Studies of Antibiotic Resistance of Beta-Lactamase Bacteria under Different Nutrition Limitations at the Single-Cell Level

Drug resistance involves many biological processes, including cell growth, cell communication, and cell cooperation. In the last few decades, bacterial drug resistance studies have made substantial progress. However, a major limitation of the traditional resistance study still exists: most of the studies have concentrated on the average behavior of enormous amounts of cells rather than surveying single cells with different phenotypes or genotypes. Here, we report our study of beta-lactamase bacterial drug resistance in a well-designed microfluidic device, which allows us to conduct more controllable experiments, such as controlling the nutrient concentration, switching the culture media, performing parallel experiments, observing single cells, and acquiring time-lapse images. By using GFP as a beta-lactamase indicator and acquiring time-lapse images at the single-cell level, we observed correlations between the bacterial heterogeneous phenotypes and their behavior in different culture media. The feedback loop between the growth rate and the beta-lactamase production suggests that the beta-lactamase bacteria are more resistant in a rich medium than in a relatively poor medium. In the poorest medium, the proportion of dormant cells may increase, which causes a lower death rate in the same generation. Our work may contribute to assaying the antibiotic resistance of pathogenic bacteria in heterogeneous complex media.     

Intrinsic Multi-Scale Dynamic Behaviors of Complex Financial Systems

The empirical mode decomposition is applied to analyze the intrinsic multi-scale dynamic behaviors of complex financial systems. In this approach, the time series of the price returns of each stock is decomposed into a small number of intrinsic mode functions, which represent the price motion from high frequency to low frequency. These intrinsic mode functions are then grouped into three modes, i.e., the fast mode, medium mode and slow mode. The probability distribution of returns and auto-correlation of volatilities for the fast and medium modes exhibit similar behaviors as those of the full time series, i.e., these characteristics are rather robust in multi time scale. However, the cross-correlation between individual stocks and the return-volatility correlation are time scale dependent. The structure of business sectors is mainly governed by the fast mode when returns are sampled at a couple of days, while by the medium mode when returns are sampled at dozens of days. More importantly, the leverage and anti-leverage effects are dominated by the medium mode.     

Effects of Sevoflurane on Young Male Adult C57BL/6 Mice Spatial Cognition

Inhalation anesthetics are reported to affect cognition in both animals and humans. The influence of inhalation anesthetics in learning and memory are contradictory. We therefore investigated the effects of sevoflurane anesthesia with different durations on cognitive performance and the levels of NMDA receptor subunit NR2B, phosphorylated ERK1/2 (p-ERK1/2) and activated caspase3 in mouse hippocampus. We anaesthetized eight-week old male C57BL/6 mice with 2.5% sevoflurane for durations ranging from one to four hours. Non-anaesthetized mice served as controls. Mice exposed to sevoflurane for one to three hours showed improved performance, whereas mice with exposure up to four hours displayed similar behavioral performance as control group. NR2B was increased both at 24h and at two weeks post sevoflurane exposure in all groups. The p-ERK1/2: total ERK1/2 ratio increased at 24h in all anesthesia groups. The ratio remained elevated at two weeks in groups with two- to four-hour exposure. Activated caspase3 was detected elevated at 24h in groups with two- to four-hour exposure. The elevated trend of activated caspase3 was still detectable at two weeks in groups with three- to four-hour exposure. At two weeks post anesthesia, the typical morphology associated with apoptotic cells was observed in the hippocampus of mice exposed to four hours of sevoflurane. Our results indicate that 2.5% sevoflurane exposure for one to three hours improved spatial cognitive performance in young adult mice. The cognitive improvement might be related to the increase of NR2B, the p-ERK1/2: total ERK1/2 ratio in hippocampus. However, exposure to sevoflurane for four hours caused neurotoxicity due to caspase3 activation and apoptosis.     

Development of a stepwise aeration control strategy for efficient docosahexaenoic acid production by Schizochytrium sp.

