Lecture 1/2 - Introduction to Bacteria Flashcards
What is PCR?
Polymerase Chain Reaction
How does PCR relate to Koch’s postulates?
Isolation of microbe along with identification
What is the ID based on when PCR is used?
NA amplification
Amplification of gene sequences
Sequence must be KNOWN!
What is a pro to using PCR?
Growth in pure culture is not needed.
What are the two components to a bacteria’s name?
Genus + Species
What is another component to the name of some bacteria?
Serotype
What are the categories for bacterial morphology?
Size
Shape
Arrangement of cells
What is the average range when it comes to the size of a bacteria?
0.2 to 2.0 um in diameter
What is the order (small to large) of the following:
Bacillus - Spirochete - Coccus
Coccus - Bacillus - Spirochete
Describe coccus.
Spheres/round
Describe bacillus.
Rod
Describe vibrio.
Curved rod
What are the two subtypes of spiral?
Spirillum + Spirochete
Describe Spirillum.
Rigid, sprial-shaped rod
Describe spirochete.
Flexible, thin, spiral-shaped rod
Describe coccobacillus.
Short rod
What is pleomorphic?
One species but several different kinds of shapes
What type of bacteria are arrangements most likely to describe?
Coccus
What is strepto?
Chain
Describe staphylo?
Grape-like cluster
What are the three major parts to the cell envelope of a bacteria?
Glycocalyx + Cell wall + Cytoplasmic membrane
What are the two things that a glycocalyx can form?
Capsule + Slime layer
What is the glycocalyz made from?
Polysaccharides + glycoproteins
Where is the glycocalyx located?
Outside of the cell wall
What special structures does the glycocalyx add to bacteria like e. coli and salmonella?
K + V antigen
What are the K and Vi antigen found on the glycocalyx?
Used for serotyping
What is the function of the glycocalyx?
Protects from drying out, from phagocytosis, and toxins
Promotes adherence to host cell = biofilm
Can be a virulent factor in some bacteria
What bacteria is virulent when a glycocaylx is present?
Streptococcus pneumoniae
What is an antigen?
Molecule that binds to Ab or Ag receptors on T/B cells
What is an immunogen?
Antigen that causes an immune response
What are the characteristics of the slime layer?
Loose, non-uniform
More diffuse
What are the characteristics of a capsule?
Rigid, uniform and closely surrounds cell
What is used to ID a capsule?
Quellung test - ID’s by serotyping
What is clinically important about the cell wall of a bacteria?
Tells you if it is gram +/- or acid fast. tells you what kind of antibiotic you should try
What two genera do not have a cell wall?
Mycoplasm + Ureaplasm
Where is the cell wall located?
Outside cell membrane
What is the function of the cell wall?
Maintain shape
Prevent uptake of too much H2O
Why is uptake of H2O a big concern?
Bacteria live in a hypotonic environment, water is constantly trying to get into cell due to concentration gradient.
What is the main component of the cell wall?
Peptidoglycan
What is the backbone of the cell wall made of?
Repeating disaccharides (NAG-NAM)
What links the backbone of the cell wall in bacteria?
Transglycosylation via glucosidases
What does PEP attach to in the cell wall?
NAM
What is crosslinked in the cell wall?
PEP - Pentapeptide
What crosslinks PEP?
Transpeptidation via transpeptidase
What PEP structure is special in gram-positive bacteria?
Pentaglycine bridge
What bacteria has pentaglycine bridge?
Staphylococcus spp.
What is the primary stain for gram staining?
Crystal violet
What is the counterstain for gram staining?
Safranin
What color is gram-negative?
Pink/Red
What color is gram-positive?
Blue/Purple
How many layers of peptidoglycan does gram-negative have?
~2
How many layers of peptidoglycan does gram-postive have?
> 25 layers
What are the major layers of the gram-negative bacteria?
Glycocalyx - Outer membrane - Periplasm space w/ cell wall - Cytoplasmic membrane
What is the periplasmic space?
In Gm(-) Space btwn cytoplasmic membrane + outer membrane
What does the periplasmic space contain?
Thin peptidoglycan layer
Transport proteins
Hydrolytic enzymes
What are the major requirements for Koch’s Postulates?
Requires growth in pure culture
First method for isolation/identification of bacterial cause of disease
Where is the outer membrane located?
External to periplasmic space
How many layers to the outer membrane?
Two - Inner and Outer
What is the structure of the inner layer of the outer membrane?
Identical to the cytoplasmic membrane
What is the structure of the outer layer of the outer membrane?
this is what contains the endotoxin aka LPS
Most gram-negative bacteria
What is the function of the outer membrane?
May impede phagocytosis
Protective permeability to large molecules + hydrophobic compounds
What are the three components of LPS? Where is LPS contained again?
Polysaccharide core Lipid A O polysaccharide (O-antigen)
Found on the Outer layer of the outer membrane
What is the structural characteristics of the O antigen?
Long, linear repeating units of carbohydrates
Highly variable
What is clinically important to know about the O-antigen when it comes to it being highly variable?
