Pathogenetic and physiological mechanisms of poplar ice nucleation active bacterial canker

Using the methods introduced by Bier, X.H., Buchinock, Wang Jing-wen, Shi Rihe et al., different varieties of poplar (poplar-Mei譗ing, Poplar-A100, Poplar-Xiaohe14 et al.) were inoculated with poplar ice nucleation active (INA) bacteria respec-tively in 1997-1999. The water content, relative turgidity, lignin content, phenylalanine ammonialyase (PAL) activity, electrolyte effusion rate, and inorganic element content of poplar bark were measured before and after inoculating. The results showed that after the poplar trees were inoculated with INA bacteria, the moisture content of bark decreased but relative turgidity increased, electrolyte effusion rate increased and had a peak at temperatures of 4 and 5 C, lignin content increased and positively cor-related with poplars disease-resistance, and the plenylalanine ammonialyase activity increased and also showed a significant positive correlation with poplars disease-resistance. For the contents of inorganic element, Cu and Fe decreased but K and Zn increased obviously, while Mn, Ca and Mg changed little.

Effects of sulfate-reducing bacteria on methylmercury at the sediment–water interface

Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria（SRB） on mercury（Hg） methylation at sediment–water interfaces. Concentrations of dissolved methyl mercury（DMe Hg） in the overlying water of the control cores with bioactivity maintained（BAC） and cores with only sulfate-reducing bacteria inhibited（SRBI） and bacteria fully inhibited（BACI） were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMe Hg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations（r =- 0.5311 and r =- 0.4977 for BAC and SRBI, respectively）. The water DMe Hg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment–water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster（hgc AB）, besides SRB,causing Hg methylation in the sediment–water system.

Response of indigenous Cd-tolerant electrochemically active bacteria in MECs toward exotic Cr（VI） based on the sensing of fluorescence probes

Electrochemically active bacteria （EAB） on the cathodes of microbial electrolysis cells （MECs） can remove metals from the catholyte, but the response of these indigenous EAB toward exotic metals has not been examined, particularly from the perspective of the co-presence of Cd（II） and Cr（VI） in a wastewater. Four known indigenous Cd-tolerant EAB of Ochrobactrum sp X l, Pseudomonas sp X3, Pseudomonas delhiensis X5, and Ochrobactrum anthropi X7 removed more Cd（II） and less Cr（VI） in the simultaneous presence of Cd（II） and Cr（VI）, compared to the controls with individual Cd（II） or single Cr（VI）. Response of these EAB toward exotic Cr（VI） was related to the associated subcellular metal distribution based on the sensing of fluorescence probes. EAB cell membrane harbored more cadmium than chromium and cytoplasm located more chromium than cadmium, among which the imaging ofintracelluler Cr（III） ions increased over time, contrary to the decreased trend for Cd（II） ions. Compared to the controls with single Cd（II）, exotic Cr（VI） decreased the imaging of Cd（II） ions in the EAB at an initial 2 h and negligibly affected therealier. However, Cd（II） diminished the imaging of Cr （III） ions in the EAB over time, compared to the controls with individual Cr（VI）. Current accelerated the harboring of cadmium at an initial 2 h and directed the accumulation of chromium in EAB over time. This study provides a viable approach for simultaneously quantitatively imaging Cd（II） and Cr （III） ions in EAB and thus gives valuable insights into the response of indigenous Cd-tolerant EAB toward exotic Cr（VI） in MECs.

Systematic and long-term technical validity of toxicity determination and early warning of heavy metal pollution based on an automatic water-toxicity-determination-system

Water toxicity determination with electrochemically active bacteria(EAB)shows promise for providing early warnings for heavy metal pollution in water.However,thus far,only idealized tests with a few types of heavy metals have been conducted.In this study,an automatic water-toxicitydetermination system with high technical maturity was established,and the toxicological properties of common heavy metals were systematically assessed.The results demonstrated that the common heavy metals linearly inhibited EAB currents in the range of 0.1 mg/L to 0.5 mg/L.The toxicity ranking of the tested heavy metals was Pb^(2+)>Tl^(3+)>Cu^(2+)>Cd^(2+)>Zn^(2+)>Ni^(2+)>Hg^(2+)>As^(3+).The toxicity interaction mainly exhibited an antagonistic effect in binary heavy metal mixtures.The system can accurately determine surface water toxicity and rapidly monitor heavy metal pollution,with good repeatability and a long lifetime.Overall,this study demonstrates that EAB are capable of long-term(>60 d)surface water quality monitoring and on-site early warning of heavy metal pollution.

Living electronics

Living electronics that converges the unique functioning modality of biological and electrical circuits has the potential to transform both fundamental biophysical/biochemical inquiries and translational biomedical/engineering applications.This article will review recent progress in overcoming the intrinsic physiochemical and signaling mismatches at biological/electronic interfaces,with specific focus on strategic approaches in forging the functional synergy through:(1)biohybrid electronics,where genetically encoded bio-machineries are hybridized with electronic transducers to facilitate the translation/interpretation of biologically derived signals;and(2)biosynthetic electronics,where biogenic electron pathways are designed and programmed to bridge the gap between internal biological and external electrical circuits.These efforts are reconstructing the way that artificial electronics communicate with living systems,and opening up new possibilities for many cross-disciplinary applications in biosynthesis,sensing,energy transduction,and hybrid information processing.

Strategies for culturing active/dormant marine microbes

Microorganisms are ubiquitous in the ocean environment and they play key roles in marine ecosystem function and service.However,many of their functions and phenotypes remain unknown because indigenous marine bacteria are mostly difficult to culture.Although many novel techniques have brought previously uncultured microbes into laboratory culture,there are still many most-wanted or key players that need to be cultured from marine environments.This review discusses possible reasons for‘unculturable microbes’and categorizes uncultured bacteria into three groups:dominant active bacteria,rare active bacteria,and dormant bacteria.This review also summarizes advances in cultivation techniques for culturing each group of unculturable bacteria.Simulating the natural environment is an effective strategy for isolating dominant active bacteria,whereas culturomics and enrichment culture methods are proposed for isolating rare active bacteria.For dormant bacteria,resuscitation culture is an appropriate strategy.Furthermore,the review provides a list of the most-wanted bacteria and proposes potential strategies for culturing these bacteria in marine environments.The review provides new insight into the development of strategies for the cultivation of specific groups of uncultured bacteria and therefore paves the way for the detection of novel microbes and their functions in marine ecosystems.