The effect of aeration on the performance of docosahexaenoic acid (DHA) production by Schizochytrium sp. was investigated in a 1,500-L bioreactor using fed-batch fermentation. Six parameters, including specific growth rate, specific glucose consumption rate, specific lipid accumulation rate, cell yield coefficient, lipid yield coefficient, and DHA yield coefficient, were used to understand the relationship between aeration and the fermentation characteristics. Based on the information obtained from the parameters, a stepwise aeration control strategy was proposed. The aeration rate was controlled at 0.4 volume of air per volume of liquid per minute (vvm) for the first 24 h, then shifted to 0.6 vvm until 96 h, and then switched back to 0.4 vvm until the end of the fermentation. High cell density (71 g/L), high lipid content (35.75 g/L), and high DHA percentage (48.95%) were achieved by using this strategy, and DHA productivity reached 119 mg/L h, which was 11.21% over the best results obtained by constant aeration rate.     

SHP2 Mediates the Localized Activation of Fyn Downstream of the α6β4 Integrin To Promote Carcinoma Invasion

Src family kinase (SFK) activity is elevated in many cancers, and this activity correlates with aggressive tumor behavior. The α6β4 integrin, which is also associated with a poor prognosis in many tumor types, can stimulate SFK activation; however, the mechanism by which it does so is not known. In the current study, we provide novel mechanistic insight into how the α6β4 integrin selectively activates the Src family member Fyn in response to receptor engagement. Both catalytic and noncatalytic functions of SHP2 are required for Fyn activation by α6β4. Specifically, the tyrosine phosphatase SHP2 is recruited to α6β4 and its catalytic activity is stimulated through a specific interaction of its N-terminal SH2 domain with pY1494 in the β4 subunit. Fyn is recruited to the α6β4/SHP2 complex through an interaction with phospho-Y580 in the C terminus of SHP2. In addition to activating Fyn, this interaction with Y580-SHP2 localizes Fyn to sites of receptor engagement, which is required for α6β4-dependent invasion. Of significance for tumor progression, phosphorylation of Y580-SHP2 and SFK activation are increased in orthotopic human breast tumors that express α6β4 and activation of this pathway is dependent upon Y1494.Expression of the α6β4 integrin, a laminin receptor, is associated with poor patient prognosis and reduced survival in many human cancers (32). For this reason, there is considerable interest in understanding how this integrin is regulated and how it functions to promote tumor progression. In normal tissues, the α6β4 integrin plays a major role in maintaining the integrity of epithelia by binding to laminins in the basement membrane and regulating the assembly of hemidesmosomes on the basal epithelial cell surface (7, 17). In pathophysiological conditions such as wound healing and cancer, the stable adhesive interactions of the α6β4 receptor are disrupted by phosphorylation of the β4 cytoplasmic domain, converting α6β4 to a signaling-competent receptor that promotes dynamic adhesion and invasion (18). Phosphorylation of the β4 subunit cytoplasmic domain on serine residues contributes to the dynamic adhesive functions of the receptor by disrupting interactions with hemidesmosomal proteins that regulate stable adhesion (33, 37). Phosphorylation of the β4 cytoplasmic domain on tyrosine residues may also contribute to the regulation of hemidesmosomes, but it is likely that the major contribution of tyrosyl phosphorylation is to mediate interactions that stimulate downstream signaling from the receptor (22).In transformed cells, engagement of the α6β4 integrin stimulates the activation of several signaling molecules, including phosphatidylinositol-3 kinase (PI3K), mitogen-activated protein kinases (MAPK), NFκB, and Src family kinases (SFKs) (10, 12, 21, 40). In previous studies, we identified Y1494 in the β4 subunit cytoplasmic domain as an important mediator of α6β4-dependent signaling by demonstrating that mutation of Y1494 inhibits the ability of α6β4 to stimulate PI3K, MAPK, and SFK activation (10, 39). Restoration of both PI3K and SFK signaling, but not MAPK signaling, rescues invasion in tumor cells expressing Y1494F-β4, indicating that PI3K and SFK signaling pathways cooperate downstream of Y1494 to promote α6β4-dependent invasion (10). Y1494 is localized within an immunoreceptor tyrosine-based inhibition motif (ITIM), a canonical binding site for Src-homology-2 (SH2) domain-containing protein-tyrosine phosphatase 1 (SHP1) and SHP2 (44). Examination of a chimeric receptor containing the extracellular domain of TrkB and the transmembrane and cytoplasmic domains of the β4 subunit demonstrated that SHP2 binds to and is activated by sequences in the β4 cytoplasmic domain in response to dimerization (23). Moreover, Y1494 is one of three tyrosine residues, along with Y1257 and Y1440, that mediate the interaction of SHP2 with the β4 subunit cytoplasmic domain in response to c-Met signaling (6). Importantly, SHP2 is essential for the activation of SFKs both by the chimeric TrkB/β4 receptor and when the β4 subunit functions as a signaling adaptor for c-Met (6, 23). However, the mechanism by which SHP2 activates SFKs in response to α6β4 engagement has not been established.Elevated SFK activity correlates strongly with breast cancer invasion and metastasis, and these kinases are frequently activated in human cancers (15). Given the parallels between α6β4 expression and SFK activation in cancer, investigation of how α6β4 contributes to the activation of this invasion-promoting pathway is warranted. In the current study, we sought to elucidate the mechanism by which engagement of α6β4 activates SFKs and the significance of the β4/SHP2/SFK signaling axis for tumor progression. Our results reveal a novel mechanism for SHP2-dependent activation of the SFK family member Fyn which involves Y580 in the C terminus of SHP2.     

