The Molecular Regulation Mechanism Of Staphylococcus Aureus Biofilm Formation Under Antibiotic Stress

Staphylococcus aureus(S.aureus),a typical gram-positive pathogen,is widely distributed in the environment.It can cause food contaminations and threat to the human health.Additionally,S.aureus has the ability to form biofilm on the surface of material,which is consistes of polysaccharide and protein,prevents the S.aureus from bad environment and can lead great threat to public health.At the presence of the antibiotic,it salve many lives to kill the bacterial,however it promote the resistance of the bacterial.In the same time,antibiotics have been widely used in the livestock,with the aim to protect domestic animals from bacterial and promote productions.Result from that,the meat,beef and chicken contain some low level antibiotic residues,which has potential threat to the human.Therefore,it is urgent needed to estimate the effects of antibiotics on the biofilm fromed by the microbe.Amide that,the influences of antibiotics on the S.aureus biofilm were evaluated in this study.The CV and XTT methods were employed to evaluate the biomass and viability of the biofilm exposure to the different types,different concentration of antibiotics.Then,based on response of S.aureus to antibiotics stress,the typical strains were selected to study its transcriptome,to find out the key genes.Using the RNA-Seq,the expressions of the key genes were obtained.1.The MIC of 12 S.aureus strains was determined according to CLSI instrument and,biofilms of S.aureus strains were quantified though the CV and XTT methods after exposure to antibiotics.The results revealed that in absent of the antbiotics,biomass of biofilm increased consistently during the incubation period,meanwhile,the viability of biofilm increased first(8 h-16 h),then reduced gradually(24 h-48 h).Under antibiotics stress,the biomass and viability of biofilm were inhibited in most of experiment groups and some groups were promoted(9%,26/288).2.And 10071 and 110749 were select as subjects,because that their biofilm biomass could be stimulated by STR,viability of biofilm could be stimulated by CIP/TCY,and biomass and viability could be stimulated by AMP.After RNA-seq and bioinformatics analysis,the differentially expressed genes were found.Though the GO analysis,the differentially expressed genes were enriched in membrane,membrane part,intrinsic component of membrane,DNA binding,transporter activity,catalytic activity,nitrogen cycle metabolic process,regulation of gene expression and purine-containing compound metabolic process.After the KEGG analysis,the differently expression genesc could be enriched in TCSs pathway.And the results of Venn analysis illustrated that 24 genes were up-regulate and 27 genes were down-regulate in all groups,in which the tagA,lytR and lipA were important to the response of S.aureus in biofilm to sub-MIC antibiotics stress.3.The expression of 24 genes belong to TCSs and 26 genes related to biofilm formation were quantified,though RT-qPCR.The results revealed that lytR,arlR,hssR,tagA,clfB,atlA,and cidA were important in the stimulation of sub-MIC to S.aureu biofilm formation.