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r
WnaL’c
J A & Azam
PH
F. Bacterioplankton
secondary
production
estimates
for coastal
waters
and California.
A&.
Environ.
Microbial.
39:1085-95.
1980.
Unw. Cal ifon lia, .%I Diego, La Jolla. CA]
I
Heterotrophlc
production
rates of nattve
manna
volved
Several
Principal
investlaators
from difplanktomc
bacteria
were esbmated
by Increases
or
ferent
institutions
studying
pl&kton
in large
enclosures.
It was an enjoyable
and intellectudirect cell counts in 3 pm-filtered
seawater
and also
ally stimulating
time. The following
winter,
I
via mcotporation
of tritiated
thymldine
tnto DNA
traveled
to Antarctica
with other Scripps
scienResults indicated
that about 25 percent of pnmaq
tists, continuing
theseexperiments
in McMurdo
production
IS consumed
by bacteria.
suggesbnc
Sound.
All the sampling
was through
the ice,
they are a mafor component
of manne food webs
and
we
traveled
to
different
locations
by helirhe SC/” indicates
that this paper has been cttec
copter
and sled (human-powered),
which
was
in more than 330 publications.]
fun. Instead
of making
holes through
the ice
ourselves,
we decided
to use breathing
holes
conveniently
maintained
by Weddell
seals. SamBacterial Growth in the Sea
pling was never interrupted
by a surprised
seal
coming
up to breathe,
but curious
penguins
Jed Fuhrman
often hopped
or tobogganed
overto
investigate.
Department
of Malogical
Sciences
Additional
experiments
were performed
in La
Allan
Hancock
Foundation
Building
107
Jolla that spring,
and by summer
a pattern
of
University
of Sou$ern
California
results
had emerged:
the heterotrophic
producLos Angeles,
CA 9OOB40371
tion
estimates
suggested
that bacteria
were
consuming
about 20-25 percent
of the total priOceanographers
and ecologists
are very inmary production,
indicating
thattheir
utilization
terested
in knowing
the pathways
and rates of
of dissolved
organic
matter is a major route in
energy
and material
flow in aquatic
and marine
marine
carbon
cycling.
While
we were writing
foodwebs.ThemostdifficuRorganisms
tostudy
this up for submission,
A. Hagstrom
eta/.* pub
in this
regard
are the
microorganisms.
lished
very similar
conclusions,
based
on a
Epifluorescence
microscopy
in the mid-1970s
completely
different
approach.
showed
that, although
they are very small, bacAn excellent
review
by P.J. le 8. Williams3
teria contribute
significantly
to the biomass
of
cited these
data as well as others
in a major
the marine
systems.’
But biomass
alone
does
rethinking
of the roles of bacteria
in thesea.
Our
not demonstrate
that the organisms
are actively
own subsequent
work included
detailed
tests of
participating
in ecological
processes,
because
they may be dormant
or growing
very slowly.
various
assumptions
we had made,
and the
results
decreased
the uncertainties
in our prior
What was needed
was a means
of measuring
growth
rates of mixed populations
of bacteria
in
conclusions.4
In the last decade,
many investigators
around
the world
have used the thyminatural
habitats.
dine incorporation
approach,
largely
becauseof
On entering
graduate
school,
and on the advice of my undergraduate
research
advisor,
Its relative
ease and simplicity.
There has been
Penny
Chisholm
at MIT, I began
working
with
little change
in the overall
conclusions
from a
Farooq
Axam at Scripps
Institution
of Oceanogdecade
ago; however,
there has been considerraphy
in La Jolla,
California.
He had already
able discussion
and debate
about methodolobeen experimenting
with estimating
RNA and
gies and how best to calculate
production
rates
DNA synthesis
rates via incorporation
of thymi‘ram thymidine
incorporation
data.5
dine, uridine,
and adenine
into these macromolExtensive
interest
in the ecological
roles of
ecules,
and I had done similar
work with pure
,lanktonic
bacteria
and the popularity
of the
cultures
as an undergraduate.
My graduate
rehymidine
method
probably
explain
why this
search
project
centered
on obtaining
quantitalaper
has been cited so often. Recently,
additive growth
rate estimates
from DNA synthesis
ional methods
for estimating
bacterial
growth
as measured
by incorporation
of tritiated
thymimd production,
particularly
leucine
incorporadine in field samples.
ion into protein,6
have become
widely accepted.
Myfirstsummer(1979),everyonefrom
thelab
rogether,
these various
tools should
help us to
traveled
to Saanich
Inlet, British
Columbia,
to
t mderstand
how microorganisms
fit into our
work
on an interdisciplinary
project
that in1Gcture of the world.
I. Ferguson R L & Rubke P. Convlbution
of bxctcria to standing crop ofcoastal plankton. Lmnol. Oceanoqr. ?1:141-5. 1976.
I
1
_I
Thic
Fuhrman
of British
Columbia,
Antarctica,
[Scripps Instmmon of Oceanography,
(Cited 190 times.)
2. Hagstrom A, Larson U, Horstedt P & Nommrk S. Frequency of dividing cells, a new approach m the determination of
bacterial growth rates in aquatic envmnments. Appl. Environ. Microbid.
37:805-i 2. 1979. (Cited I85 ttmes.)
3. WilRams P .I le B. Incorporation of micmhewmtmphic
pmcesses into the classical paradigm of the planktonic food web.
Kielcr Meeresforsck. Sonderh. 5~1-28. 1981. (Cited 165 times.)
4. Fuhmmn J A & Azam F. Thymidine incorporradon as a measure of helerixmphic
bacrerioplankton
pralucuon
in marine surface
waten: evahxion
and field results. Mar. Biul. 66 109-20. 1982. (Cited 335 limes.)
5. Ducklow H W & Carlson CA. Oceanic bacterial prcduc~ion. (Mnrchall K C. cd.1 Adwnrrs zn micmhiul rroir,q~.
New York: Plenum. 1992. Vol. 12. (In press.)
6. Simon M & Azam F. Protein content and pmtein synthesis rates of planktonic marine bacteria.
Mar. Ed-Prog.
Ser. 5 1:201-13. ,989.
Received January 20. 1992
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