Ancient Cyanobacteria

Cyanobacteria are believed to be the ancestors of plant cells. In the ancient seas, heterotrophic cells probably fed on cyanobacteria, engulfing them whole. Instead of digesting these prey, the heterotrophic cells were able to maintain them in membrane-bound sacs. The cyanobacteria continued to photosynthesize, making their own food and providing food for their new hosts. Over time, these two individual cells became an inseparable team, dependent on each other for support. The cyanobacteria acted as the light-gathering structure for the two, and the duo evolved into primitive plant cells. 

Smooth mats of Lyngbya can be found where intertidal flats are regularly covered with water. Within a mat, the cells are so tightly packed that oxygen cannot diffuse into it. As a result, anaerobic bacteria develop colonies below the mats that appear as purple or black layers. 

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Why then haven t the cyanobacteria evolved in response to the large changes in trace-metal chemistry between an ancient reducing ocean and a modem oxidizing one Why have they kept a biochemical apparatus that reflects early ocean... 

Despite these obstacles, many signature molecules have been developed and utilized for the study of ancient samples (see Schopf and Klein, 1992). Of these molecules, perhaps the most interesting group recently utilized has been the methylhopanoids, breakdown products of 2-methyl-hopanepolyols, which are produced by cyanobacteria, and are common in microbial mats. The discovery of methylhopanoids in organic-rich sediments from 2.7 Ga (Brocks et al, 1999 Summons et al., 1999) provided the single best piece of evidence for the presence of cyanobacteria at this time. 

Monomethyl and dimethylalkanes in the range C16-C20 are prominent in many cultured cyanobacteria as well as most cyanobacterial mat communities that have been studied (Section 8.03.5.3). No specific physiological role has been assigned to these hydrocarbons. Because they have probably multiple origins in ancient sediments and petroleum, these monomethyl and dimethylalkanes alone probably have limited chemotaxonomic specificity. However, they may be very useful in multivariate approaches for linking isotopic and molecular-structure data for a less ambiguous identification of sedimentary cyanobacterial lipids. 

In the late Archean eon, the plates of Earth s crust may have continued to move at a relatively high speed. Evidence of these wild times can be found in the ancient core of North America. The scars of tectonic events appear as rock outcrops throughout the part of northern North America called the Canadian Shield. One example of this kind of scar, a greenstone belt, may be the mangled remains of ancient island arcs or rifts within continents. Gold and chromium are found in the greenstone belts, and deposits of copper, zinc, and nickel. Eorma-tions of iron ore also began to form in the Archean eon, and fossils of microscopic cyanobacteria-the first life on Earth—are found imbedded in them. 

The accepted view of the Eucarya is that they derived their chloroplasts from cyanobacteria and their mitochondria from purple bacteria. Therefore they post-date these precursors. Biomarker molecules in 2.6-2.7 Ga Pilbara shales indicate that the Eucarya were in existence by this time, although Hartman and Fedorov (2002) have challenged the conventional view and believe that they could be much more ancient. 

Photosynthesis was well-established on the Earth by approximately 3.5 billion years a%o, and it is widely believed that the ancient photosynthetic organisms had metabolic capabilities similar to those of modem cyanobacteria. All photosystems are built on a general theme but with some variations. They are composed of three major components the Reaction Center (RQ that carries out photochemical charge separation and electron transport, the inner antenna consisting of pigment proteins tighdy associated with RC, and the peripheral or outer antenna. ... 

Plectonema terebrans, a species of filamentous marine cyanobacteria, accumulates gold in its sheath from an aqueous solution of AuCls. Sheaths are among the few stmctures likely to be preserved in some form in microfossils of ancient bacteria. In marine media, it is expected that AuCls (2.0 g Au/L) will formAuCl4, AuOJ, andAuClJ Biosorption of Au+, as AUCI4, by dried Pseudomonas strains of bacteria was inhibited by palladium, as Pd+, and possibly other metal ions. 

Ancient orgins determine giobai biogeography of hot and cold desert cyanobacteria. Nature Communications 2,163. 

The HeLa cells originally were transformed by the HPV-encoded oncoproteins (that neutralize p53 and Rb cellular mmor suppressor genes). Distinction between self and non-self probably did not exist when ancient chimeric cells were formed, and engulfed bacteria were accepted as self (proteobacteria for the mitochondrion cyanobacteria for the chloroplast). Malignantly transformed cells appear to be impervious, as to the distinction between self and non-self, when it comes to... 

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