Phytotoxicity and Accumulation of Antibiotics in Water Lettuce (Pistia stratiotes) and Parrot Feather (Myriophyllum aquaticum) Plants under Hydroponic Culture Conditions

The aim of this research was to investigate the accumulation of antibiotics in two kinds of plants. The hydroponic culture solution included a mixture of antibiotics, including three commonly used antibiotics in South Korea: norfloxacin (NOR), sulfamethazine (SMZ), and tetracyclines (TC). None of these antibiotics were detected in the shoots of water lettuce plants, only in the roots. However, in parrot feather plants, antibiotics were detected in both the shoots and the roots, with higher amounts detected in the shoots than in the roots. SMZ and TC were most likely to be detected in the roots and shoots of water lettuce and parrot feather plants, and about one-third of the NOR administered was later detected in the plants. The BCF (bioconcentration factor) of antibiotics ranged from 0.24 to 0.78, while that of NOR was much lower, ranging from 0.24 to 0.38. The SMZ (0.59–0.64) and TET (0.72–0.78) exhibited higher uptake accumulation in the water lettuce tissues compared with the parrot feather plants.

IMPROVEMENT OF HYDROPON INSTALLATIONS

Hydroponics is a promising area of development of modern agriculture, which provides long-term cultivation of basic vegetables and greenery in small areas with minimal consumption of water and fertilizers. This technology allows you to get a fairly large harvest of fresh vegetables within large cities, including office and residential premises. Entrepreneurs and researchers are paying close attention to developing more efficient hydroponics methods and equipment to implement them in order to reduce usable space, save water, nutrients and increase air supply and plant capacity. Several hydroponics systems are known: static solution culture, continuous flow solution (NFT) culture, deep water culture, passive irrigation, underwater and drainage irrigation systems, wastewater drainage system, deep-water fertilized culture, rotary system, aeroponics, wick system. The first three of the above methods were used commercially and industrially. The system of static culture solution does not provide the necessary saturation of plant roots with air. With the implementation of the method of continuous solution culture, minor buffering is possible due to interruptions in the flow (power outage), flooding of water in some canals, in addition, there are restrictions on the maximum length of canals (12 - 15 m). The system of deep-water culture on an industrial scale is used mainly for growing lettuce. Other mentioned systems are not efficient enough in terms of commercial use. The improved hydroponic installations presented in the article were developed taking into account the following requirements: universality of use (possibility of growing different types of plants); harmonization of optimal supply of crops with water, nutrients, light and air; maximum use of space; increasing the area for each plant and maintaining its stems and shoots. Also in the article the equation for definition of the basic parameters of the developed installations is given.

Regulating role of abscisic acid on cadmium enrichment in ramie (Boehmeria nivea L.)

Abscisic acid (ABA) is known as an important hormone regulating plant stress resistance, such as salt, drought and heavy metal resistance. However, the relationship between ABA and cadmium (Cd) enrichment in ramie (Boehmeria nivea L.) is still unclear to date. This study aimed to reveal the effect of ABA on Cd enrichment in ramie, and we received the following results: (1) Under Cd treatment, the Cd uptake of ramie increased with the increase of Cd concentration, but the chlorophyll content decreased. Under Cd treatment, the ABA content was highest in roots of ramie, followed by that in old leaves, and lowest in new leaves. Long-time treatment of high Cd concentration reduced the ability of endogenous ABA biosynthesis. (2) Spraying ABA on ramie plants (SORP) and adding ABA directly to the culture solution (ADCS) with low concentration can promote the growth of ramie and increase the amount of Cd uptake, and the effect of SORP is better. (3) The molecular reason for the decrease of chlorophyll content due to Cd stress, may be resulted from the down-regulated expression of the chlorophyll synthesis genes (BnPAO and BnNYC1) and the up-regulated expression of the chlorophyll degradation genes (BnCHLH, BnCHLG, BnHAP3A and BnPPR1). The elevated ABA content in ramie plants may due to the up-regulated expression of the ABA synthesis related genes (BnABA1, BnNCED3, and BnNCED5) and the genes (BnABCG40, BnNFXL2, BnPYL9, BnGCR2, BnGTG1, BnBGLU1, BnUTG1, BnVHAG1 and BnABI5) that encoding ABA transport and response proteins, which was consistent with the enhance the Cd uptake in ramie. Our study revealed the relationship between ABA and Cd uptake in ramie, which provided a reference for improving the enrichment of Cd in ramie.

Isolation and Identification of an Efficient Aerobic Denitrifying Pseudomonas stutzeri Strain and Characterization of Its Nitrite Degradation

Nitrogen pollution in water bodies is becoming increasingly serious, and how to remove nitrogen from water bodies economically and effectively has become a research hotspot. Especially in recent years, with the gradual expansion of aquaculture in China, the content of nitrite and other nitrogen-containing substances in water bodies has been increasing, which inhibits the growth of farm animals and is one of the causes of eutrophication in water bodies. In this study, a strain of bacteria was isolated from the sludge of an aquaculture fishpond and identified as Pseudomonas stutzeri, which can efficiently degrade nitrite. After continuous domestication in nitrite mixed solution, the nitrite nitrogen reduction capacity of P. stutzeri was significantly improved. Univariate experiments aiming to optimize the degradation conditions indicate that the optimal culture conditions for strain F2 are: medium with a carbon source of sodium succinate; C/N of 18; pH of 8; culture temperature of 28 °C; and shaking speed of 210 rpm in the shaker. Under the optimal culture conditions, the NO2−-N concentration of the culture solution was 300 mg/L, and the nitrite removal rate reached 98.67%. Meanwhile, the results of the nitrogen balance test showed that the strain converted 6.1% of the initial nitrogen into cellular organic nitrogen and 62.3% into gaseous nitrogen.

