Effects of Simulated Microgravity on Acquired Antibiotic Resistance in Klebsiella pneumoniae Exposed to Trace Antibiotic.

Objective: The purpose of this study is to gain a better understanding of the impact of microgravity on antibiotic resistance. Methods: K. pneumoniae original (KPO) strain was cultured under either simulated microgravity (SMG) conditions with background antibiotic exposure (SMGA) for the experimental strain or a normal gravity condition with background antibiotic exposure (NGA) for the control strain. The K. pneumoniae original (KPO) strain was also cultured under normal gravity (NG) as an additional control. Antibiotic susceptibility was evaluated prior to their incubation under SMGA, NGA, or NG conditions. After 20 cycles of incubation, antibiotic susceptibility, genomic, transcriptomic, and proteomic tests were conducted on them. Results: SMGA and NGA strains both showed resistance to ciprofloxacin and intermediate resistance to levofloxacin. Genes associated with antibiotic resistance of Klebsiella pneumoniae, including acrB, oqxB, oqxA, ompC, ompF, and tolC were found to be differently expressed between SMGA and NGA strains or between SMGA and NG strains. It was found that the biggest family of genes in the differently expressed gene (DEG) cluster between SMGA and NGA and between SMGA and NG was the same, paaBCDFGHI, but with opposite change direction, i.e., downregulation between SMGA and NGA strains, while upregulation between SMGA and NG strains. Besides, the top-ranking functional descriptions in terms of the number of DEGs whether between SMGA and NGA or between SMGA and NG were "amino acid transport and metabolism", "carbohydrate transport and metabolism", "transcription", and "inorganic ion transport and metabolism". Two pathways of "citrate cycle (TCA cycle)" and "oxidative phosphorylation" were significantly enriched by DEGs both between SMGA and NGA and between SMGA and NG. Conclusion: Our study confirmed that low levels of antibiotics present in SMG can select for resistant K. pneumoniae strains. However, SMG did not alter the antibiotic resistance in K. pneumoniae induced by exposure to trace antibiotic.

Effects of short-term exposure to simulated microgravity on the physiology of Bacillus subtilis and multiomic analysis.

In our study, Bacillus subtilis was disposed to a simulated microgravity (SMG) environment in high-aspect ratio rotating-wall vessel bioreactors for 14 days, while the control group was disposed to the same bioreactors in a normal gravity (NG) environment for 14 days. The B. subtilis strain exposed to the SMG (labeled BSS) showed an enhanced growth ability, increased biofilm formation ability, increased sensitivity to ampicillin sulbactam and cefotaxime, and some metabolic alterations compared with the B. subtilis strain under NG conditions (labeled BSN) and the original strain of B. subtilis (labeled BSO). The differentially expressed proteins (DEPs) associated with an increased growth rate, such as DNA strand exchange activity, oxidoreductase activity, proton-transporting ATP synthase complex, and biosynthetic process, were significantly upregulated in BSS. The enhanced biofilm formation ability may be related with the DEPs of spore germination and protein processing in BSS, and differentially expressed genes involved in protein localization and peptide secretion were also significantly enriched. The results revealed that SMG may increase the level of related functional proteins by upregulating or downregulating affiliated genes to change physiological characteristics and modulate growth ability, biofilm formation ability (epsB, epsC, epsN), antibiotic sensitivity (penP) and metabolism. Our experiment may gives new ideas for the study of space microbiology.

Decreased biofilm formation in Proteus mirabilis after short-term exposure to a simulated microgravity environment.

