Culturable Rhodobacter and Shewanella species are abundant in estuarine turbidity maxima of the Columbia River

S. L. Bräuer, C. Adams, K. Kranzler, D. Murphy, M. Xu, Peter Zuber, Holly Simon, Antonio Baptista, Bradley Tebo

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Measurements of dissolved, ascorbate-reducible and total Mn by ICP-OES revealed significantly higher concentrations during estuarine turbidity maxima (ETM) events, compared with non-events in the Columbia River. Most probable number (MPN) counts of Mn-oxidizing or Mn-reducing heterotrophs were not statistically different from that of other heterotrophs (103-104 cellsml-1) when grown in defined media, but counts of Mn oxidizers were significantly lower in nutrient-rich medium (13 cellsml-1). MPN counts of Mn oxidizers were also significantly lower on Mn(III)-pyrophosphate and glycerol (21 cellsml-1). Large numbers of Rhodobacter spp. were cultured from dilutions of 10-2 to 10-5, and many of these were capable of Mn(III) oxidation. Up to c. 30% of the colonies tested LBB positive, and all 77 of the successfully sequenced LBB positive colonies (of varying morphology) yielded sequences related to Rhodobacter spp. qPCR indicated that a cluster of Rhodobacter isolates and closely related strains (95-99% identity) represented approximately 1-3% of the total Bacteria, consistent with clone library results. Copy numbers of SSU rRNA genes for either Rhodobacter spp. or Bacteria were four to eightfold greater during ETM events compared with non-events. Strains of a Shewanella sp. were retrieved from the highest dilutions (10-5) of Mn reducers, and were also capable of Mn oxidation. The SSU rRNA gene sequences from these strains shared a high identity score (98%) with sequences obtained in clone libraries. Our results support previous findings that ETMs are zones with high microbial activity. Results indicated that Shewanella and Rhodobacter species were present in environmentally relevant concentrations, and further demonstrated that a large proportion of culturable bacteria, including Shewanella and Rhodobacter spp., were capable of Mn cycling in vitro.

Original languageEnglish (US)
Pages (from-to)589-603
Number of pages15
JournalEnvironmental Microbiology
Volume13
Issue number3
DOIs
StatePublished - Mar 2011

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Rhodobacter
Shewanella
Columbia River
Rivers
turbidity
bacterium
clone
dilution
river
oxidation
heterotrophs
gene
Bacteria
rRNA Genes
oxidants
microbial activity
bacteria
Clone Cells
ribosomal RNA
clones

ASJC Scopus subject areas

  • Microbiology
  • Ecology, Evolution, Behavior and Systematics

Cite this

Culturable Rhodobacter and Shewanella species are abundant in estuarine turbidity maxima of the Columbia River. / Bräuer, S. L.; Adams, C.; Kranzler, K.; Murphy, D.; Xu, M.; Zuber, Peter; Simon, Holly; Baptista, Antonio; Tebo, Bradley.

In: Environmental Microbiology, Vol. 13, No. 3, 03.2011, p. 589-603.

Research output: Contribution to journalArticle

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abstract = "Measurements of dissolved, ascorbate-reducible and total Mn by ICP-OES revealed significantly higher concentrations during estuarine turbidity maxima (ETM) events, compared with non-events in the Columbia River. Most probable number (MPN) counts of Mn-oxidizing or Mn-reducing heterotrophs were not statistically different from that of other heterotrophs (103-104 cellsml-1) when grown in defined media, but counts of Mn oxidizers were significantly lower in nutrient-rich medium (13 cellsml-1). MPN counts of Mn oxidizers were also significantly lower on Mn(III)-pyrophosphate and glycerol (21 cellsml-1). Large numbers of Rhodobacter spp. were cultured from dilutions of 10-2 to 10-5, and many of these were capable of Mn(III) oxidation. Up to c. 30{\%} of the colonies tested LBB positive, and all 77 of the successfully sequenced LBB positive colonies (of varying morphology) yielded sequences related to Rhodobacter spp. qPCR indicated that a cluster of Rhodobacter isolates and closely related strains (95-99{\%} identity) represented approximately 1-3{\%} of the total Bacteria, consistent with clone library results. Copy numbers of SSU rRNA genes for either Rhodobacter spp. or Bacteria were four to eightfold greater during ETM events compared with non-events. Strains of a Shewanella sp. were retrieved from the highest dilutions (10-5) of Mn reducers, and were also capable of Mn oxidation. The SSU rRNA gene sequences from these strains shared a high identity score (98{\%}) with sequences obtained in clone libraries. Our results support previous findings that ETMs are zones with high microbial activity. Results indicated that Shewanella and Rhodobacter species were present in environmentally relevant concentrations, and further demonstrated that a large proportion of culturable bacteria, including Shewanella and Rhodobacter spp., were capable of Mn cycling in vitro.",
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