Download A microbial observatory for the study of neutraphilic

Spatial and temporal variability in
microbial mat communities from preand post-eruption Loihi Volcano: A
microbial observatory for the study of
neutrophilic iron-oxidizing bacteria
Craig L. Moyer
Biology Department
Western Washington University
Image courtesy of SOEST
Loihi Seamount, Hawaii
• Fe-dominated system
• Recent eruption (1996)
• Logistically easy access
Images courtesy of MBARI
20 m contours
SUMMARY OF THE 1996 ERUPTION AND SEISMIC EVENT
• Loihi goes seismic, July & August 1996
• The largest swarm of earthquakes ever
recorded on ANY Hawaiian volcano
• There was at least one, possibly two
eruptions based on dating of lavas recovered
Pele’s Vents: 1993
Pele’s Pit: The Forbidden Vents 1996
Pele’s Pit: After the 1996 Seismic Event
Fe-Dominated Vents
2004
• Higher temp/heat
flux vents
• Lower temp/heat
flux vents
• Fe(II) between 50
and 750 μM
• Summit located in
oxygen-minima zone
(0.5 mg/l)
Initial Questions:
• Can we track changes in microbial mat
community structure using T-RFLP in
conjunction with other molecular
methods?
• What about spatial and temporal
variability?
• Are there key populations in the
community triggered by environmental
forcing functions that we can target?
Integrating Molecular Methods
• Terminal-restriction fragment length
polymorphisms (T-RFLPs) were used to
detect phylotypes within the community.
• Clone library analyses were used to
further identify these phylotypes.
• Q-PCR is used to quantify key
populations and/or groups within the
community (future work).
T-RFLP FLOWCHART
Size is limited to 50-500 basepairs
% of Populations Detected
100 Model Communities at Discrete Values of Richness
% of populations detected
UPGMA/product-moment cluster analysis
of 55 T-RFLP bacterial community
fingerprints.
Community
Tave=26°C
Community
Tave=103°C
Representative T-RFLP electropherograms of Loihi Group 1 & 2 libraries.
Phylogenetic grouping, closest neighbor, and nucleotide similarity
of OTUs from the Loihi Group 1 sample PV602 b1-4.
Operational taxonomic units (OTUs) were chosen based on 97% nucleotide
similarity of aligned 5’ 300 base SSU rDNA fragments using the program DOTUR.
Phylogenetic grouping, closest neighbor, and nucleotide similarity
of OTUs from the Loihi Group 2 sample PV601 b1-8.
Operational taxonomic units (OTUs) were chosen based on 97% nucleotide
similarity of aligned 5’ 300 base SSU rDNA fragments using the program DOTUR.
Microbial Mat Community Structure
Phylogenetic groupings and the percent abundances of clones found in Loihi
Group 1 and Group 2 SSU rDNA clone libraries.
Rarefaction curves comparing the estimated population richness from three
clone libraries generated from Loihi microbial mats. Richness is not
significantly different between Loihi Group 1 and Loihi Group 2 libraries.
Loihi Group 2
Community
Loihi Group 1
Community
Mn vs. Fe for all vent effluent samples taken from 1993 through 1997.
Wheat et al., Continuous sampling fluids from Loihi, JGR, 2000.
Butterfield Model: Hydrothermal Event Response
Loihi Group 1
Community
Loihi Group 2
Community
• Loihi Group 1 is the largest
group and containing the
most mat samples collected
over time.
• Loihi Group 2 is comprised
of only post-eruption
communities.
• Loihi Group 1 microbial mats
are dominated by phylotypes
related to the obligate
lithotrophic Fe-oxidizing
isolate ‘M. ferroxydans’.
• Loihi Group 2 communities
are dominated by a unique
group of phylotypes
belonging to the Nitrospira
division and to H2-oxidizing
ε-Proteobacteria.
• Microbial mats clustering
within Loihi Group 1 have also
been discovered from iron
dominated vent sites at the
Mariana Arc and Backarc,
and the Juan de Fuca Ridge.
• Loihi Group 2 also contains
phylotypes associated with
Thiomicrospira spp., and the
‘M. ferroxydans’ group.
PV-1 Filament Formation.
Phase
Contrast
Epifluorescent
composite
‘Mariprofundus ferroxydans’ Group
ML Phylogenetic Tree
Original marine e-Proteobacteria
ML Phylogenetic Tree
Updated e-Proteobacteria
ML Phylogenetic Tree
S-oxidizers?
H-oxidizers?
Summary
• Loihi Group 1 microbial mats are generally from cooler
(Tave=26ºC) vent sites than Loihi Group 2 microbial mats
(Tave=103 ºC). May have more groups or subgroups….?
• Loihi Group 2 consists of only post-eruption samples, most of
which became dominated by Loihi Group 1 microbial mats as the
hydrothermal vent fluids cooled over time. This suggests that the
microbial community associated with Loihi Group 2 may be an
ephemeral assemblage which becomes dominant only under the
most extreme post-eruption conditions.
• Loihi Group 1 and Loihi Group 2 microbial mats are not
significantly different in terms of species richness, but are
significantly different in terms of species composition when
calculated using the integral form of the Cramer-von Mises
statistic using the program -Libshuff (Schloss et al., 2004).
Summary (cont.)
• Loihi Group 1 microbial mats are dominated by neutrophilic Feoxidizing bacteria clustering within the ‘Mariprofundus
ferroxidans’ Group (e.g., novel z-Proteobacteria).
• Loihi Group 2 microbial mats are co-dominated by neutrophilic
Fe-oxidizing bacteria clustering within the ‘Mariprofundus
ferroxidans’ Group, putative sulphate-reducing nitrifiers (e.g.,
Nitrospira), as well as hydrogen- and sulfur-oxidizing e- and gProteobacteria.
• Loihi Group 1 (before and after event) mats are dominated by
metabolisms (e.g., Fe-oxidizing) associated with brine dominated
vent effluents and do not contain any sulfur-cycling or hydrogenoxidizing bacterial phylotypes.
• Loihi Group 2 (post-eruption only) mats contain metabolisms
associated with both brine and gas dominated vent effluents.
Acknowledgements
Funding: NSF, NOAA, BFR
Capt. & Crew of R/V KOK
Terry Kerby & HURL Team
Loihi Collaborators:
Geoff Wheat (UofAK)
Frank Sansone (UofHI)
FeMO Collaborators:
Dave Emerson (ATCC)
Katrina Edwards (WHOI)
Hubert Staudigal (SIO)
Brad Tebo (OHSU)
Moyer Lab
Graduate Students:
Richard Davis
Andrea Curtis
Leslie Chao
Racheal Zack
Undergrad Researchers:
Deborah Whitley
James Yang
Angela Olson
REU Interns Summer 2005
Travis Carney
Kelsey Leal
UPGMA/product-moment cluster analysis
of 55 T-RFLP bacterial community
fingerprints.
Community
Tave=26°C
???
Community
Tave=103°C
Possible Loihi Community Group 3???
Dominated by sulfur-oxidizing e-Proteobacteria
‘Mariprofundus ferroxydans’ Group
ML Phylogenetic Tree
Nitrospira ML Phylogenetic Tree