Moderate oxygen depletion as a factor favouring the filamentous growth of Sphaerotilus natans
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Sphaerotilus natans is a neutrophilic iron-related sheath-forming filamentous microorganism that presents dual morphotype: single cells and ensheathed cells forming filaments. As S. natans has been proposed as a sorbent for inorganic pollutants and it is occasionally involved in bulking episodes, elucidating factors affecting its filamentous growth is of crucial interest. The purpose of this work was to evaluate the effect of dissolved oxygen (DO) as a factor affecting S. natans filamentation from single cells. A method to quantify S. natans in its filamentous and single-cell morphotypes, based on a differential filtration procedure coupled with quantitative real-time PCR, was developed here. Scanning Electron Microscopy was used to validate the filtration step. Under actively aerated conditions (DO maintained at 7.6 ± 0.1 mg l−1), S. natans grew mainly as single cells throughout the experiment, while a depletion in DO concentration (to ~3 mg l−1) induced its filamentous growth. Indeed, when oxygen was reduced the proportion of single cells diminished from 83.3 ± 5.9 to 14.3 ± 3.4 % while the filaments increased from 16.7 ± 5.9 to 85.7 ± 3.4 %. Our results suggest that oxygen plays a key role in S. natans filamentation and contribute to better understanding of the filamentous proliferation of this bacterium. In addition, the proposed method will be helpful to evaluate other factors favouring filamentous growth.
KeywordsFilamentous bacteria Dissolved oxygen Sphaerotilus natans qPCR
The authors would like to thank the European Commission for providing financial support through the Erasmus Mundus Joint Doctorate Programme ETeCoS3 (Environmental Technologies for Contaminated Solids, Soils and Sediments) under the Grant agreement FPA n 2010-0009. In addition, the authors would like to thank Dr. Karim Benzerara for fruitful discussion and Imène Esteve for her help with Scanning Electron Microscope analyses. The purchase of the Scanning Electron Microscope (SEM) facility of the Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC) was supported by Région Ile-de-France grant SESAME 2006 N°I-07-593/R, INSU-CNRS, INP-CNRS, University Pierre et Marie Curie–Paris 6, and by the French National Research Agency (ANR) Grant no. ANR-07-BLAN-0124-01. The Confocal Laser Scanning Microscope (CLSM) Zeiss Axiovert 200 M LSM 510 META and the CFX 96™ Real-Time PCR Detection System (Bio Rad) used in this work are part of the MIMOSE experimental platform, and were funded by the Région Ile-de-France.
- Dias FF, Okrend H, Dondero NC (1968b) Calcium nutrition of Sphaerotilus growing in a continuos-flow apparatus. Appl Environ Microbiol 16:1364–1369Google Scholar
- Eikelboom D, Van Buijsen H. (1981) Microscopic sludge investigation manual. TNO—Research Institute for Environmental Hygiene. TNO Report A 94aGoogle Scholar
- Gridneva E, Chernousova E, Dubinina G, Akimov V, Kuever J, Detkova E, Grabovich M (2011) Taxonomic investigation of representatives of the genus Sphaerotilus: descriptions of Sphaerotilus montanus sp. nov., Sphaerotilus hippei sp. nov., Sphaerotilus natans subsp. natans subsp. nov. and Sphaerotilus natans subsp. sulfidivorans subsp. nov., and an emended description of the genus Sphaerotilus. Int J Syst Evol Microbiol 61:916–925CrossRefPubMedGoogle Scholar
- Jenkins D (1992) Towards a comprehensive model of activated sludge bulking and foaming. Water Sci Technol 25:215–230Google Scholar
- Jenkins D, Richard M, Daigger G. (2004) Manual of the causes and control of activated sludge bulking, foaming, and other solids separation problems. 3rd Edition. Lewis PublishersGoogle Scholar
- Lodi A, Solisio C, Converti A, Del Borghi M (1998) Cadmium, zinc, copper, silver and chromium (III) removal from wastewaters by Sphaerotilus natans. Bioprocess Eng 19:197–203Google Scholar
- Palm J, Parker D (1980) Relationship between organic loading, dissolved oxygen concentration and sludge settleability in the completely-mixed activated sludge process. J Water Pollut Control Fed 52:2484–2506Google Scholar
- Richard M, Hao O, Jenkins D (1985) Growth kinetics of Sphaerotilus species and their significance in activated sludge bulking. J Water Pollut Control Fed 57:68–81Google Scholar
- Silverstein J, Mines R, Sherrard J, Weber A, Aitken M (1990) Activated sludge. Res J Water Pollut Control Fed. 62:398–406Google Scholar
- Strom PF, Jenkins D (1984) Identification and significance of filamentous microorganisms in activated sludge. J Water Pollut Control Fed 56:449–459Google Scholar