This changing environment.

The earliest fossil evidence for land plants comes from microscopic dispersed spores. These microfossils are abundant and widely distributed in sediments, and the earliest generally accepted reports are from rocks of mid-Ordovician age (Llanvirn, 475 million years ago). Although distribution, morphology and ultrastructure of the spores indicate that they are derived from terrestrial plants, possibly early relatives of the bryophytes, this interpretation remains controversial as there is little in the way of direct evidence for the parent plants. An additional complicating factor is that there is a significant hiatus between the appearance of the first dispersed spores and fossils of relatively complete land plants (megafossils): spores predate the earliest megafossils (Late Silurian, 425 million year ago) by some 50 million years. Here we report the description of spore-containing plant fragments from Ordovician rocks of Oman. These fossils provide direct evidence for the nature of the spore-producing plants. They confirm that the earliest spores developed in large numbers within sporangia, providing strong evidence that they are the fossilized remains of bona fide land plants. Furthermore, analysis of spore wall ultrastructure supports liverwort affinities.

Environment↗

PubMed2003

Effects of pH and temperature on the survival of coliphages MS2 and Qbeta.

The RNA F-specific coliphages, MS2 and Qbeta, have been used as virus indicators in water and wastewater studies. It is therefore useful to have a good understanding concerning the effects of environmental factors on their survival in order to choose an appropriate candidate for assessing microbial safety in relation to water quality management. The effects of pH and temperature on the survival of these two coliphages were investigated. MS2 survived better in acidic conditions than in an alkaline environment. In contrast, Qbeta had a better survival rate in alkaline conditions than in an acidic environment. The inactivation rates of both coliphages were lowest within the pH range 6-8 and the temperature range 5-35 degrees C. The inactivation rates of both coliphages increased when the pH was decreased to below 6 or increased to above 8. The inactivation rates of both coliphages increased with increasing temperature. Qbeta behaved peculiarly in extreme pH buffers, i.e. it was inactivated very rapidly initially when subjected to an extreme pH environment, although the inactivation rate subsequently decreased. In general, MS2 was a better indicator than Qbeta. However, within the pH range 6-9 and at temperatures not above 25 degrees C, either MS2 or Qbeta could be used as a viral indicator.

Environment↗