Small Things Considered

Fine Literature: Extracellular Respiration

Occasionally, we mention a review article that we think should be called to your attention. We initiated this with a stirring piece on bacterial shape by Kevin Young; this was followed by tantalizing observations by Steven Projan on genome size and antibiotic resistance. Now we wish to highlight a review  by J. A. Granick and D. K. Newman called Extracellular Respiration.

The title refers to the procurement of energy from extracellular substrates by microbes.

Talmudic Question #18

A good TQ is one that invites another question. We previously asked: Invertebrates are said to have only innate immunity. Why do you suppose they have not evolved acquired immunity, as vertebrates have done?  Let us now turn it around and ask: Why have vertebrates evolved acquired immunity?

Lingua Franca (Lipid Division)

Prostaglandin E2 crystal
Courtesy of Michael Davidson

A long, long time ago, a biochemist friend of mine said to me jokingly (I think): "When I hear the  word lipid, I reach for my gun!" I'm not sure it was all that funny then, but any attempts at disparaging humor must cease now. A month doesn't go by without a report of a new role that lipids play in essential life processes. This is especially true for their activity as communicators between cells in multicellular organisms as well as between parasites and their hosts. Move over, proteins and peptides!

Error Bars

Error bars in histograms remind me of detonators used to set off explosives. I am tempted to ask: "What would happen if you pushed down the plunger?" You see, in the old days people used to show the whole error bar, not just the half sticking out of the top. I'm still getting use to them, but I'm not always sure what they mean. Turns out that I'm not alone. Cummings et al. wrote a paper illustrating the ways (several) in which the same innocent-looking gizmo can be used. They conclude with "eight simple rules to assist with effective use and interpretation of error bars." Have a look.

Fungal Alchemy: Using Radiation as a Source of Energy

The Alchemist in Search of the Philosopher's Stone.
Wright of Derby, 1771.

Accustomed as we are to microbial surprises, we were nonetheless taken aback by a report disclosing that certain fungi grow better when exposed to ionizing radiation. According to a paper from Albert Einstein Medical School, fungi can also use radiation as a source of energy─not exactly one's view of radiation as something malevolent and baneful. Had we paid attention to the news from Chernobyl, we would not have been surprised because the walls of the still hot reactor have become covered with mold. Not only that, but it has been known for some time that fungal species search out radioactive particles, i.e., manifest radiotropism.

The Cain Bugs

Pneumococci (Streptococcus pneumoniae) aren't the most affable of bacteria. They make antimicrobial agents such as bacteriocins and bacteriolysins that are directed not, as is the usual case, against other species, but against their own. This phenomenon, dubbed fratricide...

Dive! Dive! Dive!

By Eddy Mateescu

This urgent call, borrowed from movies about submarine warfare, applies to this non-microbial posting that is intended as an appetizer for the fascinating subject of parasite modification of host behavior. Elio promises to follow up on this subject.

Source: Shaoni Bhattacharya (2005)
Parasites Brainwash Grasshoppers Into
Death Dive. New Scientist 31: August.

In the most general sense, all living organisms must be able to detect specific, essential aspects of their environment and to react appropriately. Therefore, any component involved in the detection-decision process (from the uptake/sensory machinery and its output to the regulation/decision making system) is susceptible to manipulation by a parasite for its own advantage.

An interesting non-microbial example is that of the parasitic Nematomorph worms which brainwash grasshoppers and crickets to leave their forest habitat and take a fatal plunge into water so that the worms can emerge and mate (Movie).

Swimming by the Light of the Sun

by Merry

(c) Andrew Shimabuku & The Honolulu Advertiser

Marine bacteria have been much in the news of late, and rightfully so. There are many of them (an estimated 10²⁹ total), they occupy specific local niches in the seas, and they carry out diverse (and sometimes previously unknown) activities. A case in point: some of them harvest energy from the sun via a system other than regular photosynthesis, one based on rhodopsin and retinal instead of chlorophyll. While it has been known since the 1970s that haloarchaea use a similar light-driven mechanism under oxygen-limiting conditions, this was viewed as a novel capability pertaining only to a few extremophiles. Now, it is estimated that 13% of marine bacteria have this capability, and so does a significant fraction of Archaea. Solar power has gone mainstream. 

Planctomycetes: The Far Out Bugs

by Jennifer Gutierrez, Sabrina Perrino, Kalyn Stern, Mark Thever

I have heard there are troubles of more than one kind.
Some come from ahead and some come from behind.
Dr. Seuss

A thin section of a cryosubstituted P. staleyi
showing hump-like protrusions (arrows) and
a membrane-bound intracellular compartment.
Source: Butler et al. (2002) Intl. J. Syst.
Evol. Microb. 52: 1663.

As first year graduate students in microbiology, we are accustomed to microbial surprises, learning again and again how different and exciting bacteria can be. However, it is fair to say that we were not entirely prepared for the Planctomycetes─ bacteria that divide by budding, have no peptidoglycan, and possess a unique and perplexing body plan.

They are not rare, as they are present in many marine and soil environments, including rivers, ponds and hot springs. Nor are they hard to cultivate. Lacking peptidoglycan cell walls, they can be readily selected on media containing antibiotics that inhibit cell wall synthesis.

Pirelellula staleyi (aka Rhodopirellula baltica) is a typical Planctomycete with two life stages:  attached 'stalked' cells and flagellated swarmer cells.

Laser Pointers Make Me Dizzy

Having a point in every direction is the same as having no point at all.
The Pointed Man in Harry Nilsson's The Point!

More often than not, speakers at lectures use a laser pointer to circle around or "underline" items on a slide they wish to emphasize.