Analysis Of The Effect Of Porin Gene Mutation On The Virulence Of Salmonella

Salmonella is a Gram negative bacterium that can cause a wide range of gastrointestinal and systemic diseases.Porins are channels through which hydrophilic solutes,nutrients and toxic compounds are passively diffused through the bacterial outer membrane,with the ability of toxins to flow into or out of the outer membrane.In order to explore the effect of porin gene mutation on the virulence of Salmonella typhimurium,this study took Salmonella typhimurium as the research object and constructed related mutant strains usingλ-Red homologous recombination system.The genetic stability of the standard and mutant strains of Salmonella typhimurium in vitro and in vivo was detected by PCR,the growth curve was drawn to measure their growth,biochemical tube was used to detect their biochemical characteristics,biofilm formation ability was observed by the 96-well plate biofilm formation experiment,and the strength of locomotion ability and bacterial resistance test were observed by the hydrokinetic test The sensitivity to a variety of antibiotics was determined,the concentration of standard strain and mutant strain was adjusted by bacteria count,and then the mice were challenged.The pathogenicity test and LD₅₀test were used to observe the virulence of the mice,and the bacteria distribution on the liver and spleen of mice was detected by the bacteria loading test and spleen loading test.The results showed that the mutant STM LT2△omp D,STM LT2△omp W,STM LT2△omp S were successfully constructed.The standard strains and mutant strains could still be inherited stably after successive generations in vitro and in vivo.Compared with STM LT2,the growth rate of mutant STM LT2△omp D and STM LT2△omp W had no obvious change,while the growth rate of mutant STM LT2△omp S slowed down obviously.The motility test showed that the motility of all the mutant was weakened,and STM LT2△omp S was the most obvious.The results of 96-well plate biofilm formation experiment showed that the mutant STM LT2△omp W and STM LT2△omp D had strong biofilm formation ability,while the mutant STM LT2△omp S had weak biofilm formation ability.When the pathogenicity of standard strains and mutant strains was tested in animal pathogenicity experiments,it was found that the intestinal tract of mice had obvious lesions,intestinal cavity filling and mild bleeding.The results of LD₅₀test showed that the virulence of mutant was weakened overall compared with the standard strain of Salmonella typhimurium,and the virulence of mutant STM LT2△omp S was the most obvious.The bacterial content in liver and spleen of the mutant strain was less than that of the standard strain.The results showed that the deletion of porin omp S,omp W and omp D genes had different effects on the growth rate,motor ability,biofilm formation ability and drug resistance of Salmonella typhimurium,and omp S gene had the most obvious weakening on the motor ability and growth rate of Salmonella typhimurium.omp S,omp W and omp D genes are the core regulatory elements of biofilm formation,and their biochemical characteristics are not significantly different.Deletion of porin omp S,omp W and omp D genes can reduce the pathogenicity and virulence of Salmonella typhimurium to varying degrees.This study is helpful for researchers to effectively design and optimize the beneficial properties of various mechanisms of novel anti-infective drugs,and provides a reference for exploring the molecular mechanism of pathogenicity of Salmonella typhimurium.