細菌依靠細胞壁來防止物理和化學(xué)損害及滲透溶解，但研究人員卻在一些細菌中發(fā)現(xiàn)了被認(rèn)為沒有細胞壁的罕見的L-型細胞,。它們可能在躲避宿主免疫系統(tǒng)及青霉素等抗生素（它們以細胞壁合成為作用目標(biāo)）的識別中發(fā)揮一定作用,。
然而,，L-型細胞非常難生長和操縱，因而難以研究,。這種情況現(xiàn)在有可能改變,，因為研究人員找到了培養(yǎng)常見模型生物B. subtilis 168的可通過基因手段跟蹤的L-型細胞的一個途徑。關(guān)于這一新系統(tǒng)的早期發(fā)現(xiàn)證實，L-型細胞的復(fù)制并不需要細胞壁合成,，也不需要正常細胞分裂機制,。相反，L-型細胞利用一個“extrusion-resolution”機制來增殖,，通過一個步驟生成多種后代,。這些發(fā)現(xiàn)在演化方面可能具有一定意義。細胞壁普遍見于各種細菌,，所以很可能存在于這些古生物的最后共同祖先內(nèi),。L-型細胞所采用的這一新穎的復(fù)制過程，有可能為了解細胞壁出現(xiàn)之前的增殖模式提供一個窗口,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 457, 849-853 (12 February 2009) | doi:10.1038/nature07742
Life without a wall or division machine in Bacillus subtilis
M. Leaver1, P. Domínguez-Cuevas1, J. M. Coxhead2, R. A. Daniel1 & J. Errington1
1 Institute for Cell and Molecular Biosciences, Newcastle University, Framlington Place, Newcastle Upon Tyne NE2 4HH, UK
2 Institute for Human Genetics, Newcastle University, International Centre for Life, Central Parkway, Newcastle Upon Tyne NE1 3BZ, UK
The cell wall is an essential structure for virtually all bacteria, forming a tough outer shell that protects the cell from damage and osmotic lysis. It is the target of our best antibiotics. L-form strains are wall-deficient derivatives of common bacteria that have been studied for decades. However, they are difficult to generate and typically require growth for many generations on osmotically protective media with antibiotics or enzymes that kill walled forms. Despite their potential importance for understanding antibiotic resistance and pathogenesis, little is known about their basic cell biology or their means of propagation. We have developed a controllable system for generating L-forms in the highly tractable model bacterium Bacillus subtilis. Here, using genome sequencing, we identify a single point mutation that predisposes cells to grow without a wall. We show that propagation of L-forms does not require the normal FtsZ-dependent division machine but occurs by a remarkable extrusion-resolution mechanism. This novel form of propagation provides insights into how early forms of cellular life may have proliferated.