BACKGROUND: Microbes threaten human health in space exploration. Studies have shown that Proteus mirabilis has been found in human space habitats. In addition, the biological characteristics of P. mirabilis in space have been studied unconditionally. The simulated microgravity environment provides a platform for understanding the changes in the biological characteristics of P. mirabilis. OBJECTIVE: This study intends to explore the effect of simulated microgravity on P. mirabilis, the formation of P. mirabilis biofilm, and its related mechanism. METHODS: The strange deformable rods were cultured continuously for 14 days under microgravity simulated in high-aspect rotating vessels (HARVs). The morphology, growth rate, metabolism, and biofilm formation of the strain were measured, and the phenotypic changes of P. mirabilis were evaluated. Transcriptome sequencing was used to detect differentially expressed genes under simulated microgravity and compared with phenotype. RESULTS: The growth rate, metabolic ability, and biofilm forming ability of P. mirabilis were lower than those of normal gravity culture under the condition of simulated microgravity. Further analysis showed that the decrease of growth rate, metabolic ability, and biofilm forming ability may be caused by the downregulation of related genes (pstS, sodB, and fumC). CONCLUSION: The simulated microgravity condition enables us to explore the potential relationship between bacterial phenotype and molecular biology, thus opening up a suitable and constructive method for medical fields that have not been explored before. It provides a certain strategy for the treatment of P. mirabilis infectious diseases in space environment by exploring the microgravity of P. mirabilis.

Effects of Simulated Microgravity on the Physiology of Stenotrophomonas maltophilia and Multiomic Analysis.

Many studies have shown that the space environment plays a pivotal role in changing the characteristics of conditional pathogens, especially their pathogenicity and virulence. However, Stenotrophomonas maltophilia, a type of conditional pathogen that has shown to a gradual increase in clinical morbidity in recent years, has rarely been reported for its impact in space. In this study, S. maltophilia was exposed to a simulated microgravity (SMG) environment in high-aspect ratio rotating-wall vessel bioreactors for 14days, while the control group was exposed to the same bioreactors in a normal gravity (NG) environment. Then, combined phenotypic, genomic, transcriptomic, and proteomic analyses were conducted to compare the influence of the SMG and NG on S. maltophilia. The results showed that S. maltophilia in simulated microgravity displayed an increased growth rate, enhanced biofilm formation ability, increased swimming motility, and metabolic alterations compared with those of S. maltophilia in normal gravity and the original strain of S. maltophilia. Clusters of Orthologous Groups (COG) annotation analysis indicated that the increased growth rate might be related to the upregulation of differentially expressed genes (DEGs) involved in energy metabolism and conversion, secondary metabolite biosynthesis, transport and catabolism, intracellular trafficking, secretion, and vesicular transport. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that the increased motility might be associated the upregulation of differentially expressed proteins (DEPs) involved in locomotion, localization, biological adhesion, and binding, in accordance with the upregulated DEGs in cell motility according to COG classification, including pilP, pilM, flgE, flgG, and ronN. Additionally, the increased biofilm formation ability might be associated with the upregulation of DEPs involved in biofilm formation, the bacterial secretion system, biological adhesion, and cell adhesion, which were shown to be regulated by the differentially expressed genes (chpB, chpC, rpoN, pilA, pilG, pilH, and pilJ) through the integration of transcriptomic and proteomic analyses. These results suggested that simulated microgravity might increase the level of corresponding functional proteins by upregulating related genes to alter physiological characteristics and modulate growth rate, motility, biofilm formation, and metabolism. In conclusion, this study is the first general analysis of the phenotypic, genomic, transcriptomic, and proteomic changes in S. maltophilia under simulated microgravity and provides some suggestions for future studies of space microbiology.

OXIDATIVE STRESS IN A RAT MODEL OF COTTON SMOKE INHALATION-INDUCED PULMONARY INJURY.

BACKGROUND: Smoke inhalation injury refers to airway and lung parenchyma injury and general chemical damage caused by inhaling toxic gases and substances. The aim of this study was to explore the oxidative stress mechanism of cotton smoke inhalation-induced pulmonary injury in a rat model. MATERIALS AND METHODS: Eighteen male Sprague-Dawley rats were randomly divided into control group, 6 h group, and 24 h group (six rats in each group), which duplicated previous rat cotton smoke-inhalation injury models. Rats in 6 h and 24 h groups were euthanised at 6 h and 24 h after smoke inhalation, respectively. ELISA method was used to detect indicators in the rats' lung tissue. Quantitative iNOS mRNA and γ-GCS mRNA measurements were performed using a fluorescence PCR method. RESULTS: The concentrations of MDA, NO, iNOS, γ-GCS, iNOS mRNA, and the relative expression of γ-GCS mRNA in the rats' lung tissues in 6 h and 24 h groups were higher than control group (P < 0.05), and the concentration of NO and relative expressions of iNOS mRNA and γ-GCS mRNA in 24 h group were significantly higher than 6 h group (P < 0.05). The concentrations of GSH in 24 h and 6 h groups were significantly lower than control group (P < 0.05), and that in 24 h group was even significantly lower than 6 h group (P < 0.05). CONCLUSION: In rats with cotton smoke inhalation-induced pulmonary injury, the increased iNOS mRNA transcription can cause increase of iNOS synthesis and promotion of NO synthesis. The increased γ-GCS mRNA transcription can cause increase of γ-GCS synthesis and but decrease of GSH concentration. The activation of the antioxidant system is insufficient to combat oxidative stress damage. So the oxidant/antioxidant system is imbalanced, leading to gradual aggravation of lung injury.

