Results

1
Geochemical data

• Geochemical characteristics were significantly
  different among four groundwater samples.
• Nitrate levels were way over drinking standard
  (10 mg/L).
• Site FW113-47 was the most highly contaminated
  and also the most acidic among all samples
  examined.

2
Diversity Estimates
3
Diversity and pH relationship

• The Shannon diversity index correlated relatively
  well with pH values, suggesting that pH might be
  an important regulator of microbial communities.

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5
Distribution of 16S rRNA Sequences Based on
Taxonomic Classification

• The microbial communities were dominated by
  bacteria from phylum Proteobacteria, which
  constituted 94, 58, 81 and 79 of the
  FW113_47, FW215_49, GW835 and GW 836 clone
  libraries, respectively. A significant portion
  of the clone libraries also contained sequences
  most closely related to the phylum Bacteroidetes.
  

6
Phylogenetic Relationships of 16S rDNA Sequences

• The 16S rDNA sequences from the most highly
  contaminated site (FW113_47) were closely related
  to previously observed bacteria at the FRC such
  as
• Rhodanobacter, Pseudomonas, and Stenotrophomonas
  spp., and several uncultured iron-reducing
  bacteria. A recently completed metagenome
  sequencing effort at the same site has shown that
  this
• Rhodanobacter sp. often dominates the most
  contaminated, lowest pH environments at the FRC
  and nearly the complete genome of the organism
  has now been sequenced from other studies.

FW113-47
FW215-49
GW835
GW836

• The least contaminated groundwater sample
  (FW215_49) demonstrated enormous heterogeneity of
  16S rRNA sequences, the majority of which were
  related only to uncultured bacteria.