Week 6 Flashcards
What can we tell from the bacterial cell wall?
From the peptidoglycan in cell wall we can tell if a bacteria is gram positive or gram negative.
What happens if bacteria plasma membrane is removed?
Its contents will spill out into the environment and cell no longer exists.
Compare and contrast a bacteria’s nucleoid vs. plasmid.
Nucleoid - contains the bacteria’s genetic material. dsDNA, can be circular or linear (some more than one)
Plasmid - small, dsDNA as well, but it has fewer genes, and is non-essential to the bacteria.
True/False: Prokaryotes like bacteria have no membrane bound organelles.
True
True/False: Prokaryotes have non-expressed regions in their DNA (introns) like eukaryotes do.
False
Pili and Fimbrae play an important role in bacterial ______ to surfaces.
Adhesion
In bacteria, most of the metabolic processes are carried out in the ______.
Inner membrane
INSTEAD of in organelles in cytoplasm like in eukaryotes.
The capsule of bacteria is made up of ______ and _______.
Glycoproteins and glycolipids.
______ makes up the glycolipid layer of the outer membrane found exclusively in gram negative bacteria. It is also a major component in the membrane’s ____________.
Lipopolysaccharide (LPS)
Selective permeability
The ______ of bacteria determines its shape.
Cell wall
True/False: There is also cholesterol present in bacteria’s membranes.
False
____________ cannot grow in the presence of O2
Obligate Anaerobes
____________ must have O2 to grow.
Obligate Aerobes
What are the O2 requirements for facultative aerobic bacteria?
Facultative aerobic bacteria can perform aerobic respiration if oxygen is present but can switch to anaerobic fermentation if oxygen is absent.
Bacteria multiplies at a ______ rate.
Exponential
In the presence of adverse physiologic conditions (such as lack of nutrients) some bacteria may transform and undergo _______. They reactivate when the environment is more favorable.
Sporulation
The order of gram staining: 1) 2) 3) 4)
1) Violet dye
2) Iodide (that will bind to the violet dye)
3) Decolorizing agent
4) Counterstain pink (Safranin)
Why do gram-positive bacteria appear violet under the microscope?
Gram positive bacteria’s thick peptidoglycan cell wall retains the crystal violet-iodide dye complex even after the decolorizing agent is added.
______ staining is used to differentiate atypical bacteria (Mycobacteria and Nocardia).
Ziehl-Neelsen staining
What feature of Mycobacteria allow them to be differentiated by acid-fast staining?
Mycolic acids in their cell walls, which are stained by acid-fast staining.
Classify bacteria that take these formations: Diploids: \_\_\_\_\_ Chains: \_\_\_\_\_ Clusters: \_\_\_\_\_ Hyphae: \_\_\_\_\_
Diploids: Neisseria (pairs)
Chains: Streptococcus
Clusters: Staphylcoccus
Hyphae: Nocardia (long thread-like filaments)
Bacteria that stain _____ are gram-positive organisms; those that do not retain the purple dye and appear _____ are gram-negative.
Purple
pink
The order of how staining works and is applied:
1) _____ is added as the primary stain.
2) _____ is used as a mordant, fixing the crystal violet dye to the peptidoglycan.
3) ______ (usually alcohol or acetone) is used to rinse any unbound crystal violet stain and disintegrate lipids of the cell membranes.
4) ______ counterstain is applied, turning gram-negative bacteria reddish pink.
Crystal violet
Gram iodine
Decolorizer
Safranin red
What color do gram-positive bacteria stain and why?
Gram (+) bacteria stain purple due to their thick, cross-linked peptidoglycan cell wall.
What is metabolically inactive and enables bacteria to persist in a dormant phase when environmental conditions are not suitable or when nutrients are limited?
Spores!
When environment is favorable, then Sporulation occurs.
What are pili, and what are their functions?
Extensions on the bacteria cell wall that aid in adhesion to surfaces and other bacteria. They help enable survival of the organism by resisting washing.
Though pili, flagella and capsules are considered structural elements, they can also be ______.
Virulence factors
What are virulence factors?
