BIO 326R 1st Edition Lecture 23 Outline of Last Lecture I. Microbial Group Activities—sociomicrobiologya. Quorum sensing—Vibrio fisherii. Counter illuminationii. Bioluminescenceb. Antivirulent strategiesi. biofilmsOutline of Current Lecture I. Biofilmsa. Mechanism of antimicrobial resistanceb. Preventing biofilmsII. Symbiosisa. Rhizobia and nitrogen fixationCurrent LectureBiofilms- Bateria attached to surfaceo Quorum sensing- Free swimming planktonic cells- ~90% of all infections are biofilm related- Mechanism of antimicrobial resistanceo Capsules make up the biofilm or bacteria adhered to a surfaceo Nutrients are absorbed from the external environmento Theories of mechanism of resistance Prevent diffusionThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- This is wrong, because antibiotics are able to get in, despite the coagulation of cells Protection by resistant cells- It is possible that some cells send out a signal to other cells in the presence of antibiotics in order for them to elicit a protective mechanism against the antibiotic Slow growing cells—persister cells- Some cells may be slow growing because they have less acess to nutrients- These cells will be underdeveloped and have no cell wall- Antibiotics typically target the cell wall, so they’ll have no target Gene expression—maybe but probably wrong- Because they are attached to a surface rather than swimming, genes are different and maybe more antibiotic resistant- Preventing biofilmso Biggest problem in Hospitals and medical settings Shipping- Ocean bacteria attaches to ships, biofilms form, this creates drag Industrial plants- Piping can be effectedo Change the topography Shark skin topography is resistant to biofilm formation Have tried to mimic this topography and coat surfaces with thisSymbiosis- Rhizobia and nitrogen fixationo N2 NH4+o ~50% all nitrogen for cropso Symbiosis= mutualism, 2 organisms that interact and both benefito Rhizobia and legumes Legumes= ~18,000 species, very successful crop, includes peas, beans, alfalfa, etc. Need to interact with bacteria to grow because most soils are nitrogen poor- Typically nitrogen poor after growing corn, which is why crops are rotatedo corn takes nitrogen, legumes allow rhizobia to make it again- alpha proteobacteria are nitrogen fixingo related to most of the bacteria we have studies thus far (also proteobacteria)- conversion is very energy consuming because of the stability of the triply bonded N2o N=N is very stable high energy bond to breako Reaction produces 2NH4+o Nitrogenase enzyme is hard to keep around- Nodulation is common to rhizobial specieso Protective “tumor”- How do bacteria find the root?o Rhizosphere= area within millimeters of the root that is high in nutrients and microbes Other areas of the soil are low in nutrients The high levels of nutrients and microbes attract the rhizobiao 1st step movement of the bacteria toward the root Attracted by root exudates (amino acids and sugars)o 2nd step communication between bacterium and plant (plant always signals first) Root signal to bacteria, bacteria responds with a signal back to the root Bacteria knows there’s a plant there and knows to make a tumor- Highly specifico Signal tells bacteria what type of root it is- Ex: signal from pea plant to a bacteria that is specific to pea planto Pea root signal sent bacteria receives signal and recognizes that this is a pea plant bacteria is specific to pea plants bacteria makes tumor on pea planto 3rd step invasion and tumor formation Nodules Leghemoglobin protein binds
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