Small Things Considered

Sex (Well, Not Really) and the Single Organelle

A schematic dividing C. merolae contains
a nucleus, a V-shaped mitochondrion, a
dumbbell-shaped plastid, a microbody and
a Golgi apparatus. Source

We recently posted a piece on organellar division and─for some mitochondria─fusion. We emphasized that in the cells of many organisms (which contain more than single organelles) the mitochondria lack permanent identity. Rather, mitochondria fuse with one another and later divide. During division, they get pinched off by the action of special "strangling proteins," the dynamins. Having a large copy number, there may be no need for a special mechanism to ensure precise segregation during cell division.

But how about organisms that have but a single mitochondrion or chloroplast?

Retrospective September, 2007

Previous posts to this blog may be hard to find. We present here a lightly annotated list of our "mini-essays." You can also find them under "Categories" in the right-hand column of the Web page. (Some posts are listed in more than one category.)

Our Hundredth Post

The previous post was number 100 in the short life of this blog. We started the blog on December 1, 2006, so we have averaged slightly over 10 posts a month, which seems like a reasonable number. We derive a simple pleasure from such otherwise inconsequential-sounding landmarks.

Talmudic Question #21

Unlike many bacteria, which undergo undergo fancy morphological development (spores, hyphae, prosthecae, etc.), archaea do not. Why do you suppose this is?

Il Duomo di Milano

Daylight façade.
Source: discountmilano.com

Grime on old buildings is a microbiological concern─not because microbes cause it, but because they can help get rid of it. The gray pall shrouding old buildings comes from the conversion of chalky stone such as marble (calcium carbonate) to gypsum (calcium sulfate), a result of atmospheric pollution. Not only is gypsum more soluble (which facilitates deterioration), but smog and mineral particles stick to it, which gives venerable old buildings a mournful cast. The conventional way to clean such facades is to douse them with an ammonium carbonate-EDTA-surfactant mixture. Now there is a better way.

Microbial Endocrinology: An Update

No sooner had we posted a piece on the emerging field of Microbial Endocrinology than a pertinent and interesting paper appeared. The authors report that E. coli O157:H7 is attracted to the hormones epinephrine and norepinephine and is repelled by the bacterial metabolite, indole. Whereas the hormones enhance bacterial motility, biofilm formation, and adherence to epithelial cells, indole instead attenuates these responses. The authors present a model (Figure 5 in the paper) suggesting that colonization by the pathogenic strain is inhibited by indole-producing commensals.

A hypothetical model for E. coli O157:H7 colonization in the GI tract. For details, see the legend in the article. The authors proposed that colonization occurs only in regions where non-E. coli commensal bacteria are present.

Figure Source: Tarun Bansal et al. (2007) Differential Effects of Epinephrine, Norepinephrine, and Indole on Escherichia Coli O157:H7 Chemotaxis, Colonization, and Gene Expression. Infection and Immunity 75 (no. 9): 4597-4607

Microbes at Sea

Deep-Sea News is featuring a Microbial Week, September 9-15, 2007, during which time they will be posting articles highlighting the many roles of microbes in the deep sea. An interesting excursion.

Hermit crab from a cold seep site sampled during seeps voyage on RV Tangaroa. Note the seep-associated bacterial filaments on its claws (furry-looking covering). Deep Sea News: February 23, 2007. Image courtesy of NOAA/NIWA.

A Tale of Three Yeasts

by Merry

Yeast colonies on grapes.

This is a story of three species of yeast, three closely related Saccharomyces. For each of them, the entire genome sequence is known. So closely related are they that more than 99.95% of their genes are conserved. In other taxa, they would be considered the same species. Nonetheless, they all occupy slightly different ecological niches. S. cerevisiae, man's partner in brewing for more than 5 millennia, is typically found on fruit such as grapes and figs. S. bayanus, a cryophilic species which can grow at temperatures as low as 4° C., has played a role in cider and wine fermentation. S. mikatae, a relative newcomer, is found in nutrient-poor habitats such as soil and decaying leaves.

Recent Blog Items We've Enjoyed

At Breitbart.com, you'll find a photo of a 20 Kg mushroom from the Mexican state of Chiapas. It actually looks like a mushroom, only bigger.

Evilutionary Biologist has a lively discussion regarding experiments, new and old, that ask if bacteria get old as they multiply (with a comment by Elio). The question itself is tantalizing because cells that divide by binary fission are generally thought to be "immortal."

At Sandwalk, you'll find a witty and insightful video by Robert Ince on the Top Five Dead Scientists.

A second installment of news about the evolutionary meaning of circadian rhythms in cyanobacteria is at A Blog Around the Clock. (For the first installment, posted on our blog, click here.)

One of our favorite fungal blogs, Kathie Hodge's Cornell Mushroom Blog, carries interesting time-lapse movies. A recent one is on "Supermarket Mycology. Flyspeck disease of apples."

In Catalogue of Organisms, Christopher Taylor has an informative piece on mycolic acids of the Corynobacterinaea, which include the diphtheria bacillus, tubercle bacilli,
Nocardia, and others.

Not a blog, but the New York Times has a site for microbiological news. And of course, MicrobeWorld News (links in the right-hand column) is a steady source of this kind of news.

Some of our favorite blogs of microbiological interest are listed on the left.

From Free-Living Bacterium to Cellular Citizen

But in the end I hope you only turn out better than me
I hope you know I love you young'n, like Father, like Son

"Like Father, Like Son"
Birdman and Little Wayne

A nice mitochondrion. Credit:
Terry Frey, San Diego State University

Given the heritage of cell organelles, microbiologists may well be entitled to a familial concern for how their "bacteria" are faring now. Witness a lapel button we saw at an ASM meeting that said "Free the Organelles." (Click here for how to get one.) Mitochondria, chloroplasts, and others have drifted considerably away from their ancestors, and therein lie some great tales.