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#1
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Another episode of "CSI:Bonsai"
Part II: In our last episode, I was sent some fig trees from Florida
that had galls on them. In this episode, I examine them with the help of an expert. The samples were Fed-Ex'ed and arrived last Friday in beautiful shape. This is especially important with bacteria; if the samples get old, other bacteria begin to invade the tissue, and you can't tell which was there to begin with. I agreed to take the samples because my friend Fari is a bacteriologist and I knew he'd help me. Fari was a professor in Iran and when the Shah fell, he fled to the US to keep his son safe (otherwise he'd have been drafted into the Iranian army). Fari had a hard time finding a proper job, and for a while he worked on a turkey farm, and then for a corporate plant-care company (the people who put the weeping figs in the lobby, and the poinsettias by the elevator at Christmas). Eventually he got a job at the USDA, where he brings great joy to everyone who works here! Anyway, he and I unpacked the box, and we were both sure the galls were caused by the crown gall bacterium (look at the picture on the gallery- those swollen warty nodules are characteristic). Fari said when he worked for the plant-care company he saw hundreds of figs with crown gall, and they looked just like this. Still, we had to be sure. The first step was to try to isolate the bacterium. Although the galls have quite a lot of volume, the bacterium is found just under the surface, not inside it, so Fari used a sterile razor blade to pare off the rind (which was not sterile), then sliced off a piece just under the surface of the gall. He put the tissue in a sterile petri dish in a few drops of sterile water and teased the tissue apart to release the bacteria. After waiting for half an hour, he took some of the water and streaked it on a plate of nutrient media. On Monday I checked the plates and they were dotted with little white convex colonies of bacteria. They looked like Agrobacterium, but were they? Stay tuned for our next episode! |
#2
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Another episode of "CSI:Bonsai"
Part IV: Last episode, we learned more about crown gall; this episode
we learn a simple way to identify it. Fari the bacteriologist had to go on vacation, but before he left, he told me a simple way to identify crown gall using only a carrot. This is something that any of you could do, or your children could do as science projects. First I cut some gall tissue as described before and teased it apart in distilled water to release the bacteria. Then I surface-sterilized the carrot in bleach, then used a sterile razor blade to cut it into disks. I put the carrot pieces in Petri plates with moist filter paper on the bottom and wet the top of each carrot slice with the bacteria-containing water. I also took some of the colonies I isolated last week and smeared them on top of some of the slices. I sealed the Petri dishes to keep them moist and put them under fluorescent light. Now we wait 2 or 3 weeks. If the bacterium is Agrobacterium, weird tumors will arise from the carrot slices. I inoculated the carrots on Monday; I'll be checking them every few days to look for tumors. Wait patiently for the next episode. |
#3
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Another episode of "CSI:Bonsai"
Today when I looked at the carrot disks, I saw that the xylem
parenchyma had hypertrophied. That's how I talk at work: sorry. The center of the carrot disk was becoming lumpy, and the lumpiness was turning green, which is characteristic of crown gall on carrot. I've posted a picture on the "General discussion" gallery on the IBC webpage. This means that, without a doubt, the fig with galls was suffering from crown gall. Nina. PS- My friend Fari wants us to inoculate a baby tomato plant: that's another surefire method of identifying crown gall. Tomatoes are very suceptible, and will form galls quickly where you prick them with a needle coated in bacteria. |
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