Molecules or attributes expressed by different bacteria species that are often unique and add to their ability to cause symptoms.
How do exotoxins (from gram-negative and gram-positive bacteria) work against the host?
They are secreted and alter the host’s cell structure or function, causing harm.
Immunoglobulin A proteases are enzymes that cleave IgA, and do what?
IgA proteases from bacteria work against IgA itself on mucosa, to prevent opsonization and allow bacteria to evade the immune system.
____________ is the capability of some gram-positive species to invade host cells and either live inside of a phagosome or escape the phagosome.
Intracellular invasion
Protein A can inhibit opsonization by binding to the ____ of ____, thereby inhibiting complement fixation and phagocytosis.
Fc region of IgG.
Coagulase converts ______ to insoluble _____ capsule that surrounds the microorganism and limits access by immune cells.
Fibrinogen to insoluble Fibrin
Catalase produced by certain gram-positive species inhibits _________- mediated killing by neutrophils.
Hydrogen peroxide
_____ are lipids and proteins that can lyse red blood cells by destroying their cell membrane.
Hemolysins
What is the advantage of bacteria that can live intracellularly?
They go undetected from the immune system.
What are the two ways in which bacteria gains antibiotic resistance?
1) Plasmid exchange or conjugation
2) Bacteriophages (virus that infects bacteria) AKA transduction
Ultimately, genes of antibiotic resistance generally either result in the expression of _________ that inactivates the drug in question or results in a ________ within or on the bacterium at the drug’s target site of action.
expression of an enzyme
structural change
In terms of Catalase testing, Staphylococcus is catalase ____ and Streptococcus is catalase _____.
Catalase positive
Catalase negative
A positive coagulase test means that the bacteria can ______.
produce Coagulase.
alpha-Hemolysis, is considered a _______, will show a green darkening of the blood agar; this color change happens when hydrogen peroxide oxidizes hemoglobin.
Partial hemolysis
____, which will result in a complete clearing of blood agar.
beta-Hemolysis
______, which is designated when there is no change to the blood, again meaning no hemolysis occurs.
gamma-Hemolysis
Gram-positive bacteria uniquely produce _______.
Superantigens
What makes up peptidoglycan?
Cross-linked NAMs and NAGs
The bacterial envelope plays a large role in survival, _____, and resistance.
Virulence
Gram-negative bacteria have a _________ before the peptidoglycan layer and an additional impermeable
Periplasmic space
The outer membrane of gram-negative bacteria contains ________ and ______ that adds extra protection and resistance and porins that facilitate the diffusion of nutrients.
Lipopolysaccharides (LPS) and Lipoproteins
How do bacteria overcome an impermeable outer membrane?
Porins allow hydrophilic solutes to diffuse through and into the periplasm.
Compare LPS and exotoxins.
LPS is on the outside of the cell and is considered an endotoxin! Sometimes it can become dislodged and enter the environment without the cell necessarily dying. Exotoxins are purposely released into the surrounding environment after being produced inside the cell. BOTH are toxic to human cells.
The lipid A portion of bacteria’s LPS can bind to immune complexes and is a ________ of the immune system.
Potent stimulator
Endotoxins, like lipid A, can have effects, that if given enough time and damage, it will result in _____.
Sepsis.
Specifically, monocytes and macrophages have ____ and ____ receptors that bind lipid A.
TLR4 and CD14
Name the enzymes that determine bacterial pathogenicity.
1) Hemolysins
2) Cytolysins
3) Proteases
Name the three types of relevant Staphylococcus human pathogens.
1) S. aureus
2) S. epidermidis
3) S. saprophyticus
How will I know Staphylococci when I see them on a stain?
On gram stain, they are purple (+), and are spherical in shape and tend to cluster together like grapes.
What do Staphylococcus look like on Gram stain?
They appear as purple, grape-like clusters.
All Staphylococci are ______ organisms, meaning they are capable of aerobic and anaerobic growth.
Facultative anaerobic
Staphylococcus are catalase ____.
positive
What classifies S. aureus from all other forms of staphylococci as far as identifying between them?
A positive coagulase test, formation of clot.
