Single-celled Gossip

 

Bacterial biofilm in a hot spring in Northern Nevada

For a long time, microbiologists thought that bacteria cells acted as individual entities and did not communicate with one another. We now understand that nearly all cells communicate- whether its the stomach cells within our own body or the mass of cells within the hot spring biofilm above. 

Biofilms are dense aggregates of billions of cells that stick together to form a mass that we can actually see with our own eyes. One of the most interesting features of biofilms is that they are generally composed of a variety of different kinds of bacteria, working together as a community. In much the way our communities differentiate labor to benefit the whole (garbage collection, food production and trasnport, etc.), these aggregates of bacteria form fluid channels for transport of waste and nutrients and rely on communication to perform these tasks. 

Instead of using verbal communication, bacteria cells talk to each other using signaling molecules that are released into the environment. Different bactieral species use different signaling molecules to communicate. Within biofilms, interspecies (between two different species) communication can be very important. Communication allows indivudal bacteria cells to regulate gene expression by sensing cell density, the presence of "intruders" and the availability of nutrients. 

 

Once again nature proves it... truth is stranger than fiction.

Magnetotactic bacteria are oddities with organelles that contain magnetic minerals that allow them to orient themselves along the magnetic field of the earth.

Here at University of Nevada Las Vegas, Dr. Bazylinski is working to learn more about how... and why... these bugs precipitate magnetic material. Scientists believe this magnetic capability helps orient bacteria towards a region called the oxic-anoxic transition zone (a region within water between an area of high and low oxygen concentration). This is believed to be an optimal place for them to find food. But what?!?! Of all the things that microbes can do, I think this is one of the strangest (and coolest).

Watching magnetotactic bacteria gravitate towards a magnet through a microscope is one of the most amazing things... here is a video from Chris of Dr. Bazylinski's lab that shows cells gravitating, in culture, towards/away from a magnet. And is there anything cuter than a miniature magnet?

I'm lichen it.

Welcome to Nevada! It’s hot and dry.

This gorgeous lichen found a nice home just a few feet from an 80 degree C (175 degrees F) hot spring. Lichen is yet another example of cooperation – because fungi can’t photosynthesize, which is a neat trick in a sunny place, they partner with cyanobacteria (a bacteria that can produce energy via photosynthesis) or algae. In turn, algae or cyanobacteria get wrapped up in fungal threads, providing protection that allows them to grow in some extreme (deserts, bare rock) environments. A big fungus blanket.... cozy!

Lucky shot.

Rattler snacking on a deer mouse in Eastern Washington.... she rattled the whole time, and it took about 20 minutes for her to fit that fat little mouse into her mouth. WOW.

PHOTO: Andrius Pasukonis

Cooperation

Cooperation is EVERYWHERE (see below for cooperation between aphids and ants). Scientists think cooperation occurs for two different reasons: (1) Reciprocity: I give you something you need, and you give me something I need (i.e. aphids need protection from predators, ants need carbon-rich honeydew). (2) Kin selection: we’re closely related, so I’ll help you out even though it might hurt me (i.e. ant colonies are dubbed “the super organism” by E.O. Wilson because an ant colony functions as a cooperative unit).

Wenying Shou at the Fred Hutchison Cancer Research center is also interested in cooperation– cooperative systems are difficult to study, so Shou created her own using yeast cells. Unlike some cooperative systems, Shou’s system is obligatory– meaning, the cells have to cooperate or they will die. In her system, each cell (pictured above) is unable to generate a compound necessary for its survival (let’s call these compounds yellow and red) while each cell also over-produces the compound that its neighbor cell needs– in other words, the yellow cell over-produces yellow but cannot produce red. These cells cannot survive alone, they must be close enough to each other to exchange these essential nutrients.

In order to cooperate, each cell pays a cost- it takes energy to over-produce the compound that the other cell requires. This is analogous to each citizen’s “obligatory” participation in the government– we pay taxes, and (ideally) enjoy the common resources these taxes provide (i.e. parks, schools, police).