Association of the DNMT3B polymorphism with colorectal adenomatous polyps and adenocarcinoma

DNMT3B is an important enzyme to modulate the methylation status in mammalian cells. The aim of this study is to investigate the correlation of the DNMT3B G39179T polymorphism with the susceptibilities of colorectal adenomatous polyps and adenocarcinoma. This case-control study included 146 colorectal adenomatous polyps, 170 colorectal adenocarcinoma patients, and 157 normal controls. DNMT3B polymorphism was analyzed by polymerase chain reaction-restriction fragment length polymorphism analysis. Family history of colorectal cancer significantly increases the risk of developing colorectal adenomatous polyps and adenocarcinoma. The genotype frequency of DNMT3B polymorphism (T/T and G/T + G/G) in adenocarcinoma patients was significantly different from that in controls (P value = 0.01). Compared with DNMT3B T/T genotype, the G allelotype (G/T + G/G genotype) had lower risk to develop colorectal adenocarcinoma (OR = 0.50, 95% CI = 0.29–0.87); while there was no significant difference between the colorectal adenomatous polyps patients and controls (OR = 0.63, 95% CI = 0.37–1.09), although descending tendency could be found in this polyps group. In the stratification analysis, a significant association was confined to subgroups of age < 55 (OR = 0.31, 95% CI = 0.12–0.84) and males (OR = 0.35, 95% CI = 0.17–0.71). Meanwhile, combined G/T + G/G genotypes were found to have a lower risk in non-drinkers to develop both colorectal adenomatous polyps and adenocarcinoma (OR = 0.54, 95% CI = 0.31–0.96 and OR = 0.48, 95% CI = 0.27–0.84, respectively). This study also showed a distinct difference in the distribution of DNMT3B G39179T SNP in different ethnics. DNMT3B G39179T SNP may be a potential genetic susceptibility factor for adenocarcinoma of the colon, especially in younger Chinese Han non-drinker men.     

