Microbes in biocontrol Flashcards
what is biocontrol?
- method of introducing an agent organism into a new ecosystem to naturally prey on and supress target “pest” organisms
agent = newly introduced species (predator)
target = defined pest whose population is suppressed by the agent - prey
ex: probiotics contain certain microbes that aim to restore balance to intestinal flora (lactobacillus and bifidobacterium)
what is phage therapy
aims to treat infectious diseases with a virus targeted to the pathogen
- bacteriophages are a possible alternative to antibiotics in the fact of rising antibiotic resistance
- commercial phage products are not available to target a few food borne pathogens
what does biocontrol fo to target species
decreases the population but does not eradicate
- if preditor eradicated food source it would not survive - reach an equilibrium to shift/stabilize to a lower level
3 cases of biocontrol studied
Viral - myxomatosis and bunnies
bacterial - bacillus thuringiensis for plant protection
phage - listeria monocytogenes in foods
how were rabbit populations controlled
- yxomatosis and myxoma virus
- produced lumps (mycomata) and puffiness around the head and genital area - ultimately bunnies died within less than 2 weeks- 48Hr
- supressed rabbit growth but now some are resistant to the virus
describe myxomatosis and mycoma virus
- enveloped viron of the poxvirus family
- brack shaped with a bioconcave core
- non segmented, linear dsDNA genome
- during lifecycle produces proteins that interfere with host immune system
- transmission by biting insects
what was used to as a natural insecticide
- bacillus thuringiensis
- larvae attack plant leaves, so protect the leaves with this bacteria that produces toxins
- toxins are delta endotoxins that are prodcued during spore formation
describe - bacillus thuringiensis
- common soil bacterium: gram positive, rod shaped and forms heat and desiccation resistant spores
- first isolated in japan, pathogenic to insects but not mammals
- found in insect guts and on plants
- produces crystalline (cry) toxin during sporualtion - contained in the parasporal body, toxin genes are located on the plasmid
describe the mechanism fo action of the Cry toxin
- Cry toxin is ingested
- Cry toxis is digested by insect proteases helped by alkaline pH releasing ptotoxin form
- Protoxin binds to CAD receptor and is activated by further protease activity
- Activated toxin monomers are released
- Activated toxin oligomerizes with the help of APN and ALP
- Toxin complex forms pores in the cell membrane
- Membrane is disrupted as well as ion channel disruption, bacteria transverse the epithelium
**so now if bacteria if bacteria can get through can have sepsis and death of infected cell
what are the different strains of BT
- Kurstaki strain: targets leaf and needle feeding caterpillars
- Israelensis strain: targets mosquitoes and black flies
- San deigo strainL targets beetles
*the more species the agent the more controlled the intervenntion and fewer unintended consequences
how else can bt arrive in crops besides physically applying it
- Bt crops - cry genes inserted into plant genomes
- expressed by the plant to confer resistance to insect pests
- controversial bc get pest resistance to cry and secondary pest infestations can arise
what is listeria monocytogenes
- can be found in food preparation plants
- problematic pathogen causing serious food poisoning outbreaks -listeriodid
*YOPIs most at risk - young, old, preg and immunocompromised
*If eat food with it can cross epithelial cells go into bloog stream and go to liver, spleen, brain and can infect fetus
- it is a good born psychrophilic and ubiquitus pathogen
- mortality rate can reach 50%
how can bacteriophage work to detect L monocytogenes?
- bacteriophage have very high specificity and can only multiply in viable cells
- phage amplification strategies have been employed to detect L monocytogenes
*listeria reporter phage A511 has been fused to bacterial luciferase genes so that if they infect L. monocytes the infection can be detected by looking for light production
how can bacteriophage act as biofilm control?
- antibiotics have a hard time penetrating biofilms: carry the potential for collateral damage and can promote antimicrobial resistance
- need a selective toxic agent that can penetrate the biofilm extracellular polysaccharide layer and infiltrate bacteria to kill them and can replicate to propogate their own acitvity
*anser is virulent bacteriophage
- virulent phage are able to evolve alongside their prey minimizing the rise of resistant bacteria
oligately lytic phages as antibiofilm agents vs chemical antibiotics as antibiofilm agents
obligately lytic phages: cause single hit killing, antibacterial activity concentrated within target, can be lytic or bactericial, in situ ampliication concentration
antibiotics: multi hit activity, not all lytic, not ll bactericial, not concentrated in or on target bacteria, released extracellularly, not necessarily stand-alone anti biofilm activity
** phages good wa potential antifouling agent, coat indweling medical devices and potential sytemic treatmentment of bacterial colonization
