Advances in Cadaverine Bacterial Production and Its Applications

Cadaverine. a natural polyamine with multiple bioactivities that is widely distributed in prokaryotes and eukaryotes, is becoming an important industrial chemical. Cadaverine exhibits broad prospects for various applications, especially as an important monomer for bio-based polyamides. Cadaverine-based polyamide PA 5X has broad application prospects owing to its environmentally friendly characteristics and exceptional performance in water absorption and dimensional stability. In this review, we summarize recent findings on the biosynthesis, metabolism, and physiological function of cadaverine in bacteria, with a focus on the regu- latory mechanism of cadaverine synthesis in Escherichia coil （E. coli）. We also describe recent developments in bacterial production of cadaverine by direct fermentation and whole-cell bioconversion, and recent approaches for the separation and purification of cadaverine. In addition, we present an overview of the ap- plication of cadaverine in the synthesis of completely bio-based polyamides. Finally. we provide an outlook and suggest future developments to advance the production of cadaverine from renewable resources.

The bacterial abundance and production in the East China Sea: seasonal variations and relationships with the phytoplankton biomass and production

The East China Sea is a productive marginal sea with a wide continental shelf and plays an important role in absorbing atmospheric carbon dioxide and transferring terrigenous organic matter to the open ocean. To investigate the roles of heterotrophic bacteria in the biogeochemical dynamics in the East China Sea, bacterial biomasses （BB） and productions （BP） were measured in four cruises. The spatial distributions of the BB and the BP were highly season-dependent. Affected by the Changjiang River discharge, the BB and the BP were high in shelf waters （bottom depth not deeper than 50 m） and generally decreased offshore in August 2009. In December 2009 to lanuary 2010, and November to December 2010, the BB and the BP were high in waters with medium bottom depth. The onshore-offshore decreasing trends of the BB and the BP also existed in May-June 2011, when the BB was significantly higher than in other cruises in shelf break waters （bottom depth deeper than 50 m but not deeper than 200 m）. The results of generalized additive models （GAM） suggest that the BB increased with the temperature at a range of 8-20~C, increased with the chlorophyll concentration at a range of 0.02-3.00 mg/m3 and then declining, and decreased with the salinity from 28 to 35. The relationship between the temperature and the log-transformed bacterial specific growth rate （SGR） was linear. The estimated temperature coefficient （Q10） of the SGR was similar with that of the phytoplankton growth. The SGR also increased with the chlorophyll concentration. The ratio of the bacterial to phytoplankton production ranged from less than 0.01 to 0.40, being significantly higher in November December 2010 than in May-June 2011. Calculated from the bacterial production and growth efficiency, the bacterial respiration consumed, on average, 59%, 72% and 23% of the primary production in August 2009, November-December 2010, and May-/une 2011, respectively.

Bacterial productivity in the Prydz Bay and its adjacent waters, Antarctic

Bacterial productivity was measured using 3H-thymidine methods in the Prydz Bay and its adjacent waters in the Southern Ocean during the 16th National Antarctic Research Expedition of China (CHINARE). The results showed that bacterial productivity in our study areas ranged from 4.5 to 191 ngC·dm -3·h -1, with an average of 50.4 ngC·dm -3·h -1. These values were comparable to those reported for the Ross Sea. The mean ratio of bacterial productivity to primary productivity in our study areas was 41%. The general characteristics in the vertical profiles showed a subsurface maximum at most of the stations, which was also consistent with those observed in the other sea areas in the Southern Ocean. The spatial distribution of bacterial productivity and dissolved organic carbon in the surface waters showed that their variations were inversely correlative. The relationship among bacterial productivity, primary productivity and dissolved organic carbon suggested that bacterial productivity in the Prydz Bay and its adjacent water was influenced mostly by phytoplankton activities and the hydrologic conditions.

Spatial contrast in phytoplankton, bacteria and microzooplankton grazing between the eutrophic Yellow Sea and the oligotrophic South China Sea

Three cruises were conducted to investigate the distributions of nutrients,chlorophyll a(Chla),new and regenerated primary production,bacterial abundance and production,and microzooplankton grazing rates in the Yellow Sea(YS)and the South China Sea(SCS)during March and May.As the water column moved from low to high temperature,weak to strong stratification and high to low nutrients from the YS to the SCS,Chl-a,primary production and bacterial biomass decreased.In contrast,bacterial production,microzooplankton grazing and size preference increased from the YS to the SCS.The increasing grazing activity and decreasing f-ratio from the YS to the SCS suggest roles of regenerated nutrients in the supporting the community increased and more bacteria played important roles in the carbon flow in the oligotrophic SCS than in the eutrophic YS.These variabilities force the classical food chain dominated community in the eutrophic waters into the microbial loop,which is dominant in oligotrophic waters.As nutrients decrease,temperature and grazing activity increase from the YS to the SCS.The increasing ratio of integrated bacterial production to integrated primary production indicates that communities change from autotrophy to heterotrophy and waters change from a carbon sink to a carbon source.

