Bacterial origin of luminescence in marine animals

Bacterial luciferase activity was detected in light organ extracts of squids, fishes, and pyrosomes, suggesting that these systems are derived from bacteria-animal symbioses. In none of these cases was it possible to culture luminouis bacteria. Analyses of the decay kinetics show that the luciferases from the squid, ceratioid, and pyrosome light organs are all similar to bacterial luciferases from the genus Photobacterium, while those from the anomalopid light organs are different.     

Heliotropism in modern stromatolites

Modern microbial mats and stromatolites exhibiting a preferred orientation toward specular sunlight were found at two sites. In Hamelin Pool of Shark Bay, Western Australia, subtidal decimeter-sized columns and intertidal centimeter-sized tufts were found pointing north. In thermal spring effluents and pools of Yellowstone National Park, mats were found with columnar and conical centimeter-sized structures inclined to the south. These examples of heliotropism in modern stromatolites are each built by a different community of photosynthetic microbes under markedly different environmental conditions. These new observations support the proposal that stromatolites can orient themselves toward the sun.     

Bacterial origin of sulfuric Acid in geothermal habitats

Natural populations of Sulfolobus, a new genus of bacteria occurring in sulfur-rich, acid hot springs and soils, were found to oxidize large amounts of sulfur to sulfuric acid at temperatures up to 85 degrees C. These bacteria are important high-temperature geochemical agents in solfatara soils.     

Bacterial origin of a chloroplast intron: conserved self-splicing group I introns in cyanobacteria

A self-splicing group I intron has been found in the gene for a leucine transfer RNA in two species of Anabaena, a filamentous nitrogen-fixing cyanobacterium. The intron is similar to one that is found at the identical position in the same transfer RNA gene of chloroplasts of land plants. Because cyanobacteria were the progenitors of chloroplasts, it is likely that group I introns predated the endosymbiotic association of these eubacteria with eukaryotic cells.     

Hardened subtidal stromatolites, bahamas

Hardened, high-relief stromatolites have been discovered along the margins of some Bahamian platforms. They occur in high-energy (tidal) oolitic sand environments in waters ranging in depth from about 1 to 5 meters. Physical stress produced by actively migrating bed forms of oolitic sand appears to exclude grazing gastropods and subsequent community successions, permitting stromatolite growth.     

Algal stromatolites: use in stratigraphic correlation and paleocurrent determination

Algal stromatolites are used for detailed rock-stratigraphic correlation for a distance of 160 kilometers in the Pethei Formation, of Aphebian (Precambrian) age, in the Northwest Territories, Canada. Laterally linked stromatolites are initiated by the draping of successive laminations over intraclasts or other irregularities in the bedding surface. Stromatolite shapes and orientations are related to paleocurrent direction determined from associated sedimentary structures. Thus stromatolite geometry is at least in part environmentally controlled.     

Precambrian columnar stromatolites in australia: morphological and stratigraphic analysis

The stratigraphic distribution in Australian Precambrian rocks of columnar stromatolites, organosedimentary structures formed by blue-green algae, has been investigated. Their morphology is being studied according to methods developed in Russia. The discovery of successive different assemblages supports not only regional but also intercontinental stratigraphic correlations which are in agreement with available isotopic datings.     

Phanerozoic stromatolites: noncompetitive ecologic restriction by grazing and burrowing animals

The abundance of stromatolites (algal laminated sedimentary structures) in the Precambrian followed by a decline in the Phanerozoic is explained by the evolution and diversification during the Phanerozoic of grazing animals which feed on surface algal mats and of burrowing animals which destroy sedimentary laminations.     

Algal stromatolites: deepwater forms in the devonian of Western australia

A diverse assemblage of algal stromatolites occurs in Devonian reef complexes of the Canning Basin, Western Australia. Some forms grew on fore-reef depositional slopes down to at least 45 meters below sea level and are believed to be products of deepwater nonskeletal algae. It is concluded that algal stromatolites in the stratigraphic record are not to be regarded as diagnostic evidence for deposition in very shallow water.     