Protective effects of hydrogen sulfide inhalation on oxidative stress in rats with cotton smoke inhalation-induced lung injury.

The aim of the present study was to investigate the mechanism by which hydrogen sulfide (H2S) inhalation protects against oxidative stress in rats with cotton smoke inhalation-induced lung injury. A total of 24 male Sprague-Dawley rats were separated randomly into four groups, which included the control, H2S, smoke and smoke + H2S groups. A rat model of cotton smoke inhalation-induced lung injury was established following inhalation of 30% oxygen for 6 h. In addition, H2S (80 ppm) was inhaled by the rats in the H2S and smoke + H2S groups for 6 h following smoke or sham-smoke inhalation. Enzyme-linked immunosorbent assays were performed to measure various indices in the rat lung homogenate, while the levels of nuclear factor (NF)-κBp65 in the lung tissue of the rats were determined and semiquantitatively analyzed using immunohistochemistry. In addition, quantitative fluorescence polymerase chain reaction was employed to detect the mRNA expression of inducible nitric oxide synthase (iNOS) in the rat lung tissue. The concentrations of malondialdehyde (MDA), nitric oxide (NO), inducible iNOS and NF-κBp65, as well as the sum-integrated optical density of NF-κBp65 and the relative mRNA expression of iNOS, in the rat lung tissue from the smoke + H2S group were significantly lower when compared with the smoke group. The concentrations of MDA, NO, iNOS and NF-κBp65 in the H2S group were comparable to that of the control group. Therefore, inhalation of 80 ppm H2S may reduce iNOS mRNA transcription and the production of iNOS and NO in rats by inhibiting NF-κBp65 activation, subsequently decreasing oxidative stress and cotton smoke inhalation-induced lung injury.

[The 18F-FDG myocardial metabolic imaging in twenty seven pilots with regular aerobic training].

OBJECTIVE: To evaluate the characteristics of myocardial (18)F-FDG imaging in pilots with regular aerobic exercise training. METHODS: Twenty seven healthy male pilots with regular aerobic exercise training were included in this study. The subjects were divided into fasting (n = 17) or non-fasting group (n = 10). Fluorine-18-labeled deoxyglucose and Tc-99m-sestamibi dual-nuclide myocardial imaging were obtained at rest and at target heart rate during bicycle ergometer test. The exercise and rest myocardial perfusion imaging were analyzed for myocardial ischemia presence. The myocardial metabolism imaging was analyzed with the visual semi-quantitative analyses model of seventeen segments. RESULTS: The secondary-extreme heart rate (195-age) was achieved in all subjects. There was no myocardial ischemia in all perfusion imaging. In the visual qualitative analyses, four myocardial metabolism imaging failed in the fasting group while one failed in the non-fasting group (P > 0.05). In the visual semi-quantitative analyses, myocardial metabolism imaging scores at rest or exercise in all segments were similar between two groups (P > 0.05). In the fasting group, the myocardial metabolism imaging scores during exercise were significantly higher than those at rest in 6 segments (P < 0.05). In the non-fasting group, the scores of 3 exercise myocardial metabolism imaging were significantly higher than those at rest (P < 0.05). CONCLUSION: Satisfactory high-quality myocardial metabolism imaging could be obtained at fasting and exercise situations in subjects with regular aerobic exercise.