Chapter 3 Flashcards
Amphitrichous
Flagella at both poles of the cell.
Peritrichous arrangement
Hint: peri = around
Flagella are dispersed randomly over the surface of the cell
Lophotrichous
Small bunches, or tufts of flagella emerging from the same site
Monotrichous
Single flagellum
What is the primary function of the flagellum
Motility and propulsion
Chemotaxis
Movement of bacteria in response to chemical stimuli
Flagellum positive chemotaxis
Movement TOWARD favorable chemical stimulus
Flagellum negative chemotaxis
Movement away from a repellent
Run (flagellum)
Rotation of flagellum counterclockwise, resulting in a smooth LINEAR direction
Tumble (flagellum)
Reversal of the direction of the flagellum, causing the cell to stop and change course.
Attachment points of channels on the external surface of a bacterium
Fimbriae, pili, and nanotubes/nanowires
S layer
Single layers of thousands of copies of a single protein linked together like tiny chain link fences.
Only produced when bacteria are in a hostile environment.
Glycocalyx
Coating of repeating polysaccharide or glycoprotein units.
A glycocalyx is considered a __________ when the glycoprotein molecules are loosely associated with the cell wall.
slime layer
A glycocalyx is considered a _________ when glycoproteins are more tightly bound, denser, and thicker.
Capsule
Bacterium capsules
Formed by many pathogenic bacteria
Have greater disease-causing abilities (increased pathogenicity)
Protect against host white blood cells called phagocytes.
Biofilms
Plaque on teeth protects bacteria from becoming dislodged.
Responsible for persistent colonization of plastic catheters, IUDs, metal pacemakers, and other implanted medical devices.
Good location for bacteria to attach to and colonize.
How Archaea & Bacteria are different than Eukaryotes
How organisms are different from eukaryotes:
The way their DNA is packaged: lack of nucleus and histones.
The makeup of their cell wall: peptidoglycan and other unique chemicals.
Their internal structures: lack of membrane bound organelles
All bacterial cells possess:
Cytoplasmic membrane (holds cytoplasm inside)
Cytoplasm
Ribosomes
Cytoskeleton (structure)
One or a few chromosomes.
Most bacterial cells possess:
- Cell wall
- Surface coating called glycocalyx
SOME but not all bacterial cells possess
Flagella, pili, and fimbriae (movement)
An outer membrane
Nanotubes
Plasmids
Inclusion bodies
Endospores
Microcompartments
*Most of these are observed in archaea as well
Many bacteria function as _________ and ________, unicellular organisms.
But some act as a _______ in colonies or biofilms.
Some communicate through _______.
; independent and single-celled
; group
; nanotubes
Bacteria have an average size of ____ _________.
; 1 micrometer
Cocci (plural): circumference of ________.
; 1 micrometer
Strepto-
=chain of
ie. Streptobacilli
Staphylo-
=irregular cluster of
ie. Staphylococcus
Rods: length of _______ and width of ________.
; 2 micrometers
; 1 micrometer
Pleomorphism
variations in cell wall structure caused by slight genetic or nutritional differences
Coccus
Ball or sphere shaped, can be perfectly round or oval/bean shaped, pointed variants; grape looking
Rod/Bacillus
- varied in actual form
- blocky, spindle shaped, round ended, long and thread like, drumstick shaped
- when short and plump called “coccobacillus”
Vibrio
-gently curved rod shapes
Spirillum
Slightly curled or spiral shaped body; A rigid Helix, twisted twice or more along its axis.
Spirochete
resembles spring or corkscrew
flexible
Filaments
Multiple branches off of a basic rod structure (ie. Streptomyces)
Single coccus
one coccus
Diplococci
two coccus
Staphylococcus
irregular cluster of cocci
Tetrads
groups of four
Streptococci
chains of coccus
Sarcina
cubicle packet of 8, 16, or more cells
Diplobacilli
pair of cells
Streptobacilli
chain of bacillus
Palisades
cells of a chain that remain partially attached by a small hinger region at the ends
Fimbria/Fimbriae
Small bristle-like fibers sprouting off the surface of many bacterial cells.
Allow tight adhesion between fimbria and epithelial cells, allowing bacteria to colonize and infect host tissues.
-can be for attachment or movement of fluid around cell
Composition of cell envelope
- Lies outside the cytoplasm
- Composed of two or three basic layers that each perform a distinct function, but together act as a single protective layer
1. Cell wall
2. Cytoplasmic membrane
3. Outer membrane (in some bacteria)
bacteria that stain purple
gram-positive
bacteria that stain red
gram-negative
gram neg cell envelope
Gram neg cell envelope= closed sandwich with small middle peptidoglycan
gram pos cell envelope
open sandwich with huge peptidoglycan
The Cell Wall (in bacteria)
Provide strong structural support to keep the bacterium from bursting or collapsing because of changes in osmotic pressure:
- Certain drugs target the cell wall, disrupting its integrity and causing cell lysis, which is disintegration or rupture of the cell.
- Gains its relative rigidity from peptidoglycan.
Peptidoglycan
- Compound composed of a repeating framework of long glycan (sugar) chains crosslinked by short peptide (protein) fragments.
- Provide a strong but flexible support framework
Gram pos cell wall
Thick, homogeneous sheet of peptidoglycan:
20-80 nanometres in thickness.
Contains teichoic acid and lipoteichoic acid.
- Function in cell wall maintenance and enlargement.
