Interesting Science

Life on Earth may have announced its arrival billions of years ago with a whistle and a thump, according to planetary scientists.

Experiments by an international team of researchers back a controversial theory that life flourished on Earth after primitive organisms arrived aboard a meteorite, itself gouged from Mars by a giant impact.

...Charles Cockell (lab), at the Open University, who studies microbes in extreme environments, joined a team of German and Russian scientists to test whether microbes could survive the enormous shock of being blasted into space and crash landing on another planet.

...The findings support the theory of lithopanspermia*, which suggests life may be spread from one planet to another aboard lumps of rock that are knocked off the surface.

Writing in the journal Icarus, the scientists state: "These results strongly confirm the possibility of a 'direct transfer' scenario of 'lithopanspermia' for the route from Mars to Earth

Full article at "Microbe experiment suggests we could all be Martians" (The Guardian UK)

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Based on the paper:

Experimental evidence for the potential impact ejection of viable microorganisms from Mars and Mars-like planets

Dieter Stoffler, Gerda Horneck, Sieglinde Ott, Ulrich Hornemann, Charles S. Cockell, Ralf Moeller, Cornelia Meyer, Jean-Pierre de Vera, Jorg Fritz and Natalia A. Artemieva

Icarus: Volume 186, Issue 2 , February 2007, Pages 585-588
doi:10.1016/j.icarus.2006.11.007

Abstract

Bacterial spores (Bacillus subtilis), cyanobacteria (Chroococcidiopsis sp.), and lichen (Xanthoria elegans) embedded in martian analogue rock (gabbro) were exposed to shock pressures between 5 and 50 GPa which is the range of pressures observed in martian meteorites. The survival of Bacillus subtilis and Xanthoria elegans up to 45 GPa and of Chroococcidiopsis sp. up to 10 GPa supports the possibility of transfer of life inside meteoroids between Mars and Earth and it implies the potential for the transfer of life from any Mars-like planet to other habitable planets in the same stellar system.

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*See:

Impact Experiments in Support of "Lithopanspermia": The Route from Mars to Earth

D. Stoffler, C. Meyer, J. Fritz, G. Horneck, R. Moller, C. Cockell, S. Ott, J. P. de Vera, U. Hornemann, and N. A. Artemieva

37th Annual Lunar and Planetary Science Conference, March 13-17, 2006, League City, Texas, abstract no.1551

Introduction: Rather advanced knowledge on the physical and geological conditions for the transfer of solid rock fragments from Mars to Earth has been acquired recently by studying (a) the shock history of Martian meteorites, (b) numerical models for the meteorites' launch and transfer conditions, and (c) the formation and cosmic ray exposure ages of these meteorites. It is therefore safe to assume that sizeable rock fragments have been transferred from Mars to Earth at moderate p-T-conditions throughout its geological history. Shock pressures range from about 5 to 50 GPa and post-shock temperature increases are mostly in the 10 to 600 degrees C range; however, the temperature effects are limited to rather short times due to rapid cooling during ejection.

As various arguments had already lead to a revival of the 100 years old "panspermia" hypothesis, the described facts and some pioneering shock and acceleration experiments with primitive microbes prompted the view that the possibility of a transfer of "endolithic" microbes from Mars to Earth has to be taken into consideration seriously. This situation has stimulated the present co-operative project in which three types of microorganisms embedded in a gabbro host rock were subjected to high shock pressures and recovered for the study of the survival rates.

Lithopanspermia - Life in the Rocks (Full Text)

"Panspermia: Life is everywhere! Assuming that it truly is, how does it manage to get around? One answer: Lithopanspermia - life gets around inside rocks. Could it be that simple? Can living organisms actually hitchhike the galaxy embedded in rocks, frozen into stasis awaiting just the right conditions to thaw out, stretch out their proteins, and begin a process leading from microbe to mankind?"

