Model "microecosystems" used to study
producer-consumer interaction networks in
microbial mats
14 May 2014
Lake, located in north-central Washington State.
They characterized each consortia's membership
and metabolic function to identify the interactions
thought to recruit and maintain genetic and
functional diversity in the consortia over time.
The team's results shed light on the principles that
govern microbial communities, principles needed
for scientists to move closer to the goal of being
able to predict, engineer, and manipulate microbial
communities of importance to global carbon and
energy cycling.
These consortia are each anchored by a single
cyanobacterium-a type of autotroph-that obtains
energy from sunlight through photosynthesis and
uses the energy to produce sugars from carbon
dioxide. In turn, the autotrophs supply many
heterotrophs-organisms that consume carbon
produced by other organisms-with the carbon and
oxygen they need to harvest energy and produce
biomass.
"Primary production by microbial autotrophs and
consumption by heterotrophs are occurring
everywhere," said Dr. Steve Lindemann, PNNL
microbiologist and lead author of the study, which
Scanning and transmission electron micrographs of the appears in Frontiers in Microbiology. "If you don't
unicyanobacterial consortia Phormidesmis priestleyi str. understand the interactions, you can't predict how
ANA (top) and Phormidium sp. OSCR (bottom). Pacific
communities will respond to changing
Northwest National Laboratory scientists isolated these
environmental conditions or engineer them to
consortia from a microbial mat in a lake and
sustainably perform a useful function; for example,
characterized their membership and interactions as a
step toward using these organisms in global carbon and making them more productive-to generate more
biomass for bioenergy applications-or resilient, so
energy cycling applications.
they recover quickly from environmental shocks. It's
a big deal."
As part of their ongoing studies of the complex
world of microbial communities, scientists at Pacific
Northwest National Laboratory recently isolated
two bacterial consortia from a microbial mat in Hot
The relative simplicity and tractability of the
consortia make them useful model systems for
deciphering the interspecies interactions and
principles of microbial community assembly.
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heterotroph and heterotroph-heterotroph
interactions in each consortium are likely distinct.
Much like members of a growing village, microbial
community members occupy niches that support
their own growth, but in turn also promote other
members' growth; analogous, perhaps, to a
microbe's "occupation" within its community.
Though different microbial "villages" require similar
resources for growth, the way those resources are
produced and move through the community will
depend upon which niche each microbe is filling
and its abundance. Consequently, though similar
kinds of niches may be created in each community,
there will be distinctions in the numbers or
specialties of members occupying those niches
depending upon other members and the
community's circumstances.
Process for isolation and cultivation of the
unicyanobacterial consortia.
As Lindemann explains, "For example, while two
villages will require farmers for food production,
whether those farmers are growing wheat, rice, or
corn will impact the roles of other members of the
community-in this example, perhaps in the amounts
and types of bread made by bakers. Similarly,
different primary producers are likely to interact with
heterotrophic consumers in similar but unique
ways. These differences will then have cascading
effects upon interactions between heterotrophic
members."
The PNNL scientists found that though the
consortia shared all their members except for the
cyanobacteria, they contained very different
Such disparities in the network of interactions
abundances of each member as the communities between two microbial communities are likely to
assembled into a biofilm. This suggested that
create distinct niches in each, support different
specific interactions between the cyanobacteria and population sizes of each member species, and
heterotrophs generate a different network of
affect a community's overall functions and
interactions. These networks likely create related
properties. Comparing interactions occurring within
but unique niches that support different population these two consortia therefore brings scientists
sizes of each heterotroph.
closer to understanding the principles governing
The scientists also found that autotroph growth
rates dominated early in assembly but yielded to
heterotroph growth rates late in the growth cycle.
Although the heterotrophic species composition
was similar in both consortia, the population
dynamics of different species varied significantly as
their biofilms matured. These data suggest that,
although the niches provided by the cyanobacterial
metabolisms are sufficiently broad to retain the
same species, the resulting webs of autotroph-
similar interactions in the wild-and may allow them
to better predict and control microbial communities.
The PNNL team defined the membership and
examined the spatial structure and phototrophheterotroph succession of unicyanobacterial
consortia as they assembled into biofilms. Earlier
studies were limited to quantifying populations of
cultivable organisms and were therefore unable to
estimate the diversity of potential colonizers in
experimental "microecosystems."
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"Next-generation sequencing has greatly expanded
our ability to comprehensively characterize a
community's membership, and molecular
quantitation at the species level allows us to assess
heterotroph abundance independent of cultivation,"
Lindemann said. "We can now track the dynamics
of all of the community's members, whether we can
grow them by themselves or not."
Interestingly, though different cyanobacteria were
primary producers in each consortium, both
retained the same suite of heterotrophic species.
The team plans to subject the consortia to
environmental perturbation (such as variations in
salinity, light, temperature, or availability of specific
nutrients) to examine how changing conditions
affect the structure and composition of the
assembling consortial biofilms.
More information: Cole JK, JR Hutchison, RS
Renslow, YM Kim, WB Chrisler, HE Engelmann, A
Dohnalkova, D Hu, TO Metz, JK Fredrickson, and
SR Lindemann. 2014. "Phototrophic Biofilm
Assembly in Microbial-Mat-Derived
Unicyanobacterial Consortia: Model Systems for
the Study of Autotroph-Heterotroph Interactions."
Frontiers in Microbiology 5:109. DOI:
10.3389/fmicb.2014.00109.
Provided by Pacific Northwest National Laboratory
APA citation: Model "microecosystems" used to study producer-consumer interaction networks in
microbial mats (2014, May 14) retrieved 17 June 2017 from
https://phys.org/news/2014-05-microecosystems-producer-consumer-interaction-networks-microbial.html
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