Barak Vasker ID 036966281 Marine Biotechnology Keuter et al. 2011.

Barak VaskerID 036966281

Marine Biotechnology

Keuter et al. 2011

Introduction

Recirculation Aquaculture Systems (RAS) in which waste of

aquaculture is processed. Water and “safe” nutrients re-used.

In the biofilter, dense biofilm will be created on carrier

elements (“moving bed”), mostly comprising of: Ammonium

Oxidizing Bacteria (AOB) & Nitrite Oxidizing Bacteria (NOB)

working together as a pair.

Introduction

Nitrospira sp. Is a curved rod. Usually single celled, but also

capable of colonization (biofilm). Non-obligatory autotrophs.

NH4+ NO2

- NO3 (Requires aerobic atmosphere).

Dominant NOB, optimal activity and mechanism was not well

understood, in part due to low energy yields of Ammonia

oxidation and even lower yields on Nitrite oxidation (total work

~ 6 years (!)).

Introduction

Chemotaxonomic identification of Nitrospira sp. (Lipski 2001) via FAME (Fatty Acid Methyl Ester) Markers:

1) 16:1 cis 72) 16:1 cis 11

Results

Nitrospira cells were repeatedly diluted, enriched and transferred to fresh medium.This process repeated several times, until a new strain was isolated:“Ecomares 2.1”. (even pure, still secrets a tough polymer)

16S rRNA sequences clones were retrieved (1502 bp). 13C-bicarbonate labeled fatty acids shows Nitrospira’s role.

Results

What about the 16S rRNA?

Ecomares 2.1 (isolated in Büsum, Germany) was found to match at most 99.1 % of the sequence of Nitrospira in Rehovot, Israel. All strains showed are a part of cluster IV.

Results

Nitrospira colonies (circled) & nitrosomonas (marked “X”) colonies function as a pair, with each one enjoying the other’s produce. (mutualism?)

Discussion

High Nitrogenic load should have selected Nitrobacter (or other proteobacteria), consistent with recent strategy theories. How can Nitrospira dominate the RAS?Lab procedures/conditions. Theory / de-facto not always consistent.

Who is the most durable strain to high nitrite concentrations? Could this be enough to establish dominance? Pure Ecomares 2.1 still coated with thick, tough polymer.

Discussion

Selective Shear forces inside RAS? A stronger adherence of Nitrospira might be the final blow.

What is happening in other marine RAS? 16S rRNA sequences from other marine RAS suggest Nitrospira dominance.

Conclusions Nitrospira-like bacteria dominates RAS biofilters,

in contrast to what previously thought. Nitrospira characteristics critical for Marine aquaculture systems.

Nitrospira is supported by Nitrosomonas in an AOB/NOB biofilm.

Nitrospira Ecomares 2.1 is the most resisting strain to nitrite peaks in RAS. Therefore, it’s favorable in establishing dominance as the major Nitrite Oxidizing Bacteria (NOB) of the Biofilm.

Conclusions

Physiology is still under-investigated. Further research will reveal metabolic pathways, inhibatory effects & optimization of the process.

We might be able to get different bacteria strains growing in different conditions.

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Daims, H., Nielsen, J.L., Nielsen, P.H., Schleifer, K.H., andWagner, M. (2001) In situ characterization of Nitrospira-likenitrite-oxidizing bacteria active in wastewater treatmentplants. Appl Environ Microbiol 67: 5273–5284

Knief, C., Altendorf, K., and Lipski, A. (2003) Linkingautotrophic activity in environmental samples with specificbacterial taxa by detection of 13C-labelled fatty acids.Environ Microbiol 5: 1155–1167.

Thank you !