Lecture 3 - Microbiology Flashcards
(101 cards)
0
Q
Basic Form of Virus
A
- consists of protein coat called a capsid w/ one to several hundred genes in the form of DNA or RNA inside the capsid
- no virus contains both DNA & RNA
- Most animal, some plant, and very few bacterial viruses surround themselves with a lipid-rich envelope either borrowed from membrane of host cell or synthesized in host cell cytoplasm
- Envelope typically contains some virus-specific proteins
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Q
Viruses
A
- Tiny infectious agents, much smaller than bacteria
- comparable in size to large proteins
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Q
Virion
A
mature virus outside the host cell
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Q
What organisms experience viral infections?
A
all organisms
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Q
Bacteriophage
A
- virus that infects bacteria
- viruses adsorbs to a specific glycoprotein on host cell membrane
- when a virus infects bacteria is nucleic acid penetrates into the cell through the tail
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Q
Endocytotic Process
A
- Most viruses that infect eukaryotes are engulfed by an endocytotic process
- Once inside the cell, there are two possible paths: a lysogenic infection or a lytic infection
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Q
Lytic Infection
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- The virus commandeers the cell’s reproductive machinery & begins reproducing new viruses
- The cell may fill w/ new viruses until it lyses, or it may release the new viruses one at a time in a reverse endocytotic process
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Q
Latent Period
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- Period from infection to lysis
- Encompasses the eclipse period
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Q
Virulent Virus
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Virus following a lytic cycle
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Q
Lysogenic Infection
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- The viral DNA is incorporated into the host genome
- If the virus is an RNA virus & it possesses reverse transcriptase, DNA is reverse transcribed from RNA & incorporated into host cell genome
- When host cell replicates its DNA, the viral DNA is replicated as well
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Q
Temperate Virus
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- Virus in a lysogenic cycle
- Host cell infected w/ this may show no symptoms of infection
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Q
Provirus
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- When the viral DNA remains incorporated in the host DNA, & the virus is said to be dominant or latent
- AKA prophage if the host cell is a bacterium
- Virus may be activated when host cell is under stress, UV light, or carcinogens
- When virus becomes active, it becomes virulent
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Q
Classification of Viruses
A
One way is by the type of nucleic acid they possess
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Q
Unenveloped Plus-Strand RNA
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- Responsible for the common cold
- Not all animal viruses are enveloped
- “plus-strand” indicates that proteins can be directly translated from the RNA
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Q
Enveloped Plus-Strand RNA
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- Retroviruses such as virus that causes AIDS
- Retrovirus carries reverse transcriptase
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Q
Minus-Strand RNA
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- Measles, rabies, & the flu
- The complement to mRNA & must be transcribed to plus-RNA before being translated
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Q
What type of RNA and DNA viruses are there?
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- Double stranded RNA viruses & single and double stranded DNA viruses
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Q
Viroid
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- Related form of infectious agent
- small rings of naked RNA w/o capsids
- only infect plants
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Q
Prions
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- naked proteins that cause infection in animals
- capable of reproducing themselves w/o DNA or RNA
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Q
Antibodies
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- How the human body fights viral infections
- Bind to viral protein & w/ cytotoxic T cells, which destroy infected cells
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Q
Spike Proteins
A
- Protrude from envelope & bind to receptors on new host cell, causing virus to be infectious
- What antibodies recognize
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Q
Vaccine
A
Injection of antibodies or of a nonpathogenic virus w/ the same capsid or envelope
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Q
Carrier Population
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More than one animal may act as carrier population
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Q
Structure of Virus
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Capsid, nucleic acid, & lipid-rich protein envelope
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Structure of Bacteriophages
Tail, base plate, & tail fibers
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Prokaryotes
- no membrane bound organelles
| - split into 2 domains: Bacteria & archaea
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Archaea
- Have similarities to eukaryotes as well as bacteria
- found in extreme environments: salty lakes & boiling springs
- cell walls not made from peptidoglycan like bacteria
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Bacteria
most prokaryotes
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Kingdom Monera
contains all prokaryotes
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What do organisms require in order to grow?
the ability to acquire carbon, energy, and electrons
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Carbon Sources
- can be organic or inorganic
- most contribute oxygen and hydrogen as well
- carbon dioxide is a unique inorganic carbon source b/c it has no hydrogens
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Fixing Carbon Dioxide
- Reducing it & using the carbon to create organic molecules usually through the Calvin cycle
- All microorganisms are capable of it to some degree
- Reduction of carbon dioxide requires lots of energy & most microorganisms can't use it exclusively as their carbon source
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Autotrophs
- supply one's own food
| - capable of using carbon dioxide as sole source of carbon
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Heterotrophs
- use preformed, organic molecules as their carbon source
| - organic molecules come from other organisms both living and dead
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Where do all organisms acquire energy from?
