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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

cmarnoch@email.uark.edu

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 *