Regulation Of SepF On The Cell Division Of Streptococcus Suis

Streptococcus suis(SS)is a pathogen of acute and febrile infectious diseases that causes zoonoses.The epidemic of SS has been reported in 16 countries and areas,causes a great number of economic loss of swine industry and threat to public health of mankind.SS has been classified into 33 serotypes according to capsular antigens,of which SS2 infects with mankind and is the most pandemic and strongest virulence predominant strain.The twice outbreaks of SS2 infecting with mankind in China caused serious consequence of 229 infection and 52 death,in 1998 and 2005.With the wildly using of antibiotics,the drug resistance of SS is becoming more and more critical.The cell division protein machinery of bacterial is an important target of novel antibacterial agents.Unlike Bacillus,the Streptococcus has distinct mechanism of cell division.Nevertheless,there is little study about Streptococcus cell division mechanism.The key point of bacterial cell division is the formation of septum.FtsZ,a scaffold protein of bacterial cell division,interacts with multiple division-associated protein to form the Z ring and septum.In recent studies,it has been reported that SepF,a kind of membrane-bound protein in Bacillus subtilis,could serve as the “bridge” protein between Z ring and cell membrane,and anchor Z ring to the middle of cell membrane,which ensure the accuracy of division site.But whether the functional mechanisms of SepF in SS cells division and growth is the same as in bacillus remains unclear.In our research,we used SS as the research material to study the impact of SepF on SS growth and cell division.The results were as follows:1.The infection of SepF in SS2 growth and morphology: We used SC19 as the parent strain,then generated the sep F gene mutation strain and complementary strain.With the measurement of growth curve and Gram staining,and observation from scanning electron microscope,we found that sep F gene deletion strain shows a slow growth rate and elongated chains.Furthermore,through the observation from the projection electron microscope and super resolution microscope,we found that cell morphology become Spindle-like,and cells dividion septum is not perpendicular to the long axis,thus cells exhibited abnormal morphology.As we could see,the SepF protein indeed influenced the growth and cell division of SS.2.The interaction between SepF and FtsZ: The bacterial two-hybrid experiments showed that SepF can interact with FtsZ.With the clone,expression and purification of SepF and FtsZ,we confirmed the interaction in vitro,and found that SepF facilitate FtsZ protein polymerization.Meanwhile,SepF could interact with peptidoglycan synthetase Mur G.These results indicated that SepF assiste in the correct selection of cell division sites,effect with the morphology of division septum,and have an important function of membrane morphology stability in cell division.