Correlation Between Global Regulatory Factors And Nitrite Reduction Characteristics Of Lactobacillus Plantarum FQR

Nitrite plays important roles in both meat color and inhibiting the growth of pathogenic bacteria in the processing of meat products.However,Nitrite is very easy to remain during food processing and storage,excessive intake of nitrite over long-term can cause adverse effects such as carcinogenesis.There are still no effective alternatives to solve this problem.It has been found that Lactobacillus plantarum has the ability to degrade nitrite,and the degradation ability is restricted by various environmental factors.However the specific metabolic mechanism is still unclear.Reports found that many bacteria,including lactic acid bacteria,have evolved a regulatory system to resist the environment stress,and the global regulators transcriptional control of intracellular genes to form a huge metabolic regulation network.The global regulatory factors that have been reported include the key gene lux S in the bacterial Quorum Sensing system?QS?,and the components in Two-component signaling?TCS?.In this study,Lactobacillus plantarum FQR was used as the object to discuss the mechanism of nitrite reduction mechanism of NiR and global regulators lux S,HK4,RR4,HK5,RR5,HK6,RR6 of FQR.The main results are as follows:1.The basic characteristics of lactic acid bacteria with nitrite lowering functionThe results showed that,Gram staining results show blue purple,resisted 150 mg/ kg NaNO₂,resisted 4% Na Cl,no mucus,no amino acid decarboxylase activity,no ammonia production,no fermentation of glucose,no H2O₂,no H2 S.Bacterial morphology was single,paired or chain;The gene sequence of NCBI BLASTN showed that the strain was Lactobacillus plantarum,so it was named Lactobacillus plantarum FQR;Bacteriostasis substances may be secretory products AI-2,its supernatant can make the Vibrio harnyi BB170 fluorescence,and the lux S gene can be amplified successfully,initially verified that FQR can produce AI-2 signal molecules;In the verification experiment of TCS factors,it was found that FQR contained 13 TCSs and selected HK4,RR4,HK6,RR6,HK5 and RR5 that might have the effect of nitrite reduction to carry out the follow-up experiments.2.Correlation analysis of NiR and global regulation factors under acid stress,bile salt stress,NaNO₂ stress and Na Cl stress?1?Correlation between NiR and global regulatory factors under acid stressWhile pH value increasing,the nitrite degradation rate of FQR gradually increased,and NiRs activity increased first and then decreased,FQR at C point was most resistant to acid stress,the gene expression of NiR and global regulators lux S,HK4,RR4,HK5,RR5,HK6 all increased in different degrees with time extend,and all of them exist in positive correlation;The relative expression of lux S,HK6 and RR6 were significantly higher than actin group?p<0.01?,the relative expression of HK4,RR4,HK5 and RR5 genes were higher than actin group?p<0.05?;There was no significant relationship between NiR and other factors?P>0.05?.?2?Correlation between NiR and global regulatory factors under bile salt stressWhile the bile salts concentration increaseing,the nitrite degradation rate of FQR decreased gradually,and the activity of NiRs enzyme decreased,The FQR at C point was most resistant to bile salt stress.the gene expression of NiR and global regulators lux S,HK4,RR4,HK5,RR5,HK6 all increased in different degrees with time extend,and all of them exist in positive correlation;the relative expression of NiR,lux S,HK4,RR4,HK6 and RR6 were significantly higher than actin group?p<0.01?,the relative expression of HK5 and RR5 genes were higher than actin group?p<0.05?;The activity of NiR enzyme showed a decreasing trend.?3?Correlation between NiR and global regulatory factors under NaNO₂ stressWhile the NaNO₂ concentration increaseing,the nitrite degradation rate of FQR decreased gradually,and the activity of NiRs enzyme decreased,The FQR at C point was most resistant to bile salt stress,the gene expression of NiR and global regulators lux S,HK4,RR4,HK5,RR5,HK6 all increased in different degrees with time extend,and all of them exist in positive correlation;the relative expression of NiR,lux S,HK4,RR4,HK6 and RR6 were significantly higher than actin group?p<0.01?,the relative expression of HK5 and RR5 genes were higher than actin group?p<0.05?;The activity of NiR enzyme showed a decreasing trend.?4?Correlation between NiR and global regulatory factors under Na Cl stressWhile the Na Cl concentration increaseing,the nitrite degradation rate of FQR decreased gradually,and the activity of NiRs enzyme decreased,The FQR at C point was most resistant to bile salt stress,the gene expression of NiR and global regulators lux S,HK4,RR4,HK5,RR5,HK6 all increased in different degrees with time extend,and all of them exist in positive correlation;the relative expression of NiR,lux S,HK4,RR4,HK6 and RR6 were significantly higher than actin group?p<0.01?,the relative expression of HK5 and RR5 genes were higher than actin group?p<0.05?;The activity of NiR enzyme showed a decreasing trend.