Oxygen-dependent autoaggregation in Shewanella oneidensis MR-1
In aerobic chemostat cultures maintained at 50% dissolved O2 tension (123.5 µM dissolved O2), Shewanella oneidensis strain MR-1 rapidly aggregated upon addition of 0.68 mM CaCl2 and retained this multi-cellular phenotype at high dilution rates. Confocal microscopy analysis of the extracellular matrix material contributing to the stability of the aggregate structures revealed the presence of extracellular DNA, protein, and glycoconjugates. Upon onset of O2-limited growth (dissolved O2 below detection) however, the Ca2+-supplemented chemostat cultures of strain MR-1 rapidly disaggregated and grew as motile dispersed cells. Global transcriptome analysis comparing aerobic aggregated to O2-limited unaggregated cells identified genes encoding cell-to-cell and cell-to-surface adhesion factors whose transcription increased upon exposure to increased O2 concentrations. The aerobic aggregated cells also revealed increased expression of putative anaerobic electron transfer and homologs of metal reduction genes, including mtrD (SO1782), mtrE (SO1781), and mtrF (SO1780). Our data indicate that mechanisms involved in autoaggregation of MR-1 are dependent on the function of pilD gene which encodes a putative prepilin peptidase. Mutants of S. oneidensis strain MR-1 deficient in PilD and associated pathways, including type IV and Msh pili biogenesis, displayed a moderate increase in sensitivity to H2O2. Taken together, our evidence indicates that aggregate formation in S. oneidensis MR-1 may serve as an alternative or an addition to biochemical detoxification to reduce the oxidative stress associated with production of reactive oxygen species during aerobic metabolism while facilitating the development of hypoxic conditions within the aggregate interior.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 935603
- Report Number(s):
- PNNL-SA-47123; KP1501021; TRN: US200816%%752
- Journal Information:
- Environmental Microbiology, 10(7):1861-1876, Vol. 10, Issue 7; ISSN 1462-2912
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ADHESION
DETECTION
DETOXIFICATION
DILUTION
DNA
ELECTRON TRANSFER
GENES
MATRIX MATERIALS
METABOLISM
MICROSCOPY
MUTANTS
OXYGEN
PHENOTYPE
PRODUCTION
SENSITIVITY
STABILITY
STRAINS
TRANSCRIPTION
Shewanella oneidensis
MR-1
putative anaerobic electron transfer
homologs of metal reduction genes
putative prepilin peptidase
mutants of S. oneidensis strain