Sol–gel encapsulation of bacteria: a comparison between alkoxide and aqueous routes

Coiffier, Anne; Coradin, Thibaud; Roux, Cécile; Bouvet, Odile; Livage, Jacques

doi:10.1039/b101308o

Cited by 147 publications

(142 citation statements)

References 19 publications

(21 reference statements)

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“…To avoid complete gelation in the present study, conditions using 30 mM TEOS were applied to the bacteria that were milder than the previously reported conditions for silicification (38). Thus, only small (1.7% total concentration [vol/vol]) amounts of ethanol were also added to the bacterial suspensions, preserving the viability of the bacteria (39,40).…”

Section: Discussionmentioning

confidence: 99%

Small-Angle X-Ray Scattering for Imaging of Surface Layers on Intact Bacteria in the Native Environment

et al. 2013

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Crystalline cell surface layers (S-layers) represent a natural two-dimensional (2D) protein self-assembly system with nanometerscale periodicity that decorate many prokaryotic cells. Here, we analyze the S-layer on intact bacterial cells of the Gram-positive organism Geobacillus stearothermophilus ATCC 12980 and the Gram-negative organism Aquaspirillum serpens MW5 by smallangle X-ray scattering (SAXS) and relate it to the structure obtained by transmission electron microscopy (TEM) after platinum/ carbon shadowing. By measuring the scattering pattern of X rays obtained from a suspension of bacterial cells, integral information on structural elements such as the thickness and lattice parameters of the S-layers on intact, hydrated cells can be obtained nondestructively. In contrast, TEM of whole mounts is used to analyze the S-layer lattice type and parameters as well as the physical structure in a nonaqueous environment and local information on the structure is delivered. Application of SAXS to S-layer research on intact bacteria is a challenging task, as the scattering volume of the generally thin (3-to 30-nm) bacterial S-layers is low in comparison to the scattering volume of the bacterium itself. For enhancement of the scattering contrast of the S-layer in SAXS measurement, either silicification (treatment with tetraethyl orthosilicate) is used, or the difference between SAXS signals from an S-layer-deficient mutant and the corresponding S-layer-carrying bacterium is used for determination of the scattering signal. The good agreement of the SAXS and TEM data shows that S-layers on the bacterial cell surface are remarkably stable. Surface layers (S-layers) are a distinct cell surface decoration comprised of regularly arrayed, two-dimensional (2D) protein or glycoprotein crystals present on many prokaryotic organisms from almost all known phylogenetic branches (1-4). S-layers form upon self-assembly and exhibit nanometer-scale periodicity with oblique (p1, p2), square (p4), or hexagonal (p3, p6) lattice symmetry and species-specific lattice constant values in the range of 10 to 25 nm. The S-layer self-assembly system holds great promise as a bottom-up approach for organizing matter at the nanometer scale as required in the field of nanobiotechnology (5).Because of their cell surface location, ultrastructural studies of S-layer lattices have been frequently performed by high-resolution transmission electron microscopic (TEM) methods such as ultrathin sectioning or heavy-metal shadow casting of freezeetched or freeze-dried whole cells (6) as well as image analysis (7) or cryo-sectioning of frozen-hydrated cells (8). These electron microscopic approaches, except the latter, suffer from the drawback of the requirement for water-free specimens, implying a requirement for specific sample treatment prior to analysis. The standard procedures of chemical fixation, dehydration, and staining of cells for TEM analysis may affect cell morphology and ultrastructure and, thus, prevent the accurate determination of distinct S-l...

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Section: Discussionmentioning

confidence: 99%

Small-Angle X-Ray Scattering for Imaging of Surface Layers on Intact Bacteria in the Native Environment

et al. 2013

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“…The reaction was stopped by the addition of 240 l of 13% KH 2 PO 4 , and the absorbance of pNP was measured at 400 nm. Enzyme activity (expressed as nmol min Ϫ1 mg of protein Ϫ1 ) was calculated by using the molar extinction coefficient (ε), i.e., 18,900 M Ϫ1 cm Ϫ1 for pNP at 400 nm (2). The total protein concentration in the sample solution was measured by the Bradford method (19).…”

Section: Methodsmentioning

confidence: 99%

An Alkaline Phosphatase/Phosphodiesterase, PhoD, Induced by Salt Stress and Secreted Out of the Cells of Aphanothece halophytica, a Halotolerant Cyanobacterium

