The rhizosphere is an area of high bacteria–plant interaction and a target for improving plant growth for agricultural and energy crops in marginal soil. However, the root system in soil is inherently difficult to study due to its complexity and many location-specific variables. To gain mechanistic insights into rhizosphere, laboratorybased devices with controlled environments and controllable microbiome communities are beneficial as they allow us to delve deeper into the interactions. Massalha et al. co-inoculated the fluorescently tagged E. coli and B. subtilis in an A. thaliana root and observed the B. subtilis establishing close to the root tissue while E. coli is excluded away, hovering over the root, suggesting possible antagonistic interactions between B. subtilis and E. coli in rhizosphere. To increase the relevance of such a reduced system to the natural system, at least the taxonomically and functionally representative members of the bacteria and fungi in the rhizosphere need be co-inoculated and their live interactions quantitatively measured. In general, the taxonomic diversity decreases from the bulk soil to rhizosphere, albeit with increased metabolic activities due to the selective force by the plants and antagonistic behavior of the root colonizers, with the most abundant bacterial taxa in rhizosphere to be Proteobacteria, Acidobacteria, Actinobacteria, Furmicutes, and Bacteroidetes depending on the plant types. In this study, we demonstrated multispectral imaging of the P. simiae strains expressing 9 different fluorescent proteins. Due to the spectral overlaps among these fluorescent proteins however,cultivo de frambuesas not all 9 strains could be unmixed but were binned into 4 different spectral categories.
To increase the number of spectrally distinct bacteria in rhizosphere, there needs to be various approaches such as protein engineering to narrow the excitation and emission bandwidth of the fluorescent proteins, utilizing fluorescent dyes or quantum dots, lifetime measurement to further delineate the fluorescent species, and development of a new line of fluorescent protein expression system to expand the spectral range such as phytochrome-based fluorescent proteins for near-infrared fluorescence. With the continual development of the biosensors as well as the fluorescent protein expression system such as CRAGE-Duet that engineered the P. simiae strains in this study, the Imaging EcoFAB is poised to gain valuable spatiotemporal information of the relevant synthetic community in rhizosphere. Another interesting area to explore using Imaging EcoFAB due to its larger chamber size is defining the boundary of the rhizosphere, whose definition has varied depending on the study. In experiments where plants are grown in natural soils, it is sometimes pragmatically defined as the soil attached to the roots; in general, many studies extend the rhizosphere for up to 4 mm. However, attempts to define the rhizospheric boundaries have primarily taken a more holistic view, focusing on considerations of specific soil contexts and the activity or properties of the chemical of interest . With improved methods of capturing the spatiotemporal dynamics of the rhizosphere in devices like the imagining EcoFAB, a third or perhaps unifying definition of the rhizosphere could arise. Paired with the use of simplified or synthetic communities of fluorescently tagged microorganisms in plant root imaging systems, the Imaging EcoFAB could help define the reaches and bounds of the rhizosphere. We believe that a deeper understanding of the rhizosphere must include interrogating the spatiotemporal dynamics at high-resolution and quantitative data analysis.
The future of these developments in EcoFAB with high-resolution imaging could easily be tapped into by expanding the root imaging phenotyping tools like MyROOT 2.0 and RootNav 2.0, and the imaging analysis packages like scikit-image. Additionally, these sources ofdata could be fed as positional information into platforms such as COMETS for molecular understanding of rhizosphere dynamics. The eventual goal is to gain the mechanistic understanding of the plant–microbial interactions in the rhizosphere and drive the discoveries in improved plant growth promotion.Chemical speciation programs, such as GEOCHEM , GEOCHEM-PC , PHREEQC, MINEQL+, and MINTEQA2 have been excellent tools for scientists to use in designing appropriate solutions for their experiments. Programs of this type allow the user to estimate the interactions between metals and ligands and to calculate the free activities of the ions of interest. In doing so, the scientist can make a solution in which requisite conditions are satisfied and the design is intelligent. For many years we have used GEOCHEM-PC to formulate hydroponic solutions for plant growth, including those employing a variety of metal-chelate systems to control Fe , Fe , and Zn status. In addition, this program has been an important tool in creating test solutions for plant aluminum tolerance experiments. Thus, we are able to estimate Al3+ activities and to create solutions without significantly lowering available phosphate or sulfate. Many of the Al-containing nutrient solutions that are presently in use contain very high Al levels in order to achieve the desired root growth inhibition. These solutions may be redesigned with GEOCHEM-EZ to avoid these problems. As helpful as GEOCHEM-PC has been to a number of scientists in their work, the consensus among users was that the program was not very user friendly and suffered from several functional weaknesses. There were no help files to guide those who were new to the program. The program was written in FORTRAN to be run in a DOS environment, so naming files was limited to eight characters or less. If there were any input errors, then the program did not indicate what they were, just that there were errors.
