Small Things Considered

Talmudic Question #49

by Ian Booth

Do bacteria ever take up intact RNA molecules?

Collateral Damage

by Merry

SEM of the wings (PW) of a related folliculinid,
Eufolliculina. (AZM = adoral zone of membranelles).
Amazingly elaborate for a unicellular organism—
even for a ciliate! Source.

It's not news that coral reefs around the world are in trouble. One obvious symptom of this has been the dramatic increase in coral diseases starting in the 1980s. There is black band and white band, brown band and yellow band, white pox and white plague, galls and bleaching, and…—all adding up to over 30 different "diseases." Likely pathogens have been identified for less than 10, Koch's postulates fulfilled for only a few. Not surprisingly, among the pathogens identified are two vibrios (click here and here) and a pathogenic fungus. There is also a deadly consortium that closely resembles the microbial mats found in sunlit, sulfide-rich aquatic environments. These mats creep across coral colonies, killing the coral by a lethal combination of high local concentrations of sulfide and hypoxia. What is surprising is that a new disease has been found to be the work of a eukaryote, a single-celled ciliate.

These ciliates belong to the heterotrichs, a group that includes the well known Stentor. All are exceptionally large for single-cells; some stretch millimeters in length! They typically have complex mouth structures, more than one type of cilia, and the ability to extend or contract their "body."

Of Terms in Biology: Metabolomics and Metabonomics

by Merry

Schematic of the 'omic hierarchy: genomics,
transcriptomics, proteomics, and metabolomics.
(Yes, the figure leaves out a few others, e.g.,
epigenomics and phenomics.) Source.

What is metabolomics? Oh, that's easy. It's the study of the metabolome. Very good. Now, what is the metabolome?

• the collection of all metabolites in a biological organism, which are the end products of its gene expression. (Source)
• the complete set of small-molecule metabolites (such as metabolic intermediates, hormones and other signalling molecules, and secondary metabolites) to be found within a biological sample, such as a single organism. (Source)

Ergo, metabolomics is the study of the complete collection of metabolites present in a cell or tissue under a particular set of conditions (= the metabolome) generating a biochemical profile. (Source) It's 'omics for the small molecules.

The Secret Under the Ice

by Manuel Sanchez

Translated by permission from his article posted April 17, 2009, on his blog Curiosidades de la Microbiología.

A shot from the 1951 movie The Thing from
Another World. Source.

There is an old science fiction story called Who Goes There that was twice made into a movie. It dealt with a scientific expedition to the North Pole which, under the ice, found an extraterrestrial spaceship carrying alien forms of life. Well, now a real scientific expedition to the Antarctic found a complete ecosystem that was trapped under ice some 1.5 million years ago. The organisms of this ecosystem are of earthly origin, but they may open up the possibility that life exists on other planets.

Of Terms in Biology: Panmictic

New research refutes the hypothesis
that African lions consist of a single,
randomly breeding (panmictic)
population. (Credit: iStockphoto,
Peter Malsbury)

by Elio

A recent encounter with this term prompted a Web search for its precise meaning. Here is a sampling of the definitions we found.

1. A panmictic population is one where all individuals are potential partners. This assumes that there are no mating restrictions, neither genetic or behavioural, upon the population... (LINK)


2. Refers to a population in which mating is completely random (as opposed to assortative mating between certain adults in the population). (LINK)


3. Random mating of individuals within a population, the breeding individuals showing no tendency to choose partners with particular traits. (LINK)


4. Random mating, no sexual selection. (LINK)


5. The state of a population in which each organism has an equal chance to interbreed with every other organism. (LINK)


6. The process in a population by which mates are chosen at random with equal probability regardless of geographical location or genotype. (LINK)

Sample usage of the term in a sentence: Some species (e.g., Salmonella) were found to be clonal at all levels of analysis. At the other extreme, Neisseria gonorrhoeae is panmictic, with random association between loci.

The Bacterium That Doesn't Know How To Tie Its Own Shoelaces

by Elio

A hackberry petiole gall psyllid just after
emerging from the gall on a hackberry. The
leaf is yellow because it is autumn. The
insect is only 3 to 4 mm long. Credit: Nancy
Moran, The University of Arizona. Source.

A greater microbial wonderland there isn't than the one inside cells of insects. Many, perhaps most, insects harbor bacterial endosymbionts that are full of physiological, genomic, and structural surprises. To confirm our predilection for the subject, go to Search on the right of this page and enter “endosymbionts.” Or read recent reviews (click here or here).

In many cases, bacterial endosymbionts are known to provide their host with needed nutrients, in others their role remains unknown. The classic example is Buchnera, the endosymbiont of aphids. Aphids feed on plant sap, which is rich in sugars but poor in needed amino acids. The bacterium provides them, and thus is essential to its host. Matters can get complicated, as when two endosymbionts partner to synthesize tryptophan, one making an early precursor in the biosynthetic pathway, the other taking it the rest of the way. Partnerships of this sort (actually, ménages á trois) seem not to be unusual. This too we discussed earlier. Other bacterial endosymbionts, notably Wolbachia, manipulate the sex life of their insect hosts for their own advantage. Thus, the world of bacterial endosymbionts of insects has turned out to be ever more varied and strange.

Enter Carsonella ruddii, or, if you’re a purist, Candidatus C. ruddii (because it hasn’t been cultivated outside its host—nor is it ever likely to be).

Talmudic Question #48

Can you think of an example of an intact protein molecule being taken up by a free-living bacterium?

We jumped the gun and departed from the usual format by sending this question in advance to a few people. This netted us some intriguing thoughts from Jon Beckwith, Winfried Boos, Ian, Booth, and Andrew Wright, plus notes from a few others who told us they couldn't come up with much. Now it's your turn. Please don’t be deterred from adding your ideas and comments.

Here’s what we have so far:

The View From Hereby ShmuelRazin

Constructing a Synthetic Mycoplasma

I would like to raise an exciting issue that has become very hot recently and has been of great interest to me for a long time: the possibility of synthesizing a living cell from its components. My story starts in 1964. I spent then my first sabbatical with Prof. Harold Morowitz at Yale University. Let me first remind you that these were the early sixties, times of revolutionary ideas. It was the time of planning the trip to the moon. We had entertained the idea, promoted by Morowitz, to synthesize a living cell from its components and turn this project into an American National Goal instead of going to the moon. We started by reconstituting the mycoplasma membrane from its solubilized components. Despite early promising results and a rather provocative paper we published in the Proceedings of the National Academy of Sciences on mycoplasma membrane reconstitution, we failed to progress in this direction. Clearly, we were much ahead of the times.