by University of Utah, April 14, 2019 in WUWT
Proteins help organisms form or inhibit ice crystals
Contrary to what you may have been taught, water doesn’t always freeze to ice at 32 degrees F (zero degrees C). Knowing, or controlling, at what temperature water will freeze (starting with a process called nucleation) is critically important to answering questions such as whether or not there will be enough snow on the ski slopes or whether or not it will rain tomorrow.
Nature has come up with ways to control the formation of ice, though, and in a paper published today in the Journal of the American Chemical Society University of Utah professor Valeria Molinero and her colleagues show how key proteins produced in bacteria and insects can either promote or inhibit the formation of ice, based on their length and their ability to team up to form large ice-binding surfaces. The results have wide application, particularly in understanding precipitation in clouds.
“We’re now able to predict the temperature at which the bacterium is going to nucleate ice depending on how many ice-nucleating proteins it has,” Molinero says, “and we’re able to predict the temperature at which the antifreeze proteins, which are very small and typically don’t work at very low temperatures, can nucleate ice.”
by A. Préat et al., December 2018 in GeologicaBelgica (with .pdf)
Explaining the color of rocks is still a complex problem. This question was raised long ago in the community of geologists, particularly for the pigmentation of the ‘red marbles’ of the Frasnian of Belgium at the beginning of the last century, with many unsatisfactory hypotheses. Our recent analysis of different red carbonate rocks in Europe and North Africa (Morocco) may provide an alternative explanation for the color of these rocks. For this it was necessary to bring together diverse and complementary skills involving geologists, microbiologists and chemists. We present here a synthesis of these works. It is suggested that the red pigmentation of our studied Phanerozoic carbonate rocks, encompassing a time range from Pragian to Oxfordian, may be related to the activity of iron bacteria living in microaerophilic environments. A major conclusion is that this red color is only related to particular microenvironments and has no paleogeographic or climatic significance. All red carbonates have not necessarily acquired their pigmentation through the process established in this review. Each geological series must be analyzed in the light of a possible contribution of iron bacteria and Fungi.
by Imperial College, November 27, 2018 in ScienceDaily
The levels of oxygen dramatically rose in the atmosphere around 2.4 billion years ago, but why it happened then has been debated. Some scientists think that 2.4 billion years ago is when organisms called cyanobacteria first evolved, which could perform oxygen-producing (oxygenic) photosynthesis.
Other scientist think that cyanobacteria evolved long before 2.4 billion years ago but something prevented oxygen from accumulating in the air.
Cyanobacteria perform a relatively sophisticated form of oxygenic photosynthesis — the same type of photosynthesis that all plants do today. It has therefore been suggested that simpler forms of oxygenic photosynthesis could have existed earlier, before cyanobacteria, leading to low levels of oxygen being available to life.
Now, a research team led by Imperial College London have found that oxygenic photosynthesis arose at least one billion years before cyanobacteria evolved. Their results, published in the journal Geobiology, show that oxygenic photosynthesis could have evolved very early in Earth’s 4.5-billion-year history.
See also here