Bacterial Cell Structure and Function Flashcards
major cellular structures of bacteria
pili, capsule, flagellum, nucleoid, and ribosomes
capsule is made of
mucoid layer, slime layer, and glycocalyx
-made of some combo of polysaccharide, protein, and/or DNA
capsule function
- usually required for pathogenesis
- function = adherence or immune system avoidance
Biofilm
- organized multicellular bacterial communities which protect the bacteria until they want to propogate elsewhere
- most bacteria can form them
- forms when bacteria sense the correct density of their cohort: cell-cell communication via pheremones causes matrix synthesis
- once the matrix surrounds the whole community, it is a biofilm
- the microbiota are likely present in biofilms throughout the GI tract
biofilm functions
-adherence, controlled release of bacteria from the biofilm, immune system avoidance, alteration of bacterial growth kinetics, alteration of drug pharmacokinetics ***and activation of bacterial stress and defense responses
drug strategies to defeat biofilms
- first treat the biofilm with something like a drug that blocks pheremone communication
- then treat the bacterium
biofilms can be sites of ______
reinfection
name three main bacteria that use biofilms
- cystic fibrosis pneumonia
- urinary catheter infections
- gum disease
Biofilm levels decline towards the _______ ______ because of ….
- distal colon
- because IgA may better bind bacteria in the distal colon to inhibit their disposition at that site or may have changes in nutritional status of gut
clinical relevance of the flagellum
- flagellum dependent swimming can be required for disease
- the immunological response to flagella can be a diagnostic tool
- flagella can be organelles of attachment
flagella have a ____ at the tip which can be replaced with a ______
- cap
- adhesin
cell envelope of gram negative bacteria
-inner and outer mb with a thinner layer of peptidoglycan in between
gram positive cell envelop
-only an inner mb with a thicker layer of peptidoglycan on the outside
inner mb
- site of many biochem reactions and transport
- a separate cellular compartment
peptidoglycan
- a series of sheets of sugar residues connected by short protein cross bridges
- determine the cell’s shape
- target for anti-microbials by enzymes of the body as well as in drugs
- can be toxic
lipopolysaccharide (LPS)
- on outer leaflet of the mb
- O-specific side chain which is variable (diagnosis), Core, and lipid A toxic which spans the mb (endotoxic shock)
multidrug efflux system
- trans-envelope channel and not a porin
- usually associated with a relatively impermeable outer mb
- strongly selected for in hospitals
- gram - bacteria
- can produce a toxin with the spore that is active while the spore is not
sporulation
- small piece of cell is used to make the small spore which is then released and has a protective capsule
- spore = dorminant, resistant, and metabolically inactive
germination
-capsule comes off spore after it senses that the environment is favorable and then it grows into a full cell that is metabolically active and produces virulence factors
c. perfringens
- exudes active toxin with spore
c. difficile
-uses spores
b. anthracis (anthrax)
-uses the spore to enter the host and produces toxin only upon germination
the ______ for sporulation and germination can be imp for disease
-triggers
way to target spores with immune system
-immune system activates the spore and then immediately kills it when the capsule is off and it is vulnerable
mycoplasma
- lack a proteoglycan so the cells will deform based on the local stresses
- can squeese through filters because they are small
- lack proteoglycan, so they can’t be targeted by anti-microbials in that way
- gram +
mycobacterial envelope
- gram +
- have sugars on the cell surgace that mimic host sugars and engage macrophage receptors that facilitate uptake and sequestration into a safe intracellular compartment, and they can stimulate anti-inflammatory responses
- different tools on different mbs
