細菌應(yīng)激反應(yīng)課件

1、細菌應(yīng)激反應(yīng)Bacterial Stress Responses第七章Main content 微生物的應(yīng)激反應(yīng)定義與分類通用調(diào)節(jié)途徑熱休克反應(yīng)氧壓力滲透壓蛋白質(zhì)組學(xué)在細菌應(yīng)激反應(yīng)研究中的應(yīng)用 Bacterial Stress Responses General stress response Activation of RpoS (38) by cessation of growth Induction of Pol IV, error prone polymerase Heat-shock response Activation of RpoH (32), induction of Gro

2、E GroE protects Pol V from degradation Stringent response Amino acid deprivation, starvation Mediated by guanosine tetraphosphate, ppGpp Enhances RpoH and RpoS responses SOS response Triggered by damage to DNA LexA-RecA mediatedstress response systems細菌多生于動態(tài)多變的環(huán)境中(溫度,pH,壓力,氧化,營養(yǎng),以及各種化學(xué)物質(zhì)刺激等),細菌存在一個整

3、體調(diào)控網(wǎng)絡(luò)可以快速調(diào)節(jié)大量基因表達來快速適應(yīng)這種環(huán)境變化,這種調(diào)控網(wǎng)絡(luò)被稱為stress response系統(tǒng).stress response systems在細菌中高度相似的,有一些在真核細胞和古菌中也是保守的(如熱休克反應(yīng)).不同菌見,激活stress response 條件不一樣1975年OFarrell2D研究E.coli heat-shock proteins,2003年Hateld用microarray研究應(yīng)激反應(yīng).基因表達-轉(zhuǎn)錄,轉(zhuǎn)錄后調(diào)控,細菌中轉(zhuǎn)錄調(diào)控為主.DNA-dependent RNA polymerase, (five subunits a2bbw) 和an addi

4、tional subunit (). E. coli有7個sigma factors: 70 and the vegetative sigma factors, RpoD, RpoN, RpoS, RpoH, RpoF, RpoE, and FecI. 這些因子通過競爭和RNase核心酶結(jié)合,對轉(zhuǎn)錄調(diào)控起主要租用,另外轉(zhuǎn)錄抑制因子,激活因子, 結(jié)合因子, 抗因子,以及一些小RNAs的調(diào)控起輔助作用.Regulation of RpoS ExpressionRpoS is induced during the transition from exponential phase to statio

5、nary phase or in response to various stress conditions,引起細胞生理和形態(tài)的改變RpoS的表達受嚴(yán)格控制at the transcriptional, translational, and posttranslational levelsnlpD Fis, a global transcriptional factor, inhibits rpoS transcription by directly binding to the rpoS promoter region. Fis levels are growth-phase depend

6、ent. At the onset of stationary phase, Fis disappears and the transcription of rpoS is inducedModel for the mechanism of action of RssB in regulating S degradation by ClpXP.RpoS, a Master Regulator in Stress Responseand AdaptationMore than 10% of the E. coli genome is controlled by RpoS, most of whi

7、ch is involved in stress response, such as nutrient limitation resistance to DNA damage, osmotic shock high hydrostatic pressure, oxidative stress, ethanol resistance, adaptive mutagenesis, acid stress, and biofilm formation.RpoS controls a more degenerate promoter sequence featuring a 10 region (TA

8、YACT),Heat-shock responseIn E. coli heat-shock induces pproximately 30 genes under control of another sigma factor, RpoH (32).The RpoH-regulon is also induced by unfolded proteinsLevels of DNA Pol V are dependent on GroE because the chaperon interacts with the polymerase subunit of PolV and protects

9、 it from degradationThe groEL/ES operon, which encodes the molecular chaperone GroE, is an important member of this regulon.Heat-shock response in bacteriaheat-shock responsive genes have specific sequences in their promoters which replace the common -35 and -10 regions: these promoters are recogniz

10、ed by32 32 is encoded by the rpoH gene. The mRNA is stabilized by heat-shock leading to increased translation. In E. coli heat-shock induces approximately 30 genes under control of another sigma factor, RpoH.Heat Shock Response in Eukaryotes also have specific sequences, in this case upstream of hea

11、t-shock genes - HSE (Heat Shock Element) This is bound by (HSF)Heat Shock Factor, trimerizes using a leucine zipper. HSF is phosphorylated as a consequence of heat shock - this activates it and allows transcription to take place from the promoter 32(RpoH), the heat shock sigma factor, is rapidly deg

12、radedunder normal growth conditions by the AAA protease,FtsH, in a reaction modulated by the DnaJ/DnaK/GrpEchaperone system. During heat shock, 32 is transiently stabilized, and this stabilization results in the rapid increase in the synthesis of the heat shock proteins (Yura and Nakahigashi 1999).大腸桿菌中的活性氧造成的損傷RpoS OxyR SoxRS 金黃葡萄球菌中的抗宿主氧化損傷機制ompF基因有ompR產(chǎn)物的高親和位點ompC基因有ompR產(chǎn)物的低親和位點。滲透壓應(yīng)激反應(yīng)When bacteria are subjected to DNA damage about 30 genes are coordinately induced, a reaction known as the “SOS response”.SOS genes may be induced to some deg