1. Light : Phototrophs
| 2. Oxidation of organic or inorganic matter : Chemotrophs
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Lithotrophs
Acquire electrons or hydrogens from inorganic matter
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Organotrophs
Acquire electrons or hydrogens from organic matter
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Fixing Nitrogen
- Some bacteria are capable of it
- Atmospheric N is abundant but in strongly bound form that's useless to plants
- Process by which N2 is converted to ammonia
- Most plants unable to use ammonia & must wait for other bacteria to further process the N in a process called nitrification
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Nitrification
- Two step process that creates nitrates from ammonia, which are useful to plants
- Requires two genera of chemoautotrophic prokaryotes
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Chemoautotrophy
- Inefficient mechanism for acquiring energy, so chemoautotrophs require large amounts of substrate
- All known chemoautotrophs are prokaryotes
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Structure of Prokaryotes
- have organelles just not membrane bound
- instead of nucleus, have single, circular double stranded molecule of DNA
- Have DNA & RNA
- Molecule of DNA is twisted into supercoils & is associated with histones in Archaea & diff proteins in bacteria
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Nucleoid
- The DNA, RNA, & protein complex in prokaryotes
- AKA chromatin body, nuclear region, or nuclear body
- Not enclosed by a membrane
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Major Shapes of Bacteria
1. Cocci : Round
| 2. Bacilli : Rod
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Other Shapes of Bacteria
1. Spirilla: Rigid Helical
| 2. Spirochetes: Helical
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Mesosome
- Invaginations of the plasma membrane
| - Prokaryotes may or may not contain them
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Inclusion Bodies
- Prokaryotes have them
| - Granules of organic or inorganic matter
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Plasma Membrane of Prokaryotes
Phospholipid bilayer that surrounds cytosol
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Phospholipid
- Phosphate group, two fatty acid chains, and a glycerol backbone
- Phosphate group is polar & fatty acid chains are nonpolar = amphipathic
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Micelle
Spherical structure formed when amphipathic molecules spontaneously aggregate, turning polar ends toward solution & nonpolar ends toward each other when placed in aqueous solution
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Liposome
- Form from ultrasonic vibrations
| - Vesicle surrounded and filled by aqueous solution
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Haponoids
Steroid-like molecules embedded in plasma membrane of prokaryotes
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Proteins Embedded in Membranes
- Responsible for functional aspects of membranes
| - Act as transporters, receptors, attachment sites, and enzymes
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Integral or Intrinsic Proteins
Amphipathic proteins that traverse the membrane from the inside of the cell to the outside
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Peripheral or Extrinsic Proteins
- Situated entirely on the surfaces of the membrane
| - Ionically bonded to integral proteins or the polar group of a lipid
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Fluid Mosaic Model of the Membrane
- Forces holding the entire membrane together are intermolecular, therefore the membrane is fluid
- Its parts can move laterally but cannot separate
- The mosaic aspect is reflected in the asymmetrical layers of its proteins
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Membrane Fluidity
- Cholesterol moderates membrane fluidity in eukaryotes
| - hopanoids reduce fluidity in prokaryotes
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Brownian Motion
Random movement of molecules
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Diffusion
Movement from high to low (w/ no electrical charge)
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Chemical Concentration Gradient
A gradual change in concentration of a compound over a distance (points in direction of lower concentration)
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Electrical Gradient
For molecules with charge (points in direction positive charge molecule will tend to move)
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Electrochemical Gradient
The electrical and chemical concentration gradient added
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Semipermeability
- Slows diffusion of molecule but doesn't stop it
| - Size & polarity of the molecule affect its semipermeability
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Size & Semipermeability
The larger the molecule, the less permeable the membrane to that molecule
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Polarity & Semipermeability
The greater the polarity of a molecule the less permeable the membrane to it
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Polar molecules with molecular weight greater than 100 and Permeability
A natural membrane is impermeable to them w/o assistance
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Transport or Carrier Proteins
Facilitate diffusion of specific molecules across the membrane
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Facilitated Diffusion
- Diffusion must occur down the electro-chemical gradient of all species involved
- Most human cells rely on it for their glucose supply
- Makes the membrane selectively permeable
- Transport Proteins
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Active Transport
- Movement of compound against electrochemical gradient
- Requires energy
- Direct or indirect use of ATP
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Passive Diffusion
- Depends on lipid solubility - Are you nonpolar enough to slide through?
