PNEUMOCYSTIS pneumonia (PCP) is among the most common opportunistic infections in patients with acquired immune deficiency syndrome (AIDS).Although trimethoprim-sulfamethoxazole (TMP-SMX) is the first line therapy for...PNEUMOCYSTIS pneumonia (PCP) is among the most common opportunistic infections in patients with acquired immune deficiency syndrome (AIDS).Although trimethoprim-sulfamethoxazole (TMP-SMX) is the first line therapy for that condition given its efficacy,approximately one third of patients experienced dose-limiting toxicity.1 For cases of severe to moderate PCP,if TMP-SMX treatment fails or is contraindicated,primaquine combined with clindamycin or intravenous pentamidine is recommended as second line therapy.2 However,both primaquine and pentamidine are associated with severe adverse reactions and often unavailable at hospitals in China.3 As a result,other treatment options have been explored.展开更多
Lys R-type transcriptional regulators are involved in the regulation of numerous cellular metabolic processes in Klebsiella pneumoniae,leading to severe infection.Earlier,we found a novel Lys R family gene,named kp053...Lys R-type transcriptional regulators are involved in the regulation of numerous cellular metabolic processes in Klebsiella pneumoniae,leading to severe infection.Earlier,we found a novel Lys R family gene,named kp05372,in a strain of K.pneumoniae(designated GPKP)isolated from forest musk deer.To study the function of this gene in relation to the biological characteristics of GPKP,we used the suicide plasmid and conjugative transfer methods to construct deletion mutant strain GPKP-Δkp05372;moreover,we also constructed the GPKP-Δkp05372+complemented strain.The role of this gene was determined by comparing the following characteristics of three strains:growth curves,biofilm formation,drug resistance,stress resistance,median lethal dose(LD50),organ colonization ability,and the histopathology of GPKP.Real-time polymerase chain reaction(RT-PCR)was used to test the expression level of seven genes upstream of kp05372.There was no significant difference in the growth rates when comparing the three bacterial strains,and no significant difference was recorded at different osmotic pressures,temperatures,salt contents,or hydrogen peroxide concentrations.The GPKP-Δkp05372 mutant formed a weak biofilm,and the other two strains formed medium biofilm.The drug resistance of the GPKP-Δkp05372 mutant toward cephalothin,cotrimoxazole,and polymyxin B was changed.The acid tolerance of the deletion strain was stronger than that of the other two strains.The LD50 values of the wild-type and complemented strains were 174-fold and 77-fold higher than that of the GPKP-Δkp05372 mutant,respectively.The colonization ability of the GPKP-Δkp05372 mutant in the heart,liver,spleen,kidney,and intestine was the weakest.The three strains caused different histopathological changes in the liver and lungs.In the GPKP-Δkp05372 mutant,the relative expression levels of kp05374 and kp05379 were increased to 1.32-fold and 1.42-fold,respectively,while the level of kp05378 was decreased by 42%.Overall,the deletion of kp05372 gene leads to changes in the following:drug resistance and acid tolerance;decreases in virulence,biofilm formation,and colonization ability of GPKP;and regulation of the upstream region of adjacent genes.展开更多
1,3-Propanediol （PDO） is an important bulk industrial material. It can be produced by microbial fermentation. In this study, the microbial flora of mangrove sediment was screened to identify strains with high produc...1,3-Propanediol （PDO） is an important bulk industrial material. It can be produced by microbial fermentation. In this study, the microbial flora of mangrove sediment was screened to identify strains with high production of PDO by fermentation of glycerol. The PDO productivities of the isolated strains were tested, and the strain with highest PDO productivity was characterized using the API20E and 16-s rRNA sequence analysis. The physiological and phylogenetic analysis indicated that the strain was closed related to K. pneumoniae species and was named as K. pneumoniae HSL4. The structure of the dha cluster which was responsible for the biosynthesis of PDO was analyzed. It is observed that K. pneumoniae HSL4 was tolerant to salt and partly tolerant to acetate and lactate, which will favor industrial applications. Fed-batch fermentation experiments revealed K. pneumoniae HSL4 exhibited an excellent ability to produce PDO with high concentration （80.08 g L^-1）, productivity （2.22 g L^-1h^-1） and conversion （0.435 g g^-1 or 0.53 mol mol^-1）. The metabolic flux profile illuminated that glycerol was consumed rapidly and PDO was accumulated quickly to a high level during the exponential growth phase. This study provided important information for further fermentation and metabolic engineering of PDO production by K. pneumoniae HSL4.展开更多
文摘PNEUMOCYSTIS pneumonia (PCP) is among the most common opportunistic infections in patients with acquired immune deficiency syndrome (AIDS).Although trimethoprim-sulfamethoxazole (TMP-SMX) is the first line therapy for that condition given its efficacy,approximately one third of patients experienced dose-limiting toxicity.1 For cases of severe to moderate PCP,if TMP-SMX treatment fails or is contraindicated,primaquine combined with clindamycin or intravenous pentamidine is recommended as second line therapy.2 However,both primaquine and pentamidine are associated with severe adverse reactions and often unavailable at hospitals in China.3 As a result,other treatment options have been explored.
