Study on expression of Streptococcus suis serotype 2 sly gene, purification and activity of its product / 中华流行病学杂志

<p><b>OBJECTIVE</b>To clone and express Streptococcus suis serotype 2 (S. suis 2) sly gene for constructing an foundation on identification of S. suis 2 protective antigen.</p><p><b>METHODS</b>The sly gene was amplified from S. suis 2 clinical isolate strain 05ZYH33 genome DNA by PCR. The gene fragment was inserted into the expression vector pET-30b(+) to build pET30b-sly. When recombinant vector pET30b-sly was identified by restriction enzyme cutting and DNA sequencing as a correct one, subsequently it was transformed to E. coli Rosetta for expression under IPTG induction. The obtained fusion protein was purified by Ni-NTA affinity chromatography. The immunologic and hemolysis activity of the purified protein was proved through Western blot and hemolysis assay respectively.</p><p><b>RESULTS</b>The PCR product was around 1500 bp. The gene segment inserted into the recombinant vector was proven to be completely identical with the sly gene sequence in the total genome sequence of S. suis 2. The target protein expressed was up to 30% of the total somatic protein under IPTG induction. The protein purity reached above 80% after purification. The protein could be recognized by human serum infected with S. suis 2 and could dissolve swine erythrocytes with the Hemolytic titer as 256.</p><p><b>CONCLUSION</b>The expression vector pET30b-sly was successfully constructed. The target protein could be over-expressed in E. coli and possessed its biological activity after purification.</p>

ISOLATION AND IDENTIFICATION OF PSEUDOMONAS AERUGINOSABACTERIOPHAGE AND DETERMINATION OF PHAGE-RSISTANCEMUTATION FREQUENCE / 微生物学通报

Three bactreiophages of Pseudomonas aeruginosa were isolated from sewage and named as PaP1, PaP2 and PaP3. All belong to double-strand DNA phages, their genome is about 47kb, 34kb and 24kb respectively. The titre (pfu/mL) of three phages is respectively 109, 1011 and 1011, PaP1 is lytic phage, both PaP2 and PaP3 are lysogenic. Under electron microscope, All show icosahedral heads with diameter of 70nm, 55nm and 65nm respectively. PaPl belongs taxonomically to Myoviridae, and both of PaP2 and PaP3 belong to Pedoviridae. The phage-re-sistance and substitution phenomenon of the resistant flora for the sensitive were observed, and the mutation frequence of Pseudomonas aeruginosa resistant to the phage is about 1.4 ? 10-7 ~ 7.9 ?10-7 determined by end-point -titer method.

Prophages / 微生物学通报

It is common in bacterial genomes of the integration of prophages. As an important participant of the vital movement of their hosts, prophages affect closely the biological properties of the hosts. Therefore, if we want to comprehend a bacterial genome fully, it is essential to recognize and understand accurately prophages in it. This article is a compendious review about the classification, distribution, identification, evolution of prophages and the interaction with their hosts.