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Fe biomineralization mirrors individual metabolic activity in a nitrate-dependent Fe(II)-oxidizer.

Miot J, Remusat L, Duprat E, Gonzalez A, Pont S, Poinsot M - Front Microbiol (2015)

Bottom Line: Mineral precipitation within the periplasm is, however, thought to induce death, as a result of permeability loss preventing nutrient and waste transit across the cell wall.Carbon assimilation decreased exponentially with increasing cell-associated Fe content.Eventually, our results suggest that periplasmic Fe biomineralization may provide a signature of individual metabolic status, which could be looked for in the fossil record and in modern environmental samples.

View Article: PubMed Central - PubMed

Affiliation: Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Muséum National d'Histoire Naturelle, Université Pierre et Marie Curie - Sorbonne Universités, CNRS UMR 7590, IRD 206 Paris, France.

ABSTRACT
Microbial biomineralization sometimes leads to periplasmic encrustation, which is predicted to enhance microorganism preservation in the fossil record. Mineral precipitation within the periplasm is, however, thought to induce death, as a result of permeability loss preventing nutrient and waste transit across the cell wall. This hypothesis had, however, never been investigated down to the single cell level. Here, we cultured the nitrate reducing Fe(II) oxidizing bacteria Acidovorax sp. strain BoFeN1 that have been previously shown to promote the precipitation of a diversity of Fe minerals (lepidocrocite, goethite, Fe phosphate) encrusting the periplasm. We investigated the connection of Fe biomineralization with carbon assimilation at the single cell level, using a combination of electron microscopy and Nano-Secondary Ion Mass Spectrometry. Our analyses revealed strong individual heterogeneities of Fe biomineralization. Noteworthy, a small proportion of cells remaining free of any precipitate persisted even at advanced stages of biomineralization. Using pulse chase experiments with (13)C-acetate, we provide evidence of individual phenotypic heterogeneities of carbon assimilation, correlated with the level of Fe biomineralization. Whereas non- and moderately encrusted cells were able to assimilate acetate, higher levels of periplasmic encrustation prevented any carbon incorporation. Carbon assimilation only depended on the level of Fe encrustation and not on the nature of Fe minerals precipitated in the cell wall. Carbon assimilation decreased exponentially with increasing cell-associated Fe content. Persistence of a small proportion of non-mineralized and metabolically active cells might constitute a survival strategy in highly ferruginous environments. Eventually, our results suggest that periplasmic Fe biomineralization may provide a signature of individual metabolic status, which could be looked for in the fossil record and in modern environmental samples.

No MeSH data available.


Related in: MedlinePlus

Differences in carbon assimilation among mineralized (orange arrows) and non-mineralized (white arrows) cells in cultures of BoFeN1 grown for 4 days (tmin = 4 days) in biomineralization medium (Lp-, Mt-, FeP-, or Gt-media) then transferred to labeled medium for 4 days. NanoSIMS images of 12C14N- signal (A,E,I,M), 13C14N/12C14N ratio (B,F,J,N) and 16O- signal (C,G,K,O) and corresponding X-EDS maps showing the distribution of Fe (green, D,H,L,P). Scale bars: 2 μm.
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Figure 3: Differences in carbon assimilation among mineralized (orange arrows) and non-mineralized (white arrows) cells in cultures of BoFeN1 grown for 4 days (tmin = 4 days) in biomineralization medium (Lp-, Mt-, FeP-, or Gt-media) then transferred to labeled medium for 4 days. NanoSIMS images of 12C14N- signal (A,E,I,M), 13C14N/12C14N ratio (B,F,J,N) and 16O- signal (C,G,K,O) and corresponding X-EDS maps showing the distribution of Fe (green, D,H,L,P). Scale bars: 2 μm.

Mentions: Figure 2 displays NanoSIMS images obtained on cells collected after 4 days of biomineralization that spent only 4 h in the labeled medium. In order to differentiate mineralized vs. non-mineralized cells, we mapped both 12C14N- and 16O- secondary ions. On the one hand, the 12C14N- signal gives the distribution of organic matter (mainly bacteria) in the samples. On the other hand, we used 16O- as a proxy to locate Fe-minerals. Comparison of Fe EDX maps collected in the SEM and 16O- maps collected by NanoSIMS on the same areas (Figure 3) confirm the relevance of this proxy for Fe-mineral location (though not for Fe quantification). For simplicity, these signals are hereafter labeled 12C14N and 16O. As observed in Figure 2, most cells that can be seen on the 12C14N maps also show up in the corresponding 16O maps. These cells are thus mineralized. However, a few cells in the 12C14N map are not or only poorly visible in the 16O map (white arrows in Figure 2), indicating that a non-negligible proportion of cells are not mineralized, even after 4 days in the biomineralization medium. The co-existence of mineralized and non-mineralized cells is observed in all four media, i.e., whatever the biomineralization conditions. However, it should be noted that discrimination of mineralized vs. non-mineralized cells is more difficult in samples from Lp- and Mt-media, where extracellular precipitates are more abundant and tend to form aggregates (Figure 1). As a consequence, we took into account only cells outside Fe aggregates for the following analyses. As we do not know whether mineralized vs. non-mineralized cells have different behaviors regarding aggregation, it is possible that we under-estimated one of these two groups of cells in the Lp- and Mt-samples.