基金Project supported by the Sichuan Province Academic and Technical Leadership Development Funding Project and the Science&Technology Achievements Transfer Project of Sichuan(No.2017YSZH0008),China.
文摘Lys R-type transcriptional regulators are involved in the regulation of numerous cellular metabolic processes in Klebsiella pneumoniae,leading to severe infection.Earlier,we found a novel Lys R family gene,named kp05372,in a strain of K.pneumoniae(designated GPKP)isolated from forest musk deer.To study the function of this gene in relation to the biological characteristics of GPKP,we used the suicide plasmid and conjugative transfer methods to construct deletion mutant strain GPKP-Δkp05372;moreover,we also constructed the GPKP-Δkp05372+complemented strain.The role of this gene was determined by comparing the following characteristics of three strains:growth curves,biofilm formation,drug resistance,stress resistance,median lethal dose(LD50),organ colonization ability,and the histopathology of GPKP.Real-time polymerase chain reaction(RT-PCR)was used to test the expression level of seven genes upstream of kp05372.There was no significant difference in the growth rates when comparing the three bacterial strains,and no significant difference was recorded at different osmotic pressures,temperatures,salt contents,or hydrogen peroxide concentrations.The GPKP-Δkp05372 mutant formed a weak biofilm,and the other two strains formed medium biofilm.The drug resistance of the GPKP-Δkp05372 mutant toward cephalothin,cotrimoxazole,and polymyxin B was changed.The acid tolerance of the deletion strain was stronger than that of the other two strains.The LD50 values of the wild-type and complemented strains were 174-fold and 77-fold higher than that of the GPKP-Δkp05372 mutant,respectively.The colonization ability of the GPKP-Δkp05372 mutant in the heart,liver,spleen,kidney,and intestine was the weakest.The three strains caused different histopathological changes in the liver and lungs.In the GPKP-Δkp05372 mutant,the relative expression levels of kp05374 and kp05379 were increased to 1.32-fold and 1.42-fold,respectively,while the level of kp05378 was decreased by 42%.Overall,the deletion of kp05372 gene leads to changes in the following:drug resistance and acid tolerance;decreases in virulence,biofilm formation,and colonization ability of GPKP;and regulation of the upstream region of adjacent genes.
基金supported by the Scientific Research Project of the Marine Public Welfare Industry of China (201205020-4)Administration of Ocean and Fisheries of Guangdong Province (GD2012-D01-002)
文摘1,3-Propanediol （PDO） is an important bulk industrial material. It can be produced by microbial fermentation. In this study, the microbial flora of mangrove sediment was screened to identify strains with high production of PDO by fermentation of glycerol. The PDO productivities of the isolated strains were tested, and the strain with highest PDO productivity was characterized using the API20E and 16-s rRNA sequence analysis. The physiological and phylogenetic analysis indicated that the strain was closed related to K. pneumoniae species and was named as K. pneumoniae HSL4. The structure of the dha cluster which was responsible for the biosynthesis of PDO was analyzed. It is observed that K. pneumoniae HSL4 was tolerant to salt and partly tolerant to acetate and lactate, which will favor industrial applications. Fed-batch fermentation experiments revealed K. pneumoniae HSL4 exhibited an excellent ability to produce PDO with high concentration （80.08 g L^-1）, productivity （2.22 g L^-1h^-1） and conversion （0.435 g g^-1 or 0.53 mol mol^-1）. The metabolic flux profile illuminated that glycerol was consumed rapidly and PDO was accumulated quickly to a high level during the exponential growth phase. This study provided important information for further fermentation and metabolic engineering of PDO production by K. pneumoniae HSL4.
