Geology,
Год журнала:
2023,
Номер
51(5), С. 486 - 490
Опубликована: Март 22, 2023
Abstract
The
Cretaceous-Paleogene
(K-Pg)
boundary
marks
one
of
the
five
major
mass
extinctions
Phanerozoic.
ways
in
which
climate
system
responded
to
a
bolide
impact
and
extensive
volcanism
at
this
time
over
different
scales
are
highly
debated.
We
used
distribution
branched
tetraether
lipids
(brGDGT)
from
fossil
peats
two
sites
Saskatchewan,
Canada
(paleolatitude
~55°N),
generate
high-resolution
(millennial)
record
mean
annual
air
temperature
(MAAT)
spanning
last
~4
k.y.
Cretaceous
first
~30
Paleogene.
Our
study
shows
that
MAATs
ranged
16
29
°C,
with
highest
value
millennia
earliest
Paleogene
averaged
~25
°C—maintaining
or
enhancing
warmth
latest
Cretaceous—followed
by
general
cooling
~20
°C
following
No
abrupt
postboundary
(e.g.,
an
“impact
winter”)
warming
is
evident
our
data,
implying
if
such
phenomena
occurred,
their
duration
was
relatively
short-lived
(i.e.,
sub-millennial-scale).
Further,
no
long-term
impactor
volcanism-driven
evident.
range
change
observed
considerably
greater
than
derived
marine
proxy
records
same
interval.
findings
therefore
more
properly
place
bounds
on
magnitude
land
during
critical
interval—the
main
setting
for
demise
nonavian
dinosaurs
rise
mammals.
Geobiology,
Год журнала:
2022,
Номер
21(1), С. 102 - 118
Опубликована: Сен. 23, 2022
Abstract
Branched
glycerol
dialkyl
tetraethers
(brGDGTs)
are
bacterial
membrane
lipids
that
frequently
employed
as
paleoenvironmental
proxies
because
of
the
strong
empirical
correlations
between
their
relative
abundances
and
environmental
temperature
pH.
Despite
ubiquity
brGDGTs
in
modern
paleoenvironments,
source
organisms
these
enigmatic
compounds
have
remained
elusive,
requiring
applications
to
rely
solely
on
observed
correlations.
Previous
laboratory
studies
suggested
globally
abundant
phylum
Acidobacteria
may
be
an
important
brGDGT
producer
nature.
Here,
we
report
experiments
with
a
cultured
Acidobacterium,
Solibacter
usitatus
,
makes
large
portion
its
cellular
(24
±
9%
across
all
experiments)
out
structurally
diverse
set
including
common
Ia,
IIa,
IIIa,
Ib,
IIb.
was
grown
range
conditions
temperatures
from
15
30°C,
pH
5.0
6.5,
O
2
1%
21%,
demonstrated
pronounced
shifts
degree
methylation
growth
conditions.
The
response
culture
close
agreement
trends
published
datasets,
supporting
physiological
basis
for
relationship
number
temperature.
However,
at
lower
(15
20°C)
modulated
by
higher
systematically
increasing
methylation.
In
contrast,
had
little
effect
cyclization,
hypothesis
changes
community
composition
underlie
link
cyclization
samples.
Oxygen
concentration
likewise
affected
highlighting
potential
this
parameter
impact
paleotemperature
reconstruction.
Low
further
resulted
production
uncommon
isomers
could
indicators
limitation.
Finally,
brGTGTs
(trialkyl
tetraethers)
addition
previously
discovered
iso‐C15‐based
mono‐
diethers
S.
suggests
biosynthetic
pathway
uses
homologs
archaeal
tetraether
synthase
(Tes)
enzyme
synthesis
diethers.
Numerous
proxy
reconstructions
have
provided
general
insight
into
late
Quaternary
East
Asian
Monsoon
variability.
However,
challenges
persist
in
precisely
assessing
absolute
temperature
impacts
on
variations.
Here,
we
use
two
independent
paleothermometers,
based
bacterial
membrane
lipids
and
clumped
isotopes
of
snail
shells,
the
same
section
western
Chinese
Loess
Plateau
to
establish
a
robust
land
surface
record
spanning
past
approximately
21,000
years.
Our
records
consistently
reveal
(i)
similar
temperatures
between
Last
Glacial
Maximum
Holocene
(ii)
gradual
cooling
Holocene,
which
contrasts
with
climate
model
predictions.
We
propose
that
changes
soil
moisture
availability
over
deglaciation
modulates
recorded
by
proxies.
A
energy
partitioning
confirms
this
mechanism,
suggesting
effects
should
be
properly
considered
when
comparing
outputs.
Climate of the past,
Год журнала:
2024,
Номер
20(4), С. 841 - 864
Опубликована: Апрель 8, 2024
Abstract.
