Tag Archives: Cell Biology

The Serengeti Rules: The Quest to Discover How Life Works and Why It Matters (Book Review)

Sean B. Carroll is coming out with a new book called The Serengeti Rules: The Quest to Discover How Life Works and Why It Matters.

This is the molecular biologist Sean Carroll, as distinct from the physicist (who wrote this).

Homeostasis is one of the basic principles of biology. The term can be applied broadly to mean that certain numbers are maintained within a certain range. This could refer to energy flowing through a system, numbers of specific cellular products like enzymes, numbers of individual organisms in an ecological system, etc. It is not so much that numbers don’t change. Change in numbers is often central to a physiological process. But the change is either demanded by a system of regulating numbers, or is a perturbation in a system that is responded to by regulation. Regulation is one of those key concepts that can be applied across pretty much all systems, and provides a powerful point of view from which to understand what is happening in any living system.

Carroll is a molecular biologist, so much of his training and work is about regulation: identifying it, characterizing it, figuring it out. What Carroll has done in this book is to apply this point of view broadly to biological systems, looking at things inside cells and things inside major ecosystems. The title of the book comes from his own experience visiting the Serengeti as a safari-going tourist, in combination with the fact that this particular ecosystem is one of the best studied in the world. Many different scientists studying everything from grass to microbes to lions to antelopes have spent countless hours observing, characterizing, and trying to explain the dynamics of the Serengeti. As Carroll points out, this is true of a number of different ecosystems, and he could well have named his book, “The Lake Erie Rules,” but that would not have been as cool of a name.

So Carroll has done, then, something that is very dangerous and often does not go well. He’s taken insight derived from his expertise in small scale, mostly sub-cellular, biological systems, and using the touchstone of regulation, applied this insight to help observe, describe, and understand biological systems generally, with a strong focus on ecology. When a scientist steps out of their normal realm to do such a thing, we often get something better ignored, because, in fact, it is not easy or, in some cases, appropriate to make this leap. In this case, however, it worked beautifully. Carroll’s book is fantastic, a success story in going form the specific to the general.

It helps that Carroll is a gifted writer, captivating and thoughtful, and highly respectful of the reader.

Carroll brings in the history of thought and research in the relevant areas of physiology, ecology etc. His messages are framed in the larger context of the Earth’s overall health and important environmental issues. He links the subject matter to key central themes in biological theory (such as natural selection and evolution). And this is all done very well.

You’ve seen the synthetic overviews of life and evolution framed in chaos theory, complexity theory, even quantum physics. This is better.

This is a book to give to your favorite biology teacher (high school or college), and that teacher will take from it examples, connections, lessons, ways of telling, that will enrich their teaching immeasurably.

I don’t think the book is available yet, but you can pre-order it.

Insect Wings Can Shred Bacteria To Pieces

The “clanger cicada” can physically kill bacteria by poking and shredding them with tiny pointy structures that seem to look a little like an old fashioned cheese grater. Keep in mind that this happens at a very small spacial scale, so the relationship between objects is different than in normal human experience. Essentially, the membrane of a bacterium spreads itself over the pointy nano-spikes of the insect wing. This is a little like a failed “laying on the bed of nails” attempt, but where the force involved with the bed of nails is gravity, gravity has nothing to do with the bacterium interacting with the nano spikes. Also, the bacterium does not shred because the nano spikes pierce it. Rather, the bacterial membrane is stretched to breaking point and falls apart that way. From the write-up in Nature News:

The clanger cicada (Psaltoda claripennis) is a locust-like insect whose wings are covered by a vast hexagonal array of ‘nanopillars’ β€” blunted spikes on a similar size scale to bacteria (see video, bottom). When a bacterium settles on the wing surface, its cellular membrane sticks to the surface of the nanopillars and stretches into the crevices between them, where it experiences the most strain. If the membrane is soft enough, it ruptures…

Here’s the model:

Not all bacteria are subject to this effect; it depends on the rigidity of the cell membrane.

Obviously, we want to make all doorknobs and toilet seats out of this stuff.

Pogodin, Et Al. 2013. Biophysical Model of Bacterial Cell Interactions with Nanopatterned Cicada Wing Surfaces. Biophysical Journal 104(4):835-840. The article was published on Feb. 19th in Biophysical Journal. Abstract:

The nanopattern on the surface of Clanger cicada (Psaltoda claripennis) wings represents the first example of a new class of biomaterials that can kill bacteria on contact based solely on their physical surface structure. The wings provide a model for the development of novel functional surfaces that possess an increased resistance to bacterial contamination and infection. We propose a biophysical model of the interactions between bacterial cells and cicada wing surface structures, and show that mechanical properties, in particular cell rigidity, are key factors in determining bacterial resistance/sensitivity to the bactericidal nature of the wing surface. We confirmed this experimentally by decreasing the rigidity of surface-resistant strains through microwave irradiation of the cells, which renders them susceptible to the wing effects. Our findings demonstrate the potential benefits of incorporating cicada wing nanopatterns into the design of antibacterial nanomaterials.

