Magnetite biomineralization in M. gryphiswaldense

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1 Magnetite biomineralization in M. gryphiswaldense Damien Faivre th, 2006 June June 2006 Damien Faivre Workshop on Complex Materials

2 Biomineralization formation of minerals by living organisms (bacteria, higher organisms ) armature attack defense

3 Iron biomineralization Iron oxide Organism Position Function Magnetite Bacteria Cells Orientation Fe 3 O 4 Chitons Teeth Hardness Fish Head Orientation Birds Head Orientation Goethite α-feooh Patels Teeth Hardness Lepidocrocite Sponges Spicule Anchoring γ-feooh Chitons Teeth Hardness Ferrihydrite Animals Ferritine Stocking 5Fe 2 O 3.9H 2 O plants Chitons Teeth Precursor

4 Iron biomineralization: example Chiton Radulae: Magnetite (Fe 3 O 4 ): on the surface Lepidocrocite (γ-feooh): fine underlying layer Dahllite ([Ca 5 (PO 4 - CO 3 ) 3 (OH)]): interior

5 Magnetotactic bacteria microaerophilic α-proteobacterium synthesizing magnetosomes

6 Magnetotaxis S N

7 S Magnetic orientation relies on magnetosomes OXIC MICROOXIC N ANOXIC

8 Magnetosomes Species-specific morphology Membraneenclosed Biocompatible *Schüler, 1999 Scale bar 100 nm

9 Magnetosomes Nano-crystals: nm Narrow size distribution frequency (%) size (nm) *Faivre et al., 2006 *Posfai et al., 2006

10 Functionalized magnetosomes Applications in Biotechnology: In vitro In vivo Immunoassays Separation of biomolecules Magnetic drug targeting Hyperthermia Magnetic resonance imaging

11 Fluorescence of isolated particles

12 Size within single magnetic-domain Below ~ 25 nm superparamagnetic Above 100 nm multidomain High coercivity Magnetic properties 6500 A m -1 (magnetosomes) in comparison to 20 A m -1 (Schering) (Eberbeck, 2004) *Simpson et al., 2005

13 Why iron biomineralization? biotechnological applications proxies for environmental change model for nanomolecular interactions between living (bacteria) and non-living (minerals) systems model for biomineralization in higher organisms magnetoreception

14 whole genome shotgun 482 kb WGS trna genes Genomic Island 130 kb region 50K 100K 150K 200K 250K 300K 350K 400K 450K 130 kb core region 220K 230K 240K 250K 260K 270K 280K 290K 300K 310K 320K 330K 340K 350K mms/mam genes transposase genes hypothetical genes genes with other attributed functions The mam-genes encoding magnetosome membrane proteins are arranged in genomic island (Ullrich et al., 2005)

15 The chain under genetic control* *Scheffel et al., Nature, 2006

16 The chain under genetic control* *Scheffel et al., Nature, 2006 and Komeili et al., Science, 2006

17 Biochemistry of magnetite formation *Bazylinski and Frankel., Nature Rev., 2004

18 Proposed reaction pathway* 1. Fe(III) cell exterior But: Fe(II) cell interior 1. No controlled conditions 2. Low density Fe(III) oxyde 2. Lack 3. Ferrihydrite dynamic of process 4. Magnetite 3. Need association with some other techniques *Frankel et al., 1983

19 Controlled growth in fermentor Control of: 1.Temperature 2.pH 3.P O2

20 Induction experiments 0 min 55 min 100 min 220 min 340 min Allow to follow the dynamic of the process

21 Minimal medium How to study chain formation in growing cells? OD565 ( *1000) time (h) Iron uptake just for magnetite formation, 2.00 not for growth Parameters such as # Cmag (a. u.) crystals / cell not disturbed by cell division

22 Evolution of mineralogical properties time after induction 0h55 1h40 2h10 2h40 3h40 5h40 Magnetism crystals per cell Average size of crystals (nm) Inter-crystal distance (nm)

23 Implications 1. classical iron storage 2. Magnetic pool

24 Magnetite biomineralization Magnetization really due to pure Magnetite? Magnetite / Maghemite mixture? Is there any intermediate? What is the nature of the other pool of iron? Mössbauer spectroscopy

25 Magnetite or Maghemite Magnetite : Maghemite : Magnetite: 2 Sextets (δ = 0.26 & δ = 0.67 mms -1 ) a ratio of 1:2 for the Sextet above the Verwey transistion (T > 119 K), 1:1 below Maghemite: 1 Sextet (δ = 0.32 mms -1 ) at room temperature At 4.2K the spectrum splits into two Sextets (δ = 0.40 & δ = 0.48 mms -1 )

26 Identification of the iron pools 1,00 0,95 Relative Transmission 0,90 0,85 0,80 0,75 Spectra Simulation A B Ferritin 4Fe4S FEII velocity (mm/s)

27 Isolated magnetosomes Relative Transmission 1,00 0,98 0,96 0,94 0,92 0,90 0,88 0,86 0,84 0,82 spectrum simulation A B 0, velocity (mm/s)

28 Dynamic of magnetite formation Relative Transmission 1,1 1,0 0,9 20m 40m 60m 95m 125m 155m 215m 20h30m 0, velocity (mm/s)

29 Iron uptake in non-magnetic mutant whole genome shotgun 482 kb WGS trna genes 130 kb region 50K 100K 150K 200K 250K 300K 350K 400K 450K 130 kb core region 220K 230K 240K 250K 260K 270K 280K 290K 300K 310K 320K 330K 340K 350K mms/mam genes transposase genes hypothetical genes genes with other attributed functions MSR-1B lacks the complete genomic island

30 Identification of the iron pools 1,000 0,995 Relative Transmission 0,990 0,985 0,980 0,975 0,970 spectrum simulation 4Fe4S unknown Ferritin 0, velocity (mm/s) The Ferritin-like component split into a magnetic sextett at low temperature.

31 Implications Different pools of iron: 1. Ferrous, ferritin, [Fe-S] and magnetite in WT, and no magnetite but unknown compounds in mutant 2. No ferric, no ferrihydrite Certainly no intermediate for magnetite biomineralization No trace of maghemite

32 1. Fe(III) cell exterior or Fe(II) cell exterior 2. Fe(II) cell interior + ferritin and [Fe-S] 3. Magnetite

33 But: 1. Ferritin + [Fe-S] 2. Magnetite Fe OR? Fe 1. Ferritin + [Fe-S] 2. Magnetite

34 Acknowledgements The Magneto-Lab Dr. N. Menguy E. Simpson Dr. R. Dunin Borkowski L. Boettger Prof. B. Matzanke

35 Thank you for your attention