한빛사인터뷰
- 조회6,089
Princeton University
We show here using microfabrication that bacteria can use the physical boundaries of the environment in conjunction with chemotaxis to enhance their local concentration. When cells are grown to a moderate density within a confining microenvironment, they create traveling waves of high cell density and find and collapse into confining topologies. This is first observed in mazes designed to mimic complex environments, then more clearly in a simpler geometry consisting of a large open area surrounding a square (250 250 m) with a narrow opening of 10 m. Our results thus show that under nutrient-deprived conditions bacteria search out each other using self-producing attractants and then the bacteria can dynamically confine themselves to highly enclosed spaces.
Social mobility: Study shows bacteria seek each other out
Modified from Princeton Weekly Bulletin (Oct. 20, 2003) and Chemical Engineering News (Jul 14, 2003)
Biologists had previously believed that bacteria's ability to move and follow chemical signals -- a process called chemotaxis -- was primarily a means of dispersing and seeking food. Our studies show that chemotaxis may also be important for facilitating cooperative behavior.
I initially noticed unusual clustering when E. coli were loaded into microfabricated small mazes made of silicone. This clustering was more clearly observed in a simpler geometry consisting of a large open area surrounding a square (250 x 250 um) with a narrow opening (10 um). I discovered that bacteria themselves emit a key chemical attractant and that those lacking the gene for the receptor that senses that attractant did not cluster as normal bacteria did. The cells gathered by releasing a come-hither scent of amino acids. E. coli secreted mainly the chemoattractant glycine (Nov. 17 issue of PNAS).
Clustering also allows bacteria to perform a coordinated activity called quorum sensing in which they turn on certain genes only when they sense that they are part of a dense population. Some disease-causing bacteria are believed to rely on quorum sensing in mounting a successful infection. The V. harveyi in the experiment glowed as a result of quorum sensing after they gathered into a dense population (Jul. 11 issue of Science).
The behavior observed in the experiment also may have been a survival mechanism. The research was conducted with the bacteria in a nutrient-depleted environment that resembles the natural conditions for bacteria much of the time. I believe that the bacteria are chasing amino acids released from their own cell bodies during starvation conditions. So by getting close to each other they have a better chance of getting nutrients.
We also have developed a mathematical model that simulates the bacterial congregation. We plan further research to investigate the relation between bacterial behavior and the size and geometry of their physical environment.
- Can you please tell us the main difficulties you had in the laboratory work and how you overcame them?
My main problems came from myself: I was not sure if my experiments were working; I felt I was stupid. How could I overcome these difficulties? I have never overcome these; I would rather say these difficulties have temporally disappeared. You know that doing science is not easy!
2. Please introduce your laboratory, university or organization to bio-researchers in Korea.
Our laboratory led by Prof. Robert Austin at Princeton University developed the first DNA separation chip (1992, Nature) and since then has developed numerous genuine devices, such as DNA prism (2002, Nature Biotechnology) and Tango (or bumper) array (2003 in press). These achievements came through numerous collaborations with nanofabrication experts, molecular biologists, and chemists. More details are found in http://feynman.princeton.edu/~austin/
3. Please tell us your experiences and your thoughts related to research activities abroad.
I have experienced several different areas: biosensors, molecular cloning, Bio-MEMS, and Nano- and Microfluidics. The areas belong to Nanobiotechnology or Bionanotechnology. Research activities around me are more focused on new ideas and cool experiments to understand the biology at a molecular level or a smaller scale.
Let's work hard!
| Received for article November 20, 2003 |
등록일 2003.11.20
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