Unit 2 Flashcards
Domain bacteria are
Single-celled organisms
Prokaryotic
Ubiquitous
Always include what characteristics when describing bacteria
Morphology (shape)
Size of individual cell
Arrangement
Gram stain result
Cocci (singular coccus)
Spheres
Bacilli (singular bacillus)
Rods or filaments
Coccobacilli (singular coccobacillus)
Short plump rods, almost ovals
Vibrios
Comma-shaped (curved rod)
Singular
Spirilla
Rigid helix
Have flagella for motility
Singular (less common in chains)
Spirochetes
Corkscrew (telephone cord)
Motility: flagella to wind or by spring type creeping
Singular
Pleiomorphism
Having more than one shape or form
The variability of bacteria can depend on
The health of bacteria during various stages of growth, or if growth under different conditions
True or false
Always measure individual cells
True
What unit are measurements of bacteria taken in
Microns
How to measure cocci
Take the diameter of the sphere
How to measure bacilli
Give width and length of each rod
How to measure spirilla, spirochetes, and filamentous
Give length while it is still curved/folded
True or false
Always measure the longest bacterium
FALSE
measure the most commonly represented size
Arrangement of cocci: singular
Coccus
Arrangement of cocci: diplococci
Pairs
Arrangement of cocci: streptococci
Chains
Arrangement of cocci: staphylococci
Grape like clusters
Arrangement of cocci: tetrads
4 in a square
Arrangement of cocci: sarcinae
8 coccus in a cube
Arrangement of bacilli: bacillus
Singles
Arrangement of bacilli: diplobacilli
Pairs (end to end)
Arrangement of bacilli: streptobacilli
Chains of 3 or more (end to end)
Arrangement of bacilli: palisades
“Picket fence” arranged side by side
Bacteria colony
Mound of bacteria cells visible to the naked eye
True or false
All cells in a bacteria colony are derived from a single bacteria cell
True
Different bacteria produce colonies with distinct shapes and colors when grown in vitro, what do these characteristics help identify
The genus
What is a colony forming unit
The single bacterium that started a colony
True or false
All the cells in a colony are identical
True
True or false
Each colony represents one colony forming unit
True
A bacterial cell
Unicellular
Prokaryotic
Lack membranes
Cytoplasmic membrane/cell membrane/ plasma membrane
Thin flexible membrane that surrounds EVERY living cell
Selectively permeable
Contains carbohydrates, proteins and cholesterol
What is the main component of a cytoplasmic membrane
The phospholipid bilayer
What are the proteins a cytoplasmic membrane contains (5)
Channels and transporter proteins Signal receptor proteins Metabolic proteins Attachment proteins Surface antigen proteins
What are channel and transporter proteins in a cytoplasmic membrane
They move substances in and out of the cell
How do some antibiotics enter cells
By targeting bacteria with transporter and channel proteins to get into the cell
What are signal receptor proteins in cytoplasmic membranes
Proteins that bind to signals from the environment
What are some things a signal receptor protein may tell a the bacterium to do
Start or stop replicating
Move away from harm
Produce enzymes for metabolism
Produce enzymes to inactivate some antibiotics
What are metabolic proteins in cytoplasmic membranes
Energy producing proteins located along the folds in the cytoplasmic membranes (because bacteria do not have mitochondria which are membrane bound organelles)
Mesosomes
The folds or invagination on cytoplasmic membranes
What are attachment proteins on cytoplasmic membranes
Attach bacterium to specific cells in the host
(Certain bacteria can only attach to certain cells)
Essential for infection to occur
What are surface antigens on cytoplasmic membranes
Any protein on the surface of the bacteria that can be recognized by the host’s immune system
“Molecular ID tags”
What can surface antigens aid in when staining
Can be used to identify different strains of the same species
Functions of the cytoplasmic membrane (6)
Encloses cytoplasm
Barrier function
Regulates movement of molecules in/out of the cell
Interacts with environment via signal receptors
Site for energy production
Attachment
Cytoplasm
The fluid that fills the cell (60-70%)
Where is the cytoskeleton
Molecular scaffold that spans across the cytoplasm
true or false
the cytoplasm is metabolically active
