Block D Part 2: Microbes and the Environment Flashcards
What results in mutation in bacteria?
High rates of horizontal gene transfer
(Lecture 2, Slide 3)
What is an ecosystem?
The sum total of all organisms and abiotic factors in a particular environment
(Lecture 2, Slide 4)
What is a habitat?
A portion of an ecosystem where a community could reside
(Lecture 2, Slide 4)
What are guilds?
Metabolically related microbial populations
(Lecture 2, Slide 4)
What do sets of guilds form?
Microbial communities that interact with macroorganisms and abiotic factors in the ecosystem
(Lecture 2, Slide 4)
What is a niche?
A habitat shared by a guild that supplies nutrients as well as conditions for growth
(Lecture 2, Slide 4)
What is symbiosis?
A close, long-term relationship between two organisms (usually co-evolved)
(Lecture 2, Slide 7)
What are the 3 types of symbiosis and what do they involve?
Mutualism: both organisms benefit
Commensalism: one organism benefits, the other is unaffected
Parasitism: one organism benefits and the other is harmed
(Lecture 2, Slide 7)
Are symbiotic interactions required?
They can be forced or voluntary (obligate or faculative)
(Lecture 2, Slide 7)
Why do bacteria have to work co-operatively to affect their enviroment?
As they are relatively small
(Lecture 2, Slide 8)
How do bacteria sense and respond to their environmental stimuli?
One way: Two component systems
(Lecture 2, Slide 10)
What are the steps one way: two component systems in bacteria?
- Sensor kinase recognizes signal
- Sensor kinase histidine is phosphorylated
- Receptor transfers phosphate to the response regulator
- Response regulator activity (output)
(Lecture 2, Slide 10)
Name 3 examples of bacteria responding to their environment.
Quorum sensing
Biofilm formation
Sporulation
(Lecture 2, Slide 11)
What is quorum sensing?
when bacteria communicate to each other and coordinate their behaviour based on their population density
(Lecture 2, Slide 13)
What is the function of autoinducers in quorum sensing?
They are sensed by receptor proteins, allowing the bacteria to determine when their cell density has reached a certain level (quorum)
(Lecture 2, Slide 13)
What happens after bacteria have sensed they have reached a quorum?
They co-ordinate expression of genes involved in group behaviours
(Lecture 2, Slide 13)
Are bacteria signals in quorum sensing specific?
Yes
(Lecture 2, Slide 13)
What is the role of the agr system (often found in quorum sensing)?
It regulates other genes by specific base-pairing with their mRNA
(Lecture 2, Slide 22)
What signalling molecules do gram-negative bacteria use in quorum sensing?
Mostly AHLs
(Lecture 2, Slide 24)
What signalling molecules do gram-positive bacteria use in quorum sensing?
Short peptides
(Lecture 2, Slide 24)
What are biofilms?
Microbial communities typically attached to a surface (abiotic or biotic)
(Lecture 2, Slide 28)
What are biofilms important for in many bacteria?
Pathogenesis
(Lecture 2, Slide 28)
What are cells in biofilms embedded in, and what is this typically made of?
They are embedded in a matrix, typically made of polysaccharides, proteins and nucleic acids
(Lecture 2, Slide 28)
What are monoxenic biofilms?
Biofilms consisting of a single microbial species
(Lecture 2, Slide 29)
What are monoxenic biofilms often considered and associated with?
Considered as “artificial” and often associated with infections
(Lecture 2, Slide 29)
What is a mixed biofilm?
A biofilm consisting of multiple different microbial species
(Lecture 2, Slide 29)
How do mixed biofilms occur?
Naturally
(Lecture 2, Slide 29)
How are mixed biofilms important?
They are important to the environment
(Lecture 2, Slide 29)
Name 2 ways in which the biofilm structure helps promote growth and survival.
Helps trap and concentrate nutrients
Helps locate growth to favourable locations
Helps prevent detachment in flowing systems
Provides defence
Allows community associations and division of labour
(Lecture 2, Slide 30)
Name 2 stresses biofilms are resistant to.
Antimicrobials can’t penetrate past the matrix
They grow and divide more slowly (many antimicrobials target growth / division systems)
Expression of resistance genes
Usually at least some cells survive antibiotic treatment and the biofilm regrows
(Lecture 2, Slide 31)
What regulates biofilm formation?
Quorum sensing and often small molecule signals like cyclic di-GMP
(Lecture 2, Slide 32)
What is the first stage of biofilm formation and what 2 things does it require?
Attachment, requiring motility (self-propulsion) and surface attachment
(Lecture 2, Slide 32)
What is the second stage of biofilm formation?
Aggregation
(Lecture 2, Slide 32)
What is the third stage of biofilm formation?
Microcolony formation
(Lecture 2, Slide 32)
What is the fourth stage of biofilm formation and what does this involve?
Maturation; further adaptation to life in a biofilm (production of a matrix, antibiotic resistance)
(Lecture 2, Slide 32)
What is the fifth and final stage of biofilm formation?
Detachment
(Lecture 2, Slide 32)
Name 3 reasons biofilms are a huge clinical problem.
Diseases are caused by bacteria forming biofilms
Bacteria forming biofilms on medical devices / implants
Bacteria resisting antibiotic treatment / causing reoccurring infections
(Lecture 2, Slide 33)
Name 2 possible solutions to biofilms.
Physical disruption (i.e ultrasound)
Prevent biofilm formations / enhance detachment
Develop drugs or drug therapies to disable persister phenotype
Incorporate drugs into surfaces to prevent colonization
(Lecture 2, Slide 33)
What can some gram-positive bacteria differentiate into?
Endospores
(Lecture 2, Slide 36)
What is sporulation done in response to?
Stress conditions (e.g desiccation, starvation, cell density)
(Lecture 2, Slide 36)
What are spores?
Metabolically dormant cells
(Lecture 2, Slide 36)
What are 4 things are spores resistant to?
Heat, desiccation (removal of moisture), toxins and radiation
(Lecture 2, Slide 36)
What 2 things do spores allow?
Survival of adverse conditions and dispersal
(Lecture 2, Slide 36)
What do spores do after conditions become favourable?
Germinate
(Lecture 2, Slide 36)
What 2 things can spores survive without?
Nutrients and water
(Lecture 2, Slide 39)
How long can spores remain dormant for?
Many years
(Lecture 2, Slide 39)
What are spores a problem in and why?
In food, as it makes pathogens resistant to many anti-microbial treatments
(Lecture 2, Slide 39)
What do endospores germinate to form and what are these cells capable of?
A vegetable cell, capable of sporulating again
(Lecture 2, Slide 40)
What receptors sense a favourable environment in endospores so they know when to germinate?
Germinant receptors
(Lecture 2, Slide 40)
What happens in germination after a favourable condition is sensed?
Endospores structures are degraded and dipicolinic acid is released
(Lecture 2, Slide 40)
What step in germination occurs after the endospore structures are degraded?
Outgrowth
(Lecture 2, Slide 40)
What does the outgrowth stage in germination involve?
Swelling of core, expansion of the cell and a return to normal metabolic activity
(Lecture 2, Slide 40)
