Humic substance and

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Humic substance and aquatic microbial ecology
Ahn, Tae-Seok
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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)

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Introduction
A. HS is biologically inert in aquatic
ecosystem B. Ecological function of HS is
related to iron, phosphate bioavailability, pH
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
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Introduction
D. HS is consisted with acidic materials, so the
streams and lakes with HS are acidic state E.
Acidic lake (pH about 4) in Japan zooplankton is
abundant, but there is no phytoplankton.
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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)

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Introduction
G. HS is coming from forest, low nutrient
concentration
Brown colored HS in stream of forest July, 2009,
Forest near Bayreuth
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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
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HS vs Microbial loop
FISH
Phytoplankton
grazing
Low pH
Zooplankton
Exudate stimulates
inhibits
HS
Stimulates Eutrophication
grazing
Energy ? P source ?
Natural source
Bacteria
Energy and Nutrient supply
Over growth Saprobic state
HS N, P
Waste water
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Methods
1. Bacterial community structure in HS
conatinning stream and poultry waste water

• ? Total bacterial number (Invitrogen, 1998)
• Community with DGGE FISH method
• ? ß-glucosidase phsophatese activities (Chróst,
  1989) -MUF method

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Methods
Profiles of microbial community by DGGE
Total sample DNA
PCR amplicon
Community Fingerprinting
Samples
DNA extraction
PCR
DGGE
Phylogenetic functional diversity
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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 Hybridization 45?, 4 hrs, Washing 45?, 20 min
Bacillus sp. from Lake Baikal by FISH
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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
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Expected results

• Microbial availability of HS
• HS is source for energy and matter. So by the
  changes of enzymatic activities
• hypothesis if phosphatase activity is
  increasingHS would be source for phosphate
• if glucosidase activity is highHS is for
  energy
• 2. Profile of microbial community
• HS would be acting as trigger for bacterial
  succession how? What is the effects?

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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?