True
Ribosomes
Complex structures consisting of protein and ribosomal RNA
Site or protein synthesis (where RNA is read to assemble proteins)
What is the process of translation
Where RNA is read and used to assemble proteins
Chromosomal DNA
A single, circular strand of DNA that contains all essential genes
True or false
There are fewer genes in chromosomal DNA in eukaryotic cells
True
Where is chromosomal DNA located
In the nucleoid
What are plasmids
“Extra” circular pieces of DNA containing 1-2 genes (not a part of chromosomal DNA) (located outside the nucleoid)
Are the genes located on plasmids essential to life
No, but they are beneficial to survival by providing advantages
What are some advantages of some genes in plasmids
Proteins that provide antibiotic resistance
Genes for specific toxins or attachment proteins
Genes that enable bacteria to produce capsules
Do all bacteria have plasmids
No, some have one, more than one or none
Do plasmids replicate independently of chromosomal DNA
Yes
True or false
Plasmids are very resistant to degradation and can even survive after the bacteria have been destroyed
True
What are 3 ways plasmids are transferred between cells
Replication
Transformation
Conjugation
Transfer of plasmids via Replication
When a bacteria cell divides, plasmids also duplicate and an equal number of plasmids are given to the daughter cell
Transfer of plasmids via transformation
Where the cell membrane opens up and allows the cell to take up a plasmid from the environment from a bacteria that has died but the plasmid survived
Transfer of plasmids via conjugation
When the direct contact between 2 bacteria cells through the creation of a temporary bridge allows the transfer of plasmids
The cell wall surrounds
The cytoplasmic membrane
Categories of cell walls
Gram positive
Gram negative
Acid fast
(Based on staining properties)
The type of cell wall helps identify
The genus
Functions of the cell wall
Maintains shape
Protects from lysis Due to osmotic pressure
Protects from toxic materials
Attachment
Prevents phagocytosis by WBCs in the immune system
Two ways to break down the cell wall
Lysozymes: breaks linkages of cell wall
Beta-lactames: class of antibiotics that prevent proper synthesis of the cell wall
Penicillin and cephalosporins are in what class of antibiotics
Beta-lactames
Cell wall structure and components
Primary component: peptidoglycan (2 different polysaccharides linked together)
Peptide cross links: short peptide chains that link peptidoglycans together
Gram positive wall
Thick: 40-90% of cell mass
20-80 layers of peptidoglycan Joined by peptide cross links
What is transpeptidase
Enzyme required to make the peptide cross links in cell walls
What is teichoic acid in the cell wall
Long molecules that help embed the cell wall to the cytoplasmic membrane
Also on the surface of the cell to help attach bacteria to other bacteria
Why are gram positive bacteria susceptible to the beta-lactam class of antibiotics?
These antibiotics bind to and block the function of transpeptidase enzyme and prevent the formation of peptide cross links between peptidoglycan strands
(Makes susceptible to osmotic pressure lysis)
Gram negative cell wall
Thin: 10% of cell mass
Only 1-2 layers of peptidoglycan
Layers of a gram negative cell wall
Peptidoglycan layer: 1-2 layers, closest to cytoplasmic membrane
Outer membrane: 2 layers of lipids (inner layer is a single sheet of phospholipids, outer layer is a single sheet of lipopolysaccharides LPS)
Periplasmic space: space between the cytoplasmic membrane and outer membrane (peptidoglycan layer is in this space)
What are lipopolysaccharides
The molecule that makes up the outermost layer of a gram negative cell wall (part of the outer membrane)
What are lipopolysaccharides important for?
To bacteria: establishing infection
To host: to fight infection
What are the 3 parts of a lipopolysaccharide
O-antigen Core polysaccharide Lipid A (endotoxin)
What is the O-antigen on lipopolysaccharides
Repeats of polysaccharide units (hydrophilic)
Smooth: bacteria with long chains
Rough: bacteria with short or no chain
True or false
Some species or strains are distinguishable by the sugar molecule in their o-chain (gram negative wall)
True
Why are the O antigens on gram negative cell walls important for bacteria to establish infection?