Lithopanspermia in Star Forming Clusters

Adams FC, Spergel DN

Astrobiology. 2005 Aug;5(4):497-514

This paper considers the lithopanspermia hypothesis in star forming groups and clusters, where the chances of biological material spreading from one solar system to another is greatly enhanced (relative to the field) due to the close proximity of the systems and lower relative velocities. These effects more than compensate for the reduced time spent in such crowded environments. This paper uses 300,000 Monte Carlo scattering calculations to determine the cross sections for rocks to be captured by binaries and provides fitting formulae for other applications. We assess the odds of transfer as a function of the ejection speed and number of members in the birth aggregate. The odds of any given ejected meteroid being recaptured by another solar system are relatively low. Because the number of ejected rocks per system can be large, virtually all solar systems are likely to share rocky ejecta with all of the other solar systems in their birth cluster. The number of ejected rocks that carry living microorganisms is much smaller and less certain, but we estimate that several million rocks can be ejected from a biologically active solar system. For typical birth environments, the capture of life bearing rocks is expected to occur 10 - 16,000 times per cluster (under favorable conditions), depending on the ejection speeds. Only a small fraction of the captured rocks impact the surfaces of terrestrial planets, so that only a few lithopanspermia events are expected (per cluster).

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A recent post: "NASA Study Finds New Kind of Organics in Stardust Mission (Video)"

Technorati: lithopanspermia, panspermia, life, earth, controversial, theory, primitive, organisms, meteorite, mars, impact, microbes, planet, spread, journal, icarus, experiment, microbe, the guardian, uk, spores, martian, history, meteorites, panspermia, rocks, nasa, stardust, mission, solar, system, stellar, video

Permanent Link posted by John Latter @ 7:16 PM 0 comments

An international group of researchers has succeeded in identifying a previously unknown group of algae. As currently reported in the scientific journal Science, the newly discovered algae are found among the smallest members of photosynthetic plankton - the picoplankton*. On account of the minute size of the organisms (no more than a few thousandth of a millimetre) and the appearance of phycobili-proteins, researchers have termed the new group Picobiliphytes.

Approximately 50 percent of global photosynthesis is conducted in the world's oceans where it is dominated by microscopic algae, the so-called phytoplankton. Scientists estimate that up to 90 percent of phytoplanktonic species are currently unidentified. In the present study, scientists used molecular techniques to investigate the smallest members of the plankton, the picoplankton. Because picoplankton algae are so extremely small, they are almost impossible to study by means of microscopy.

Researchers investigated gene sequences of the 18S gene, common to all cells. The identity of new organisms can be deduced from a comparison of familiar and unfamiliar gene sequences. "The gene sequences found in these algae could not be associated with any previously known group of organisms", explain Dr Klaus Valentin and Dr. Linda Medlin, co-authors of the study and molecularbiologists at the Alfred Wegener Institute* in Bremerhaven. The algae in this study were found in plankton samples originating from various regions of the North Atlantic and the Mediterranean. The scientists have discovered a group of organisms which, despite being completely new to science, have a wide distribution. "This is a good indication for how much there is still to discover in the oceans, especially using molecular tools", says Valentin.

Apart from the unfamiliar gene sequences, the researchers also extracted phycobili-proteins from the algae. In red algae, for example, these proteins occur as colour pigments. However, in the newly discovered algal group, the phycobili-proteins are found at the sites for photosynthesis, i.e. in the plastids. This location of pigment proteins represents a novelty in that it has not been reported for any other algal species. Hence, it provides a clear indication that the researchers are dealing with a previously unidentified species of algae. Referring to their small size and the presence of phycobili proteins, the researchers named the new group Picobiliphytes.

Original press release (dated 12.01.07) from the Alfred Wegener Institute is available via this link

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Based on the journal Science paper:

Picobiliphytes: A Marine Picoplanktonic Algal Group with Unknown Affinities to Other Eukaryotes

Klaus Valentin and Linda Medlin et al.

Science 12 January 2007:
Vol. 315. no. 5809, pp. 253 - 255
DOI: 10.1126/science.1136264

Abstract

Environmental sequencing has revealed unimagined diversity among eukaryotic picoplankton. A distinct picoplanktonic algal group, initially detected from 18S ribosomal DNA (rDNA) sequences, was hybridized with rRNA {lambda}-targeted (rRNA-targeted) probes, detected by tyramide signal amplification-fluorescent in situ hybridization, and showed an organelle-like body with orange fluorescence indicative of phycobilins. Using this fluorescence signal, cells were sorted by flow cytometry and probed. Hybridized cells contained a 4',6'-diamidino-2-phenylindole-stained organelle resembling a plastid with a nucleomorph. This suggests that they may be secondary endosymbiotic algae. Pending the isolation of living cells and their formal description, these algae have been termed picobiliphytes.

