Growing Fungi and Bacteria of Plants
Introduction There are both virulent and non-virulent bacteria and fungi that grow on plants. It is difficult to distinguish between the two without proper inspection and diagnosis of the diseased plant to know whether the bacteria or the fungus in question is the virulent or non-virulent one. Therefore pure cultures need to be isolated to know with absolute certainty which is the causative bacteria or fungus. Potato dextrose agar is a good nutrient agar for mycelia to thrive on which is present in most fungal moulds. Standard nutrient agar is a general utility used for non-fastidious microorganisms. 2 Aim The aim is to isolate fungi and bacteria colonies from diseased and healthy leaves. Materials and Methods Materials used for the experiment was two of each: standard nutrient agar plate and potato dextrose agar plate. To remove any epiphytic or saprophytic microbes from the plant surface the leaf is superficially sterilized with 100% ethanol. A scalpel to cut the leaf
Sterile water for macerating the leaves. To isolate the fungi: Cut 5 pieces of leaf from the diseased leaf around the edges of the diseased area so it contains both healthy and diseased parts, place it on the one potato dextrose agar plate. Then cut 5 pieces from the healthy leaf and place them on the second dextrose agar plates. To isolate bacteria: Macerate both the healthy and diseased leaves separately in the sterile water and streak it onto the two separate standard nutrient agar plate.
Incubate all four plates at 25? C for up to 7 days. Discussion There is growth on both the healthy and diseased agar plates for both bacteria and fungi. For the healthy fungal plate there is a single type of growth which suggests that it is a natural non-pathogenic fungus that grows on plants. On the diseased plants there are 5 different colonies of fungus from the 5 different pieces of leaves. The one area has a clear zone where the fungus has inhibited the growth of the other colonies.
On the healthy bacterial plate there is some bacterial growth which can also suggest non-pathogenic bacteria that grows on plants. On the diseased plant bacterial plate there is some bacterial growth but not a lot and still fungal growth. Conclusion The lack of bacterial colonies on the bacterial plate and the fungal growth on the same plate suggests that the disease on the plant is caused by a fungal pathogen and not a bacterial one. There are fungi and bacteria that grow on plants that are not harmful towards the plant. ?