Printing press spells out bugs' behaviour
AROUND 1452 the first operational printing press was created, followed in 1799 by lithographic printing. Now, these inventions are reflected in the world's first bacterial printing press.
The press will print live bacteria onto solid surfaces in precise patterns, a technique that may help explain how bacteria influence each other spatially. Understanding these relationships will help find ways of thwarting their attacks and using them to clean up pollutants.
For instance, bacteria sometimes form biofilms, unique communities of sticky, sugary plaques which cling to surfaces (New Scientist, 20 November 2004, p 34). In this state bacteria are better at resisting antibiotics and more efficient at processing waste. But we do not know which conditions prompt bacteria to form these biofilms and why they are more resilient when they do. "One thing we want to study is the distance dependence for signalling between two adjacent bacteria on a surface," says Doug Weibel, a member of the Harvard University team that built the printing press.
Biologists already have crude techniques for patterning bacteria, including dipping an array of evenly spaced pins into a bacterial solution and letting the drops fall onto a fresh surface. But the liquid spreads out, making it impossible to create delicate, reproducible patterns.
To create intricate patterns of many different types of bacteria, Weibel borrowed a technique from the computer chip industry called photolithography. Conventionally, this involves coating a silicon wafer with a thin layer of light-sensitive polymer, shining UV light onto it through a template, and then dissolving the affected areas to create a pattern.
Weibel uses this patterned chip as a mould, into which he pours a liquid polymer. This cools, sets and is popped out, forming a stamp. This is then coated with agarose, a nutrient gel that bacteria will grow on. He pipettes solutions of bacteria onto the agarose, which sucks out the water, leaving a solid layer of bacteria.
To print the bacteria, this stamp is simply pressed into a clean nutrient gel, producing a living replica of the original pattern, with features as small as 1 micrometre across, the size of one bacterium. As some bacteria remain on the stamp, it is "re-inked" by warming until the bacteria multiply to form a fresh carpet over its surface.
Weibel has used his stamp to form patterns of different types of bacteria, and of the same bacteria on surfaces with different chemical compositions, as well as to grow biofilms. He will publish the results in an upcoming issue of the journal Langmuir.
據(jù)《新科學(xué)家》雜志網(wǎng)站2005年5月30日消息，1452年第一臺(tái)印刷機(jī)誕生,，隨后在1799年人們發(fā)明了平版印刷技術(shù)?，F(xiàn)在，這些舊日的發(fā)明都在世界上第一臺(tái)細(xì)菌印刷機(jī)上得到了體現(xiàn),。
這種設(shè)備能夠以精細(xì)的圖案將活細(xì)菌印刷到固體表面,，它將有助于研究細(xì)菌之間怎樣相互作用。如果能夠了解它們之間的關(guān)系,，科學(xué)家們就能夠找出方法來抵擋細(xì)菌的進(jìn)攻,，或者利用細(xì)菌來分解污染物。
例如,，細(xì)菌有時(shí)能構(gòu)成生物被膜,，這種獨(dú)特的細(xì)菌群落具有粘性、富含糖分,，而且可以粘附在物體的表面,。這種狀態(tài)下的細(xì)菌具有更強(qiáng)的能力來抵抗抗生素，同時(shí)在處理廢物的時(shí)候效率也會(huì)變高,。但是我們還不知道在什么情況下細(xì)菌會(huì)形成這樣的生物被膜,，以及為什么在形成被膜后細(xì)菌的復(fù)原能力也會(huì)增強(qiáng)。“我們目前計(jì)劃研究在同一物體表面上相鄰兩個(gè)細(xì)菌的細(xì)菌信號(hào)的依賴距離,，”來自哈佛大學(xué)的Doug Weibel說,，他所在的研究小組研制了那種可以印刷細(xì)菌的印刷機(jī),。
生物學(xué)家已經(jīng)能夠利用簡(jiǎn)單的辦法來排列細(xì)菌，其中包括將排列整齊間距相等的一組針頭浸入細(xì)菌溶液中,，然后將液體滴到干凈的物體表面。但是液體有時(shí)會(huì)擴(kuò)散,，這樣一來就無法制造既精細(xì)又能夠繁殖細(xì)菌的圖案,。
為了精細(xì)地制造各種不同的細(xì)菌排列，Weibel借用了計(jì)算機(jī)芯片制造中的微影技術(shù),。和傳統(tǒng)方法一樣,，先給硅片薄薄地涂上一層對(duì)光線十分敏感的聚合物，再隔著一個(gè)模板用紫外線照射硅片,，然后溶解那些受到影響的區(qū)域,，這樣就制成了一個(gè)圖案。
Weibel把已經(jīng)被照射過的硅片作為模具,，然后將一種聚合液體到入其中,。隨后取出冷卻固定后看起來像印章的聚合液體。在印章上圖一層瓊脂糖,，細(xì)菌就能夠在這種營(yíng)養(yǎng)凝膠體上生長(zhǎng),。然后他用吸液管將細(xì)菌溶液滴到瓊脂糖上，在瓊脂糖吸干了溶液中的水分后,，印章表面就會(huì)形成一層固體細(xì)菌,。
印刷細(xì)菌時(shí)，只需簡(jiǎn)單地將這個(gè)印章放入干凈的營(yíng)養(yǎng)凝膠中就能夠制造出一個(gè)和原有圖案相同的,，活的復(fù)制品,，而且這種圖案的細(xì)節(jié)能夠精確到一微米，猶如單個(gè)細(xì)菌的大小,。如果在印章上仍然有細(xì)菌存在,，可以利用加熱的方法來給印章“重新加墨”，在其表面繁殖新的一層細(xì)菌,。
Weibel已經(jīng)使用這種印章制作了多種不同細(xì)菌的圖案,，并且還將相同的細(xì)菌放到由不同化學(xué)物質(zhì)成分的表面來培養(yǎng)生物被膜。他將在下一期的《Langmuir》上發(fā)表其研究結(jié)果,。