Study on Enhanced Oil Recovery Using Microorganism Generating Foam in Presence of Nanobubbles

Both high cost and environmental load of surfactant are issues to be solved in foam EOR. Moreover, it is difficult to control the injection of surfactant and gas so that the foam is generated in only high permeable zones selectively in oil reservoir. The authors have found a foam generating microorganism and hit upon an idea of the microbial foam EOR which makes the microorganism do generating foam in oil reservoir. The mechanism of the microbial foam generation and culture condition suitable for the foam generation were studied in this study. A species of Pseudomonas aeruginosa was used as a foam producer in this study. It was cultured in the medium consisting of glucose and eight kinds of minerals at 30 °C and atmospheric pressure under anaerobic conditions. Because P. aeruginosa generally grows better under aerobic conditions, the microorganism was supplied with oxygen nanobubbles as the oxygen source. The carbon dioxide nanobubbles were also used as a comparison target in this study. The state of foam generation in the culture solution was observed during the cultivation. The surface tension, surfactant concentration, protein concentration, polysaccharides concentration and bacterial population of the culture solution were measured respectively. The foam was started to be generated by the microorganism after 2 days of cultivation and its volume became maximum after 3 days of cultivation. The foam generation was found in the culture solution which contained both oxygen nanobubbles and carbon dioxide nanobubbles whereas little foam was found in non-nanobubbles culture solution. The foam generation found in the culture solution containing carbon dioxide nanobubbles was more than that in the culture solution containing oxygen nanobubbles. Both gas and protein concentration increased along with the formation of the foam whereas surfactant and polysaccharides were not increased, therefore, the foam was assumed to be generated with gas and protein which were generated by P. aeruginosa. It was found that the carbon dioxide nanobubbles were positively charged in the culture medium whereas they were negatively charged in tap water through the measurement of zeta potential of nanobubbles, therefore, the carbon dioxide nanobubbles attracted cations in the culture medium and became positively charged. Positively charged carbon dioxide nanobubbles transported cations to the microbial cells of P. aeruginosa. Among cations in the culture medium, ferrous ions are essential for the protein generation of P. aeruginosa, therefore, the positively charged carbon dioxide nanobubbles attracted ferrous ions and transport them to the microbial cells, resulting the growth and metabolism of P. aeruginosa were activated. Those results suggest that the microbial foam EOR can be materialized by supplying the microorganism with carbon dioxide nanobubbles or ferrous ions.

Cryopreservation of 13 Commercial Cannabis sativa Genotypes Using In Vitro Nodal Explants

Cannabis has developed into a multi-billion-dollar industry that relies on clonal propagation of elite genetics with desirable agronomic and chemical phenotypes. While the goal of clonal propagation is to produce genetically uniform plants, somatic mutations can accumulate during growth and compromise long-term genetic fidelity. Cryopreservation is a process in which tissues are stored at cryogenic temperatures, halting cell division and metabolic processes to facilitate high fidelity germplasm preservation. In this study, a series of experiments were conducted to optimize various stages of cryopreservation and develop a protocol for long-term germplasm storage of Cannabis sativa. The resulting protocol uses a standard vitrification procedure to cryopreserve nodal explants from in vitro shoots as follows: nodes were cultured for 17 h in a pre-culture solution (PCS), followed by a 20-min treatment in a loading solution (LS), and a 60 min incubation in plant vitrification solution 2 (PVS2). The nodes were then flash frozen in liquid nitrogen, re-warmed in an unloading solution at 40 °C, and cultured on basal MS culture medium in the dark for 5 days followed by transfer to standard culture conditions. This protocol was tested across 13 genotypes to assess the genotypic variability. The protocol was successful across all 13 genotypes, but significant variation was observed in tissue survival (43.3–80%) and regrowth of shoots (26.7–66.7%). Plants grown from cryopreserved samples were morphologically and chemically similar to control plants for most major traits, but some differences were observed in the minor cannabinoid and terpene profiles. While further improvements are likely possible, this study provides a functional cryopreservation system that works across multiple commercial genotypes for long-term germplasm preservation.

