Antibiotic usually target G(+) because
G(-) has a membrane-wall-membrane structure, makes it almost impermeable to anything.
- rods like sub, only exists in G+ cell wall
- sometimes referred to as G+ endotoxin because immune system can actually detect them
- charged, sometimes binds Ca2+ and Mg2+ and other molecule, helps stabilize the peptidoglycan
Genus of bacteria that lack cell wall:
- Genus of bacteria that lack cell wall.
- Genetically G(+), stained as G(-).
- No Ab affects it
- Can squeeze through 0.2um filter, most commonly found contamination in cell culture
- M. pneumoniae: Atypical pneumonia respiratory infection.
- Some Mycoplasma might be linked to cancer.
- preferred term
- aka Exopolysaccharide Capsule (not always made of sugar; Anthrax is made of AAs), or Glycocalyx
- aka Exopolysaccharide (EPS) or
- Extracellular Polymeric Substance (EPS, preferred term; Formed from a number of structures, not only sugars)
Capsules are formed by ______ bacteria.
Most capsules are composed of ____, but some are composed of ______.
The capsule is a _______ layer outside the _____ - not like the _____.
- G+ and G-
- thick distinct
- cell wall
- slime layer
The ______, _______ in which the culture is grown as well as the ____ of the culture will affect capsule formation.
Condition of bacteria in which they grow changes will change the _______ of the capsule This phenomena is called _____: bacteria grow differently in different conditions, it changes shape.
- composition and the thickness
_______ cultures are more likely to exhibit capsule production.
Staining of capsules
- The capsule is not usually charged, and most dyes are binding to charged molecules
- negative stain (such as India ink) stains everything but the capsule
- The ghosty space left is the capsule
A slime layer is ______ associated with the bacterium and can _____ washed off.
Capsule is attached _____ to the bacterium and has _______.
- be easily
- definite boundaries
Slime layer is a layer of molecules that the cell ______.
Biofilms are attached to the surface, eg enamel. All bacteria that are involved in any disease of the oral cavity are part of the biofilm. If they’re not attached to the surface, they are going to be swallowed. After they are attached to the surface, they are going to secrete a compound, EPS, can be made from _____________.
___ is a very sticky molecule w/ _____. Some cells in the immune system can squirt it out to bind to bacteria, make it sticky so that it will attach to the surface.
- sugars, debris, proteins, DNA
- negative charges
Functions of Capsules and EPS
Not necessary for growth, mainly for protection/survive host responses:
- Physical barrier (e.g., desiccation).
- Chemical barrier (e.g., detergents).
- Protection from phagocytosis (prevent the cells being detected).
- Protection from viruses (same as immune).
More functions of slime layer
- Other than protection
- Nutrient trap: can trap material from the media on the biofilm
- Carbon storage: if cells are deprived of food, it can break this down and use it
- Biofilm formation: very sticky compound, cells can grow and other cells can come in and stick to that
- Bacterial attachment to surfaces
- Cell aggregation
Produces 90+ types of polysaccharides
Only ______ producing strains are virulent (prevent opsonization of the complement system).
- Capsulation is considered a virulence factor
Smooth vs rough colony
- Capsule makes the colony smooth and shiny on the serum agar plate, called smooth strain or smooth isolate.
- After many repeated cycles of culture, the bacteria lose capsule (doesn’t need it again, not assaulted by the immune system), and are no more virulent.
- Thus need to study bacteria freshly isolated from a patient.
Fred Griffth's experiment in 1928
Animal tested w/ R strain:
Animal tested w/ S strain:
Animal tested w/ heat-killed S strain:
Animal tested w/ R strain plus heat-killed S strain:
Dead S strain treated w/ protease, repeat:
Dead S strain treated w/ DNase, repeat:
- Genetic material is DNA
- R strain picked up something from dead S strain, the genetic material, and converted to S strain. What is the material?
- The material has to be DNA
_______ causes strep throat. It also causes _____ and _____
- Streptococcus pyogenes
- Rheumatic fever
- Puerperal fever - childbed fever; "The Doctor's Plague"; Ignaz Philipp Semmelweis, "savior of mothers”
Rheumatic fever induced by infection of Streptococcus pyogenes is ___________, caused by _________.
- an autoimmune disease
- immune cells attacking certain tissue which contains hyaluronic acid in the extracellular matrix, which is also the major component of the bacteria's capsule, NAG-Glucuronic acid (Hyaluronic acid capsule)
S. pyogenes _______ required for invasive soft tissue infection in mice
Anthrax is caused by __________, which has a ________ capsule, which is ________.
- Bacillus anthracis
- Poly-D-glutamic acid
- required for dissemination in murine inhalation anthrax (migrate from one organ to another)
- Glucan capsule/slime layer; from sucrose
- required for caries induction
- poly-N-acetylglucosamine capsule
- Attach to tissues, cells, and biomaterials
- Biofilm formation
- Protection from antimicrobial killing and phagocytosis
capsules are used to produce vaccines because
- Immunogenic: appropriate immune response; rapid secondary immune response.
