Antisymbiosis Flashcards
Antibiotic vs antimicrobial
Antibiotic- small molecular that kills or inhibits replication of bacteria (Waksman)
Antimicrobial – any compound that kills inhibits replication of microbes (bacteria, fungi, viruses, Protista)
Discovery timeline of antibiotics
New class of antibiotic – one that targets different molecule/protein or part of ribosome in bacteria
By using different classes of antibiotics microbes will different mechanisms to evolve to resist these
Discovery rates declined
Antibiotic resistance - how does it occur, what are the consequences?
Deployment of drugs – antibiotic resistance shortly follows
Resistance can occur quickly as resistance genes mostly come from soil bacteria – uses horizontal gene transfer
CONSEQUENCES:
Chemotherapy suppresses immune system – rely on antibiotic therapy as protective regime to prevent infections
Antimicrobial resistance can already prevent surgery particularly of intestine as lots of microbes in gut
Biopsies
Childbirth
Antibiotic discovery (Selman Waksman)
METHOD
Soil cultures can be enriched for good competitors by mixing with target organism
Plate out and screen against target pathogen
Streps can be ‘challenged’ to produce different metabolites via chemical stress, mutagenesis, change of nutrient supply to alter drug expression
Clear zone – microbe releasing antibiotic
Antibiotic screening
Screen for toxicity
Screen for good pharmacodynamics (ability to spread through the body
Desirable to have drugs that can be ingested as easier than injection
Screening takes a long time and is labour intensive
What’s the iChip?
iChip – minimized microbial competition allowing researchers to isolate difficult to culture organisms – perforated frame that can be dipped into very dilute solution of soil so that one microbe would colonise each well of frame, can sandwich membranes on each side of cells and place unit inside soil
Why do streptomycin form secondary metabolites? What is the result of this?
Streptomyces form spores – form sun/heat/dessication resistant stage when they run out of nutrients or when the soil dessicates they produce interesting secondary metabolites
Aerial spore masses – when they start to produce antibiotics
Streptomycetes produce antibiotics late in growth – when nutrients depleted- just before sporulation
Hypothesis – produce antibiotics in scorched earth tactics to ensure offspring by releasing antibiotics into environment
Why do beetles produce antimicrobial secretions?
Beetles produce antimicrobial secretions which change the microbial composition of decomposing cadaver
How do beewolfs use steptomyces?
Beewolf coats pupae with streptomyces on antannae to preserve pupae over winter
Commercial exploitation of natural microbes
Epiphytic (plant associated) microbes produce wide range of antimicrobials, including antifungals
Bacteria can supress fungi
Commercial interest as they can suppress disease and promote growth in plants
What is serenade ASO?
Serenade ASO inhibit colonization of roots by fungal pathogen causing Clubroot
Why should biologicals be used? What are the limitations?
Chemical fungicides are often toxic & resistance is increasing
Biologicals are welcome alternatives but can be more costly than chemicals
Efficacy of biologicals can vary depending on how they are applied and on the specific target
What are bacteriophages? How can they be used?
Bacteriophage are viruses that specifically target bacteria
Engineered bacteriophages an be used instead of antibiotics
Bacteriophage limitations
Resistance can evolve extremely rapidly-
Cocktails (mixtures) often needed for effective treatment
Can be hard to deliver to site of infection
Drug licensing laws poorly equipped to deal with biological products with specific action
New study used intravenous injection & GM phage- both novel steps
How to reduce antibiotic resistance?
Reduce usage of antibiotics, including shorter courses
Reduce transmission in hospitals (working for MRSA)
Reduce environmental contamination with antimicrobials
Multiple antimicrobials simultaneously eg HIV & Tuberculosis (effective but risky)
Increase heterogeneity of selection (different products in time & space)