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An earlier post on the Alfred Wegener Institute: "Antarctic research within the International Polar Year IPY 2007/2008"

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*A 2001 paper on picoplankton from the journal of Applied and Environmental Microbiology:

Beatriz Diez, Carlos Pedros-Alio, and Ramon Massana

Applied and Environmental Microbiology, July 2001, p. 2932-2941, Vol. 67, No. 7
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.7.2932-2941.2001

Study of Genetic Diversity of Eukaryotic Picoplankton in Different Oceanic Regions by Small-Subunit rRNA Gene Cloning and Sequencing

Abstract

Very small eukaryotic organisms (picoeukaryotes) are fundamental components of marine planktonic systems, often accounting for a significant fraction of the biomass and activity in a system. Their identity, however, has remained elusive, since the small cells lack morphological features for identification.

We determined the diversity of marine picoeukaryotes by sequencing cloned 18S rRNA genes in five genetic libraries from North Atlantic, Southern Ocean, and Mediterranean Sea surface waters. Picoplankton were obtained by filter size fractionation, a step that excluded most large eukaryotes and recovered most picoeukaryotes.

Genetic libraries of eukaryotic ribosomal DNA were screened by restriction fragment length polymorphism analysis, and at least one clone of each operational taxonomic unit (OTU) was partially sequenced. In general, the phylogenetic diversity in each library was rather great, and each library included many different OTUs and members of very distantly related phylogenetic groups. Of 225 eukaryotic clones, 126 were affiliated with algal classes, especially the Prasinophyceae, the Prymnesiophyceae, the Bacillariophyceae, and the Dinophyceae. A minor fraction (27 clones) was affiliated with clearly heterotrophic organisms, such as ciliates, the chrysomonad Paraphysomonas, cercomonads, and fungi. There were two relatively abundant novel lineages, novel stramenopiles (53 clones) and novel alveolates (19 clones).

These lineages are very different from any organism that has been isolated, suggesting that there are previously unknown picoeukaryotes. Prasinophytes and novel stramenopile clones were very abundant in all of the libraries analyzed. These findings underscore the importance of attempts to grow the small eukaryotic plankton in pure culture.

Permanent Link posted by John Latter @ 9:54 PM 0 comments

Researchers at Johns Hopkins have discovered that a tiny piece of genetic code apparently goes where no bit of it has gone before, and it gets there under its own internal code.

A report on the renegade ribonucleic acid, and the code that directs its movement, will be published January 5 in the journal Science*.

MicroRNAs, already implicated in cancer and normal development, latch on to and gum up larger strands of RNA that carry instructions for making the proteins that do all the cell's work. They are, says Joshua Mendell, M.D., Ph.D., an assistant professor in the McKusick-Nathans Institute of Genetic Medicine at Hopkins, like "molecular rheostats that fine-tune how much protein is being made from each gene."

That's why normally microRNAs always have appeared to stick close to the cell's protein-making machinery.

But during a survey of more than 200 of the 500 known microRNAs found in human cells, Mendell's team discovered one lone microRNA "miles away" - in cellular terms - from all the others.

"It was so clearly in the wrong place at the wrong time for what we thought it was supposed to be doing that we just had to figure out why," says Hun-Way Hwang, a graduate student in human genetics and contributor to the study.

Consisting of only 20 to 25 nucleotide building blocks (compared to other types of RNA that can be thousands of nucleotides long), each microRNA has a different combination of blocks. Mendell's team realized that six building blocks at the end of the wayward miR-29b microRNA were noticeably different from the ends of other microRNAs.

Suspicious that the six-block end might have something to do with miR-29b's location, the researchers chopped them off and stuck them on the end of another microRNA. When put into cells, the new microRNA behaved just like miR-29b, wandering far away from the cell's protein-making machinery and into the nucleus, where the cell's genetic material is kept.

The researchers then stuck the same six-block end onto another type of small RNA, a small-interfering RNA or siRNA that turns off genes. This also forced the siRNA into the nucleus.

