CAS BI 114 Lecture Notes - Lecture 2: Biofilm, Nanowire, Glycocalyx
30 Apr 2018
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Infectious Organisms
Prokaryotes (unicellular organisms)
•Main Structures
•DNA
•Not contained in a membrane-bound nucleus
•Not condensed around proteins
•Cell Wall
•Walls are made of peptidoglycan (sugars and amino acids)
•Internal Structures
•Contains very few organelles which are not membrane bound
•Structures common to all bacteria: Cell Membrane, Cytoplasm, Ribosomes, Nucleoid/
Chromosomes (DNA clusters), Cytoskeleton
•Structures common to most bacteria: Glycocalyx (capsules & slime layers - a type of glue)
•Structures common to some bacteria: Appendages (flagella, pili, fimbriae - to help with
movement), Outer Membrane, Inclusions, Endospore, Plasmid, Intracellular Membrane
Prokaryotic Life
•Most bacteria live on their own
•Each cell is capable of its own reproduction, metabolism, nutrient processing and storage
•Usually act as an individual (once reproduced, they live separately from parents)
•But some types of bacteria can act as a group (ex: colonies, biofilms - plaque on teeth, surface
bacteria in our bodies)
•Individual bacteria can adapt to living in a group (ex: produce new compounds, stop producing
old compounds)
•This is not necessary but done in order to achieve a purpose
•Bacterial Communities
•Bacteria living in communities can change their communication with each other as well as their
behavior in the colony
•Communication through cell signals sent through nanowire
Prokaryote Diversity
•Size
•Most bacteria are 1-2 microns
•Some can be as small as 0.2 micros while some can be as large as 0.5 millimeters
•Naming/Classifying Bacteria
•First name is capitalized and abbreviated
•Last name is not capitalized or abbreviated
•Kept in italics
•Named due to its characteristics (typically shape)
•Shape, Colonial Arrangement (how they interact with each other)!
Appendages
•Appendages - extensions off the cell itself
•Extensions of the cytoskeleton can help unicellular organisms stay put/move around/connect to others
•Movement: flagella, axial filaments/periplasmic flagella
•Flagella
•Long, whip-like extensions
•Help bacteria to achieve rapid directional motion
•Chemotaxis - movement in response to a chemical
•When chemical receptors bind to the flagella to spark movement
•Chemical detection and flagella are linked intracellularly
•Connection to Others: pilli, nanotubes
•Pili
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•Long, rigid, hollow extensions
•Only located on gram-negative
•Utilized in plasmids & conjugation
•Staying in Place: fimbriae
•Fimbriae
•Several of these exist, usually all over the cell
•Helps in forming the initial biofilm
•Helps adhere to the surface of bacteria
Surface Structures
•Glycocalyx
•Contributes to the surface coating of polysaccharides
•Loose arrangements of polysaccharides are called the slime layer
•Polysaccharides that are held more tightly to the cell are called a capsule
•Biofilms
•Glycocalyces can be instrumental in the formation of biofilms
•Cells stick to the coating on the surface
•As cells divide, they form a dense mat bound together by the sticky glycocalces
•Additional microbes are attracted to the film to create a mature community
•*strength in diversity
•Capsules
•Often found on pathogenic bacteria
•Help prevent against white blood cells and immune system responses from engulfing/destroying
them
•Often, capsulated bacteria that lose their capsules lose their pathogenicity (infectivity) as well
Gram-Positive v. Gram. Negative
•Measures whether or not a bacteria will retain all the properties of the gram stain
•2 common cell envelop arrangements
•Membrane + thick Peptidoglycan Layer
•Membrane + thin Peptidoglycan Layer + Outer Membrane
•Gram stains can be used to distinguish between these two arrangements
The Outer Membrane
•Similar to the cytoplasmic/cell membrane except it has a carbohydrate called lipopolysaccharide
(LPS) among the phospholipids
•LPS - an important and common component to gram-negative bacteria
•Can alert and trigger huge immune responses
•Used in diagnostics and research
Inside Bacterial Cells
•No nucleus or membrane-bound organelles
•Can include bacterial chromosomes + plasmids
•Ribosomes
•Bacterial (Prokaryotic) & Eukaryotic ribosomes are similar but not the same
•Both consist of two subunits but have different densities
•Bacterial Ribosomes have a density of 70S while Eukaryotic Ribosomes have a density of 80S
•We want to create drugs/antibiotics that are unique to prokaryotes so their effectivity is increased
•Inclusions/Granules
•No DNA
•Membrane-bound sacs that contain things
•Can manufacture inclusions to better cope with environmental properties
•Uses of inclusions:
•Store food
find more resources at oneclass.com
find more resources at oneclass.com