Kageyama

Tripathi

Kumar

et al. 2011

Appl Environ Microbiol

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Alkaline phosphatases (APases) are important enzymes in organophosphate utilization. Three prokaryotic APase gene families, PhoA, PhoX, and PhoD, are known; however, their functional characterization in cyanobacteria largely remains to be clarified. In this study, we cloned the phoD gene from a halotolerant cyanobacterium, Aphanothece halophytica (phoD Ap ). The deduced protein, PhoD Ap , contains Tat consensus motifs and a peptidase cleavage site at the N terminus. The PhoD Ap enzyme was activated by Ca 2؉ and exhibited APase and phosphodiesterase (APDase) activities. Subcellular localization experiments revealed the secretion and processing of PhoD Ap in a transformed cyanobacterium. Expression of the phoD Ap gene in A. halophytica cells was upregulated not only by phosphorus (P) starvation but also under salt stress conditions. Our results suggest that A. halophytica cells possess a PhoD that participates in the assimilation of P under salinity stress.Phosphorus (P) is an essential nonmetal nutrient for all living cells. Despite its relative abundance in the ecosystem, P is sometimes a limiting factor for organisms in terrestrial, oceanic, and freshwater environments (1, 11). This is because while all organisms can utilize soluble inorganic phosphate (P i ), the P-containing organic compounds generally found in nature are complex insoluble forms that are not readily available to cells (1, 11). Alkaline phosphatases (APases) release free P i from organic compounds. To date, three prokaryotic APase gene families-PhoA, PhoX, and PhoD-have been documented (7). In addition to different levels of homology among these APases, dissimilar metal requirements for their activities have been reported (7). A recent metagenomics analysis revealed that PhoX, a recently characterized phosphatase, is more abundant in marine bacteria than the previously considered classical PhoA (12). However, it has also been shown that PhoD is more abundant in marine bacteria than PhoA or PhoX (7), suggesting an important role for PhoD in marine bacteria. PhoD encompasses a family of phosphatase/phosphodiesterases (APase/APDase). Except for Bacillus subtilis PhoD (PhoD Bs ) (3), little is known on other PhoD proteins. PhoD Bs was shown to be secreted into extracellular medium by the Tat pathway, which recognizes targeted proteins by their N-terminal twin-arginine signal peptides containing the Tat consensus (SRRXFLK) motif (3, 9).Cyanobacteria inhabit a broad range of ecosystems and play a vital role in the global cycling of nutrients, including P.Hitherto, extensive studies on the regulation of gene expression during phosphate stress have been carried out (14). In contrast, functional properties of cyanobacterial APases have been reported only on classical PhoA (8), atypical APase (11), PhoV (21), and PhoX (5), and there is no report on the cyanobacterial PhoD. Moreover, little is known on the role of APase under high-salinity conditions, and this encouraged us to examine the role of cyanobacterial PhoD under high-salinity conditions.Aphanot...

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“…Bacteria at concentration ~ 10 6 were inoculated in LB medium(13 g•l -1 ) supplemented with sodium arsenate solution at concentration of 2 mg•l -1 to 200 mg•l -1 .…”

Section: Determination Of Micmentioning

confidence: 99%

“…as substrate [4,5]. An ideal bio matrix for its wide range of applications should possess the following characteristics such as high mechanical strength, inertness, biocompatibility and non-toxicity vs. active biological agents [6].…”

Section: Introductionmentioning

confidence: 99%

Development of Nano Mullite Based Mesoporous Silica Biocer With Incorporated Bacteria for Arsenic Remediation

Kar¹,

Nandy²,

Basu³

et al. 2016

Ceramics - Silikaty

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Sol–gel encapsulation of bacteria: a comparison between alkoxide and aqueous routes

Cited by 147 publications

References 19 publications

Small-Angle X-Ray Scattering for Imaging of Surface Layers on Intact Bacteria in the Native Environment

Small-Angle X-Ray Scattering for Imaging of Surface Layers on Intact Bacteria in the Native Environment

An Alkaline Phosphatase/Phosphodiesterase, PhoD, Induced by Salt Stress and Secreted Out of the Cells of Aphanothece halophytica, a Halotolerant Cyanobacterium

Development of Nano Mullite Based Mesoporous Silica Biocer With Incorporated Bacteria for Arsenic Remediation

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