How did you get started in science? Eve always been interested in nature and animals, and in puzzles and mystery books I really like curing things out. As an undergraduate at LLC Davis, I worked in a lab on a bacterial project while taking courses in both biochemistry and genetics. Then, as a graduate student at Johns Hopkins, I learned a lot of biochemistry while studying marine bacteria. The bacteria belong to the genus Brio, and was working on checkmates, movement by cells toward food or away from noxious chemicals in the environment.
What are the advantages of using bacteria for research in cell biology? Bacteria have been the foundation of molecular biology for the last 100 years because they re accessible. They grow fast, they form clones of identical cells, ND they re amenable to biochemical and genetic analyses. Most of what we initially learned about molecular biology about genes and proteins and other bimolecular came from work done on bacteria. Because of evolutionary history, the most basic and ancient life processes that happen in bacteria also happen in humans and other higher organisms.
Humans have more 92 UNIT TWO When I was noshing my graduate work, heard a talk by Mike Silverman, a scientist with the Ground Institute in San Diego, about how bacteria talk to each other, count their own numbers, and coordinate their behavior. Mike had been working on a electrocuting bluestocking) marine bacterium called Brio shier that lives symbiotically inside a variety of marine animals. The animal provides nutrients for the bacteria, which live in an enclosed space within the animal s body. In return, the bacteria provide light that been TTS the animal by scaring away predators or attracting prey or a mate.
But if only a small number of bacteria are present, they do not make light producing light would waste energy because the light would t be visible. The word quorum means the number needed to do something, and bacteria can sense whether there is a quorum or not and CT accordingly. The way quorum sensing works is that bacteria release certain signaling chemicals into the environment. As the bacterial cells increase in number, the molecules reach a concentration at which many of them bind to receptor proteins on the surface of or inside the bacteria.
The signaling molecule TTS together with the receptor like a key in a lock. In the case of the surface receptors, each receptor molecule has a part on the outside Of the cell and a part on the inside. The signaling chemical binds to the outer part of the receptor, tickling the protein so that it makes something happen inside the ell. For instance, in Brio shier, binding of signaling molecules ultimately turns on genes that code for enzymes that make light. Mike had worked out this mechanism of how cells of Brio shier turn on light in synchrony.
It s important to understand that back then, we just din t think about bacteria like that we thought bacteria ignored each other and did their own thing as solitary cells. Was totally fascinated. Thought, He s either crazy or he s brilliant but I just have to work on that. Went up to the podium after his talk and begged him to let me be his postcode. Finally he said yes, even though he was a geneticist and I was a biochemist! He took a chance on me. How does a genetic approach differ from a biochemical one?
Geneticists make lots of mutant organisms, then think up clever strategies to ND the ones with mutations in the genes they re interested in. In the case of quorum sensing in bluestocking bacteria, you look for cells that remain dark. If you have mutated genes involved in quorum sensing, you would expect the bacteria not to make light because light emission depends on the cells communicating with each other. Eventually, you would hope to identify he components that function in normal light-emitting bacteria but not in the mutants.
Biochemists, on the other hand, start by isolating molecules and studying their properties directly. Genetics and biochemistry are complementary approaches. I m glad I know both because the combination is more effective than either approach by itself. What did you learn about quorum sensing as a postcode? In Mike s lab, I worked on another species of bluestocking Brio called Brio Harvey. Because these bacteria are free-living in the ocean, we thought their quorum-sensing molecular circuitry might be more complicated than hat of Brio shier.
What I found was that Brio Harvey has two parallel systems for quorum sensing, one that senses cells of the same species and one that counts bacteria of other species. Fast-forwarding a decade or so, this second system seems to be present in many bacteria, and the second signaling molecule appears to be universal. So, apparently bacteria can measure the ratios of these two signals, and they re saying, How many of us and how many of you are there? Then they do different things, depending on who is in the majority. And this sin t just restricted to fluorescence.
Other bacterial behaviors are also controlled by quorum sensing, such as forming an organized thin layer (called a bio Im) on your teeth or coordinating virulent infection. Tell us more about bio alms. We used to think that most bacteria lived as individual cells suspended in liquid environments. But we now understand that in the wild, they live attached to surfaces in bio alms, and they secrete carbohydrates and other molecules that form a protective slime on the bio Im surface. Most of us have noticed the bio Im coating our teeth every morning.
Believe it or not, there are about 600 bacterial species in that bio Im just trying to make a living, eating nutrients from us, but the side effect is that we get cavities. And when someone has a lung infection or an implant or heart valve that harbors an infection, the bacteria are growing as a bio Im in the lungs or on the introduced device. So we now understand why these infections are so hard to treat: It s because the slime on the bio Im is providing a protective shield that antibiotics can t penetrate.