- Contribute to the acidic charge on the cell surface.
gram neg cell wall
Thin, single sheet of Peptidoglycan:
-much thinner than gram pos
1-3 nanometers in thickness (vs 20-80nm in gram pos)
Thinness gives gram neg cells more susceptibility to lysis (cell breakdown).
Steps in Gram Staining
- Crystal violet stain (stains gram pos and neg purple)
- Gram’s iodine is added (stabilizer that causes dye to form complex mesh works in the peptidoglycan)
- Alcohol rinse (gram neg loses colour due to its thin layer of peptidoglycan and gram pos stays purple due to thick peptidoglycan trapping dye)
- Safranin (red dye) is then added causing the previously clear gram neg cell wall to turn red and the gram pos stays purple
Non typical cell walls: acid-fast bacteria:
Mycobacterium and Norcardia
-Contain peptidoglycan and stain gram-positive (purple), but bulk of cell wall is composed of unique lipids.
Mycolic Acid (found in mycobacterium):
- Very long chain fatty acid.
- Found in the cell walls of acid-fast bacteria.
- Contributes to the pathogenicity of the bacteria. Makes bacteria highly resistant to certain chemicals and dyes.
Non typical cell walls: archaea
Exhibit unusual and chemically distinct cell walls.
Some have cell walls composed entirely of polysaccharides.
—» others have cell walls made of pure protein.
All LACK true peptidoglycan structure.
Some lack a cell wall entirely.
Mycoplasms (genus of bacterium)
Naturally lack a cell wall
Sterols(fats) in the cell membrane stabilize the cell wall against lysis
Mycoplasma Pneumoniae: “walking pneumonia” (not as dramatic as bacterial pneumonia)
L forms
Some bacteria that naturally have a cell wall but lose it during part of their life cycle
Role in persistent infections
Resistant to antibiotics
The gram negative outer membrane
*Similar in composition to most membranes, except it contains specialized polysaccharides and proteins.
Lipopolysaccharides: lipids and then bunch of sugars
- Signaling molecules and receptors
- Endotoxin (harmful to human body - fever and shock)
Porin Proteins (think of pores in our face- membrane channels)
-Specialized membrane channels that only the outer membrane allows certain chemicals to penetrate
Cytoplasmic Membrane Structure
A lipid bilayer with proteins embedded.
Serves as a site for:
Energy reactions
Nutrient processing
Synthesis
Regulates transport of nutrients and wastes —->
Selectively permeable: special carrier mechanisms for passage of most molecules
Selectively Permeable Reasons of importance
Too much water out= cell shrinks and dies
Too much water in= cells bursts and dies
Too much sugar out= not enough food and dies
Differences in Cell Envelope Structure *gram neg
Outer membrane of gram-negative bacteria has an extra barrier:
Resistant to certain antimicrobial chemicals
More difficult to inhibit or kill than gram positive bacteria (as neg has extra structure)
Alcohol based compounds dissolve lipids in the outer membrane and therefore damage the cell:
-Alcohol swabs used to cleanse the skin before certain medical procedures
**Treatment of infections caused by gram negative bacteria requires drugs that can cross the outer membrane.
The Cytoplasm
70-80% water
sugars, amino acids, salts
Bacterial Chromosomes and Plasmids:
The hereditary material of most bacteria exists in the bacterial chromosomes
-DNA is aggregated in the nucleoid
Plasmids: nonessential pieces of DNA
-confer protective traits such as drug resistance and toxin/enzyme production
Ribosomes
- site of protein synthesis
- 60% rRNA and 40% protein
Inclusion Bodies/Microcompartments
- food storage
- pack gas into vesicles for buoyancy
- store crystals of iron oxide
Cytoskeleton
- some bacteria produce long polymers (protein) similar to eukaryotic cells for the cytoskeleton
- in eukaryotic cells may be a potential target for antibiotic development
Sporulation
induced by environmental conditions
______ are the dormant type of cells that regrow into a new bacterium when the environmental conditions become favorable.
They are a result of _______.
; Endospores
; Sporulation
Endospores
resist extremes of heat, drying, and freezing, radiation, and chemicals that would kill vegetative cells
-» really hard to kill and prevent infection
Medical significance of Bacillus anthracis
agent of anthrax
medical significance of Clostridium tetani
agent of tetanus
medical significance of Clostridium perfringens
cause of gas gangrene
Medical significance of Clostridium botulinium
cause of Botulism
medical significance of Clostridium difficile
a serious gastro disease
Archaea
- a third cell type in a separate super kingdom
- exhibit a novel method of DNA compaction
- -> unique membrane lipids, cell wall components, and pilin proteins
Archaea Extremophiles
- some live at extreme high or low temps
- some live on sulfur or methane
- some need extremely high salt or acid concentrations to survive
- Some live on the human body and may be capable of causing human disease
Bacterial Species
- A collection of bacterial cells, all of which have an overall similar pattern of traits
- And share at least 95% of their genes as matches
Subspecies, strain, or type:
-Bacteria of the same species that have differing characteristics
Serotype
-Representatives of a species that stimulate a distinct pattern of antibody (serum) responses because of unique surface molecules
Gracilicutes
taxonomic category of bacteria that have gram-neg envelopes; thin skinned
Firmicutes
Taxonomic category of bacteria that have gram-pos cell envelopes; thick strong
Trick: A-firm-itive = gram pos
Tenericutes
taxonomic category of bacteria that lack cell walls
Mendosicutes
taxonomic category of bacteria that have unusual cell walls; archaea
