Changing microspatial patterns of sulfate-reducing microorganisms (SRM) during cycling of marine stromatolite mats.

Microspatial arrangements of sulfate-reducing microorganisms (SRM) in surface microbial mats (~1.5 mm) forming open marine stromatolites were investigated. Previous research revealed three different mat types associated with these stromatolites, each with a unique petrographic signature. Here we focused on comparing "non-lithifying" (Type-1) and "lithifying" (Type-2) mats. Our results revealed three major trends: (1) Molecular typing using the dsrA probe revealed a shift in the SRM community composition between Type-1 and Type-2 mats. Fluorescence in-situ hybridization (FISH) coupled to confocal scanning-laser microscopy (CSLM)-based image analyses, and 35SO4(2-)-silver foil patterns showed that SRM were present in surfaces of both mat types, but in significantly (p < 0.05) higher abundances in Type-2 mats. Over 85% of SRM cells in the top 0.5 mm of Type-2 mats were contained in a dense 130 µm thick horizontal layer comprised of clusters of varying sizes; (2) Microspatial mapping revealed that locations of SRM and CaCO3 precipitation were significantly correlated (p < 0.05); (3) Extracts from Type-2 mats contained acylhomoserine-lactones (C4- ,C6- ,oxo-C6,C7- ,C8- ,C10- ,C12- , C14-AHLs) involved in cell-cell communication. Similar AHLs were produced by SRM mat-isolates. These trends suggest that development of a microspatially-organized SRM community is closely-associated with the hallmark transition of stromatolite surface mats from a non-lithifying to a lithifying state.

Reconstruction and computation of microscale biovolumes using geographical information systems: potential difficulties.

Biofilms are bacterial colonies enveloped in a matrix of extracellular polymeric secretions. Confocal scanning laser microscopy has been used in conjunction with different image analysis techniques to investigate the structure of biofilms. A major goal is to reconstitute the three-dimensional structure of biofilms, and compute or estimate the biovolumes. Our previous research focused on the utilization of remote sensing techniques and Geographical Information Systems for quantitative analyses of confocal images. The present study investigates potential problems in microbial imaging, and uses two approaches, the program COMSTAT and a Geographical Information Systems-based method, to reconstitute three-dimensional structures and estimate biovolumes. Volumes of thirty fluorescent polymeric microspheres with a known diameter were estimated and used as a ground truth, to statistically compare both methods. In a next step, the two approaches were used to estimate the biovolume of a section through a Pseudomonas aeruginosa biofilm. Difficulties were encountered in image acquisition due to the optical properties of the microbeads. Our results indicate that the Geographical Information Systems approach produced results consistent with the existing COMSTAT approach, and close to theoretical values, despite many problems inherent to each phase of this process. Also, the image classification process encountered several limitations. It is suggested that the unique constraints of the microscopic world may generate additional problems, especially related to image classification.

Using geographical information techniques to quantify the spatial structure of endolithic boring processes within sediment grains of marine stromatolites.

Marine stromatolites are generated through the interactions of environmental parameters and specific microbial processes. The activities of endolithic bacteria, that bore canals through calcium carbonate (CaCO(3)) sand grains (ooids) and reprecipitate the CaCO(3) as a single layer (i.e. micritic laminae) are especially important in the longer term stability of the stromatolite macrostructure. Image analysis and classification approaches have been used previously, but only seldom as a quantitative microscopic tool. Here, we develop a new approach that enables the quantification of microscale (i.e. micrometers to millimeters) spatial structure within marine stromatolites. To demonstrate our approach, images were acquired from two different layers of a stromatolite: "orange layers", where microboring of canals within ooids was relatively abundant, and "white layers" where microboring was greatly reduced or lacking. Images were then transformed into spatial maps. Computation of canal and ooid grain areas within each image was conducted and statistically compared between replicate samples from the two stromatolite layers. This allowed quantification of the areas of ooid grains that were microbored. Based on our results, we suggest that our method could be widely applicable to sedimentary environments, and other areas of fundamental research.

Electronic Health Care Records in Europe: confidentiality issues from an American perspective.

The confidentiality and security issues related to the European Electronic Health Care Records have been approached in the United States as well. This paper synthesizes several solutions and comments on these issues from the legal viewpoint in the United States, as well as some preoccupations of the academic world to improve and standardize the quality of the security and confidentiality of data from studies involving human subjects.