Fe biomineralization mirrors individual metabolic activity in a nitrate-dependent Fe(II)-oxidizer.

Miot J, Remusat L, Duprat E, Gonzalez A, Pont S, Poinsot M - Front Microbiol (2015)

Differences in carbon assimilation among mineralized (orange arrows) and non-mineralized (white arrows) cells in cultures of BoFeN1 grown for 4 days (tmin = 4 days) in biomineralization medium (Lp-, Mt-, FeP-, or Gt-media) then transferred to labeled medium for 4 days. NanoSIMS images of 12C14N- signal (A,E,I,M), 13C14N/12C14N ratio (B,F,J,N) and 16O- signal (C,G,K,O) and corresponding X-EDS maps showing the distribution of Fe (green, D,H,L,P). Scale bars: 2 μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4562303&req=5

Figure 3: Differences in carbon assimilation among mineralized (orange arrows) and non-mineralized (white arrows) cells in cultures of BoFeN1 grown for 4 days (tmin = 4 days) in biomineralization medium (Lp-, Mt-, FeP-, or Gt-media) then transferred to labeled medium for 4 days. NanoSIMS images of 12C14N- signal (A,E,I,M), 13C14N/12C14N ratio (B,F,J,N) and 16O- signal (C,G,K,O) and corresponding X-EDS maps showing the distribution of Fe (green, D,H,L,P). Scale bars: 2 μm.
Mentions: Figure 2 displays NanoSIMS images obtained on cells collected after 4 days of biomineralization that spent only 4 h in the labeled medium. In order to differentiate mineralized vs. non-mineralized cells, we mapped both 12C14N- and 16O- secondary ions. On the one hand, the 12C14N- signal gives the distribution of organic matter (mainly bacteria) in the samples. On the other hand, we used 16O- as a proxy to locate Fe-minerals. Comparison of Fe EDX maps collected in the SEM and 16O- maps collected by NanoSIMS on the same areas (Figure 3) confirm the relevance of this proxy for Fe-mineral location (though not for Fe quantification). For simplicity, these signals are hereafter labeled 12C14N and 16O. As observed in Figure 2, most cells that can be seen on the 12C14N maps also show up in the corresponding 16O maps. These cells are thus mineralized. However, a few cells in the 12C14N map are not or only poorly visible in the 16O map (white arrows in Figure 2), indicating that a non-negligible proportion of cells are not mineralized, even after 4 days in the biomineralization medium. The co-existence of mineralized and non-mineralized cells is observed in all four media, i.e., whatever the biomineralization conditions. However, it should be noted that discrimination of mineralized vs. non-mineralized cells is more difficult in samples from Lp- and Mt-media, where extracellular precipitates are more abundant and tend to form aggregates (Figure 1). As a consequence, we took into account only cells outside Fe aggregates for the following analyses. As we do not know whether mineralized vs. non-mineralized cells have different behaviors regarding aggregation, it is possible that we under-estimated one of these two groups of cells in the Lp- and Mt-samples.

Bottom Line: Mineral precipitation within the periplasm is, however, thought to induce death, as a result of permeability loss preventing nutrient and waste transit across the cell wall.Carbon assimilation decreased exponentially with increasing cell-associated Fe content.Eventually, our results suggest that periplasmic Fe biomineralization may provide a signature of individual metabolic status, which could be looked for in the fossil record and in modern environmental samples.

View Article: PubMed Central - PubMed

Affiliation: Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Muséum National d'Histoire Naturelle, Université Pierre et Marie Curie - Sorbonne Universités, CNRS UMR 7590, IRD 206 Paris, France.

ABSTRACT
Microbial biomineralization sometimes leads to periplasmic encrustation, which is predicted to enhance microorganism preservation in the fossil record. Mineral precipitation within the periplasm is, however, thought to induce death, as a result of permeability loss preventing nutrient and waste transit across the cell wall. This hypothesis had, however, never been investigated down to the single cell level. Here, we cultured the nitrate reducing Fe(II) oxidizing bacteria Acidovorax sp. strain BoFeN1 that have been previously shown to promote the precipitation of a diversity of Fe minerals (lepidocrocite, goethite, Fe phosphate) encrusting the periplasm. We investigated the connection of Fe biomineralization with carbon assimilation at the single cell level, using a combination of electron microscopy and Nano-Secondary Ion Mass Spectrometry. Our analyses revealed strong individual heterogeneities of Fe biomineralization. Noteworthy, a small proportion of cells remaining free of any precipitate persisted even at advanced stages of biomineralization. Using pulse chase experiments with (13)C-acetate, we provide evidence of individual phenotypic heterogeneities of carbon assimilation, correlated with the level of Fe biomineralization. Whereas non- and moderately encrusted cells were able to assimilate acetate, higher levels of periplasmic encrustation prevented any carbon incorporation. Carbon assimilation only depended on the level of Fe encrustation and not on the nature of Fe minerals precipitated in the cell wall. Carbon assimilation decreased exponentially with increasing cell-associated Fe content. Persistence of a small proportion of non-mineralized and metabolically active cells might constitute a survival strategy in highly ferruginous environments. Eventually, our results suggest that periplasmic Fe biomineralization may provide a signature of individual metabolic status, which could be looked for in the fossil record and in modern environmental samples.

No MeSH data available.


Related in: MedlinePlus