Lecture 27 Flashcards
Bdellovibrio has what type of relationship with other cells?
It is a parasite - preys on other Gram-negative cells.
What is the lifestyle (oxygen requirement, etc.) of Bdellovibrio?
Aerobic, obligate parasites.
Give 6 examples of Bdellovibrio habitats.
Soil, freshwater, marine, sediments, biofilms, sewage
(Also may follow fungal hyphae)
What are the 4 phases of the Bdellovibrio life cycle?
- Attack phase
- Protein synthesis and enzyme secretion
- Growth
- Cell division
Describe what happens in the attack phase of Bdellovibrio, including:
a) motility
b) impact on host cell
c) time taken
Bdellovibrio swim very fast and impact the host cell. They attempt to attach themselves to the host cell, but are usually not successful.
When they are successful, their outer membrane component interact. Their lipopolysaccharides and proteins will also interact with one another. They can also attach via pilli.
Once they have attached, they will twist to penetrate into the host periplasm through a small pore. At this point, they lose their flagella. They end up between two membranes.
This entire process takes 5-10 mins.
Name the 4 main substances secreted by Bdellovibrio during their protein synthesis and enzyme secretion phase.
- Muramidases, glucanses, lipases
- Proteases, peptidases, nucleases
- Pore protein (like OmpF)
- Transporter proteins
What is the function of muramidases, glycanses, and lipases in Bdellovibrio?
They partially break down the host cell wall and lipids. They result in the formation of Bdelloplasts, which are osmotically stable.
What is the function of proteases, peptidases, and nucleases in Bdellovibrio?
They degrade host proteins, DNA, and RNA
What is the function of pore protein in Bdellovibrio?
It gets inserted into the host membrane and allows nutrients to flow out of the host.
What is the function of transporter proteins in Bdellovibrio?
They allow the uptake of host nutrients into Bdellovibrio. These proteins are located in the Bdellovibrio cytoplasmic membrane.
Describe what happens during the growth phase of the Bdellovibio life cycle.
They absorb host nutrients and grow bigger (WITHOUT division). They also acquire lipids directly from the host cell. Contact with the host is required to initiate its DNA replication, as it can’t synthesize all amino acids on its own.
Describe what happens during the cell division phase of the Bdellovibrio life cycle.
The large Bdellovibrio cell divides into several smaller cells. The host cell lyses and the Bdellovibrio progeny can escape.
What are the main types of genes present in Bdellovibrio (e.g. what is their function)? What do they lack?
They have many genes dedicated to attacking and consuming bacteria cell, such as degradative enzymes, transporters, etc. They also have basic pathways such as glycolytic, TCA cycle, etc., allowing it to generate its own energy. They can also generate their own DNA from scratch, as they have complete translation machinery.
Note that they have no genes for the detection of prey via quorum sensing, and also do not receive genes from the host.
They do, however, some amino acids and have to get them from the host or from the environment. They can only synthesize 11 amino acids on their own. They also lack the genes for the degradation of 10 amino acids.
What is the main use of Bdellovibrio? How widespread is this use? Why?
It has been proposed as a way to control gram negative bacteria such as E. coli in the food industry or plant pathogens. However, since Bdellovibrio have trouble with biofilms, clay, etc. that prevent them from hitting prey, this does not appear to be very viable.
Myxobacteria has what type of relationship with other cells?
They are predators.