- Depends on size too
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Protoplast
The bacterial plasma membrane and everything in it
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Bacterial Envelope
- Surrounds protoplast
- Cell wall is a component & is adjacent to plasma membrane
- Cell wall functions to prevent protoplast from bursting
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Hypertonic
- Most bacteria are hypertonic to their environment
| - The aqueous solution of their cytosol contains more particles than the aqueous solution surrounding them
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Isotonic
Cytosol contains same amount of particles
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Hypotonic
Cytosol contains less particles
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Hydrostatic Pressure & Osmotic Pressure
As cell fills with water and the hydrostatic pressure builds, it eventually equals the osmotic pressure & the filling stops
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Cell Wall of Bacteria
Made of peptidoglycan
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Peptidoglycan
- Series of disaccharide polymer chains w/ amino acids, 3 of which are not found in proteins
- More elastic than cellulose & porous
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Lysozyme
Enzyme produced naturally by humans - attacks disaccharide linkage in peptidoglycan
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Classification of Bacteria by Type of Cell Wall
gram staining
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Gram-Positive Bacteria
- Thick peptidoglycan cell wall
- Prevents gram stain from leaking out
- Purple
- Have cell wall 4x thicker than plasma membrane
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Gram-Negative Bacteria
- Thin peptidoglycan cell wall - allows most of stain to wash off
- Pink
- Have a phospholipid bilayer outside the cell wall
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Bacterial Flagella
- Long, hollow, rigid, helical cylinders made from globular protein called flagellin
- Rotate counterclockwise to propel bacteria in single direction
- When they are rotated clockwise, bacteria tumbles
- Flagellum is propelled using energy from proton gradient rather than ATP
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Bacterial Reproduction
- Three forms of genetic recombination: Conjugation, transformation, & transduction
- Cell division: binary fission - asexual reproduction
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Binary Fission
- Circular DNA is replicated
- Two DNA polymerases begin at same point on circle (origin of rep) & move in opposite directions making complementary single strands that combine with their template strands to form 2 complete DNA double stranded circles
- The cell then divides, leaving 1 circular chromosome in each daughter cell. The 2 daughter cells are genetically identical
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Conjugation
- Requires that one bacterium have a plasmid w/ the gene that codes for the sex pilus
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Plasmid
Small circles of DNA that exist & replicate independently of the bacterial chromosome
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Sex Pilus
Hollow, protein tube that connects 2 bacteria to allow the passage of DNA
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F Plasmid (Conjugative Plasmid)
Donates resistance to certain antibiotics
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Transformation
Process by which bacteria may incorporate DNA from their external environment into their genome
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Transduction
When capsid of a bacteriophage mistakenly encapsulates a DNA fragment of host cell, and then when they infect a new bacteria they inject the harmless bacterial DNA fragment instead of a virulent viral DNA fragment
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Endospores
- some gram + bacteria can form them
- can lie dormant for hundreds of years
- Resistant to heat, UV radiation, chemical disinfectants and desiccation
- can survive in boiling water for over an hour
- Formation is triggered by lack of nutrients
- Formed when bacterium divides within its cell wall & one side then engulfs the other
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Kingdom Fungi
- Lots of diversity
- Three divisions w/in kingdom: Zygomycota, Ascomycota, & Basidiomycota
- Separated into divisions, not phyla, like plants
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Fungi
- All are eukaryotic heterotrophs - obtain food by absorption rather than ingestion
- Most considered saprophytic
- Most possess cell walls called septa, made of the polysaccharide chitin
- With exception of yeast, they are multicellular
- cell may contain one or more nuclei
- Nuclei w/in single cell may or may not be identical
- Lack centrioles
- Mitosis takes place entirely in the nucleus
- The nuclear envelope never breaks down
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Fungi - Absorption of Food
They secrete digestive enzymes outside their bodies & then absorb the products of digestion
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Saprophytic
Live off dead organic matter, but many fungi don't distinguish between living and dead matter & thus can be potent pathogens
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Fungi's Growth State
They consist of a tangled mass called a mycellium of multiple branched thread-like structures called hyphae
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Chitin
- More resistant to microbial attack than is cellulose
| - Same substance the exoskeleton of arthropods is made
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Septa
- Usually perforated to allow exchange of cytoplasm between cells called cytoplasmic streaming
- cytoplasmic streaming allows for very rapid growth
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Fungi Reproduction
- Alternate between haploid & diploid stages, but haploid stage predominates & is their growth stage
- Hyphae are haploid
- Can reproduce sexually or asexually
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Fungi Asexual Reproduction
- Occurs by producing spores or budding (cell fission)
| - Occurs when conditions are good
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Fungi Sexual Reproduction
- Occurs between hyphae from 2 mycelia of different mating types + and -
- Occurs when conditions are tough
