Lecture 6: Microbial Physiology Flashcards
What do bacteria have instead of membrane bound organelles?
they have internal organization
What gives bacterial cytoplasm/cytosol a gelatinous consistency?
very high concentration of protein, nucleic acid, carbohydrates, and ions
What shape is bacterial genome?
Circular with a few exceptions
What is genome?
chromosomes plus plasmids
What are plasmids?
small circular self replicating DNA strands
What is a chromosome?
one long DNA chain
What does bacteria do instead of having a cell nucleus?
may partition genetic material to different parts of the cell
Where does DNA partition when bacterial cells divide?
partitions to plasma membrane on either side of the division plane
What are ribosomes?
the structures
responsible for translation of mRNA
What do ribosomes do?
converts gene sequence to polypeptide
What are ribosomes made of?
RNA (called rRNA or ribosomal RNA) and protein
What are the subunits of ribosomes?
- 50S (bacterial)
- 30S (bacterial)
(40, 60, and 80 are for eukaryotes)
What is the final ribosome?
70S
What does S mean?
- Svedberg Unit
- sedimentation rate
- how long it takes for a particular piece to end up where it belongs
What does the kind of ribosome tell you?
the target of a number of antibiotics
Are ribosomes present in every cell?
Yes, they are in every cell of every kind. Cells cannot function without them
carboxysomes
contain ribulose 1,5
diphosphate carboxylase enzyme for CO2 fixation by photosynthetic bacteria
What do metachromatic granules do?
store inorganic phosphate (volutin) in Corynebacterium diphtheriae
Forms of nutrient storage
- carboxysomes
- metachromatic granules
- polysaccharide granules
- sulfur granules in thiobacillus
- lipid inclusions (PHB)
PHB
polyhydroxy butyric acid
Functional inclusions
- ex: take energy from iron and use it for themselves?
- magnetosomes from magnetospirillum magneticum
- cyanobacterial gas vacuole
How do some bacteria respond to stress/heat/fryness/freezing/radiation?
by forming hardy endospores that are resistant to the stresses
why sterilize things with an autoclave?
because the heat can kill the bacteria
What kind of bacteria produces endospores?
gram positive
- clostridium and bacillus primarily
what do vegetative cells do in response to stress?
start sporulation (takes several hours)
What is sporulation?
spores form inside vegetative cell and then the cell body breaks apart, leaving the spore intact
How to get rid of spores?
special sterilization techniques are needed
what components of bacteria are good targets for antibiotics? What properties of a bacterial cell component make it a good antibiotic target?
- peptidoglycan, cell, ribosomes (different), DNA/RNA replication, transcription, gyrase (unwind DNA in bacteria)
- essential to cell viability and replication
- is common in many/all bacteria
- not present in human cells
Biofilm physiology
- Heightened
resistance to antibiotics
– Catheter infections - Very strongly adherent to surface
- Plaque on teeth
- Highly differentiated substructure
- Anaerobic regions
- Nutrient micropores
Bacteria that is harmless on your skin, but dangerous if it gets on your heart? (for example)
Staphylococcus Epidermis
How does biofilm cause cavities?
Bacteria at the bottom of the biofilm are not exposed to oxygen, so when they are exposed to sugars, they ferment and produce acids that degrade the teeth
What are some significant morphological changes that species of bacteria go through?
Biofilm formation
- fruiting body formation (myxobacteria)
- caulobacter crescentus (stalked/swarmer transition)
Most bacteria in the world are in… (about 90%)
biofilms (mostly mixed species biofilms)
What are myxobacteria?
predatory bacteria
- fruiting body formation that is controlled by cell-cell contact, response to starvation
- individual cells also undergo morphogenesis into spores
Caulobacter crescentus
great model for programs of cell differentiation
cell cycle in bacteria
- stalked cell attaches to a surface
- elongates (pre-divisional cell)
- asymmetrically divides
-produces a cell without a stalk, but a single polar flagellum (swarmer cell) - swarmer uses flagellum to move on and attach somewhere else
- turns into a stalked cell to continue the cycle
(swarmer never makes swarmer and stalked never makes stalked)
What is quorum sensing?
coordinated behavior
What bacteria have virulence quorum sensing?
S. aureus
What bacteria have symbioses quorum sensing?
- vibrio fischeri (that squid “Tom Kleindinst”)
- euprymna scolopes
What bacteria have horizontal gene transfer quorum sensing?
- agrobacterium (crown gall - a cancer in plants)
- enterococcus
quorum sensing - autoinducer
Gram negative:
- lux I: makes the signal
- Lux R: site of binding to make a dimer?
- amphipathic ring with a fatty acid tail
Gram positive:
- peptides cant go across membranes so ComQ/X gives a way to send the signal across the surface?
- ComP auto-phosphorylates comA, activating transcription
What things does the bacterium need to
do before and during division?
- Divide cytoplasm in two
- Replicate DNA
- Partition critical cellular proteins, cofactors,
substrates - Invaginate membrane(s), divide into two separate cells
DNA replication in bacteria
- circular genome
- has an origin of replication
- bidirectional replication
- DNA pol III (dominant)
- DNA pol I – okazaki
fragments (dominant) - Topoisomerase - unwind DNA (gyrase for bacteria, also good for antibiotic target cause all bacteria have it)
Binary fission
- DNA replicates
- partitioning of daughter strands
- septum formation
–FtsZ: related to eukaryotic tubulin
– ring structure at nascent division site - membrane invagination
fts
filamentous temperature sensitive
What does mutagenesis result in?
FTS mutants
