Download Soil Fungi Diversity: Exploring Decomposers, Mutualists, and Pathogens in Different Soils and more Lab Reports Biology in PDF only on Docsity! Darren Yondorf Bi 432 Mycology Prof. Jeff Stone March 16, 2007 Diversity of Soil Fungi Introduction The purpose of this lab was to investigate the hidden world of fungal habitats in soil from various locations. Beneath your feet, the hyphae of a myriad of different fungi overlap in the soil, similar in appearance but vastly different in function. Three types of fungi occupy the habitat of the soil, each differing in strategy. Decomposers – saprophytic fungi – convert dead organic material into fungal biomass, carbon dioxide, and small molecules, such as organic acids. They help increase the accumulation of humic-acid rich organic matter that is resistant to degradation and may stay in the soil for hundreds of years. Mutualists – the mycorrhizal fungi – colonize plant roots. In exchange for carbon from the plant, mycorrhizal fungi help bring soil nutrients to the plant. The third group of fungi, pathogens or parasites, cause reduced production or death when they colonize roots and other organisms. These fungi are important in maintaining forest diversity, as an intermediate disturbance, or as control agents on insects or nematodes. This lab intended to quantify and compare the diversity of abundant soil fungi in different habitats. Materials and Methods Fungi will be collected from five soil samples, each representing a different location for the purposes of comparison. The types are agricultural soil (garden or pasture), aged compost, forest soil, sandy soil, and wetland soil. The soil will be diluted and plated on media. Two types of media are used, a very low nutrient medium (CMC) and a rich semi-selective medium (DRB). Both media contain antibacterial agents. DRB medium contains in addition the antifungal agents rose bengal and dichloran, which inhibit fast growing fungi, allowing slower growing species to grow. The dilution procedure is as follows: Sieve 10 grams of soil, while also weighing a wet sample for wet-dry weight conversion (reweigh and record after 48 hours of oven drying). Add the 10 gram sample to 90 mL of 0.2% water agar and mix well. Next, serially dilute the soil by aliquots of 1 mL into 9 mL 0.2% water agar test tubes, again, mix well to suspend the soil uniformly in the agar. After two dilutions are prepared, a 1:100 and a 1:1000, plate the samples on the selective media (starting with the most dilute). Do this by dispensing 0.5 mL from a pipette onto each plate, changing the tip between soil samples. Spread the sample evenly using a bent glass rod. Make 4 replicate plates per sample on both the DRB and CMC media. Label each plate with the sample site, dilution and number. Next, incubate the plates for a few days. After the plates are colonized, count the colonies on ‘the best’ dilution. With this information, calculate the culturable fungi per unit area. Record soil sample type, dilution factor and average colony counts for each plate. Isolate subcultures onto malt agar and identify five of the most distinctive conidial anamorphs. Results Table 1: Calculation of Culturable Fungi Soil Sample Type WW/DW Dilution Avg colony count cfu P3 1.30 2000.00 41.00 106707.00 F2 1.37 2000.00 74.00 203310.58 F6 1.38 2000.00 98.50 271788.27 F4 1.75 2000.00 76.50 267119.51 G1 1.35 2000.00 102.50 275771.92
