Small Things Considered

Gleanings

It gives us pleasure to host the translation of an article by Miguel Vicente that appeared in the Spanish blog, Esos Pequeños Bichitos.

Genome Synthesized by Scientists. So What?

by Miguel Vicente

It's in the news! The genome of Mycoplasma genitalium has been synthesized! Once again, Craig Venter’s group makes headlines. The excitement reminds me of a similar occasion—the day almost eleven years ago when the existence of Dolly, the first cloned sheep, was made public. Results like this trigger a variety of responses, especially in the realm of public opinion.

Artificial or synthetic? First, we should attempt to define the true nature of the reported accomplishment.

Pathogen On Board (River Blindness)

Row of blind men led by children. Source: BBC

River blindness is a dreadful disease—the leading cause of blindness in tropical areas of the world. Its effects devastate the lives of entire villages. It has long been associated with infection by the filarial nematode, Onchocerca volvulus. The scarring of the cornea that leads to blindness was assumed to be caused by the inflammatory response to the worms. But the story turned out to be more intricate.

Talmudic Question # 27

Do all genes have some homology with others? If all are derived from the genome of LUCA (Last Universal Common Ancestor), the answer is easy. But, to start an argument, what if there were extraneously made pieces of genetic material lying around waiting to be picked up by LUCA's descendents? (Courtesy of Enrique Merino and Ana Gutierrez)

Seeing Double Is Believing

AFM image of E. coli. © Arizona State
University Ask a Biologist and Dee Hartung

If you've ever longed to take a high resolution look at a bacterium in a biofilm under physiological conditions and to identify the cells at the same time, here is your chance. Technically-skilled researchers at the universities of Duisburg and Mannheim in Germany have successfully married two techniques, atomic force microscopy (AFM) and fluorescence microscopy (FM), so that the same cells can be examined sequentially by both methods.

Subtle Bacillus subtilis

When Bacillus subtilis sporulates, the cell destined to make a spore divides asymmetrically; one cell, the “forespore,” becomes the spore; the other, a short-lived sacrificial “mother cell.” You’d expect that a nucleoid would be partitioned between these two compartments before they even think of dividing. Not so. Cell division and chromosome segregation get out of sync and the septum between the two cells narrows before the DNA is completely transferred into the future spore. Never mind why this is so—the reasons are elusive. Regardless, about 2/3 of the DNA destined for the spore has to traverse a narrow pore in the forespore septum. A protein called SpoIIIE (names like this one mean something to sporulation mavens) is deeply involved and acts as a DNA translocase.

Prochlorococci to the Head of the Class

by Merry

P. marinus SS120. Note the
characteristic concentric
photosynthetic lamellae.
Credit: Genoscope

Since their discovery in 1988, cyanobacteria of the genus Prochlorococcus have been making up for lost time, going from unknown organism to favored research subject. They are the smallest photosynthetic organisms known (0.5 - 0.8 micron in diameter), yet they represent 40% to 50% of the phytoplankton biomass in nutrient-poor (oligotrophic) regions of the oceans between latitudes 40° N and 40° S. They outnumber all the others, with more than 100,000 cells in a single milliliter. You can find them in the bright surface waters as well as 200 m down, where the light is one thousand times weaker. Within that range, they cope with varying temperature, pH, nutrient availability, and predators. One wonders how they fit all the necessary tools into their small genomic toolbox. Just how small is it? From 1.6 Mbp to 2.7 Mbp. That variation is a clue that prompts us to take a closer look at their genomes.

Lost City Ramblings

Who hath desired the Sea? -- the immense and contemptuous surges?
                  Rudyard Kipling

Lost City Locator Map. Credit: Univ of Washington

While exploring the Mid-Atlantic Ridge in 2000, a research submarine traveled 15 km west towards the dome-like Atlantis Massif. Here its crew encountered tall underwater structures that resembled glistening white cathedral spires. The area was dubbed the Lost City hydrothermal field. Some of the towers were 30 to 60 meters tall—taller than any of the celebrated black smokers—with as many as 30 of them in a single cluster. One of the people involved in their discovery, Jeff Karson commented: If this vent field was on land, it would be a national park. Considering the location, an international park would be more likely.

Talmudic Question #26

Given that hardly anything in biology is more central yet more elusive than the concept of species, can you conceive of a way to portray evolutionary history that is not based on the species concept?

¡Atención Hispanoparlantes!

Por primera vez, un articulo de este blog ha sido traducido al castellano (un idioma que Elio maneja). Vease http://weblogs.madrimasd.org/microbiologia/archive/2007/12/23/81281.aspx. Tomen la oportunidad de visitar este blog madrileño, que es de primera clase.

Varios de Uds. abrán notado que este blog otorga la opción de traducir un entero documento a varios idiomas. Como la traducción es hecha “a maquina”, el resultado es frecuentemente chistoso.

For our non-Spanish speakers:

Attention Spanish Speakers. For the first time, an article from this blog has been translated for posting on a Spanish microbiology blog. See http://weblogs.madrimasd.org/microbiologia/archive/2007/12/23/81281.aspx. This is a first class blog that comes to us from Madrid.

Some of you will have noticed the TRANSLATION button on our blog which quickly translates the entire document into any of several languages. Being that this is done by machine, the result can be hilarious.

Protein Origami

by Merry

E. coli expressing the functional
amyloid fiber, curli. Credit: Matthew
Chapman, Univ of Michigan

Prions are proteins of ill repute, as they keep company with "mad cow disease," Alzheimer's, and other neurodegenerative maladies. But prions are not foreign pathogens; they are alternative states of normal cellular proteins. Proteins behaving as prions typically assume a characteristic ß-sheet secondary structure and aggregate to form exceptionally stable fibers called amyloids. Small amyloid aggregates can act as "seeds." They recruit more protein molecules to join the growing fiber, a successful strategy that gets around the energy barrier that impedes de novo aggregate formation.

Biological systems appear to have avoided making amyloids, perhaps because they can easily get out of hand. Nonetheless, you might be thinking that likely there is an organism that uses amyloid fibers to good advantage.