1. Us
Us
Maya
Sederholm,
Bradley
Schmitz,
Luisa
Ikner,
Alexander
Wassimi,
Maria
Campillo,
and
Ian
Pepper
Department
of
Soil,
Water
and
Environmental
Science
!
College
of
Agriculture
and
Life
Sciences
The
University
of
Arizona
Objec)ves
•
Determine
the
effects
of
a
commonly
used
soil
fumigant
on
soil
microbes
in
terms
of
numbers,
acHvity,
and
diversity
•
Does
the
community
return
to
pre-­‐applicaHon
condiHons?
•
Is
the
soil
quality
diminished
for
future
agricultural
use?
•
Can
it
be
used
to
convert
Class
B
biosolids
to
Class
A?
Background
Informa)on
•
Metam
sodium
(MS)
is
one
of
the
most
widely
used
soil
fumigants
in
the
United
States
(EPA)
•
Primarily
used
as
an
agricultural
crop
pretreatment
for
pests
•
MS
hydrolyzes
to
MITC
(a
tear
gas,
the
acHve
component)
in
water
• MITC
infiltrates
cell
walls
to
adversely
impact
or
kill
organisms
•
Studies
have
been
conducted
on
pathogens
in
MS-­‐treated
biosolids,
but
not
much
is
known
about
the
effects
of
MS
on
soil
microbial
populaHons
Methods
Sampling
Times
" Pre-­‐applicaHon
" APer
24
hours
" APer
7
days
" APer
14
days
" APer
21
days
" APer
28
days
Culturable
&
Biochemical
Assays
•
Heterotrophic
plate
counts
(HPCs)-­‐
Number
of
culturable
heterotrophic
bacteria
in
the
soil
•
LuminUltra®-­‐
Total
ATP
producHon
and
microbial
equivalents
(MEs)
•
Dehydrogenase
Assay-­‐
Total
TTC
reducHon
to
TPF
Molecular
Methods
DNA
extracHon
(MoBio
PowerSoil
DNA
IsolaHon
Kit)
>
PCR
>
Illumina
HiSeq
2500
sequencing
>
BioinformaHc
analysis
Questions? Email mayas4@email.arizona.edu
Schema)cs
&
Sampling
Control
plots
Treated
plots
1
2
3
3
2
1
Triplicate
cores
per
plot
Composite
sample
10
g
soil
in
95
mL
water
to
start
dilu)on
series
(10-­‐1
to
10-­‐9)
Photo
by
Rich
Wagner,
U
of
A
Campus
Agricultural
Center
Results:
Numbers
Applica)on
of
Metam
Sodium
•
ApplicaHon
rate
=
75
gallons
Vapam/acre
soil
•
Plots=
3
square
feet
•
36-­‐gallon
carboys
gravity-­‐fed
through
drip
system
onto
the
plots
•
Plots
covered
with
clear
plasHc
tarp
0%
5%
10%
15%
20%
6
6.5
7
7.5
8
8.5
Pre-­‐applicaHon
24
hours
7
days
14
days
21
days
28
days
Moisture
Content
Log10
CFUs
or
MEs/g
dry
soil
HPC
Control
HPC
Treated
LU
Control
LU
Treated
MC
0
10
20
30
40
50
Pre-­‐applicaHon
24
hours
7
days
14
days
21
days
28
days
μg
TPF/g
dry
soil
Dehydrogenase
Assay
C
C+G
T
T+G
3
3.5
4
4.5
5
5.5
6
Pre-­‐applicaHon
24
hours
7
days
14
days
21
days
28
days
Log10
pg
ATP/g
dry
soil
LuminUltra®
Control
Treated
Results:
Total
Ac)vity
Results:
Diversity
(ongoing)
Heterotrophic
Plate
Counts
(HPC):
CFUs
LuminUltra®
(LU):
MEs
0%
20%
40%
60%
80%
100%
Control
Treated
Control
Treated
Control
Treated
Control
Treated
Pre-­‐
applicaHon
24
hours
7
days
28
days
Rela)ve
Abundance
Alphaproteobacteria
Clostridia
AcHnobacteria
Gammaproteobacteria
Bacilli
Deltaproteobacteria
Other
Unclassified
RelaHve
abundances
of
top
6
classes
from
each
Hme
period.
Other
top
classes
not
listed:
Betaproteobacteria,
Sphingobacteriia,
and
Thermoleophilia.
Richness
and
evenness
throughout
the
study
TBD.