WBCs unable to grab onto smooth bacteria
Aid in attaching to epithelial cells
Some bacteria can alter the sugars that make the O-antigen: can evade the immune system
The immune system can recognize sugars in the O antigen when fighting infection, what happens
The immune system targets these for destruction
The O chain will trigger non-specific inflammation
Lipid A (AKA endotoxin)
The tail of lipopolysaccharides made of lipid chains
They are the same in all gram negative bacteria
Hydrophobic
Holds lipopolysaccharide in place
True or false
Lipid A is one of the strongest activators of inflammation
True
Endotoxic shock
Condition where excess inflammation causes blood vessels to dilate, drop blood pressure, and cause systemic shock
Caused by a release of large amounts of lipid A during gram negative infection
Can be fatal
Why can endotoxic shock never happen in gram positive bacteria
Gram positive cell walls do NOT contain lipopolysaccharides (which have lipid A) only gram negative cell walls do
Why do some bacteria do not gram stain?
They have no cell wall structures similar to gram positive and negative walls
Acid fast bacteria
Their cell wall is similar to gram positive but contain large amounts of mycolic acid (waxy) (long chain of fatty acids)
Ex. Mycobacterium
Mycoplasma
Do not have cell walls
Plasma membrane more resistant to osmotic pressure
Very pleiomorphic
What does the Periplasmic space contain
Proteins to digest macronutrients
Proteins to break down toxic compounds before the cross the plasma membrane
Synthesis and storage of pathogenic factors
Flagella
Threadlike projections that allow motility
All spirochetes and spirilla have them
What does the immune system recognize in flagella
The proteins that make the flagella (act as antigens)
Location and number of flagella on a bacterium determine
Type and speed of movement
Bacteria with many flagella that move together tend to be
Faster
True or false
You can see the flagella on bacteria
False
But you can see fast motility
Benefits of motility on bacteria
Can move towards supportive environments
Can move away from harmful substances
Flagella movement
Fastest
Flagella acts as a propeller to swim through lipids
Spirochetes motility
Corkscrew motion due to Periplasmic flagella (specific to Spirochetes)
Twitching motility
Mediated fimbriae, crawling on surface or through lipids
Gliding motility
Pushed by slime made by the bacteria
Chemotaxis
Process of identifying and then moving away from a chemical via receptors that tell the bacteria what to do
Positive chemotaxis
Moving towards attractants
Negative chemotaxis
Moving away from repellants
Fimbriae (singular fimbria)
Short, thin, hair like protein structures that extend out of the cell wall
Primary function: attachment to surfaces
Pili
Very large protein structures that extend from cell wall
2 functions:
Attachment
Forms connection during conjugation
Capsules
Polysaccharide secreted around the cell wall
Sugar units well organized
Attached to cell, not easily removed
Primary functions:
Resistance/protection (from drying out)
Attachment
Slime layers
Polysaccharide secreted around the cell wall
Sugar units are not uniform, loose coating, easily removed
Primary functions: Resistance/protection Attachment Motility formation of biofilms
Advantages of capsules and slime layers (5)
Resistance to phagocytosis and bacteriophages
Protection from drying out
Protects from detergents and antibiotics
Attachment
Motility (slime)
Biofilms
Communities of bacteria (and yeast) embedded in a matrix that attach to a surface
Single or hundreds of different species of bacteria
Matrix sticks microbes to one another and onto a surface (usually moist)
4 steps in biofilm formation
1) cell attachment to surface (by receptors, flagella, fimbriae)
2) cell produces exopolysaccharides (outside cell)
3) biofilm matures (increase in size and number)
4) cells from biofilm disperse and can reattach elsewhere
Where are biofilms common to?
Standing water Rough surfaces Surgical implants Catheters Heart valves Teeth
Biofilms are self-sustaining so they are
Hard to treat with antibiotics or disinfectants