- Long term protection
Passive and active vaccinations
- Active: compound that body uses to build up immunity
- Passive: inject with Ab
- Human-specific bacterium that colonizes mucosal surfaces; causing pneumonia and meningitis
- Produces 6 (A-F) different capsules
Haemophilus influenzae vaccine
- Capsules of Type B was used to produce vaccine Hib, not effective for children under 18 due to low immune response
- conjugate vaccine: H. influenzae linked to toxin (i.e. tetanus toxin or diphtheria toxin); protein toxin makes polysaccharide more immunogenic
Causes meningitis, blood infections, ear infections.
- Pneumococcal conjugate vaccine (PCV13) protects against 13 pneumococcal bacteria (13 polysaccharide types).
- 13 types Conjugated with toxin
DPT vaccine is a ____ based vaccine, acting against:
- three infectious diseases: diphtheria, pertussis and tetanus.
- Diphtheria: an upper respiratory tract illness caused by Corynebacterium diphtheriae.
- Pertussis, or whooping cough: bacterial disease caused by Bordetella pertussis.
- Tetanus: a medical condition characterized by a prolonged contraction of skeletal muscle fibers caused by Clostridium tetani.
- A part of the cell envelope found in some archaea.
- contains N-acetylgucosamine (NAG) and N-acetyltalosaminuronic acid (NATM) which are linked by β-1,3-glycosidic bonds.
- Peptidoglycan has NAG and N-acetylmuramic acid (NAM) via β-1,4-glycosidic bonds.
- Archaea are resistant to lysozyme, which can break down bacterial peptidoglycan.
Surface layer (S-layer)
- Paracrystalline protein layer
- A cell surface protein layer found in archaea and some bacteria.
- Protection against bacteriophages and phagocytosis
- Barrier against high-molecular-weight substances such as lytic enzymes.
- Involved with survival
________ of G(-) make it very difficult for compounds to diffuse through.
- Inner and outer membrane and periplasmic space with peptidoglycans
- necessary to have transporting system
Functions of membrane proteins
- Anchor for capsule
The ______ contains high amounts of porins.
outer membrane of G-
Porins are ___________ proteins that cross _______ and act as _________ through which molecules can diffuse.
- beta barrel
- a cellular membrane
- a pore
Porin Allow ________ to flow.
- small molecules (<1.5kDa)
- - Typical sugar = a couple hundred Daltons.
- - Amino acid = 120 Daltons.
- - Lysozyme which cleaves the peptidoglycan is about 14.7kDa; therefore active against Gram + but not G-
Porin is found in ______.
outer membranes of Gram (-), mitochondria, and chloroplasts
Mitochondria, and Chloroplasts in Eukaryotic cells are originally from ______.
- Same size of bacteria
- Have their own DNA (mtDNA; maternal)
- Look like gram (-) bacteria (Inner/Outer membrane and porins in outer membrane).
Types of transporter
Mechanisms of transport
- Simple transport: use [H] gradient, no ATP required; no change to the transported sub.
- Group translocation: ATP needed; sub is modified (phosphorylated)
- ABC system: three components; ATP required; no change to sub
- A: chaperone, periplasmic binding protein, binds sub and help the transporation
- B: (inner) membrane transporter
- C: ATPase, hydrolyzes ATP to provide energy.
Eg of simple transport
Eg. of group translocation
phosphotransferase for glucose and mannose, using phosphoenolpyruvate as the source of phosphate
There are ___ types of protein secretion systems.
Type I system components
- Outer membrane protein (OMP)
- Membrane fusion protein
- Inner membrane protein
- Similar to the ABC transporter system. Transports various molecules, such as ions and proteins of various sizes from 20 to 900 kDa).
- E. coli alpha hemolysin
- Bordetella pertussis toxin
- Aa leukotoxin
Type II system
- Outer membrane porin
- Inner membrane ABC system: TAT (for folded proteins; N-terminal signal sequence) or SEC (unfolded)
Type III system
- homologous to flagellum basal body
- syringe-like, inject protein directly into attached eukaryotic cell, therefor for transportation from bacteria to mammalian cells
Type IV system looks similar to ______, is homologous to _______ and is used to _________.
- type I system
- conjugation machinery of bacteria
- deliver DNA and proteins from one cell to another
Type V system
- autotransporter system
- Inner membrane ABC system SEC or TAT transfer protein to periplasmic space
- C-terminal of the proteins form beta-barrels on outer membrane.
- Remaining part of the proteins (passenger domain) go through the newly formed porin.
- Could be a system to transport porins
- Found in Aa: Aae; helps the bacteria to attach to the buccal epi cells
Release of outer membrane vesicles
Used to secrete or release compounds. Portions of the outer membrane pinch off, forming spherical structures made of a lipid bilayer enclosing periplasmic materials.
- poly-beta-hydroxyalkanoates (PHA)
- carbon storage form in bacteria when excessive, or in the form of glycogen.
- Inorganic phosphate (PO43-) in globules.
- Could be used as a source of phosphate for: nucleic acid, phospholipids, ATP.
Intracellular particles of the iron mineral magnetite (Fe3O4) that allow organisms to respond to a magnetic field.
- Gas-filled structures made of protein that confer buoyancy on cells. Allows the cell to position itself in a water column in response to environmental signals.
- Air is up; nutrition is down.
- more resistant; can only be killed by autoclave at higher than 100
- formed by vegetative bacteria (only some G+ do this)
- contains DNA, cells die and the spores can survive very long time