Download Humic substance and aquatic microbial ecology

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, 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
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.
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 pH
Zooplankton
Exudate
stimulates
inhibits
Stimulates
=Eutrophication
HS
Natural
source
grazing
Energy ?
P source ?
Bacteria
HS + N, P
Waste water
Energy and
Nutrient
supply
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
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?