Removal of nutrients and heavy metals from wastewater with mangrove Sonneratia apetala Buch-Ham

Mangrove wetlands are important in the removal of nutrients, heavy metals, and organic pollutants from wastewater within estuarine systems due to the presence of oxidized and reduced conditions, periodic flooding by incoming and outgoing tides, and high clay and organic matter content. This study investigated the removal efficiency of nutrients and heavy metals from wastewater by the mangrove Sonneratia apetala Buch-Ham in a simulated wetland. Eight different treatments, namely, three concentration levels of wastewaters, with and without planting of the mangrove species, and one control (with salted water) each for both with and without planting of the mangrove species, were employed in this study. Results showed that the amounts of total mangrove biomass from different treatments were in the following order: PL-TW (planted with ten times higher-than-normal wastewater concentration) > PL-FW (planted with five times higher-than-normal wastewater concentration) > PL-SW (planted with normal wastewater concentration) > PL-NW (planted with no wastewater), whereas the magnitude of the heavy metal contents in the biomass was in the following order: Cu > Pb > Cd > Zn. Very good linear correlations existed between the biomass and the nutrients or heavy metals. The Sonneratia apetala Buch-Ham species had its own selectivity for uptake of heavy metals regardless of the initial heavy metal contents and was more effective in the removal of nutrients than heavy metals. Our study suggested that mangrove wetlands with Sonneratia apetala Buch-Ham species had great potential for the removal of nutrients and heavy metals in coastal areas.     

The thylakoid protease Deg1 is involved in photosystem‐II assembly in Arabidopsis thaliana

DegP proteases have been shown to possess both chaperone and protease activities. The proteolytic activities of chloroplast DegP‐like proteases have been well documented. However, whether chloroplast Deg proteases also have chaperone activities has remained unknown. Here we show that chloroplast Deg1 also has chaperone activities, like its Escherichia coli ortholog DegP. Transgenic plants with reduced levels of Deg1 accumulated normal levels of different subunits of the major photosynthetic protein complexes, but their levels of photosystem‐II (PSII) dimers and supercomplexes were reduced. In vivo pulse‐chase protein labeling experiments showed that the assembly of newly synthesized proteins into PSII dimers and supercomplexes was impaired, although the synthesis rate of chloroplast proteins was unaffected in the transgenic lines. Protein overlay assays provided direct evidence that Deg1 interacts with the PSII reaction center protein D2. These results suggest that Deg1 assists the assembly of the PSII complex, probably through interaction with the PSII reaction center D2 protein.     

Receptor‐like kinase OsSIK1 improves drought and salt stress tolerance in rice (Oryza sativa) plants

Receptor‐like kinases (RLKs) play essential roles in plant growth, development and responses to environmental stresses. A putative RLK gene, OsSIK1, with extracellular leucine‐rich repeats was cloned and characterized in rice (Oryza sativa). OsSIK1 exhibits kinase activity in the presence of Mn²⁺, and the OsSIK1 kinase domain has the ability to autophosphorylate and phosphorylate myelin basic protein (MBP). OsSIK1 promoter‐GUS analysis revealed that OsSIK1 is expressed mainly in the stem and spikelet in rice. The expression of OsSIK1 is mainly induced by salt, drought and H₂O₂ treatments. Transgenic rice plants with overexpression of OsSIK1 show higher tolerance to salt and drought stresses than control plants. On the contrary, the knock‐out mutants sik1‐1 and sik1‐2, as well as RNA interference (RNAi) plants, are sensitive to drought and salt stresses. The activities of peroxidase, superoxide dismutase and catalase are enhanced significantly in OsSIK1‐overexpressing plants. Also, the accumulation of H₂O₂ in leaves of OsSIK1‐overexpressing plants is much less than that of the mutants, RNAi plants and control plants, as measured by 3,3′‐diamino benzidine (DAB) staining. We also show that OsSIK1 affects stomatal density in the abaxial and adaxial leaf epidermis of rice. These results indicate that OsSIK1 plays important roles in salt and drought stress tolerance in rice, through the activation of the antioxidative system.