Data entry involved parsing the salts added to the solution into the individual metals and ligands, calculating their respective concentrations, and then entering these concentrations as the –log into a DAT input file. Some calculations may have taken several iterations, which involved having to save the file, run the calculation, examine the output file, then make appropriate corrections, input the data again, save the file, and make additional calculations. In discussing these issues with the authors of GEOCHEM-PC we were encouraged to build upon and improve the existing program, so that it would work in a Windows XP or Vista environment and would have increased power and function.Included in GEOCHEM-EZ are improvements which would be expected by modern users , while maintaining complete backward compatibility to the GEOCHEM-PC format. A customizable database of common salts has been included, which eliminates the need to parse and to calculate the concentration of each metal or ligand. In addition, the user is no longer limited to enter concentration as nM, µM, or mM, but can now enter the concentrations as g/L or mg/ L,maceta 40 litros provided the salts of interest are part of the salts database. These last two features will make data input more rapid and help in eliminating the most common user errors. The program does automatically check for errors in data entry, convergence, and case similarity. The user can instantly preview input and output files and make necessary corrections , something that formerly involved having to save these files and run the calculations a second or third time. Within the Help menu we have included a Unit Converter which can convert any salt in the database from g/L or mg/L to molar concentrations or vice versa. Shown below is the GEOCHEM-EZ interface. This example is for a basal Murashige –Skoog medium, with the salt, metal, and ligand concentrations entered in mg/L. Note that the entries are mostly salts that are contained within the salts database and are accessed via the drop down list on the left side. However, the user may still add individual metals or ligands, if that is preferred. This entry for the M-S medium represents a simple case . Note that there are two tabs open , representing two separate cases that are being run simultaneously. Many cases can be run at the same time, another feature that makes solution analyses more rapid.In 2005, as part of China’s Eleventh Five-Year Plan, the Chinese government threw its weight behind a new campaign—“Building a Socialist New Countryside” , or “New Countryside” for short. The ambitious goal was to completely modernize China’s “backward” rural society. Since its initial implementation, development projects have been launched in villages countrywide, transforming Chinese rural society according to a particular notion of modernity, focusing on the new, on orderliness, on cleanliness, on density, and on tall buildings. Every rural region in China—in particular the central and western inland regions previously excluded from the rapid economic development of recent decades—is now undergoing a transformation. By 2030, through further urbanization and industrialization, the Chinese government hopes to reduce the proportion of the agricultural population to less than 30 percent .1 Over the next two decades, this campaign will inevitably affect the lives of hundreds of millions of Chinese, making it as significant in terms of scope and impact as some of the mass campaigns of the Maoist era. To be sure, China’s current effort to reform the countryside is nothing new.
A longstanding reform tradition goes back to the Rural Reconstruction Movement of the 1930s, a tradition that was subsequently vigorously pursued by the Communists during the 1940s to 1980s. It is worth noticing that rural and land reforms constituted an integral part of Mao’s vision of Communism from the beginning. Indeed, after the CCP took over political control of the nation in 1949, Chinese agriculture was subjected to a series of wrenching transformations, from land redistribution to agricultural collectivization, and then to the dismantling of the collectives in favor of small household farms . However, the year 2006 marked a momentous change in Chinese agricultural policy for two reasons. First, the “New Countryside” campaign was launched as part of a new national five-year plan. Second, taxes on the peasantry, which had essentially been in place continuously for at least two thousand years, were abolished nationwide. How did this “New Countryside” campaign come about? After three decades of radical economic reforms focused on an export-oriented industrialization model, China’s economy has become one of the largest in the world and continues to grow at a remarkable rate. However, not all Chinese citizens have benefited equally from such successes. The gap in standard of living between rural and urban populations has become even wider. In 1991, an influential Chinese economist, Lin Yifu—who would later become chief economist and senior vice president of the World Bank—proposed at several Chinese central government meetings the need for a “new village movement” as a comprehensive solution to an underdeveloped agriculture and an inert countryside . The proposal included issuing government bonds to finance infrastructure expenses in rural areas, and taking steps to encourage rural-to-urban migration. Adopting a Keynesian macroeconomic approach, he saw the central government as the key promoter of rural development, which itself would then accelerate domestic demand on industrial overproduction of manufactured goods . However, Lin’s solution to the problems of agriculture and the “backward” countryside did not receive the central government’s attention until another well-known agrarian economist and rural reformer, Wen Tiejun , coined the term sannong problems. The three problems referred to were the decline in the agricultural labor force, the stagnation of the peasant household-based agrarian economy, and the lack of basic infrastructure and social welfare in rural society. Wen’s catchy phrase was well received and served as a wake-up call for a re-evaluation of the place of agriculture in China’s road to state capitalism. Eventually, Lin and Wen’s rural development proposals became the basis for the “New Countryside” campaign—first introduced in 2005 as part of China’s Eleventh Five Year Plan. The plan was designed to address the sannong issue through formal and comprehensive government intervention. The campaign aimed to achieve urban-rural integration and improve social and economic conditions in the countryside, while simultaneously reducing the gap in income, quality of life, and social welfare between rural and urban areas.In support of this national campaign, local administrative officials were asked and encouraged to embark on a program of land consolidation involving the “transfer of land use rights” —or “land transfer” for short—to rural entrepreneurs. Simultaneously, there has been a major push towards “agricultural modernization” , involving high-tech mechanization and scientific management. This approach is driven by the larger goal of increasing agricultural productivity, largely in response to growing concerns in recent years with guarding China’s “national grain security” . In 2006, the government calculated that it was necessary to cultivate approximately 120 million hectares of land in order to produce enough food for the whole nation.