Résumé
Intensive surveillance of human S.suis infection was carried out in July and August of 2005 in Guangdong Province, which coincided with the Sichuan outbreak. Five isolated cases of human infections were identified during this period, from which 5 S. suis serotype 2 isolates were recovered. MLST analysis showed that these 5 isolates shared identical sequences of 6 MLST housekeeping genes except for one point mutation found within the thrA gene fragment, a neutral mutation (TTA to TTG) in the third nucleotide (360 nt) of the codon for leucine. MLST analysis identified 2 sequence types in the Guangdong sporadic infection. Three Guangdong isolates L-SS002, L-SS003 and L-SS005 belonged to ST7, while the other two isolates L-SS004 and L-SS006 belonged to ST1, but they all belonged to ST1 clonal complex. This finding represents a striking feature that differs from the Sichuan outbreak caused by a single ST7 SS2 clone. The 3 isolates of ST7 were probably imported from Sichuan Province, while the origin of the other 2 isolates of ST1 still remain to be clarified.
Sujets)
Animaux , Humains , Techniques de typage bactérien , Méthodes , Chine , ADN bactérien , Génétique , Analyse de séquence d'ADN , Infections à streptocoques , Microbiologie , Streptococcus suis , Classification , Génétique , Virulence , Suidae , Maladies des porcs , Microbiologie , Zoonoses , MicrobiologieRésumé
In order to improve the optimum temperature of lipases, The Penicillum expansum lipase (PEL) gene was mutated by site-directed mutagenesis using overlap extension PCR technique. The recombinant plasmid pPIC3.5K-lip-E83V containing matant gene was expressed in Pichia pastoris GS115. The comparison experiments of the mutant PEL-E83V-GS with the wild-type PEL-GS showed that: the optimum temperature of the mutant (45℃) was higher by 5℃ than that of the wild type. The thermostability of the mutant was similar to the wild type. The enzymatic activity of the mutant was 188 U/mL at 37 ℃, which was 80% that of the wild type at the same conditions. The hydrophobic interaction may be enhanced in the surface region by the hydrophilic amino acid, Glu substituted with the hydrophobic amino acid, Val, and be responsible for the improvement of optimum temperature.