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For the purposes of this article, we’ll focus on the fundamental difference between two major types of life-forms: those that have a cell wall but few or no internal subdivisions, and those that possess cells containing a nucleus, mitochondria, chloroplasts and other smaller substructures, or organelles.

Even before quorum sensing was discovered in V. fischeri, scientists had noted many examples of coordinated action, such as “swarming,” in which a colony of bacteria moves as a unit across a surface, and the development of “fruiting bodies,” in which bacteria glom together to form inert spores as a means of surviving severe environmental conditions.

Bacteria can live solitary lives, of course, but they prefer to aggregate in biofilms, also known as “slime cities.” Biofilms usually form on a surface, whether it’s the inner lining of the intestines or inside water pipes or on your teeth. In these close-knit colonies, bacteria coordinate group production of a slimy translucent coating and fibers called “curli” and “pili” that attach the colony to something else. Biofilms can harbor multiple types of bacteria as well as fungi and protists (microscopic eukaryotes). A complex vascular system for transporting nutrients and chemical signals through a biofilm may also develop. As Tim Friend described in his book The Third Domain, explorers diving to the wreck of the Titanic found these features in “rusticles” — draped colonies of microbes — feeding on the iron in the Titanic‘s hull and skeleton, more than 2 miles under the surface.

in practice, the medical notion of friendly microbes has yet to extend much past the idea that eating yogurt is good for you. For most doctors and medical microbiologists, microbes are enemies in a permanent war. Medicine certainly has good reason to view microbes as dangerous, since the germ theory of disease and the subsequent development of antibiotics are two of medical science’s greatest accomplishments.

When threatened, bacteria become defensive, often producing toxins that make the host even sicker. They also tend to speed up their acquisition of and purging of genes when under external selection pressure, of which antibiotics are an obvious and powerful example.

Gut bacteria play a role in obesity, which affects about a third of American adults.

Research in animals supports the idea that gut bacteria play a role in weight regulation.

bacteria produce some of the same types of neurotransmitters that regulate the function of the human brain.

it’s been known for a while that sick people get depressed and anxious. This seems so obvious as to be a no-brainer, but research suggests that some of the fear and fatigue associated with infections stems from immune responses affecting the brain.

As it turns out, however, very few bacteria can be grown in the relatively austere conditions of laboratories. In fact, only about 0.1 percent of all bacteria are currently culturable. Many bacteria don’t do well in monoculture, preferring to live in mixed communities of microorganisms. Those living in extreme temperatures and pressures require very specialized equipment to grow in a typical lab.

In fact, they wrote, the genes that enable these processes today “may have been distributed across a common global gene pool, before cellular differentiation and vertical genetic transmission evolved as we know it today.”

The grand story of human exceptionalism — the idea that humans are separate from and superior to everything else in the biosphere — has taken a terminal blow from the new knowledge about bacteria. Whether humanity decides to sanctify them in some way or merely admire them and learn what they’re really doing, there’s no going back.

Scientists know that certain bits of DNA on the end of chromosomes called “telomeres” shorten each time the cell divides, playing a role in cell aging and eventual cell death

New research has uncovered how stress levels and diet can affect the biological age of an organism as opposed to chronological age, or calendar years.

For years scientists thought that sequencing DNA would uncover the “gene-for” almost everything, unraveling the mysteries of disease and resulting in new drugs and gene-specific treatments. It didn’t exactly pan out that way.

So to uncover the calculus within the genome, it might take some looking beyond the genome. Genes may contribute a few elements to the inner clock, but they interact within a larger scaffolding of cell processes and environmental factors.

fat cells generally do not generate after puberty -- as your body stores more fat, the number of fat cells remains the same. Each fat cell simply gets bigger!

The alternative has been a shift to a balance-of-power strategy in which the United States relies on the natural schisms that exist in every region to block the emergence of regional hegemons and contain unrest and groups that could threaten U.S. interests.

The new strategy can be seen in Syria, where rather than directly intervening the United States has stood back and allowed the warring factions to expend their energy on each other, preventing either side from diverting resources to activities that might challenge U.S. interests.

On one side, there are those who consciously support the Syria model for the United States as not necessarily the best moral option but the only practical option there is.