Making comparable measurements of bacterial respiration and production in the subtropical coastal waters

Accurate estimates of bacterial carbon metabolic rates are indispensable for understanding the regulation of carbon fluxes in aquatic environments.Here,changes in bacterial growth,production,and cell volume in both pre-filtered and unfiltered seawater during 24 h incubation were monitored.The methodological artifacts during Winkler bacterial respiration(BR)measurements in subtropical Hong Kong coastal waters were assessed.Bacterial abundance increased by 3-and 1.8-fold in the pre-filtered and unfiltered seawater after incubation,respectively.Bacterial production(BP)and cell volume also showed significant enhancement.Compared with the BR measurements obtained by the Winkler method,the instantaneous free-living BR measurements,after correction,decreased by~70%.The time-integrated free-living BR and BP during 24 h incubation in the pre-filtered sample provided an improved estimate of bacterial growth efficiency,which increased by~52%compared to the common estimations using the noncomparable measurements of integrated free-living BR and instantaneous total BP.The overestimation of BR also exaggerated the contribution of bacteria to community respiration,affecting the understanding on the metabolic state of the marine ecosystems.Furthermore,the BR estimates by the Winkler method may be more biased in environments with a higher bacterial growth rate and tightly coupled grazing mortality,as well as in those with higher nutrient concentrations.These results reveal obvious problems associated with the BR methodology and raise a warning for caution when comparing BP and BR,as well as when making estimations of carbon flow through the complex microbial networks in aquatic ecosystems.

Sensitivity of Planktonic Aquatic Bacteria to Ciprofloxacin

Many anthropogenic compounds, such as antibiotics, are found at trace levels (-1) in aquatic and terrestrial systems. The effect of these compounds on the metabolism and function of microbes are difficult to assess because the assays used, such as the minimum inhibitory concentration (MIC) and the disk diffusion methods, lack the sensitivities to measure bacterial response to these very low levels of antibiotics on bacterial populations. Therefore, we theorized that the [3H] thymidine incorporation into DNA method might be sensitive in determining the effect of DNA inhibiting antibiotics on DNA production in planktonic bacteria in aquatic systems. Utilizing the 3H thymidine method, we measured the effects of ciprofloxacin on DNA production on planktonic bacteria in river and pond waters. Ciprofloxacin significantly (P < 0.02) inhibited river water bacteria at a concentration of 25 μg·L-1 but significant inhibition (P < 0.01) occurred at 1000 μg·L-1in pond water. The very low concentration required to inhibit DNA production in river water bacteria indicates that bacteria are extremely sensitive to antibiotics at very low concentrations. A likely reason for the differences in inhibition between the two waters is due to ciprofloxacin becoming bound, and possibly becoming biologically inactive, in the pond water due to higher dissolved organic carbon content. This work demonstrates that bacteria in some aquatic systems can be significantly impacted by low concentrations of anthropogenic antibiotics finding their way into these systems and that our assumptions as to the concentrations at which antibiotics affect microbes are highly underestimated.

Potential acute effects of suspended aluminum nitride (AlN) nanoparticles on soluble microbial products (SMP) of activated sludge

The study aims to identify the potential acute effects of suspended aluminum nitride（Al N）nanoparticles（NPs） on soluble microbial products（SMP） of activated sludge.Cultured activated sludge loaded with 1,10,50,100,150 and 200 mg/L of Al N NPs were carried out in this study.As results showed,Al N NPs had a highly inverse proportionality to bacterial dehydrogenase and OUR,indicating its direct toxicity to the activated sludge viability.The toxicity of Al N NPs was mainly due to the nano-scale of Al N NPs.In SMP,Al N NPs led to the decrease of polysaccharide and humic compounds,but had slight effects on protein.The decrease of tryptophan-like substances in SMP indicated the inhibition of Al N NPs on the bacterial metabolism.Additionally,Al N NPs reduced obviously the molecular weight of SMP,which might be due to the nano-scale of Al N.