Microbial communication

• available water (moisture) • nutrients ( concrete pipes) • surface

• inducible operon • concentration within environment regulates gene expression • regulators must interact with the components produced by cell

• to understand - inhibit biofilm growth by interrupting communication

uptake of DNA found in environment • increase possibility for horizontal gene transfers • uptake for a source of protein

• pheromones :

-all lipid and tend to be gram - -

-it is an enhancer for the operon and allows RNA pol to bind (transcription) and in turn increase AHL productions and compounds leading to luminescence

The regulation of gene expression in response to fluctuations in cell population density Produce and release signal molecules into the environment called autoinducers

chemicals capable of acting outside the body of the secreting individual to impact the behaviour of the receiving individual. It is usually the case that we are not aware of the pheromone, it simply triggers a response

• lux operon ( Intra-species) vibrio fischeri inside squids 1. ) low levels of cell density and AHL results in no glow. 2. ) increased level of cells and therefor increased AHL levels 3. ) AHL levels high enough for dimer formation 4. ) dimers will activate lux promoter and in turn transcribe +translates operon and proteins 5. ) translated proteins create luminescence.

• Inter-kingdom (mutualistic relationship ) 1. Plant secretes flavonoids and attract Rhizobium bac 2. bac create Biofilm cap 3. Infection of thread (bac proliferation after nod gene expression)–> actin depolymerisation 4. infection grows into root cortex 5. infected threads release bac cells –> bacteroids (no cell wall at this point) into root cells 6. Bacterial cytokinins lead to nodule development + plant cortical cells to divide 7. plant supplies nutrients and O2 for bacteroids

• soil borne plant pathogen • cause infectious crown gall disease • genes for infection are vir genes on Ti plasmid ( infectious viral DNA) 1. ) virus enters host via wounds ( virA and virG attracted by acetosyringione) 2. ) DNA incorporated and leads to auxin and cytokinin and opines productions

– major role in coordination of many growth and behavioral processes in the plant’s life cycle and are essential for plant body development

plant growth regulators

food source for bac specific to Agrobacterium so it has a selective advantage

• tra genes transfer Ti plasmid into bac (if it is lost) • Tra/Tral is regualred by quorum sensing • opines inhibit AccR –> transcription • TraR produced only if opines around • TraR recognize AHL + activate conjugation

• demonstration of cross-talk b/n rhizosphere bac • -> rhizosphere produce three pigmented antibiotics/phenazines • phenazine prodcution is reg. by quorum sensing • phenazine production is reg by PhzR/PhzI systems • -> I procudes AHL and R is a transcriptional reg.

• mutant bac regain phenazone production ability via AHL signals

• bac inhibit wild type bac to produce phenzaine production via diffusible signals

• do not have classical AHL mediated quorum • use gamma-butyrolactones to regulate genes ( resemble AHL somewhat) • use small peptides and act by de-repressing gene expression • -> respond Al-2 • two component sensing system+ Autoinducidble peptide= three component system

• sensor protein (within cell membrane and senses changes in external envir.) –> communicates with RR (via phosphorylation-dephosphorylation reactions) • response-reg (RR) (regulate expression of key genes to respond to external stimulus)

• three component system - positive and negative regulation

• bac in communities use to enhance their survival (and their community) • behavior at a larger scale arises from the detailed structure • exterio cells are exposed first to chemical and antibiotic attacks + first exposed to nutrients • periphery growth is limited so nutrients can be used for the inner cells as well • keeping the inner cells alive and well ther biofilm as a whole will better survive an antibiotic treatment.