Of the three species mentioned, only S. aureus is _________, resulting in complete lysis of red blood cells.
Beta-hemolytic
S. epidermidis is a commensal of the skin, but can cause severe endogenous infections in immunosuppressed patients and those with _____ catheters and ____ catheters.
Central venous
Foley
S. Saprophyticus is part of the ________ flora, and predominantly implicated in GU tract infections in sexually active young women.
Normal vaginal flora
Where are S. aureus, S. epidermidis, and S. saprophyticus found in the human body?
1) Nose
2) Skin
3) Vagina, respectively.
What virulence factor is unique to S. aureus and helps resist phagocytosis?
Protein A is the unique virulence factor that helps S. aureus resist phagocytosis.
_____: causes TSS and is historically associated with tampon use and foreign bodies.
TSST-1
______: is heat resistant and causes rapid-onset food poisoning.
Enterotoxin
_______: is a proteolytic exotoxin that cleaves the desmosomes, causing blister just below the stratum corneum of the epidermal skin.
Exfoliatin
What is an exotoxin that initiates potent activation of the immune response by facilitating binding of MHC II on antigen-presenting cells with the TCR of CD4 T cells?
Superantigens
Which S. aureus toxins are superantigens?
TSST-1 and enterotoxin
Most S. aureus strains resistant to conventional penicillin because of their ability to produce _______ enzyme.
Beta-lactamase enzyme
Can cleave penicillin’s beta-lactam ring and thus making the drug ineffective.
Only S. saprophyticus is _______ resistant.
Novobiocin
from the Novobiocin test.
______ is a selective lactose-containing media. Bacteria are streaked onto the plate, and lactose fermenters containing lactase can break down the sugar, turning the media pink.
MacConkey agar
What can MacConkey agar test for?
Used to differentiate among types of gram-negative bacteria and their ability to ferment lactose.
In the Hemolysis test, E. coli is ______.
Beta-hemolytic
Virulence factor in E. coli, ______, use fimbriae to attach to the brush border of the small intestines, causing what is commonly known as traveler’s diarrhea.
Enterotoxigenic E. coli (ETEC)
Enterotoxins (2) of ETEC are:
1) Heat labile (cAMP-inducing toxin)
2) heat-stable (cGMP-inducing toxin).
Both alter enzymes in intestinal cells, resulting in increased release of water and electrolytes, leading to diarrhea.
Why is traveler’s diarrhea caused by entertoxigenic E. coli not commonly associated with inflammation and fever?
ETEC use fimbriae to attach to the surface of enterocytes and do not invade the cell. So there is no cell destruction to induce inflammatory responses and cytokine release to result in fever or bloody diarrhea.
Enteropathogenic E. coli also cause noninflammatory diarrhea but by different mechanisms. EPEC attach the brush border of small intestines and use enzymes to _____ the microvilli.
Flatten (efface)
Enteroinvasive E. coli invade the large intestines. They contain enzymes that force host cells to ______ the bacterial cells. Furthermore, this leads to necrosis, further toward ______.
Endocytose
Dysentery
_______: cause dysentery, hemorrhagic colitis, and HUS (hemolytic uremic syndrome). They also cause microvilli effacement.
Enterohemorrhagic E. coli (EHEC)
How do Shiga-like toxins affect host cell metabolic processes?
They inhibit 28S on the 60S ribosome subunit and disrupt cellular protein synthesis.
_______: use a special kind of fimbriae called P pili to attach to the urinary tract and create a biofilm to evade immunologic recognition and eradication.
Uropathogenic E. coli
Why is the fecal-oral route the most common route of E. coli transmission?
E. coli are natural colonizers of the human GI tract. A large concentration is found in human feces, and it is therefore the largest source of infection.
What part of the gram-negative cell wall in an endotoxin that can mount an inflammatory response?
The LPS can trigger inflammatory responses and potentially lead to symptoms of sepsis.
When bacteria reach the bloodstream, like in bacteremia, ______ can occur.
Systemic inflammatory response syndrome (SIRS)
______ can occur from bacteremia and dissemination to the meninges from other sources such as an abscess or in immunocompromised hosts and infants.
Meningitis