On the other, there are those who argue on behalf of moral interventions, as we saw in Libya, and removing tyrants as an end in itself.

for all the rhetoric, the United States is by default falling into a balance-of-power model.

Russia emerged as a problem for the United States after the Orange Revolution in 2004, when the United States, supporting anti-Russian factions in Ukraine, succeeded in crafting a relatively pro-Western, anti-Russian government.

The Russian response was to use its own covert capabilities, in conjunction with economic pressure from natural gas cutoffs, to undermine Ukraine's government and to use its war with Georgia as a striking reminder of the resurrection of Russian military capabilities.

Washington had two options. One was to allow the balance of power to assert itself, in this case relying on the Europeans to contain the Russians. The other was to continue to follow the balance of power model but at a notch higher than pure passivity.

The next step was the lowest possible level of involvement to contain the Russians and counter their moves in the Middle East.

Russia is not a global power, and its military has many weaknesses, but it is by far the strongest in the region and is able to project power in the former Soviet periphery

The only correlation of forces that matters is what exists at a given point in time in a given place. In that sense, the closer U.S. forces get to the Russian homeland, the greater the advantage the Russians have.

Instead, the United States did the same thing that it did prior to the Orange Revolution: back the type of intervention that both the human rights advocates and the balance-of-power advocates could support.

it appeared that it was the Germans who were particularly pressing the issue, and that they were the ones virtually controlling one of the leaders of the protests, Vitali Klitschko.

Although Germany's move should not be dismissed, its meaning was not as clear as it seemed. In her cell phone call, Nuland is clearly dismissing the Germans, Klitschko and all their efforts in Ukraine.

This could mean that the strategy was too feeble for American tastes (Berlin cannot, after all, risk too big a confrontation with Moscow). Or it could mean that when the Germans said they were planning to be more assertive, their new boldness was meant to head off U.S. efforts. Looking at this week's events, it is not clear what the Germans meant.

This is a touchy issue for human rights advocates, or should be. Yanukovich is the elected president of Ukraine, winner of an election that is generally agreed to have been honest (even though his constitutional amendments and subsequent parliamentary elections may not have been). He was acting within his authority in rejecting the deal with the European Union. If demonstrators can unseat an elected president because they disagree with his actions, they have set a precedent that undermines constitutionalism. Even if he was rough in suppressing the demonstrators, it does not nullify his election.

A pro-Western, even ambiguous, Ukraine poses a profound strategic problem for Russia.

It creates a real strategic challenge for the Russians and forces them on the defensive. Second, it reminds Russia that Washington has capabilities and options that make challenging the United States difficult.

even if the play fails, the United States will have demonstrated that it is back in the game

The mere willingness of the United States to engage will change the expectations of Central Europe, cause tensions between the Central Europeans and the Germans and create an opening for the United States.

Of course, the question is whether and where the Russians will answer the Americans, or even if they will consider the U.S. actions significant at all.

if the United States ups the ante in Central Europe, Russian inroads there will dissolve.

If the Russians are now an American problem, which they are, and if the United States is not going to revert to a direct intervention mode, which it cannot, then this strategy makes sense.

The public interception of Nuland's phone call was not all that embarrassing. It showed the world that the United States, not Germany, is leading the way in Ukraine. And it showed the Russians that the Americans care so little, they will express it on an open cell phone line. Nuland's obscene dismissal of the European Union and treatment of Russia as a problem to deal with confirms a U.S. policy: The United States is not going to war, but passivity is over.

We can go for about six hours in this glucose-burning mode, which is why we tend to get a bit cranky if we have to go without food for longer than that.

Now, whether you like it or not, you will enter into a state of ketosis should you go without food for six hours or more; this represents the first significant metabolic phase shift as you enter into starvation.

Fascinatingly, humans may be the only species who have brains that don't require the ongoing ingestion of glucose to function. Most animals are forced to break down skeletal muscles at a higher rate. The going theory is that, because we humans are so greatly dependent on our intelligence to survive, we have evolved the capacity to stay cognitively sharp while in the midst of prolonged starvation, thus allowing us to search for food.

You have now entered into the regrettable phase called autophagy where your muscle mass starts to waste away. You are literally cannibalizing yourself. Thankfully, our bodies are able to selectively decide which cells will break down and which will not — a process that balances the metabolic needs of the body, along with the critical need to prolong our ability to remain active (and look for food).

