Humic substance and aquatic microbial ecology Ahn TaeSeok
Humic substance and aquatic microbial ecology Ahn, Tae-Seok
Introduction v DOC and POC • Most allochthonous dissolved organic carbon (DOC) and particle organic carbon (POC) in aquatic ecosystem are coming from terrestrial ecosystem v DOC • From exudate (Rhizosphere) • Resultant of microbial degradation v POC • From debris of plant (lignin, cellulose from leaves, wooden particles) Therefore, The characteristics of DOC and POC depend on land use More over Dissolved humic substances (HS) comprise 50 -80 % of DOC in aquatic ecosystem (Farjalla et al, 2009)
Introduction A. HS is biologically inert in aquatic ecosystem B. Ecological function of HS is related to iron, phosphate bioavailability, p. H condtion and light penetration (Steinberg et al 2008) C. DOC and HS enter planktonic food web through Microbial Loop (Azam et al 1983), and are important source of energy and matter
Introduction D. HS is consisted with acidic materials, so the streams and lakes with HS are acidic state E. Acidic lake (p. H about 4) in Japan zooplankton is abundant, but there is no phytoplankton.
Introduction Zooplankton are eating bacteria and phytoplankton Red: phytoplankton Blue: bacteria stained with DTAF These microphotographys are evidence of the MICROBIAL LOOP (Sim and Ahn, 1983)
Introduction G. HS is coming from forest, low nutrient concentration Brown colored HS in stream of forest July, 2009, Forest near Bayreuth
Introduction H. Another source of HS is coming from poultry waste, with high concentration of nutrient Over flow of black colored waste water form poultry June 2006, Pusan, Korea
HS vs Microbial loop Phytoplankton FISH grazing Low p. H Exudate stimulates inhibits Stimulates =Eutrophication HS Natural source HS + N, P Waste water grazing Energy ? P source ? Bacteria Energy and Nutrient supply Zooplankton Over growth = Saprobic state
Methods 1. Bacterial community structure in HS conatinning stream and poultry waste water Total bacterial number (Invitrogen, 1998) Community with DGGE & FISH method β-glucosidase & phsophatese activities (Chróst, 1989) -MUF method
Methods Profiles of microbial community by DGGE Samples Total sample DNA extraction Phylogenetic & functional diversity PCR amplicon PCR Community Fingerprinting DGGE Sequence analysis
Methods Detection of Bacillus by fluorescent in situ hybridization (FISH) Probe name probe sequence S-G-Bacill-0597 -a-A-22 5’-GGGTCATTGGAAACTGGGGAAC-3’ Hybridization : 45℃, 4 hrs, Washing : 45℃, 20 min Bacillus sp. from Lake Baikal by FISH
Methods 2. Role of HS in aquatic ecosystem After addition of HS containing water to natural lake water, and the change of bacterial community and activity will be analyzed Grazing behavior of Zooplankton will be defined
Expected results 1. Microbial availability of HS • HS is source for energy and matter…. So by the changes of enzymatic activities hypothesis : if phosphatase activity is increasing=HS would be source for phosphate if glucosidase activity is high=HS is for energy 2. Profile of microbial community • HS would be acting as trigger for bacterial succession = how? What is the effects?
Expected results 3. Different effect of nutrient rich or poor HS to aquatic ecosystem Do Zooplankton change their grazing behavior by HS ? And nutrient is effecting for grazing behavior? If that what is the machanism?
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