Lecture 4: Microbial Physiology Flashcards
What are the three basic shapes of prokaryotic cells?
- rod
- coccus
- spirillum
What size are prokaryotic cells?
1-5 micrometers
Additional morphologies of prokaryotic cells
- Star shaped: stella
- rectangular Haloarcula (Archaea)
Pleomorphic Bacteria Shapes
Rhizobium and Corynebacterium
Largest bacteria ever
Thiomargarita Magnifica
Cell wall
- peptidoglycan
- Sugar chains cross linked by peptides
- Cell wall building/turnover during growth and division can influence cell shape
Turgor Pressure
- Cells contain lots of stuff-DNA, proteins, sugars,
salts - If cells are in an aqueous (watery) environment,
the surrounding medium has less stuff in it - Because of this disparity, water tends to flow into
the cells, results in turgor pressure
Rod Shaped
- bacilli (bacillus is a genus name)
- G+ and G- rods
What axis do bacilli divide?
divide along narrow axis
Streotiobacilli
long chains of rods
diplobacilli
pairs of rods attached end to end
coccobacilli
very short rods, almost cocci
vibrios “curved rods”
- Vibrio cholerae the agent of cholera
- In the book described as spiral bacteria, but phylogenetically aligned with G- rods
cocci
sphere
- gram negative and positive
different cocci have ___ division planes
different
What possible advantage is there to being rod or spirillum shaped vs. cocci?
The way they associate with surfaces is different. Rod shaped has more contact with the surface than spheres. The way they stack/pack is also more beneficial.
Streptococci
divide along a single plane, form chains
Staphylococci
divide along all planes, form clumps
how do other cocci divide?
form tetrads and sarcinae, as well as pairs (diplococci)
Spirillum
- one or two turns around helical axis
- external flagella
Spirochete
- flagella sheathed, run along length of cell
- “corkscrew motility”
- Borrellia Burgdorferi (Lyme disease) , treponema pallidum (syphilis)
Prokaryote Physiology
- Cell Membrane
- Outer membrane
- Cell wall (peptidoglycan)
- Exopolysaccharide matrix
- Flagella
- Pili and Fimbriae
- Genome Structure
- Ribosomes
Overall Bacterial Structure
- External structures
(pili, flagella, fimbriae)
Outer Membrane G-
only
Cell wall
(peptidoglycan sacculus or wall)
Cell membrane
Cytosol
3 parts of Flagella
3 parts
- filament (made of the protein flagellin)
- hook (different protein)
- Basal body
Flagellar Assembly
- flagellin subunits travel up through the middle of the flagellum, to the growing tip
- similar, evolutionarily related to Type III secretion important in pathogenesis.
_____ flagella-distributed over cell body
Peritrichous
On cell surface, flagella can also be at….
the poles
monotrichous
single at one end
lophotrichous
clump of flagella at one end
Amphitrichous
flagella at both ends
Spirochete Flagella
- Very cool structure
Doesn’t emerge from the cells
Cool propulsion mechanism
Cryoelectron tomography
Are all bacteria motile?
No
Types of motility
- Tumble and swim
chemotaxis - “gliding motility”
- Spirochete corkscrew motility
Fimbriae
- generally smaller and spread throughout a cell
- Fimbriae-protein filaments on cell outer surface
- Either at poles or evenly distributed
- Important in cell attachment to surfaces
- Well studied in Neisseria gonorrhoeae
- Fimbriae are a virulence factor for enteric, urogenital pathogens
What do bacteria secrete/their pathways?
- make proteins to be exported to periplasm and
surroundings - Sec pathway (general secretion)
- Sec independent (type II)
- Type III (virulence)
- there are 10 known secretion pathways
pilus/pili
- generally larger/longer and more sparse on the cell
- involved in cell-cell attachment
phenomena, in preparation for DNA
transfer (conjugation) - Pili are sometimes the site of attachment for bacteriophages, viruses that infect bacteria
Exopolysaccharide (EPS) Matrix (glycocalyx)
- Environmental bacteria often live on surfaces covered in EPS
- Called a biofilm
- In pathogenic microbes, this is often called the slime capsule
- An important defense against the immune
system - A virulence factor, esp. for G+ cocci pathogens
S. Pneumoniae Capsule
- Streptococci are known for the production of capsule
- Primary component
hyaluronic acid - Mutants that don’t make capsule are avirulent
- This was used to prove that DNA is the genetic material
(1941)
