Lecture 30 Flashcards
1
Q
What are general characteristics of Bdellovibrio?
A
- Bdell= leech, vibrio= curved rod
- Gram negative, Deltaproteobacteria
- Prey on (parasitize) other Gram negative cells
- Aerobic, obligate parasites (wild-type strains non-culturable) => some mutant strains are culturable
- First isolated during an attempt to isolate bacteriophages
- may follow fungal hyphal “highways” in the soil
2
Q
What is the habitat of Bdellovibrio?
A
- Soil, freshwater, marine, sediments, biofilms, sewage
- Wherever there is prey
3
Q
How many phases does the bdellovibrio life cycle counts? What are they?
A
8 stages
Simplified to 4 stages:
- Attack phase
- Protein synthesis and enzyme secretion
- Growth
- Cell division
4
Q
Describe the attack phase of bdellovibrio
A
- Cell swims very fast (100 cell lenghts/sec)
- Impact host cell
- Attachment (most attacks not successful)
- Outer membrane compotnents interact
- LPS-LPS and protein -protein interactions
- Attachment also via oili - Twist to penetrate into periplasm through small pore
- Then lose flagella
- Total time= 5-10 min
5
Q
What are the protein and enzymes synthesized and secreted in phase 2?
A
- Muramidases, glycanases, lipases
- Proteases, peptidases, nucleases
- Pore protein
- Transporter proteins
6
Q
Describe the growth phase of bdellovibrio
A
- Absorbs host nutrients and grows
- Acquires some lipids directly from host cell
- Depends on contact with host to initiate DNA replication
- Likely related to inability to synthesize all a.a.
7
Q
Describe the cell division phase of bdellovibrio
A
- Large Bdellovibrio cell divides into several smaller cells
- Look like sausage links at first
- Host cell lyses
- Bdellovibrio progeny escape
8
Q
What are genetic characteristics of bdellovibrio?
A
- Genome sequence determined
- No evidence of recent transfer of genes from host species
- Many genes for attacking and consuming bacterial cells (degradation enzymes, transporters etc)
- Able to synthesize DNA from scratch ( does not require nucleotides from host)
- Translation machinary complete (tRNAs etc)
- NEED TO ACQUIRE A.a. FROM HOST (or environment)
- Only having genes for SYNTHESIS of 11 a.a.
- Also missing genes for DEGRADATION of 10 a.a.
9
Q
What are uses of Bdellovibrio?
A
- Many uses proposed over the years
- Most not practical are taken seriously (or even really work)
- Proposed as a method to control Gram negative bacteria (E.coli contaminants in food industry… biocontrol of plant pathogens…)
- But Bdellovibrio have trouble with biofilms, clay or anything that prevents them from hitting prey
10
Q
The deltaproteobacteria class includes what type of bacteria?
A
- Bdellovibrio
- Myxobacteria
- Sulfate-reducing bacteria
11
Q
What are characteristics of Myxobacteria?
A
- Gram negative rods
- Deltaproteobacteria
- Model species= myxococcus xanthus
- Assimilate nutrients heterotrophically or prey on other cells
- GLIDING motility
- First isolated as fruiting bodies via “dung isolation”
12
Q
What is the habitat of myxobacteria?
A
- Soil, herbivore dung, decaying plant material esp wood, bark, leaves, freshwater
- fierce competition for limited nutrients
- either attack and kill or run away
- Prefer neutral pH range, mesophilic, but extreme known
- Global range
- Antarctic, tropical desert, seashore, peat bogs
13
Q
What are genetic and genomics characteristics of myxobacteria?
A
- These bacteria are of interest to geneticists because of their multicellular life cycle, overall complexity
- Myxococcus xanthus has a genome 2x the genome of E.coli
- Interest for biotechnology (secondary metabolites => antibiotics)
14
Q
What are the “2” steps in life cycle?
A
- vegetative cells and predation
2. fruiting body
15
Q
What are characteristics of the vegetative cells and predation part of life cycle?
A
- Vegetative cells can be either heterotrophic or predatory
- Team up with other cells (quorum) to digest macromolecules => cellulose or to prey on other bacteria, yeast, algae, fungi
- The bigger the quorum the more exoenzymes can be produced- Chitinases, cellulases, muramidases, proteases, lipases, nucleases, glucanses
- Able to TRACK DOWN food and prey
- Swarm and assimilate (resistance is futile) rippling waves
- Synergistic cell-cell communication (chemical and tactile)
- CHEMOTAXIS
- Cell-cell contact