Every so often, our intestines find their way through these holes—in the way that noodles sneak out of a sieve—forming an inguinal hernia.

As a consequence, in those moments in which the epiglottis does not have time to cover the trachea, we choke.

If my theory is true, then we can minimize digital distractions by giving our students more to think about and do during class.

The term "digital ink" usually refers to the ability to draw using a digital device, typically with a stylus. If I could pass out stylus-equipped iPads to all my students, that would be great. Since I can't, I have students participate in "digital ink" activities on the cheap.

On a couple of occasions, I've sent my students a link to a Google Doc spreadsheet and asked them to contribute to it during class.

In my cryptography class the other year, I learned how to pipe the contents of a properly formatted Google Doc spreadsheet into an interactive, online timeline.

Crowdsourcing is a nice framework for thinking about the use of mobile devices in the classroom.

Again I asked students to work in groups, this time to identify arguments for or against various points of view in this debate.

I'm a big fan of teaching with clickers. (I did happen to write the book on this topic.) When I teach a course, I ask my students to purchase clickers because I know I'll use them regularly throughout the course.

Many of us simply roll our eyes and click away when yet another medical study contradicts the last study—so what else is new? Coffee’s bad for you, until it’s good for you—and so is red wine. Antioxidants are essential, or they’re useless. And so on. Contradictory studies are an essential part of the science-news stream—and, in fact, an important part of science itself. But that doesn’t make it any less frustrating.

The fact that it didn’t, and that the two studies conflict, has unintentionally revealed a different truth about diet and aging. In both studies, the monkeys that ate less were healthier by a number of measures—and suffered far less from age-related disease. Even better, when taken together, both studies reveal a different path toward living a healthier life—one that doesn’t require self-starvation.

Over the years, various researchers have shown that caloric restriction can extend life in bats, dogs, and even spiders, and on down to nematode worms and single-celled organisms like yeast. After decades of work, it remains the only way known to increase maximum lifespan. So a lot is riding on the concept, scientifically speaking.

In the 1990s, Leonard Guarente of MIT discovered a class of longevity genes in yeast called sirtuins that appear to be activated by a lack of food. Sirtuins appeared to be “conserved” in evolution, meaning that they appear in nearly all species, on up to humans. Sirtuins are thought to have evolved as a way to enable animals to survive periods of famine. They seem to work by regulating certain metabolic pathways and reduce the amount of damage cells endure.

If researchers could somehow identify and isolate that mechanism, they’d be that much closer to some kind of longevity pill. Except for one inconvenient fact: Caloric restriction itself does not always work.

While 80 percent of the monkeys were still alive, the restricted animals had better measures of cardiovascular health, hormone levels, and blood-sugar management, an early indicator of diabetes risk. So it came as a bit of a surprise, eight years later, to find that the hungry monkeys are not actually living longer.

In fact, caloric restriction really seemed to work best in standard laboratory mice. This may be because they are predisposed to eat a lot, gain weight, and reproduce early—and thus are more sensitive to reduced food intake. (Slate’s Daniel Engber has written about how overfed lab mice have distorted scientific research.)

But in a long-awaited, well-funded monkey study like this, an “odd” result could not be ignored. Still stranger was the fact that even though the underfed monkeys were healthier than the others, they still didn’t live longer. They had lower incidence of cardiovascular disease, as well as diabetes and cancer—and when these diseases did appear, they did so later

At first, it seemed like a scientist’s nightmare: The control group is indistinguishable from the test group. In clinical trials, a result like this would kill any drug candidate. Then de Cabo took a closer look at a seemingly minor difference between the Wisconsin and NIA studies: the animals’ diets.

Furthermore, the NIA diet consisted of 4 percent sucrose—while in the Wisconsin diet, sucrose accounted for some 28 percent of the total calories.

“In physics, a calorie is a calorie,” says de Cabo. “In nutrition and animal physiology, there is more and more data coming out that says that the state of the animal is going to depend more on where the calories are coming from.”

In his study based on the two-year experience, Walford reported that the main effect of caloric restriction was to drastically lower his fellow crew members’ cholesterol levels, to 140 and below—well below the average for people in the industrialized world. Walford concluded that a calorie-restricted diet would have the same beneficial effects that he and other scientists had observed in mice.

