Objective To explore the effect of intestinal nitrates on the growth of Klebsiella pneumoniae and its regulatory mechanisms. Methods K. pneumoniae strains with nitrate reductase narG and narZ single or double gene knockout or with NarXL gene knockout were constructed and observed for both aerobic and anaerobic growth in the presence of KNO3 using an automated bacterial growth analyzer and a spectrophotometer, respectively. The mRNA expressions of narG and narZ in K. pneumoniae in anaerobic cultures in the presence of KNO3 and the effect of the binary regulatory system NarXL on their expresisons were detected using qRT-PCR. Electrophoretic mobility shift assays (EMSA) and MST analysis were performed to explore the specific regulatory mechanisms of NarXL in sensing and utilizing nitrates. Competitive experiments were conducted to examine anaerobic growth advantages of narG and narZ gene knockout strains of K. pneumoniae in the presence of KNO3. Results The presence of KNO3 in anaerobic conditions, but not in aerobic conditions, promoted bacterial growth more effectively in the wild-type K. pneumoniae strain than in the narXL gene knockout strain. In anaerobic conditions, the narXL gene knockout strain showed significantly lowered mRNA expressions of narG and narZ (P<0.0001). EMSA and MST experiments demonstrated that the NarXL regulator could directly bind to narG and narZ promoter regions. The wild-type K. pneumoniae strain in anaerobic cultures showed significantly increased expressions of narG and narZ mRNAs in the presence of KNO3 (P<0.01), and narG gene knockout resulted in significantly attenuated anaerobic growth and competitive growth abilities of K. pneumoniae in the presence of KNO3 (P<0.01). Conclusion The binary regulatory system NarXL of K. pneumoniae can sense changes in intestinal nitrate concentration and directly regulate the expression of nitrate reductase genes narG and narZ to promote bacterial growth.

Objective To explore the effect of intestinal nitrates on the growth of Klebsiella pneumoniae and its regulatory mechanisms. Methods K. pneumoniae strains with nitrate reductase narG and narZ single or double gene knockout or with NarXL gene knockout were constructed and observed for both aerobic and anaerobic growth in the presence of KNO3 using an automated bacterial growth analyzer and a spectrophotometer, respectively. The mRNA expressions of narG and narZ in K. pneumoniae in anaerobic cultures in the presence of KNO3 and the effect of the binary regulatory system NarXL on their expresisons were detected using qRT-PCR. Electrophoretic mobility shift assays (EMSA) and MST analysis were performed to explore the specific regulatory mechanisms of NarXL in sensing and utilizing nitrates. Competitive experiments were conducted to examine anaerobic growth advantages of narG and narZ gene knockout strains of K. pneumoniae in the presence of KNO3. Results The presence of KNO3 in anaerobic conditions, but not in aerobic conditions, promoted bacterial growth more effectively in the wild-type K. pneumoniae strain than in the narXL gene knockout strain. In anaerobic conditions, the narXL gene knockout strain showed significantly lowered mRNA expressions of narG and narZ (P<0.0001). EMSA and MST experiments demonstrated that the NarXL regulator could directly bind to narG and narZ promoter regions. The wild-type K. pneumoniae strain in anaerobic cultures showed significantly increased expressions of narG and narZ mRNAs in the presence of KNO3 (P<0.01), and narG gene knockout resulted in significantly attenuated anaerobic growth and competitive growth abilities of K. pneumoniae in the presence of KNO3 (P<0.01). Conclusion The binary regulatory system NarXL of K. pneumoniae can sense changes in intestinal nitrate concentration and directly regulate the expression of nitrate reductase genes narG and narZ to promote bacterial growth.

Objective:To investigate the relationship between discharge readiness and nutritional status of patients undergoing gastric cancer surgery in the context of enhanced recovery after surgery (ERAS) , so as to provide individualized guidance for patients after discharge.Methods:Using the convenient sampling method, a total of 120 patients who underwent radical gastrectomy for gastric cancer from June 2020 to June 2021 in Ningbo First Hospital were selected as research objects, and they all received ERAS nursing care. One day before discharge, Nutritional Risk Screening Table and Discharge Readiness Scale were used for questionnaire analysis.Results:The total score of discharge readiness of 120 patients with gastric cancer after surgery was (81.42±6.87) . Among the three dimensions, personal status was (19.65±2.19) , adaptability was (29.67±3.10) and anticipatory support was (32.10±2.61) . 57.5% (69/120) of gastric cancer patients discharged from hospital had nutritional risk. The scores of hospital discharge readiness and the scores of each dimension in the nutritional risk group were lower than those in the non-nutritional risk group, and the differences were statistically significant ( P<0.05) . Multivariate analysis showed that nutritional status was an influencing factor for the total score of hospital discharge readiness in patients with gastric cancer surgery (standardized regression coefficient was 0.321, P<0.05) . Conclusions:Under the background of ERAS, the discharge readiness of patients after gastric cancer surgery is at a moderate level, postoperative patients are generally at nutritional risk and the discharge readiness of patients with nutritional risk is lower than that of patients without nutritional risk. Perioperative nutrition management by nursing staff can improve the discharge readiness of patients undergoing gastric cancer surgery, and continuous nutrition management should be carried out for discharged patients with nutritional risk, in order to promote home rehabilitation of patients with gastric cancer surgery.