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Why is microbiology important?
- Microbes cause disease
- can affect food supply
- can be beneficial for digestion, protection, bio-remediation and food procession
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Characteristics of bacteria
- unicellular, prokaryotic
- no nuclear membrane, mitochondria, Golgi or ER
- reproduce asexually
- many can be beneficial
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Characteristics of Viruses
- cause many of the biggest public health threats
- smallest infectious particle
- contain DNA or RNA housed inside a protein coat
- require host cell for replication
- can infect animals, plants and other microbes
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Characteristics of fungi
- eukaryotic
- contain nucleus, golgi, mitochondria and ER
- can be unicellular (reproduce asexually) or multicellular (asexual or sexual)
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Characteristics of Parasites
- most complex microbes
- eukaryotic
- infections are often chronic
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Name the smallest type of microbe
viruses
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which microbes are eukaryotic? which are prokaryotic?
- Eukaryoticfungi & parasites
- Prokaryoticbacteria
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Name the 5 methods of transmission
- inhalation
- ingestion
- direct contact
- indirect contact
- animal vectored
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Method of Transmission: Inhalation
- transmitted by infectious droplets from cough, sneeze, etc.
- eg. Flu, TB, common cold
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Method of Transmission: Ingestion
- germs get on your hands and then on food or skin
- can occur from unwashed produce and contaminated meat
- eg. salmonella, e. coli
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Method of transmission: direct contact
- spread directly from one person to another
- eg. HIV, gonnorhea
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Method of transmission: indirect contact
- disease is spread via fomites (inanimate objects harboring germs)
- eg. tissues, door knobs, toilets, phones
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Method of Transmission: Animal Vectored
- transmission through insect bite
- eg. Malaria, Lyme disease
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Influential ideas in Microbiology:
Hooke- 1664
coined the term "cells". uses microscope to describe mold
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Influential ideas in Microbiology:
van Leewenhoek- 1674
first describes bacteria in detail
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Influential ideas in Microbiology:
Redi- 1668
hypothesizes against spontaneous generation of maggots on meat
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Influential ideas in Microbiology:
Spallanzani- 1768
shows that if air is removed form flask, no bacteria grows
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Influential ideas in Microbiology:
Jenner- 1788
father of vaccines. discovers a cure for small pox
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Influential ideas in Microbiology:
Semmelweis- 1840
introduced antiseptic practice to medicine
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Influential ideas in Microbiology:
Henle- 1800s...
formally described germ theory
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Influential ideas in Microbiology:
Koch- 1800s...
- developed methods for pure culture and aseptic technique.
- Kochs postulate
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Influential ideas in Microbiology:
Gram 1800s...
develops methods for pure culture and aseptic technique
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Influential ideas in Microbiology:
Fleming- 1928
discovered first antibiotic (penicillin)
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Spontaneous generation
- belief in spontaneous creation of life from organic matter.
- Redi, Spallanzani, and Pasteur contributed to the debunking of that myth
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Describe germ theory
proposal that diseases are caused by microorganisms. contagions are organic and living.
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Koch's postulate
- the bacteria must be present in every case of the disease
- the bacteria must be isolated from the host with disease and grown in pure culture
- the specific disease must be reproduced when pure culture is inoculated into a healthy susceptible host
- the bacteria must be recoverable from experimentally infected host
- n/a if particular bacteria cannot be "grown in pure culture"
- if no animal model of infection with a particular.
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Name four categories for classifying bacteria
- appearance
- growth and metabolism
- antigenicity
- genotype
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Appearances of a bacterium
can either be macroscopic (colony morphology) or micro (cell morphology)
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Descriptive terms of colony vs cell morphology
- colony: form, elevation, margin, color, smell and mucoid/dry
- cell: shape, arrangement and gram stain
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Description of growth and metabolism of bacteria
- antibiotic resistance
- sugar fermentation
- oxygen requirement
- production of metabolic products and enzymes
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What is a key method for using antigenicity
serotyping: when antibodies detect antigen on bacterial surfaces
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What method of classification can be used for growing organisms that are difficult/dangerous to grow
antigenicity
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Describe classification by genotype
- detection of specific DNA sequences (PCR)
- does not require living growing bacteria
- used for rapid detection of slow-growing organisms
- can be used to identify organisms that cannot be cultured
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What is PCR
- polymerase chain reaction.
- method for amplifying DNA
- generates large quantities of DNA from small amounts of starting material
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Steps of PCR
- denaturation
- annealing
- extension
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Gel Electrophoresis
- Sorts DNA based on size and change
- DNA naturally carries a negative charge
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Function of bacterial cell envelope
- protects the cell against chemical and biological threats (antibiotics, dessication)
- makes surface colonization possible
- provides shape and structure to cell
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Capsule/slime layer (glycocalyx)
- found in almost all bacteria
- unnecessary for growth
- impedes ingestion by immune cell
- barrier to toxic hydrophobic molecules
- promotes adherence to other bacteria or host tissue (virulence factor)
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Flagella
provide motility and are anchored in bacterial membrane
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chemotaxis
swim and tumble movement
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Fimbrae
- hairlike structures
- promote adherence to other bacteria or host cells
- virulence factor for many bacteria
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Gm+ cell envelope
- have thick peptidoglycan layer close to exterior surface.
- have only one cellular membrane
- can contain teichoic and lipoteichoic acids
- Shed teichoic and lipoteichoic acidsin host and invoke eimmune response
- promote adherence to other bacteria
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Gm- cell envelope
- have 2 cell membrane layers (outer and inner) after the cytoplasmic membrane
- has a thin peptidoglycan layer
- has no teichoic or lipoteichoic acids
- outer membrane contains LPS
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Antibiotic treatments effective agains Gm+ bacteria attack what part of the cell? Give an example of a treatment.
- Gm+ antibiotic treatments attack the cell wall.
- Eg. vancomycin and bacitracin
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Antibiotic treatments effective against Gm- bacteria attack what part of the cell? Give an example of a treatment
- Gm- antibiotics bind to the lipid A portion of LPS in order to weaken the cell
- Eg. Polymyxin B
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Functions of the outer membrane of a cell
- serves as a permeability barrier to large foreign objects
- provides protection from the environment
- contains the endo-toxin Lipopolysaccharide (LPS)
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Lipopolysaccharide (LPS)
- induces fever and shock
- found in Gm- outer membrane
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Parts of LPS
- Lipid A
- core polysaccharides
- O antigen
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Lipid A
- essential for bacteria viability
- responsible for endotoxing activity
- conserved
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Core polysaccharides
- 9-12 sugars essentials for LPS structure
- moderately variable
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O antigen
- polysaccharide side chains
- highly variable
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Peptidoglycan layer
- provides rigidity and shape.
- barrier against toxic chemicals
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cytoplasmic membrane function
- energy production
- uptake of metabolites
- release of substance
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plasmids
- small extrachromosomal DNA
- common in Gm-
- confer selective advantage to bacterium
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Spores
- produced by Gm+, but not Gm-
- dehydrated multi-shelled protective structure
- protects from heat, radiation, enzymes, chemicals
- complete chromosome, but minimum proteins
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