Microbes and Environment: Sporulation, vectors, quorum Flashcards
Define Ecosystem
The sum total of all organisms and abiotic factors in a particular environment.
Define Habitat
Portion of an ecosystem where a community could reside.
• An ecosystem contains many habitats
Define Parasitism
when one member in the relationship is harmed and the other benefits
Define Mutualism
Both species benefit
Define Commensalism
One species benefits, the other is neither harmed not helped
Define Species Richness
total number of different species present
Define Species abundance
proportion of each species in an ecosystem
Define Guilds
Metabolically related microbial populations
Define Niche
Habitat shared by a Guild, supplies nutrients as well as conditions for growth
Define Biogeochemistry
The study of biologically mediated chemical transformations
Define Microenviroment
The immediate environmental surroundings of a microbial cell or group of cells
Define Biofilms
Assemblages of bacterial cells adhered to a surface and enclosed in an adhesive matrix excreted by the cells
What are biofilms made up of
-The matrix is typically a mixture of polysaccharides
Give three reasons bacteria form biofilms
- Self-defence- Biofilms resist physical forces that sweep away unattached cells, phagocytosis by immune system cells, and penetration of toxins e.g. antibiotics
- Allows cells to remain in a favourable niche
- Allows bacterial cells to live in close association with one another
What is Pseudomonas aeruginosa?
Biofilm producing, gram negative, rod shaped bacterium.
What intracellular signaling molecules does Pseudomonas aeruginosa use?
acylated homoserine lactones
Define Quorum sensing
mechanism by which bacteria asses their population density
-Ensures that a sufficient number of cells re present before initiating a response that, to be effective, requires a certain cell density (e.g. toxin production in pathogenic bacterium.
What are the main properties of autoinducer molecules that allow quorum sensing to take place?
- Diffuses freely across the cell envelope
- Reaches high concentrations inside cell only if many cells are near
- Binds to specific activator protein and triggers transcription of specific genes
What is Acyl homoserine lactone (AHL) an example of
An autoinducer molecule
What encodes for bioilluminesence in becteria such as Aliivibrio fischeri?
Lux operon
Give two examples of quorum sensing
- Virulence factors
- Switching from free-living to growing as a biofilm
Is quorum sensing sensing present in microbial eukaryotes?
some eukaryotes
Is quorum sensing sensing present in archaea?
Likely
What is the name given to the process by which prokaryotic cells respond to other cells of the same species
Quorum sensing
Give two examples of Virulence factors
Escherichia Coli
Staphylococcus aureus
What does straphylococcus aureus do to the host?
• -Secretes small peptides that damage host cells or alter host’s immune system
What are endospores?
- Highly differentiated cells resistant to heat, harsh chemicals and radiation
- ‘Dormant’ stage of bacterial life cycle
Are endospores present in gram-positive bacteria
Present in some gram-positive bacteria
