Evidence for Microbial Involvement in Pool Finger Precipitation,Hidden Cave,New Mexico

Although speleothems are usually considered inorganic precipitates, recent work has demonstrated hitherto unsuspected biogenic influence in some twilight areas. We have expanded this notion to the dark zone, examining pool fingers from Hidden Cave, New Mexico, to test for possible bacterial involvement. The pool fingers in Hidden Cave are pendant speleothems that formed subaqueously in paleo-pools. They are 1 to 4 cm in diameter and 5 to 50 cm long. A knobby, irregular external shape is underlaid by a layered interior on two scales, a 0.5 to 1.0 cm alternation between dense and porous layers and a mm-scale alternation between dark micritic calcite and clear dogtooth spar. The micrite is similar to microbialites identified in modern and ancient carbonates. Fossil bacteria were found in all layers. These include (1) calcified filaments 1 w m in diameter and 5–50 w m long and (2) micro-rods 0.1 w m by 1–2 w m. Most filaments are curved rods with a smooth surface but rare examples display a diamond crosshatch surface. The micro-rods occur as isolated crystals to dense meshes. We interpret the micro-rods as calcified bacilliform bacteria and the filaments as calcified filamentous bacteria. Carbon isotopic data are slightly more negative (by - 0.5 to - 1.0% in micritic layers than in dogtooth spar layers, suggesting a greater microbial influence in the micritic layers. Based on these similarities to known microbialites (e.g., petrographic fabrics, the presence of fossil bacteria, and the suggestive carbon isotopic data), we conclude that microbial activity was an intimate part of pool finger formation in Hidden Cave. The significance of such involvement goes beyond speleological contexts to wider questions of identification of biosignatures in rocks on earth and beyond.     

Involvement of the Hipk family in regulation of eyeball size, lens formation and retinal morphogenesis

Members of the homeodomain-interacting protein kinase (HIPK) family are involved in various intracellular regulatory mechanisms. The present study focused on clarifying the functions of HIPK family members in ocular organization during late embryogenesis. HIPK1 and HIPK2 were expressed in the inner retina during late embryogenesis. Hipk1^+/−Hipk2^−/− mice had a greater frequency of small eyes with a lens deficiency and abnormally laminated and thickened retinas than did wild-type littermates. These data indicate that Hipk1 and Hipk2 are involved in regulation of eye size, lens formation and retinal lamination during late embryogenesis.     

Microbial influence in the Messinian sedimentation: Example of Cap Bon (NE Tunisia)

Messinian sedimentation in Tunisia is characterized by the absence of large carbonate platforms known in many Mediterranean marginal basins. As a result, correlations are not easy to establish in order to integrate it into a general pattern of development at the regional level. However, the discovery of microbial constructions of metric scale makes it possible to precise uncertain points. Thus in the sector of Cap Bon in the northeast of Tunisia, stromatolitic constructions can form, over distances of several hundred meters, domes containing columnar structures at different scales as well as carbonate beds showing sedimentary ripples also of microbialite nature. The highlighting of an assemblage of microbialites, associated with oolitic deposits, allows linking these formations to the Terminal Carbonate Complex which finds its place at a part of the so-called Messinian Salinity Crisis.