Several studies have shown that excessive leanness—seen often in calorie-restricting humans—can be as risky as obesity. Taken together, these studies suggest that the optimal body-mass index is about 25, which is on the verge of being overweight.

But if it’s OK to be almost overweight, it might not pay to go beyond that. Another key difference between the two monkey studies has to do with the definition of “ad libitum.” While the Wisconsin control-group monkeys were allowed to stuff themselves, with the equivalent of an all-you-can-eat buffet for several hours at feeding times, the NIA monkeys were given a fixed amount of food. “You could view it as the Wisconsin monkeys were overindulging, like the rest of the American population,” says Rozalyn Anderson, a member of the Wisconsin team. Compared with           their Wisconsin brothers, then, the NIA monkeys in the non-calorie-restricted control group were arguably practicing a mild form of calorie restriction—and that, Anderson suggests, might have made a difference.

While we don't really have 500 billion different ancestors, we can still look at the reverse of that idea: is there a single common ancestor that every person on Earth shares? As we know with Mitochondrial Eve, that answer is a resounding "yes" - but let's now take a look at the Most Recent Common Ancestor, or MRCA. The name says it all, really - this is simply the most recent person who, through any and all genetic lines, can be connected to every single person alive today.

American policy became ready, fire, aim.

In looking back at the past nine years, two conclusions can be drawn: There were no more large-scale attacks on the United States by militant Islamists, and the United States was left with the legacy of responses that took place in the first two years after 9/11.

Even in hindsight, aligning U.S. actions with the apparent outcome is difficult and controversial. But still we know two things: It has been nine years since Sept. 11, 2001, and the war goes on.

an act of terrorism was allowed to redefine U.S. grand strategy.

the United States proceeded with a strategy whose goal, like that of the United Kingdom, was to nip potential regional hegemons in the bud. The U.S. war with Iraq in 1990-91 and the war with Serbia/Yugoslavia in 1999 were examples of this strategy.

The most significant effect of 9/11 was that it knocked the United States off its strategy. Rather than adapting its standing global strategy to better address the counterterrorism issue, the United States became obsessed with a single region, the area between the Mediterranean and the Hindu Kush.

as a long-term U.S. strategy — the long war that the U.S. Department of Defense is preparing for — it leaves the rest of the world uncovered.

The single most important result of 9/11 was that it shifted the United States from a global stance to a regional one, allowing other powers to take advantage of this focus to create significant potential challenges to the United States.

The issue there is not whether the United States can or can’t win, however that is defined. The issue is whether it is worth the effort considering what is going on in the rest of the world.

And let me just -- let me end with one story. This illustrates how brilliant the Chinese geopolitical behavior can be. You know, in my previous book, I tell this story. You know, after -- as you know, after United States invaded Iraq, in March 2003, you discovered you had a problem because there was no Security Council resolution -- (inaudible) -- invasion. Technically, the American/British occupation of Iraq was therefore illegal under international law. And the previous Security Council sanctions were still in place for America to not export Iraqi oil.

it takes much more subtle forms, and we’re all guilty of it from time to time.

the enjoyment of a good conversation is becoming more of a rarity these days. In our time of cell phones, text messaging, and emails, we’re having less face-to-face interactions, and thus when we do meet up with people in the flesh, our social skills can be a bit rusty.

A good conversation is an interesting thing; it can’t be a solely individual endeavor—it has to be a group effort.

During a conversation, each person makes initiatives. These initiatives can either be attention-giving or attention-getting. Conversational narcissists concentrate more on the latter because they are focused on gratifying their own needs. Attention-getting initiatives can take two forms: active and passive.

The shift-response if often very subtle. People put in a nice transition to disguise it by prefacing their response with something like, “That’s interesting,” “Really? “I can see that,” right before they make a comment about themselves.

it’s fine to share things about yourself, as long as you loop the conversation back to the person who initiated the topic.

Background acknowledgments

Supportive assertions

Supportive questions

Once someone introduces a topic, your job is to draw out the narrative from them by giving them encouragement in the form of background acknowledgments and supportive assertions, and moving their narrative along by asking supportive questions.