The antiquity of oxygenic photosynthesis: evidence from stromatolites in sulphate-deficient Archaean lakes

The Tumbiana Formation, about 2700 million years old, was largely deposited in ephemeral saline lakes, as judged by the unusual evaporite paragenesis of carbonate and halite with no sulfate. Stromatolites of diverse morphology occur in the lacustrine sediments, some with palimpsest fabrics after erect filaments. These stromatolites were probably accreted by phototropic microbes that, from their habitat in shallow isolated basins with negligible sulfate concentrations, almost certainly metabolized by ozygenic photosynthesis.     

Bacterial flagella: polarity of elongation

Newly synthesized regions of Bacillus subtilis flagella were labeled with fluorophenylalanine or [(3)H]leucine. The flagella were then examined for altered gross morphology or by radioautography. Results of both experiments indicate that flagella elongate in vivo by polymerization of flagellin subunits onto the distal end of the filament.     

Bacterial domestication: underlying assumptions

On the basis of well-established principles of evolutionary biology and microbiology, I conclude that (i) the deliberate introduction of a novel bacterial strain to the environment is not substantially more dangerous than the accidental release of a smaller number of cells; (ii) distant organisms are less (rather than more) likely to yield dangerous hybrids than more closely related ones; and (iii) the complex attribute of pathogenicity is not likely to emerge from genetic alterations in nonpathogens. If these conclusions are correct, most engineered bacteria need not be regulated more strictly than the bacterial strains that have been tested in the field in the past. The only exceptions would be strains derived from cells, or appropriate genes, of microbes pathogenic for plants or animals. Microbiologists not only recognize the need to handle pathogens with caution: they have long accepted regulations, such as those governing transportation, that reinforce that recognition. It is remarkable that we can still be arguing, on the basis of analogies rather than firm scientific principles or evidence, about hypothetical disasters from kinds of organisms that are being produced in hundreds or thousands of laboratories without a trace of demonstrable harm. RAC required 6 years to adjust its initially conservative guidelines to the emerging understanding of the scientific realities, while maintaining public confidence. Since the level of public concern is not nearly as great today, EPA should be able to relax its excessive restrictions much more quickly. Even better would be a return to having RAC, or a single successor group, evaluate the problems of danger for all classes of engineered bacteria, since the applicable shared principles outweigh any specialized differences in the nature or use of the specific strains. But the regulations are unlikely to be unified in this way, or to be divested of unproductive restrictions, without broad encouragement from the scientific community-including, hopefully, many ecologists. The agenda has been set for too long by apocalyptic activists. To protect this promising field of research and technological application the scientific community must take initiative in helping the public and decision-makers to distinguish reasonable probabilities from remote fantasies.     

Volcanic sunset-glow stratum: origin

Reexamination of the phenomenon of volcanic-dust sunsets, as typified by the Krakatoa event, supports a theory that the scattering layer is produced by the interaction of ozone and sulfur dioxide in much the same manner as is the normal "Junge"aerosol layer at 20 kilometers.     

Siliceous algal and bacterial stromatolites in hot spring and geyser effluents of yellowstone national park

Growing algal and bacterial stromatolites composed of nearly amorphous silica occur around hot springs and geysers in Yellowstone National Park, Wyoming. Some Precambrian stromatolites may be bacterial rather than algal, which has important implications in atmospheric evolution, since bacterial photo-synthesis does not release oxygen. Conophyton stromatolites were thought to have become extinct at the end of the Precambrian, but are still growing in hot spring effluents.     

Bacterial invasion: the paradigms of enteroinvasive pathogens

Invasive bacteria actively induce their own uptake by phagocytosis in normally nonphagocytic cells and then either establish a protected niche within which they survive and replicate, or disseminate from cell to cell by means of an actin-based motility process. The mechanisms underlying bacterial entry, phagosome maturation, and dissemination reveal common strategies as well as unique tactics evolved by individual species to establish infection.