Some Physiological Characteristics And The Differential Proteins Of Two Forms Of The Xenorhabdus Nematophilus

Xenorhabdus nematophila(X.nematophila)is a gram negative bacterium which is mutualism with the steinernema carpocapsae in the gut of pathogenic nematodes.It has been attracted great attentions because it can produce many kinds of secondary metabolites such as insecticidal toxins,antibacterial substance and anti-cancer active substance.X.nematophila has two types,the primary bacteria and the secondary type.The primary bacteria are very unstable and can easily convert into the secondary bacteria.The morphology and a variety of physiological characteristics were changed between the primary and the second of X.nematophila which limiting its wild application in agriculture.In this paper,some physiological characteristics and differential proteins between the primary and secondary bacteria were studied based on the variation of the X.nematophila.The main researches contents are as follows:1.Screening and identification of the X.nematophila.The primary bacteria were isolated from nematode larvae,nematode adults and infected wax moth respectively.It was found that screening the primary bacteria from the infected wax moth was optimal method.The secondary bacteria can not only be screened from the adult worms and the infected wax moth,but also can be obtained from the multi-times subculture of the primary bacteria.The SEM detection showed that the primary bacteria were rod-shaped with a length of 4-5 μm,and surface is uneven.16 S rDNA identifications results indicated the homology between 16 S rDNA of objective strain and X.nematophilusATCC 19061 was 99 %,which proved that the objective strains were successfully screened.2.Studies on some physiological characteristics of X.nematophila.The growth curves of X.nematophila were measured and the effects of temperature and pH on the growth of this strain were studied.At the same time morphology change of this strain,pH change of culture medium,some physiological and biochemical reactions were studied.Results showed that temperature and pH value had a great influence on the growth of the primary bacteria.And its growth rate is very slow When were cultured under the condition of below 25 ℃ or in weak acid conditions.The time of entering the exponential growth phase of the primary bacteria was 8-16 hours later than that of the secondary bacteria,when the temperature reaches 25 ℃ or non-acidic condition conditions.The primary bacteria gradually transformed into the secondary bacteria after 24 h,and all of them were transformed into secondary bacteria at 72 h.X.nematophila can produce acidic through the decompose of glucose,while lactose and sucrose couldn’t be utilized by this strains.3.Studies on the differential proteins between primary and secondary bacteria.A total number of 367 differentially expressed proteins were detected using ITRAQ technique.Besides Xenocoumacin and Xnph1 proteins that had been wild studied by some other scholars,other specific proteins in primary bacteria were excavated are as follows: Xcn and Xnph1 protein with antibacterial property,proteins related to the attachment of X.nematophila to the host insects including flagellin,fimbrial adaptor,fimbrial adhesion and capsular synthesis regulator component B,glutamate synthase that playing an important role in multiple metabolic pathways in the primary bacteria,multidrug resistance secretion protein with the property of tumor drug resistance and defense effects against cytotoxic compounds produced by normal cells and malignant cells.