What questions are you and your lab asking now? My group is interested in how information outside an organism gets inside so that the organism does the right thing at the right time. We work on bacteria because they re simple, but we hope that we will have insights for people working on higher organisms. And we re curious about how collective behaviors rest evolved on Earth. How did multicultural come about? We know that the rest organisms were bacteria, but how did they begin to do things together?
How did groups of cells in your body come to act like a liver or a heart? We re very interested in how the owe of information through networks facilitates multicultural. Where do you think this led is going? Think we II be turning our attention to the possibility of communication teens organisms from different kingdoms and different domains. Bacteria have been around for over 4 billion years and have probably been living with multicultural eukaryotic hosts for hundreds of millions of years.
So why would t these hosts have evolved strategies to listen in, say, to the conversation being carried out by a group of pathogenic bacteria? Does our immune system hear bacterial signaling molecules? Do hosts actively prevent quorum sensing among pathogenic bacteria? Do they tune in and help the good bacteria? I think this is going to be a dialogue, not a monologue. What do you enjoy most about your life as a scientist? Eve what I work on. I greed out as a postcode how much fun this life in science is that it is not about me against other scientists or who is going to discover something rest.
Instead, it s me against this bacterium, and we are in it head-to-head for the rest of our lives, in a contest of wills between bacteria trying to keep their secrets and me trying to discover them. Also, the basic question Of how groups work together fascinates me. I work with a fantastic group of students and we share everything everybody gives everybody everything, and then we all get more. That s quorum sensing! Both my electoral and monomolecular lives involve getting the group to do more than the individual. I love that parallelism!
My gang of students show me their data, and it s my job to help them guru out the science and get on with their careers. I m so lucky having 24 hands and 12 brains is so much better than two hands and one brain. The science is always changing and trying to keep up with these young and tireless people is hugely challenging and rewarding. What is your advice to an undergraduate who is considering a career in biology? For undergraduates who are considering a life in science, my advice is to work n something that you are passionate about.
Don t be limited by thinking that bench science is the only thing a scientist can do. There are so many potential careers for a biologist. You Are there applications for the basic research you could work on Capitol Hill as a scientist c advisor or policymaker. When you re asking fundamental questions, you hope that surrey could teach. You could be a lawyer. You could be a writer who prices, things you never thought of, will come out of helps the public understand science. You could work on science edit. Now that we know that bacteria talk to each auction at the kindergarten level.
Figure out your particular Other and perform group activities, the combinations of personality traits and what you really love Zion is whether we could interfere with doing as a scientist; then make that niche for yourself and these conversations for therapeutic purring science to that career. The sky s the limit for bibliophiles. Could we make molecules that The sky s the limit for gist because biology is the science of the 21 SST century keep bacteria from talking or heard it touches every part of our lives. Biologists because ins ? Maybe these would be new an- diabetics.
Bio alms are a terrible logy is the science problem in medicine and dental health, and now that we are starting to of the 21 SST century and know the molecular basis for their formation, maybe we can learn how to prêt touches every part vent them from forming. Of our lives. Bacteria get a lot Of bad press for the negative things they do. On the Other hand, bacteria also do many miraculous things that keep us alive; they are working for us every instant of our lives. You are covered with a bacterial bio Im that acts as invisible body armor these good bacteria occupy all the spaces on your skin, preventing invading bacteria from attaching.
Throughout your gut you have a huge mass of bacteria, and they re making vitamins for you and helping you digest your food. So all bio Aims arena t bad and for the good bio alms, what if we could ND a molecule to make quorum sensing better? Rather than an antibiotic, this would be a proportion. Bonnie Baseless (left) with Lisa aura (center) and Jane Race 6 OVERVIEW The Fundamental Units of Life Given the scope of biology, you may wonder sometimes how A Tour of the Cell you will ever learn all the material in this course!
The answer involves cells, which are as fundamental to the living systems of biology as the atom is to hammiest. The contraction of muscle cells moves your eyes as you read this sentence. The words on the page are translated into signals that nerve cells carry to your brain. Figure 6. 1 shows extensions from one nerve cell (purple) making contact with another nerve cell (orange) in the brain. As you study, your goal is to make connections like these that solidify memories and permit learning to occur. All organisms are made of cells.
In the hierarchy of biological organization, the cell is the simplest collection of matter that can be alive. Indeed, many forms of life exist as conscienceless organisms. More complex organisms, including plants and animals, are multicultural; their bodies are cooperatives of many kinds of specialized cells that could not survive for long on their own. Even when cells are arranged into higher levels of organization, such as tissues and organs, the cell remains the organism s basic unit of structure and function. All cells are related by their descent from earlier cells.
However, they have been mood deed in many different ways during the long evolutionary history of life on Earth. But although cells can differ substantially from one another, they share common features. In this chapter, we II rest examine the tools and techniques hat allow us to understand cells, then tour the cell and become acquainted with its components. CONCEPT * Figure 6. 1 How do your brain cells help you learn about biology?