According to Mendell, these results demonstrate for the first time that despite their tiny size, microRNAs contain elements consisting of short stretches of nucleotide building blocks that can control their behavior in a cell. Mendell hopes to take advantage of the built-in "cellular zip code" discovered in miR-29b as an experimental tool. For example, he plans to force other microRNAs and siRNAs into the nucleus to turn off specific sets of genes.

Mendell's team is actively hunting for additional hidden microRNA elements that control other aspects of their behavior in cells. They also are curious to figure out what miR-29b is doing in the nucleus. Because microRNAs have been implicated in cancer as well as normal development, Mendell hopes that further study of miR-29b will reveal other, hidden functions of microRNAs.

Original Johns Hopkins press release (dated 1/4/07) available via this link

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*Based on the paper:

A Hexanucleotide Element Directs MicroRNA Nuclear Import
Hun-Way Hwang, Erik A. Wentzel, Joshua T. Mendell

Science 5 January 2007:
Vol. 315. no. 5808, pp. 97 - 100
DOI: 10.1126/science.1136235

Abstract

MicroRNAs (miRNAs) negatively regulate partially complementary target messenger RNAs. Target selection in animals is dictated primarily by sequences at the miRNA 5' end. We demonstrated that despite their small size, specific miRNAs contain additional sequence elements that control their posttranscriptional behavior, including their subcellular localization. We showed that human miR-29b, in contrast to other studied animal miRNAs, is predominantly localized to the nucleus. The distinctive hexanucleotide terminal motif of miR-29b acts as a transferable nuclear localization element that directs nuclear enrichment of miRNAs or small interfering RNAs to which it is attached. Our results indicate that miRNAs sharing common 5' sequences, considered to be largely redundant, might have distinct functions because of the influence of cis-acting regulatory motifs.

Technorati: johns hopkins, genetic, code, renegade, ribonucleic, acid, journal, science, rna, proteins, cell, medicine, human, cells, microrna, nucleus, nucleotide, genes, mendell, messenger, behavior

Permanent Link posted by John Latter @ 6:46 PM 0 comments

The Bronx Zoo-based Wildlife Conservation Society (WCS) announced today that a camera-trap study in the mountains of Southern Tanzania has now recorded Africa's least-known and probably rarest carnivore: Jackson's mongoose (info), known only from a few observations and museum specimens. The findings, reported in the latest issue of the journal Oryx, mark not only a range extension for the bushy-tailed carnivore, previously known to exist only in Kenya, but also another species for the Udzungwa Mountains, a veritable 'lost world' of rare and unique wildlife.

WCS scientist Dr. Daniela De Luca - together with Dr. Francesco Rovero from Italy's Trento Museum of Natural Sciences - captured several images of the Jackson's mongoose in Matundu Forest within the Udzungwa Mountains National Park. Most of the photos were taken between the hours of 7 p.m. and 6 a.m., indicating that the animal is largely nocturnal.

"These mongooses may represent a separate subspecies from the one that exists in Kenya," said Dr. De Luca of WCS' Tanzania Program. "Given the fragmentation and small sizes of the forest patches in which they live, full protection of nearby forests would improve conditions for conserving this species."

Continued at "Africa's least-known carnivore in Tanzania"

Also reported (with images) by the Environmental News Service

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Based on the paper:

First records in Tanzania of the Vulnerable Jackson's mongoose Bdeogale jacksoni (Herpestidae)

Abstract

New records in Tanzania of the Vulnerable Jackson's mongoose Bdeogale jacksoni expand its distribution by over 900 km to the south. During two independent camera-trap surveys over 3 years B. jacksoni, one of Africa's most cryptic small carnivores and previously thought to be endemic to Kenya, was recorded in forests of the Udzungwa Mountains. All records were highly localized within Matundu forest, at a maximum of 2.65 km apart. Most of the records (73%) were between 19.00 and 00.00, confirming that the species is primarily nocturnal. Conservation recommendations include further ecological research, genetic analyses, surveys in other Eastern Arc and ground-water dependent forests, and greater protection for Matundu.

Technorati: bronx, zoo, wildlife, conservation, society, wcs, camera, trap, mountains, southern, tanzania, africa, rarest, carnivore, jackson's, mongoose, museum, specimens, findings, journal, oryx, kenya, species, italy, natural, sciences, national, park, nocturnal, forest, research

Permanent Link posted by John Latter @ 10:37 AM 0 comments