Not everyone wants to cooperate, however. When a cell, or person, continues to take the common resource but stops contributing to the system (halts excess compound production or evades taxes) we call them “cheaters”. And cooperation begets cheaters. That’s why we’ve developed the IRS, an entire division of the government that stops cheaters via “policing”. Now Shou’s lab asks– what “policing” methods do cells use to combat cheating?

Cancer cells are ultimate cheaters. Imagine the lung cells in your body as cooperators– working together to deliver oxygen to your body. Cancerous cells (cells that have a mutation causing continued, uncontrollable replication) arise in our body every day but our body has “policing” mechanisms to destroy these mutant cells. By studying cooperation and cheaters, we can learn more about how our body polices cheater cells and why these policing strategies sometimes fail.

Shou WY, Ram S, Villar JMG (2007): Synthetic cooperation in engineered yeast populations. PNAS 104: 1877-1882.

Dancing birds

Patel, Iverson, Bregman, Schulz (2009) - Current Biology

Although youtube may claim otherwise (this study was actually inspired by a youtube video), scientists had not documented dancing in non-human species.... until now. In a recent study, the sulphur-breasted cockatoo (named Snowball, pictured above) was shown to "spontaneously adjust (to) the tempo of its rhythmic movements to stay synchronized with the beat ". The beat of The Backstreet Boys.

Which confirms what I've suspected all along- birds have poor taste in music.

Where are all the women science professors? .

Percentage of Women Doctoral Scientists and Engineers in

Academic Institutions by Field and Rank in 2003

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	All Science and Engineering			Biology and Life Sciences	Physical Sciences	Engineering	Math and Statistics	Computer Science
Assistant Professor	41			38.4	24.5	16	29.2	23.3
Associate Professor	31.1			29.4	19.2	11.9	15.9	19.9
Full Professor	17.6			19	6.8	3.8	9.2	12.3
Total	29.8			32.1	14.8	10.3	17.1	18.3
Source: Commission on Professionals in Science and Technology, 2007.
Note: The percentages in the “total” category include instructors and lecturers. Although the numbers of women receiving degrees in Engineering, Science and Math have increased substantially, the number of women science professors is still low. Just four years ago, Harvard University president Summers tried to argue why this might be... (1) Women with children can't work 80 hours a week (2) fewer girls than boys have top scores in math and science in high school- and these discrepancies are probably genetic and (3) discrimination within the hiring process cannot possibly play a role because schools that did not discriminate would be able to hire top women within the science field, and we have not witnessed this trend How do we fix this? A good start might be to re-educate individuals like Summers: (1) Women who desire a family don't typically have the same options as men to work 80 hours a week (biological differences like pregnancy and breast feeding are just the beginning) (2) there is no genetic basis for lower math and science test scores in girls, but changes in early education can help alleviate these discrepancies and (3) discrimination exists within academia, making it more difficult for women (and all minorities) to secure higher level positions.

Aphid Tending- the parasitic-mutualistic train

A bizarre mutualism that you have to squint to observe - aphids are tiny insects that suck phloem (sugars that plants use for food) from a plant like sucking water from a coconut with a straw. They can be devastating to crops and gardens because they are such skillful phloem-stealers. Because of their constant sugar intake, aphid poop is carbon-rich and forms as a translucent bubble clinging to their rear (called honeydew). Aphid poop is so attractive to foraging ants that many species have gone the "extra mile" to secure this resource for their own colony.

Out at the Pot Holes in Eastern Washington, Formica sp. ants are especially adapt at aphid tending. Formica have an incredible defensive adaptation- spraying Formic acid at their enemies! They flip onto their back, lift their little butts and take aim at any threat. Formica nit-pick over their aphids like an overprotective mother- cleaning them with their antennae (research has shown this prevents fungal infections), defending them from predators (we tried poking at a cluster of aphids- and were sprayed with gas and bitten!) and, of course, transporting bubbles of honeydew back to the colony. Amazing!