Q-RT-PCR for assessing archaea, bacteria, and fungi during leaf decomposition in a stream.

Leaf disks of Tilia cordata were exposed for up to 5 weeks in a first-order stream in Nova Scotia, Canada. The exponential decay rate k was 0.008 day(-1). Ergosterol levels increased linearly to a maximum of 134 microg g(-1) dry leaf mass. Release of conidia peaked at 700 day(-1) mg(-1) on leaves that had been exposed for 3 weeks; after 5 weeks, it declined to 15 mg(-1). In total, 23 taxa of aquatic hyphomycetes were distinguished. Anguillospora filiformis contributed over 76% of the conidia during weeks 1, 2, and 3, and 16.5% in week 5. Three sets of primers specific for Bacteria, Archaea, and Fungi were applied in quantitative real-time polymerase chain reaction (Q-RT-PCR) to estimate relative DNA amounts. Archaeal DNA was consistently present at low levels. Bacterial and fungal DNA peaked between weeks 2 and 3, and declined in week 5. With the exception of week 1, fungal DNA exceeded bacterial DNA by between 12 and 110%.