cellular respiration to harvest energy (endosymbiosis, origin of mitochondria, chloroplasts, and hydrogenosomes)

last universal common ancestor (LUCA)

-most recent organism from which all three types of life arose

-archaea and eukarya evolved independently of bacteria

archaea and eukarya diverged from common ancestry

-eukaryotes increased diversity through sexual reproduction

-HGT caused increase in gene pool (horizontal gene transfer)

taxonomy

science of classifying living things

-classification (grouping microbes based on characteristics/structure/behavior)

-nomenclature

-identification (connecting isolates via taxons)

strain

descendants of a pure microbial culture

can differ biochemically, morphologically, and pathogenically

Girolamo Fracastoro

“spores” or transferable tiny particles could cause disease. clothes carry these contagious microbes and pass it btwn ppl (transmission)

role of microorganisms in disease

the idea that death is contagious + infects ppl, but in reality disease is

(blood, phlegm, yellow bile, and black bile)

robert hoooke

created first compound microscope + illumination system (multi lens, glass, leather, very nice)

coined the term cell for describing biological organisms

anton van leeuwenhoek

first to observe adn describe single cell organisms (animalcules: “little animals”)

defined shape, purpose, activity. created microscope used by most ppl. has a tiny lense + not as nice but very practical. accessible.

spontaneous generation

idea that living organisms can develop from nonliving or decomposing matter

francesco redi

disproved spontaneous generation by maggots on decaying meat coming from fly eggs.

open, cork sealed, and gauze covered container

john needham

did not believe francisco + made own theory.

observed that boiled hay gave rise to microorganisms + some extracts have what it takes to confer life from non-living material.

used heat, sterilized + things grew, but still had open system → not right

lazzaro spallanzani

proved that hay itself didnt make microorganisms if in sealed environment.

completed same experiment as Needham but with cork. nothing grew!!!

louis pasteur

disproved spontaneous generation via ‘swan-neck flask’ experiments

system: allowed air to move in and out but nothing can fall in

creates breathing with environment

broken flask: growth occurs.

neck intact: airbone microbes trapped + broth is sterile

louis pasteur accomplishments

-discovered microorganisms cause fermentation + disease

-originated the process of pasteurization (saved beer, wine, and silk industries)

-developed vaccines against anthrax and rabies

robert koch

founder of modern bacteriology

-grew + identify bacteria + worked on it (media, stains)

established relationship btwn bacillus anthracis + anthrax

demonstrated mycobacterium tuberculosis causes TB

-provided evidence to cement “germ theory” of disease

germ theory

-each microorganism causes particular disease in susceptible individuals

susceptibility of individual depends on: infecting agent, factors involving environment, factors involving host

koch’s postulates

set of criteria to establish the cause of an infectious disease

links btwn microorganism and disease

postulate 1

microorganism must be present in every case of the disease but absent from healthy organisms

microbe + disease must BOTH be present

postulate 2

suspected microorganism must be isolated and grown in a pure culture

-these cells r viable

-if dead can’t be responsible for disease

postulate 3

the same disease must result when the isolated microorganism is inoculated in to a healthy host

-observed in sick + will do same in healthy

-tested on guinea pigs

postulate 4

same microorganism must be isolated again from the diseased host

-bc cause + effect or random???

-have to prove microbe was in dead guinea pig

forms link btwn bacteria + disease

limitations of postulates

-some organisms can’t be grown in pure culture bc they rely on host cells

-possible lack of animal model bc CANT use human subjects

-molecular and gentic evidence may replace and overcome these limits

edward jenner

used vaccination procedure to protect against smallpox

recognized same symptoms as cowpox and how they might be related

-prepped immune system

joseph lister

provided indirect evidence microorganisms were causal agents of disease

-developed antiseptic surgery to prevent microorganisms from entering wounds

-study of lactic fermentation demonstrated specific cause of milk souring.

sir alexander fleming

-spores came through window and landed on petri dish and started to grow

-microbes are problem and can also be solution (started antibiotics)

magnification

how much bigger the image is than the sample

resolution

the ability to see objects that are small and close together as actual separate objects

bright-field microscope

typical/basic

light background

stained or unstained

dark-field microscope

dark background

living

unstained

observe internal structures in eukaryotes

phase contrast microscope

deviated + undeviated light combined to generate more detailed image

-microbial movement (live cells) and detecting structures.

differential interference contrast (DIC) microscope

creates image by detecting differences in refractive indices and thickness of different parts of specimen

-adds contrast through extra lenses/prisms

fluorescence microscope

provides image by exciting specimen w/ wavelength of light that triggers object to emit fluorescence light

-can show localization of specific proteins in cells

confocal microscopy

-uses laser bean to illuminate a fluorescently labeled specimen

creates a sharp, composite 3D image of specimens

can be used to study biofilms

staining of specimens

increased visibility of specimen (better contrast to background)

used to ascertain size, shape, or arrangement of cells or to detect presence or absence of structures

often divides organisms into groups based on staining properties. elect

electron microscopy

wavelength of electron beam is 100,000x shorter than visible light, resulting in higher resolution image

-controlled process, enclosed, often under vacuum

-allowed for microbial morphology to be studied in detail

Transmission (TEM)

electron beams that pass through specimen to visualize small images, useful to observe small, thin specimen

scanning (SEM)

electron beams to visualize surfaces; used to observe the three-dimensional surface details of specimens

cryo-electron microscopy

-samples rapidly frozen, then multiple TEM images captured at different angles combined to give 3D image

-used to visualize biomolecules + generate high resolution structures