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Objective:To construct a mutant strain of hypervirulent Klebsiella pneumoniae NTHU-K2044 with hfq gene deletion and to analyze its biological characteristics. Methods:The hfq gene of NTUH-K2044 was knocked out by homologous recombination technology to construct △ hfq mutant strain. Its biological characteristics including growth rate, environmental stress tolerance, biofilm formation, capsular polysaccharide synthesis, resistance to neutrophil phagocytosis and lethality to Galleria mellonella larvae were analyzed by comparing with the wild-type strain using phenotypic experiments. Results:The △ hfq mutant strain of hypervirulent Klebsiella pneumoniae NTHU-K2044 was successfully constructed. Phenotypic experiments showed that the △ hfq mutant strain had significantly slower growth rate, smaller colonies and decreased hypermucoviscosity. Its growth was significantly inhibited under different environmental stress conditions such as pH9, pH5.5, 0.7 mmol/L SDS, 5% NaCl, 0.1% H 2O 2 and high temperature of 50℃. In terms of virulence and pathogenicity, the △ hfq mutant strain showed decreased ability to form biofilm and capsule, significantly down-regulated expression of magA and rmpA genes required for capsule synthesis, lower survival rate in the neutrophil bactericidal test and obviously reduced lethality to Galleria mellonella larvae. Conclusions:As a RNA chaperone, Hfq protein could participate in post-transcriptional regulation and play an important role in regulating the physiology, environmental adaptability and virulence of hypervirulent Klebsiella pneumoniae. This study provided reference for further study on hypervirulent Klebsiella pneumoniae.
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Close attention of the Course of Environmental Adaptation should be paid in rehabilitation professional training. Its teaching strategy should include:arousing the interest of learning, and developing the working habits concerning the environmental condition of the patients; mastering the international standard of barrier-free design; encouraging researching of practical design of environmental adapta-tion, emphasizing the intern operation training of environmental adaptation, and concerning the universal education of the knowledge of bar-rier-free design.
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@#Close attention of the Course of Environmental Adaptation should be paid in rehabilitation professional training. Its teaching strategy should include: arousing the interest of learning, and developing the working habits concerning the environmental condition of the patients; mastering the international standard of barrier- free design; encouraging researching of practical design of environmental adaptation, emphasizing the intern operation training of environmental adaptation, and concerning the universal education of the knowledge of barrier- free design.
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Tropical natives (TROP) are capable of tolerating tropical heat because of their long-term adaptation to tropical environments. When exposed to heat stress, these natives tend to respond with lower sweat output, which is generally thought to be the result of heat acclimatization. The main objective of this study was to clarify central mechanisms inherent to suppressed thermal sweating in tropical natives (Malaysians) by comparing their sweating responses to those of temperate native (TEMP) (Koreans). This experiment was conducted in a thermoneutral climatic chamber (24+/-0.5 degrees C, 40+/-3% relative humidity). Heat loads were applied to each subject by the immersion of their lower legs in a hot water bath (43 degrees C for 30 min). Sweat onset-time and sweat volume were compared between TROP and TEMP. The sweat onset-times on four selected points on the body ranged from 10.25 to 13.47 min in TEMP subjects, and from 16.24 to 17.83 min in TROP subjects (p<0.001). The local sweat volumes at the same sites ranged from 4.30 to 9.74 mg/cm2 in TEMP subjects, and from between 1.80 to 4.40 mg/cm2 in TROP subjects (p<0.001). These results demonstrated a significant difference between TROP and TEMP subjects with regard to the manner in which they regulate their body temperatures when exposed to heat loads, and verified that long-term thermal adaptation blunts sweating sensitivities.