Millennial-scale
climate
variations
during
the
last
glacial
period,
such
as
Dansgaard–Oeschger
(DO)
cycles
and
Heinrich
events,
have
been
extensively
studied
using
ice
core
marine
proxy
records.
However,
there
is
a
limited
understanding
of
magnitude
these
temperature
fluctuations
in
continental
regions,
questions
remain
about
seasonal
signal
events.
This
study
presents
60
000-year-long
reconstruction
based
on
branched
glycerol
dialkyl
tetraethers
(brGDGTs)
extracted
from
lake
sediments
Eifel
Volcanic
Field,
Germany.
brGDGTs
are
bacterial
membrane-spanning
lipids
that
known
to
strong
relationship
with
temperature,
making
them
suitable
for
reconstructions.
We
test
several
calibration
models
modern
samples
taken
soils
multiple
maar
lakes.
find
negative
bias
brGDGT-based
estimates
associated
water
depth
anoxic
conditions
can
be
corrected
by
accounting
brGDGT
isomer
only
produced
conditions.
The
correlates
model
spanning
same
time
validating
approach
we
selected.
millennial-scale
variability
significantly
dampened
record,
contrast
other
Northern
Hemisphere
records,
stadials,
temperatures
actually
increase.
demonstrate
apparent
discrepancies
explained
unique
response
paleothermometer
months
above
freezing
(TMAF).
Our
data
support
view
warm-season
Europe
varied
minimally
period
abrupt
events
were
defined
colder,
longer
winters.
continuous
high-resolution
provides
important
information
used
inform
studies
paleoecological
change.
Proceedings of the National Academy of Sciences,
Год журнала:
2024,
Номер
121(24)
Опубликована: Июнь 4, 2024
Understanding
how
microbial
lipidomes
adapt
to
environmental
and
nutrient
stress
is
crucial
for
comprehending
survival
functionality.
Certain
anaerobic
bacteria
can
synthesize
glycerolipids
with
ether/ester
bonds,
yet
the
complexities
of
their
lipidome
remodeling
under
varying
physicochemical
nutritional
conditions
remain
largely
unexplored.
In
this
study,
we
thoroughly
examined
adaptations
Desulfatibacillum
alkenivorans
strain
PF2803
T
,
a
mesophilic
sulfate-reducing
bacterium
known
its
high
proportions
alkylglycerol
ether
lipids
in
membrane,
various
cultivation
including
temperature,
pH,
salinity,
ammonium
phosphorous
concentrations.
Employing
an
extensive
analytical
computational
lipidomic
methodology,
identified
assemblage
nearly
400
distinct
lipids,
range
glycerol
polar
head
groups.
Information
theory-based
analysis
revealed
that
temperature
fluctuations
phosphate
scarcity
profoundly
influenced
lipidome’s
composition,
leading
enhanced
diversity
specificity
novel
lipids.
Notably,
limitation
led
biosynthesis
glucuronosylglycerols
sulfur-containing
aminolipids,
termed
butyramide
cysteine
glycerols,
featuring
bonds.
This
suggests
adaptive
strategy
heterotrophs
thrive
phosphorus-depleted
conditions,
characterized
by
diverse
array
nitrogen-
groups,
moving
beyond
reliance
on
conventional
nonphospholipid
types.
Organic Geochemistry,
Год журнала:
2023,
Номер
187, С. 104706 - 104706
Опубликована: Ноя. 22, 2023
Glycerol
dialkyl
glycerol
tetraethers
(GDGTs)
are
microbial
membrane-spanning
lipids
that
produced
in
a
variety
of
environments.
To
better
understand
the
potentially
confounding
effect
soil
chemistry
on
temperature
relationship
branched
GDGTs
(brGDGTs),
isoprenoid
(isoGDGTs)
and
GDGT-based
proxies
MBT'5ME
TEX86,
soils
from
6
elevation
transects
(mean
annual
air
0
–
26
℃,
n=74)
were
analyzed.
Corroborating
earlier
work,
index
correlates
well
with
mean
low
pH
(pH<7),
non-arid
under
study
(r=0.87,
p<0.001).
However,
clear
over-estimation
reconstructed
lowest
(<3.5)
is
observed,
explained
by
correlation
between
brGDGT
Ia
free
acidity.
TEX86
also
shows
significant
(r=0.45,
p<0.001),
driven
dependent
concentration
changes
isoGDGTs
3
cren'.
an
overarching
P/E
values
dominates
all
supposed
Thaumarchaeotal
(GDGT1-3,
cren
cren'),
implying
potential
impact
moisture
values.
In
addition
to
identifying
these
factors
proxy,
GDGT
ratios
can
be
used
constrain
chemistry,
specifically
exchangeable
Ca2+,
sum
basic
cations,
Fe3+
metals
proposed
(0.53