Gives it antigenic variation = it can change the O antigen on it’s surface allowing it to evade the immune system and stay safe in host longer.
What is the “function” of the O antigen?
Antigen/Immunogen
Helps us ID the bacteria
What is antigenic variation?
Change in genetic codings for a structural proteins, leading to the creation of a new bacterial antigen.
What is the structure of the core polysaccharide?
Branched polysaccharide that is 9 to 12 sugars long
Contain KDO
What is KDO, found within LPS core?
Ketodeoxyoctonoix acid, a unique sugar found in LPS
Where is Lipid A found on LPS?
Attacted to the outer phospholipid layer of the outer membrane
What is a virulence factor?
Structure or substance that enhances the pathogenesis of the microbe
What is the basic description of an Exotoxin?
Secreted proteins
What is the basic description of an Endotoxin?
Structural lipopolysaccharide
What kind of bacteria are porins found in?
Gram-negative
What are the structural components of porin?
3 part protein = channel forming, span out membrane
What is the function of porins?
Control diffusion of small molecules
For example: Sugars, metal ions, AB’s
What are the special characteristics only found in the cell wall of a gram-positive bacteria?
Teichoic + Lipotheichoic acid within the huge layer of peptidoglycan
What is the importance of Teichoic + Lipoteichoic acids?
Virulence factors of gram-positive bacteria
What makes up the cell wall of a gram-positive bacteria?
Cytoplasmic membrane
– and –
Peptidoglycan
What is teichoic acid?
Adhesins; polymers of ribitol phosphate/glycerol phosphate
Covalently linked to muramic acid
What is the function of teichoic acids?
Help stitch together the huge peptidoglycan layer
What is lipoteichoic acids?
LTA; teichoic acid anchored to cytoplasmic membrane
What do antimicrobial cell wall inhibitors tend to focus on?
Transpeptidation
Cell wall synthesis
What is transpeptidation in regards to the peptidoglycan of the cell wall?
The cross-linking of these molecules
What is the function of a lysozyme?
Degrades glycan backbone - breaks the bond between NAG + NAM
What is a lysozyme a component of?
Lytic enzyme of the innate immune system
Where in the body are lysozymes found?
Tears - Saliva - Mucus - Lysosomes of WBC
What is within the cell envelope of an acid-fast bacteria?
Cell membrane
Peptidoglycan
Mycolic acid layer
Where is the mycolic acid layer found?
Outer layer of outer membrane
Covalently linked to peptidoglycan
What type of bacteria is going to be acid-fast?
Gram-positive
What does the mycolic acid do?
Allows cell to resist desiccation + some AB’s + Phagocytosis by creating a waxy layer.
What is the primary stain of an acid-fast stain?
Carbolfuschin
What is the counterstain of the acid-fast stain?
Methylene blue
What color does an acid fast bacteria stain?
Red
What is an example of an acid fast bacteria given in lecture?
Mycobacterium
What is missing from the cytoplasmic membrane of bacteria?
Sterols
What is the function of the cytoplasmic membrane?
Active transport
Synthesis of cell wall material
Secretion of enzymes/toxins
ETC
What are the four major groupings of bacteria in regards to their staining abilities?
Gm (-)
Gm (+)
Acid-Fast
No cell walls
What are the two general external structures of a bacteria?
Flagella + Fimbria/Pilus
What is the structure of the flagella?
Filamentous protein structures that are anchored to the cell membrane
What is the function of the flagella?
Motility + taxis
Source of H antigen
What does polar refer in regards to external structure location?
Found on one or both ends
What is peritrichous in regards to the location of external structures on a bacteria?
Lateral, over entire cell surface
What is the structure of fimbria/pilus?
Associated w/ cell membrane, hair-like protein structures
How are pili arrange on the bacteria?
Peritrichously
What is the function of pili?
Promote adherence to host cell
Act as sex pilus
What exactly is a sex pilus?
Structure on SOME bacteria for congugation
What are the four basic internal structures of a bacteria?
Nuclear region
Ribosomes
Inclusion bodies
Endospores
What is the structure of the nuclear region in a bacteria?
NO nuclear membrane
Area that contains chromosomal DNA
What is the benefit of having no nuclear membrane in a bacteria?
Can synthesize protein quicker via coupled transcription and translation
What are the two basic types of bacterial DNA?
Chromosome + Plasmid
What is the structure of a bacterial chromosomal DNA?
dsDNA
CCC
Supercoiled
Haploid
What is the downside of being a hapliod?
No extra copy, mutations are expressed easily
What is the normal function of a plasmid?
Not essential for survival, encodes for things like AB resistance and toxins
What is the basic mechanism by which the plasmid is regulated?
Replicates separately from bacteria, but does use it’s machinery
What are inclusion bodies?
Storage for energy molecules in a bacteria
What is the structure of an inclusion body
Nonunit, membrane
What tends to produce endospores?
Gram-positive bacteria
What is an endospore?
Dormant protective stage of bacteria
What is the endospore made of?
Keratin = Coat
Dipicolinic acid = internal
What are the two gram-positive pathogenic genera that make endospores?
Bacillus + Clostridium