The Effect On The Expression Of Aquaporin Gene GlpFof Escherichia Coli When The Osmotic Pressure Changes

Objective:To explore the growth of the Escherichia coli in the medium of thedifferent osmotic pressure, the changes of the Escherichia coli’s growth andreproduction when the osmotic pressure of the medium suddenly changed,and in this case, the expression of the GlpF(glycerol protein ficilitator), andthus in-depth understanding of the physiological function of the GlpF.Method:1. Preparing the liquid mediums with the different osmotic pressure:the Isotonic liquid medium was used to increase the Escherichia coli. Inaddition, another liquid mediums with the1/4IM,1/2IM,2IM,4IM,8IMwill be made by change the content of the NaCl, the other components ofthe medium will be the standard ratio of the specification. The specificamount of the component is: Yeast extact5g/L, Peptone10g/L,NaCl2.25g/L、4.5g/L、18g/L、36g/L、72g/L respectively.2. The E.coli was inoculated and cultivated in the isotonic liquid medium,18hours later, transferred to the mediums which osmotic pressureis1/4IM、1/2IM、2IM、4IM、8IM respectively, all the test tubes were setto the37℃incubator and were cultured2,4,8,12,18,24,30,36,48and72hour. At each time point, every medium was taken out to detected itsOD600nm and to analysis the growth and reproduction of E.coli.3. The E.coli was inoculated and cultivated in the isotonic liquidmedium,18hours later, put the isotonic liquid medium into the small testtubes, and change the osmotic pressure of the liqiud medium suddengly for1/4IM、1/2IM、2IM、4IM、8IM, in addition, the1/4IM compare groupand the1/2IM compare group must be set,for these groups, the osmoticpressure of medium did not change, and the concentration of nutrients ofthe medium was same with the experimental tube. Each test tube wereplaced in the37℃incubator.4. At the culture time point of30minutes,60minutes,120minutes,every medium was taken out to detected its OD600nm and to analysis thegrowth and reproduction of E.coli.5. For the group of1/2IM、1/2IM compare、1IM、2IM, the GlpFfragment was amplified by RT-PCR, the expression of the GlpF wasanalysised by the imaging system, so that, the mRNA transcription amountof the Escherichia coli GlpF can be compared.Result:1. The growth and multiplication of E.coli changed with different osmotic pressures which changed suddenly. Small-scale changes in osmoticpressure has little effect on bacterial growth, the greater the magnitude ofchanges in osmotic pressure, the more obvious the bacterial growth wereinhibited.2. The number of E.coli decreased in different degrees after suddenchange of osmotic pressures. Comparing with their respective controlgroup, the change of OD600nmvalue in1/2IM (isotonic medium) group and1/4IM group were not obvious, but the expressions of GlpF were reducedsignificantly. In the hypertonic group, OD600nmvalue in2IM group changedlittle comparing with isotonic group, but the expressions of GlpF wereincreased significantly.Conclusion:GlpF plays important roles in regulating intracellular water of E.coliand maintaining intracellular homeostasis. When osmotic pressures in theenvironment were suddenly changed, bacteria can regulate the expressionof GlpF to achieve the regulation of water inside and outside the bacterialcells to maintain intracellular homeostasis, especially in the high osmoticpressures environment.The expression of GlpF changed with differentosmotic pressures, it reduced while osmotic pressures declining, and itincreased significantly while osmotic pressures raising.