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Biological Transport
Published in Lelio G. Colombetti, Biological Transport of Radiotracers, 2020
The Isua rocks of Greenland, which have been radiometrically dated as 3,800 million years old, contain carbon compounds in which the isotope ratios are similar to those resulting from the activity of living organisms. This finding is not, of course, an assurance that life existed that long ago, and the inference drawn by some investigators, that those rocks components are of biogenic origin has been challenged by others. There is no dispute, however, about the authenticity of fossilized cellular organisms present in Australian stromatolites 3,400 million years old. The species in the stromatolites appear to have mastered the metabolic trick of photosynthesis; by that time, then, life forms had become so complex that they depended absolutely upon transport, perhaps mechanistically simple, but efficient enough to enable the cells to capture the nutrients necessary to keep them alive. It seems quite safe to say that transport is by no means a new phenomenon.
Macro and Micro Algal Impact on Marine Ecosystem
Published in Gokare A. Ravishankar, Ranga Rao Ambati, Handbook of Algal Technologies and Phytochemicals, 2019
In oceanic ecosystems, cyanobacteria have been recognized as key players in the precipitation of calcium carbonate. Cyano-prokaryotes both produce extracellular polysaccharides which act as binding sites for calcium and carbonate ions as well as elevate the pH of the water body through photosynthesis. Both processes have been known to impact the mineralogy and morphology of the carbonate minerals (Dittrich and Sibler 2010). Studies on cyanobacterial extracellular polymeric substances indicate that polysaccharides secreted by cyanobacteria possess a strong capacity to exchange protons with the surrounding environments. Lab scale studies with Synechococcus sp. demonstrated that extracellular polysaccharides were able to precipitate calcium carbonate. Examples of cyanobacterial calcification include Stromatolites and whiting events. Whiting events are characterized by the large-scale precipitation of calcium carbonate crystals in conjunction with the production of organic compounds like polysaccharides by cyanobacterial cells (Thompson et al. 1997, Yates and Robbins 2001).
Evaluation of gallstone classification and their diagnosis through serum parameters as emerging tools in treatment: a narrative review
Published in Postgraduate Medicine, 2022
Bhavna Sharma, Shubha Rani Sharma
Nakayama (1968) introduced the classification of gallstones based on chemical analysis. They were categorized into black pigment, fatty acid calcium stones, brown pigment, and cholesterol. It was observed that brown pigment stones were different from cholesterol and black pigment stones in their composition as well as etiology [26]. Maki et al., (1982) classified pigment gallstones into two types – black-pigmented or pure pigmented and calcium bilirubinate gallstones, based on the chemical constitution, external features, and pathogenesis. Pure pigment stones are formed in the case of metabolic imbalances like liver cirrhosis, and hepatic anemia. Fu et al., (1984) considered the chemical components and profile structure of gallstones and classified them into 8 types – radial, sand bed-like stromatolite, radial annual ring-like, rock strata-like stromatolite, silt-like, black, cast amorphous and complex stones. In these stones, there was cholesterol (radial, radial annual ring-like, and rock strata-like stromatolite stones) and pigment stones (cast amorphous, sand bed-like stromatolite and silt-like stones) [27]. Malet (1984) observed dissimilarities in the structure as well as composition between the black noncarbonate and brown pigment gallstones which strengthens the hypothesis that two different mechanisms are involved in the formation of these two major types of pigment gallstone types [28].
An overview on cyanobacterial blooms and toxins production: their occurrence and influencing factors
Published in Toxin Reviews, 2022
Isaac Yaw Massey, Muwaffak Al osman, Fei Yang
The ancient cyanobacteria organisms, noticeable in rocks dating from the first thousand million years of the earth’s history and belong to the kingdom monera (Prokaryota), division eubacteria and class cyanobacteria (Ressom et al.1994, Omidi et al.2018), are a type of photosynthetic bacteria that live in water surface. As cyanobacteria colonies occur in shallow water, they appear in the fossil record in sedimentary rocks deposited in shallow seas and lakes. Cyanobacteria colonies identified as stromatolites emerge in rocks as fossilized mushroom shapes and sheets. Falconer (2005) reported that the Gunflint chert was one of the best stromatolite formations known in Lake Erie. It is of interest cyanobacteria was shown to possess a single circular chromosome completely sequenced in several species, plasmids and small circular strands of DNA (Schwabe 1988, Kaneko et al.1996). Whitton and Potts (2000) found that the chlorophyll-a and pigment phycocyanin observed in cyanobacteria photosynthetic membranes were responsible for the characteristic blue-green color of the many species. Pigments such as carotenoids and phycoerythrin which give a strong red color to some species may also be present (Bryant 1994).