, 2011). Briefly, recently fallen leaves were placed in leaf litter bags and immersed in the stream; learn more samples were collected intensively for bacterial biomass and enzymatic
activity until day 112 after immersion. Leaf samples were collected, rinsed with filtered stream water (0.2 μm), and cut to disks (1.1 cm diameter) with a metal borer. For phenol oxidase activity assays, disk samples were kept at 4 °C until analyzed in the laboratory (within 20 h). Samples for the determination of bacterial density were fixed with formaldehyde (2%). Finally, samples for molecular analyses were stored frozen (−20 °C). Bacterial densities were estimated according to the protocol of Porter & Feig (1980). Leaf disks were sonicated (2 + 2 min) in an ultrasonic bath (40 W power, 40 kHz frequency; Selecta, Spain), diluted (1 : 4), and stained for 5 min with 4, 6-diamidino-2-phenylindole (DAPI) at a final concentration of 2 μg mL−1. Bacterial suspensions were, then, filtered through 0.2 μm irgalan black–stained polycarbonate filters Selleckchem GSK1120212 (Nuclepore; Whatman International Ltd., Maidstone, UK) and counted using a fluorescence
microscope (Nikon Eclipse 600W, Tokyo, Japan) under ×1250 magnification. Bacterial densities were transformed into biomass units based on 2.2 × 10−13 g C μm3 conversion factors (Bratbak & Dundas, 1984) and using a mean bacterial biovolume of 0.163 μm3 (J. Artigas, unpublished data). Phenoloxidase enzyme activity (EC 188.8.131.52 and 184.108.40.206) was determined using L-3,4-dihidroxyphenylalanine C59 cost (L-DOPA) substrate and following the methodology described by Sinsabaugh et al. (1994). Triplicate leaf samples from each sampling date were pooled for the DNA extraction. The DNA was extracted from 100 to 200 mg of lyophilized leaf
material. Nucleic acids were extracted with the FastDNA® SPIN for Soil Kit (MP Biomedicals) following the instructions provided by the manufacturer, with the following modifications. The homogenizing step was repeated three times in a FastPrep Instrument (MP Biomedicals) using cycles of 30 s at a speed setting of 5.5. Samples were placed on ice for 5 min between every homogenizing step. The LmPH gene was amplified in a GeneAmp PCR system 2700 with the primer pair PheUf/PheUr (Futamata et al., 2001). PCR mixtures contained 1× PCR buffer, 1.5 mM MgCl2, 200 μM total dNTPs, 0.5 μM of each primer, 10 ng of the DNA extracts, and 0.5 units of Taq polymerase (Go Taq; Promega, Madison, WI) in a total volume of 30 μL. Amplification reactions were carried out exactly as previously described (Futamata et al., 2001). PCR products were analyzed by electrophoresis on 1.5% agarose gels and visualized after staining with ethidium bromide (0.2 mg L−1). The analysis of LmPH gene diversity was determined through cloning experiments.