Pyrosequencing Analysis of Bacterial Communities in
Rock Coatings from Swedish Lapland Cassandra L. Marnocha1, John C. Dixon1,2
1Arkansas Center for Space and Planetary Sciences, University of Arkansas 2Department of Geological Sciences, University of Arkansas
Figure 4. Putative rock coatings at an ancient stream bed
at Gale Crater taken by Curiosity (MSL). Credit: NASA
Figure 2: Phyla represented in coatings as distributed by coating type.
Table 1. Selected genera and putative physiologies. * denotes genera
represented at 2% or greater in at least one coating type.
Introduction • Kärkevagge: glacially eroded, u-shaped
valley in Swedish Lapland (Fig. 1)
• Ubiquitous rock coatings:
• Al glazes: Basaluminite, alunite
• Sulfate crusts: Jarosite, gypsum
• Fe/Mn films: Goethite, hematite
• Rock coatings observed on Mars since
Viking landers [1]
• Objective: Assess the bacterial
communities and mineralization-relevant
metabolic capacity of those communities
Methods • Rock coatings sampled along transects
on the eastern and western valley wall
• Samples collected in sterile tubes,
transported, and stored at -20°C
• Three of each primary coating type
submitted to Research and Testing Lab,
Lubbock TX, for bacterial 16S
pyrosequencing
• Sequence clean-up and taxonomic
assignment performed by RTL
• Bioinformatics analysis performed using
mothur software [2]
• 15 phyla represented across all samples (Fig. 2)
• α-proteobacteria most common Proteobacterium
• Acidophiles common; thermophiles,
psychrophiles, halophiles, and radiation resistant
bacteria also present
• Diverse communities (D < 0.14)
• Community makeup significantly differs based on
coating mineralogy (UniFrac P-value < 0.01)
• Diversity in microbial metabolisms associated
with biomineralization and scavenging of
chemical species (Table 1)
Conclusions • Community structure appears to be based on coating
mineralogy (Fig. 3)
• Bacteria capable of growth in extreme conditions
• Functional capacity of communities includes metabolisms
that produce mineral byproducts
• Putative rock coatings (Fig. 4) should be high priority
science targets for Curiosity, especially instruments such
as ChemCam.
Results
Figure 1. Location of Kärkevagge in Scandinavia.
Acknowledgements: We gratefully acknowledge the American Philosophical Society
and the Lewis and Clark Fund for Exploration and Field Research in Astrobiology for
funding the 2012 field season. We also thank Abiskonaturvetenskapliga and staff for
logistical support in Swedish Lapland.
References: [1] Strickland, E.L.
(1979) LPSC X. [2] Schloss, P.D.
(2009) Applied Environmental
Microbiology.
Genus Physiology
Acidimicrobium Fe(II) oxidation, Fe(III) reduction
Acidiphilium Fe(III), Cr(VI) reduction *
Acidisphaera Fe(III) reduction *
Acidithiobacillus S reduction; Fe(II), S, sulfide oxidation
Acidobacterium Fe(III) reduction,, Fe(II) oxidation *
Acinetobacter Cr(VI), Mn(IV) reduction *
Aquabacterium Fe(II) oxidation
Arcobacter Sulfide oxidation
Arthrobacter Mn and Fe(II) oxidation, Mn reduction
Bacillus Fe/Mn oxidation and reduction
Bacteroides Fe(III) reduction
Carnobacterium Mn(IV) reduction
Dechloromonas Perchlorate reduction
Deferribacter Fe(III) reduction
Dehalococcoides Hydrogen oxidation
Desulfomicrobium Sulfate, arsenate reduction; Mn oxidation
Desulfotomaculum Sulfate reduction
Desulfuromonas Elemental S, sulfate, Fe(III) reduction
Ferrimicrobium Fe(III) reduction
Ferrithrix Fe(III) reduction
Geopsychrobacter Fe(III) reduction
Hyphomicrobium Mn oxidation
Leptothrix Fe(II), Mn oxidation
Polaromonas Sulfur oxidation *
Pseudonocardia Sulfide oxidation *
Sarcina Cr(VI) reduction
Staphylococcus Hg, Fe(III) reduction *
Thiobacillus Fe(II), S, U oxidation; V reduction
Thiomonas Sulfur oxidation, arsenic oxidation *
Variovorax Sulfite reduction *