Search Results (4)

Bone minerals may be more complex than the prevailing opinion suggests. Understanding its biomaterial properties in health and disease may address fundamental geo/biomorphological ambiguities recurrent within its calcified cancellous hierarchy of macro-, micro-, and nano-skeletal networks. (i) There is evidence that the outer mineral macroskeleton of interconnected trabeculae (150 µm diameter) is modulated according to axes of tensile stress by permeating arrays of periosteal Sharpey’s fibres (collagen type III/VI, 5–25 µm thick) studded with tenascin organiser protein. (ii) Its substructural mineral microskeleton is a reticulation of bridged and deformable calcium phosphate/carbonate microspheres (about 1 µm diameter). These organically enshrouded (e.g., bone sialoprotein, osteocalcin, osteopontin) objects, configured by the adhesive organiser protein fibronectin and tempered by trace elements (e.g., Si, Mg, Fe, Al), display differential histochemistry (e.g., acid phosphatase, carbonic anhydrase) and anomalous traits (tetracycline binding, gram-positive microbial staining and nucleic acid staining affinity). The calcified microspheres are intracellular fabrications of osteocyte cohorts developed within “switched on” Golgi cisternae prior to aggregation at the extracellular calcification front in chains and looped assemblies. (iii) Within each microsphere, a less dense centre is encircled by a mineral nanoskeleton of beaded filaments (5 nm in diameter) transmutable in electron density, with a trait for lateral fusion into ladder-like struts, stays and senescent fenestrated plates, constituting domains of microparticle slip and crystal fracture. The evidence suggests a bone mineral biosystem of integrated complexity within which a particulate assemblage at the animate: inanimate calcification front resembles a colonial construct of prokaryote-like, Golgi-fabricated objects calcified with phosphate and harbouring a resident biochemistry. A self-contained “Petrified Microbiome” is proposed to be orchestrated according to a biodynamic primordial paradigm. Full article

The Galapagos Islands (Ecuador) have a unique ecosystem on Earth due to their outstanding biodiversity and geological features. This also extends to their subterranean heritage, such as volcanic caves, with plenty of secondary mineral deposits, including coralloid-type speleothems and moonmilk deposits. In this study, the bacterial communities associated with speleothems from two lava tubes of Santa Cruz Island were investigated. Field emission scanning electron microscopy (FESEM) was carried out for the morphological characterization and detection of microbial features associated with moonmilk and coralloid speleothems from Bellavista and Royal Palm Caves. Microbial cells, especially filamentous bacteria in close association with extracellular polymeric substances (EPS), were abundant in both types of speleothems. Furthermore, reticulated filaments and Actinobacteria-like cells were observed by FESEM. The analysis of 16S rDNA revealed the presence of different bacterial phylotypes, many of them associated with the carbon, nitrogen, iron and sulfur cycles, and some others with pollutants. This study gives insights into subsurface microbial diversity of the Galapagos Islands and further shows the interest of the conservation of these subterranean geoheritage sites used as show caves. Full article

The filamentous cyanobacterium, Pseudanabaena, has been shown to produce reticulate patterns that are thought to be the result of its gliding motility. Similar fossilized structures found in the geological record constitute some of the earliest signs of life on Earth. It is difficult to tie these fossils, which are billions of years old, directly to the specific microorganisms that built them. Identifying the physicochemical conditions and microorganism properties that lead microbial mats to form macroscopic structures can lead to a better understanding of the conditions on Earth at the dawn of life. In this article, a cell-based model is used to simulate the formation of reticulate patterns in cultures of Pseudanabaena. A minimal system of long and flexible trichomes capable of gliding motility is shown to be sufficient to produce stable patterns consisting of a network of streams. Varying model parameters indicate that systems with little to no cohesion, high trichome density and persistent movement are conducive to reticulate pattern formation, in conformance with experimental observations. Full article

Some modern filamentous oxygenic photosynthetic bacteria (cyanobacteria) form macroscopic tufts, laminated cones and ridges that are very similar to some Archean and Proterozoic stromatolites. However, it remains unclear whether microbes that constructed Archean clumps, tufts, cones and ridges also produced oxygen. Here, we address this question by examining the physiology of cyanobacterial clumps, aggregates ~0.5 mm in diameter that initiate the growth of modern mm- and cm-scale cones. Clumps contain more particulate organic carbon in the form of denser, bowed and bent cyanobacterial filaments, abandoned sheaths and non-cyanobacterial cells relative to the surrounding areas. Increasing concentrations of oxygen in the solution enhance the bending of filaments and the persistence of clumps by reducing the lateral migration of filaments away from clumps. Clumped mats in oxic media also release less glycolate, a soluble photorespiration product, and retain a larger pool of carbon in the mat. Clumping thus benefits filamentous mat builders whose incorporation of inorganic carbon is sensitive to oxygen. The morphogenetic sequence of mm-scale clumps, reticulate ridges and conical stromatolites from the 2.7 Ga Tumbiana Formation likely records similar O₂-dependent behaviors, preserving currently the oldest morphological signature of oxygenated environments on Early Earth. Full article