根據(jù)巴恩大學(xué)的研究人員發(fā)表于PNAS的研究指出,，發(fā)光桿菌會(huì)制造一種抗生素，抑制一種昆蟲(chóng)免疫系統(tǒng)用于保護(hù)自己的酵素,。
雖然這種基因?qū)虻慕换プ饔迷诩膊≈惺欠浅Ｆ毡榈模遣≡械膯我换蛎闇?zhǔn)動(dòng)物或人類(lèi)宿主的單一基因的例子，是非常罕見(jiàn)的,。
只需極少量的發(fā)光桿菌就會(huì)殺死昆蟲(chóng)，大約10-100 個(gè)細(xì)菌就足夠了,，但是對(duì)于人類(lèi)是無(wú)害的,，因此可以利用發(fā)光桿菌當(dāng)成取代殺蟲(chóng)劑的生物控制機(jī)制。
巴恩大學(xué)的研究人員Bristol and Exeter利用Manduca sexta這種昆蟲(chóng)研究細(xì)菌的劇毒基因,。研究人員可以研究細(xì)菌的整個(gè)基因組,，以了解它如何殺死宿主。
昆蟲(chóng)的免疫系統(tǒng)中使用一種名為對(duì)酚氧化酶(phenoloxidase)的酵素,，可以殺死細(xì)菌并且將它們濃縮成致密的黑色素外套,。研究員發(fā)現(xiàn)發(fā)光桿菌會(huì)制造一種特殊的對(duì)酚氧化酶抑制劑，以保護(hù)自己免受這種酵素的攻擊,。他們辨出抑制劑中的一個(gè)小分子1,3-dihydroxy-2-(isopropyl)-5-(2-phenylethenyl)benzene,，縮寫(xiě)為ST，這個(gè)分子也是發(fā)光桿菌制造的抗生素,，可用于殺死已死亡的昆蟲(chóng)尸體上的其它微生物一旦細(xì)菌沒(méi)有了ST,，毒性就減弱了。研究人員利用RNA干擾技術(shù)阻止昆蟲(chóng)制造對(duì)酚氧化酶,，這些昆蟲(chóng)對(duì)于發(fā)光桿菌的敏感性更高,。但是當(dāng)昆蟲(chóng)無(wú)法制造對(duì)酚氧化酶，發(fā)光桿菌是否具有制造ST的能力,，就變得沒(méi)有影響,。
（編譯/姜欣慧） (資料來(lái)源 : biocompare)
英文原文鏈接：
http://news.biocompare.com/newsstory.asp?id=181333
原始出處：
Published online before print February 6, 2007, 10.1073/pnas.0610525104
PNAS | February 13, 2007 | vol. 104 | no. 7 | 2419-2424
An antibiotic produced by an insect-pathogenic bacterium suppresses host defenses through phenoloxidase inhibition
Ioannis Eleftherianos*, Sam Boundy*, Susan A. Joyce*, Shazia Aslam*, James W. Marshall, Russell J. Cox, Thomas J. Simpson, David J. Clarke*, Richard H. ffrench-Constant, and Stuart E. Reynolds*,
*Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom; School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom; and Centre for Ecology and Conservation, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, United Kingdom
Communicated by David L. Denlinger, Ohio State University, Columbus, OH, December 7, 2006 (received for review April 25, 2006)
Photorhabdus is a virulent pathogen that kills its insect host by overcoming immune responses. The bacterium also secretes a range of antibiotics to suppress the growth of other invading microorganisms. Here we show that Photorhabdus produces a small-molecule antibiotic (E)-1,3-dihydroxy-2-(isopropyl)-5-(2-phenylethenyl)benzene (ST) that also acts as an inhibitor of phenoloxidase (PO) in the insect host Manduca sexta. The Photorhabdus gene stlA encodes an enzyme that produces cinnamic acid, a key precursor for production of ST, and a mutation in stlA results in loss of ST production and PO inhibitory activity, which are both restored by genetic complementation of the mutant and also by supplying cinnamic acid. ST is produced both in vitro and in vivo in sufficient quantities to account for PO inhibition and is the only detectable solvent-extractable inhibitor. A Photorhabdus stlA– mutant is significantly less virulent, proliferates slower within the host, and provokes the formation of significantly more melanotic nodules than wild-type bacteria. Virulence of the stlA– mutant is also rescued by supplying cinnamic acid. The proximate cause of the virulence effect, however, is the inhibition of PO, because the effect of the stlA– mutation on virulence is abolished in insects in which PO has been knocked down by RNA interference (RNAi). Thus, ST has a dual function both as a PO inhibitor to counter host immune reactions and also as an antibiotic to exclude microbial competitors from the insect cadaver.
Photorhabdus luminescens | RNA interference | stilbene | virulence