Primary Cilia Connect

Here is a press release from BioMed Central that is just so interesting I had to give it to you as it is without delay:

Connecting cilia: cellular antennae help cells stick together

Primary cilia are hair-like structures which protrude from almost all mammalian cells. They are thought to be sensory and involved in sampling the cell’s environment. New research, published in BioMed Central’s open access journal Cilia, launched today, shows that cilia on cells in the retina and liver are able to make stable connections with each other – indicating that cilia not only are able to sense their environment but are also involved in cell communication.

Primary cilia are structurally and functionally very similar to eukaryotic flagella (motile tails used to propel microorganisms). For many decades it was thought that cilia on human cells were primarily for movement, for example, cilia on respiratory cells drive mucous up and out of the airways by beating together, however it is now believed that they are also ‘cellular antennae’ – important for cell to cell communication.

In order to find out how these cilia could physically communicate Carolyn Ott and Jennifer Lippincott-Schwartz, from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, examined primary cilia from the retina, bile duct and in cultured cells. In all cases, cilia between nearby cells formed long-lasting contacts with each other, something that has never been observed before. The adhesions between cilia lasted hours or days and were dependent on interactions between glycoproteins (proteins with a sugar molecule attached).

Jennifer Lippincott-Schwartz explained, “A number of human genetic diseases, including Bardet-Biedl syndrome, nephronophthisis, Joubert, and Meckel-Gruber syndrome, are due to defects in ciliary trafficking and signaling. Our study suggests that cilia are active transmitters and seek out neighboring cells to communicate with. These newly discovered cilia-cilia contacts may be disrupted in ciliopathies, an intriguing possibility that requires further investigation.”

The findings are published in Cilia, a new Open Access journal from BioMed Central. Cilia is a peer-reviewed journal that publishes high quality basic and translational research on the biology of cilia and diseases associated with ciliary dysfunction. Research approaches include cell and developmental biology, use of model organisms, and human and molecular genetics.

Reference: Primary cilia utilize glycoprotein-dependent adhesion mechanisms to stabilize long-lasting cilia-cilia contacts. Carolyn M Ott, Natalie Elia, Suh Young Jeong, Christine Insinna, Prabuddha Sengupta and Jennifer Lippincott-Schwartz. Cilia (in press)

Apparently, cells have been created from … Science!

Scientists are reporting that they have made a living cell from DNA that was originally synthesized in a lab. This isn’t quite a synthetic organism. But the result is an important, and some would say troubling step on the road to creating life in the lab.

Craig Venter is the scientist behind the effort. Many scientists have strong opinions about Venter, but even his detractors will admit he’s a man who thinks big.

details here

Diatoms Large and Small

ResearchBlogging.orgDiatoms are algae with hard parts. They make up a major part of the plankton found in fresh and salt water environments. Usually, diatoms exist as single celled free floating organisms, but they can also be colonies of several single cells. Their tiny little ‘shells’ are made up of silica (these shells are called “fustules”).
Continue reading Diatoms Large and Small

How brains work, how brain imaging works: Astrocytes

ResearchBlogging.orgBlood flow in the brain is linked to neuronal activity. Therefore, various ‘brain scanning’ techniques can be used to observe neuronal activity in the brain. This has led to an astonishing revolution in knowledge of how the brain works. Of course, you knew that already.Also astonishing is that the reason for changes in blood flow in relation to what neurons are doing is unknown! We know this system works, but we don’t know why!Until now… Continue reading How brains work, how brain imaging works: Astrocytes

New Research on How Visual Memory Works

i-eb1c570ee1369fa42b7a582ef19ee402-lily.jpgLife is complex. The way a living system works can be described in a series of increasingly refined models, each fleshing out details of the previous model. Typically, description at one level raises questions about what is happening at the finer level. These questions induce hypotheses which drive experimental work which produces ever more detailed knowledge.A paper about memory, just published, is an example of one incremental step in this process. In short, this research works out some of the fine detail at the molecular level for the process of forming visual memories. Continue reading New Research on How Visual Memory Works

What’s in the air?

i-fc0baa42c324cefa8495fdb0044234b2-dice.jpgGood question … what IS in the air?The simple answer is that the air … the Earth’s atmosphere … is about 78% nitrogen, 21% oxygen, with a tiny amount of some other gases including water vapor. Then, there’s dirt. I want to talk a little about the oxygen, one of the other gases (carbon dioxide to be exact), the water vapor, and the dirt. Continue reading What’s in the air?