Antibiotic Resistance Gene Transformation and Ultrastructural Alterations of Lettuce (Lactuca sativa L.) Resulting from Sulfadiazine Accumulation in Culture Solution

The research herein explored the possible mechanism of toxicity of the antibiotic sulfadiazine (SD) and the related antibiotic resistance gene transformation in lettuce by systematically investigating its growth responses, ultrastructural changes, and antibiotic resistance gene transformation via solution culture experiments. The results showed that SD mainly accumulated in the roots of lettuce at concentrations ranging from 6.48 to 120.87 μg/kg, which were significantly higher than those in leaves (3.90 to 16.74 μg/kg). Lower concentrations of SD (0.5 and 2.0 mg/L) in the culture nutrient solution exerted little effect on lettuce growth, while at SD concentrations higher than 10 mg/L, the growth of lettuce was significantly inhibited, manifesting as shorter root length and lower dry matter yield of whole lettuce plants. Compared with that for the control group, the absolute abundance of bacteria in the root endophyte, rhizosphere, and phyllosphere communities under different concentrations of SD treatment decreased significantly. sul1 and sul2 mainly accumulated in the root endophyte community, at levels significantly higher than those in the leaf endophyte community. Studies of electrolyte leakage and ultrastructural characteristics of root and leaf cells indicated that lettuce grown in culture solutions with high SD concentrations suffered severe damage and disintegration of the cell walls of organs, especially chloroplasts, in leaves. Furthermore, the possible mechanism of SD toxicity in lettuce was confirmed to start with the roots, followed by a free flow of SD into the leaves to destroy the chloroplasts in the leaf cells, which ultimately reduced photosynthesis and decreased plant growth. Studies have shown that antibiotic residues have negative effects on the growth of lettuce and highlight a potential risk of the development and spread of antibiotic resistance in vegetable endophyte systems.

The Growth of Leaf Lettuce and Bacterial Communities in a Closed Aquaponics System with Catfish

Aquaponics is a circulating and sustainable system that combines aquaculture and hydroponics and forms a symbiotic relationship between fish, plants, and microorganisms. We hypothesized that feed alone could support plant growth, but the symbiosis with fish adds some beneficial effects on plant growth in aquaponics. In this study, we created three closed culture systems, namely, aquaponics, hydroponics without nitrogen (N) and phosphorus (P), and aquaculture, and added the same amount of feed containing N and P to all the treatments in order to test the hypothesis. Accumulation of NO3− and PO43− was alleviated in aquaponics and hydroponics as a result of plant uptake. Lettuce plants grown in aquaponics grew vigorously until 2 weeks and contained a constant level of N in plants throughout the production period, whereas those in hydroponics grew slowly in the early stage and then vigorously after 2 weeks with a late increment of N concentration. These results suggest that catfish help with the faster decomposition of the feed, but, in hydroponics, feed can be slowly dissolved and decomposed owing to the absence of the fish. The bacterial community structures of the culture solution were investigated using 16S rRNA gene amplicon sequencing. At the class level, Actinobacteria, Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria were the major microbial groups in the solutions. Aquaponics prevented the pollution of tank solution and maintained a higher water quality compared with hydroponics and aquaculture, suggesting that aquaponics is a more sustainable cultivation system even in a small-scale system.

Analysis of the efficiency factors of electrotransformation of Bacillus subtilis to inactivate the aroK gene by the method of homologous recombination

A hyper-osmotic electrotransformation method was developed for strain Bacillus subtilis. Sorbitol and mannitol are included in the hyper-osmotic electroporation medium and recovery medium. In this study, the hyper-osmotic electroporation method was optimised to increase the transformation efficiency of B. subtilis strain 5434 (non-transformable by chemical methods) by 430 fold, with a maximum value of 8.6 ⋅ 105 CFU/µg of integrative plasmid DNA. With the electroporation setted 25 µF, 23 kV/cm, 200 Ω, the method was optimised as follows: a) the OD600 value of the bacterial culture solution was increased to about 1.2, which significantly enhanced survival of bacteria and quantity of viable B.subtilis strain 5434 cells after electroporation; b) the elution frequency of washing solution (hyper-osmotic electroporation medium) for complement cells was increased from 3 to 5 times, resulted in significantly reducing the conductivity of the hyper-osmotic electoporation medium with competent cells (electrocompetent cultue), and effectively extending the pulse time under the same electric field strength; c) quantity of integrative plasmid DNA added to hyper-osmotic electrocompetent culture was optimised. These results indicate that increasing the number of viable B. subtilis strain 5434 cells and reducing the number of metal ions in the electroporation solution mix (integrative plasmid DNA, competent cells of B. subtilis strain 5434, electroporation medium) are useful approach to improve transfomation efficiency of B. subtilis strain 5434. Concentration of shikimic acid in the fermentation medium was quantified by high performance liquid chromatography. Quantification of shikimic acid revealed that B. subtilis strain 5434p4SA produced 403.98 ± 9.1 µg/mL of shikimic acid.

Influence of humic acids in lowland peat on the remediation properties of wheat plants against heavy metal contamination

Phytoremediation is a promising technology for removing heavy metals from soil and water. Despite the pronounced increase in heavy metal accumulation by cultivated plants under the influence of naturally occurring complexing agents, such as humic acids, their efficiency in phytoremediation has been poorly studied. In this regard, the aim of this work is to elucidate the effect of peat humic acid formulations on the remediation potential of wheat plants (Triticum aestivum L.) against heavy metal contamination. The influence of polymetallic pollution on the remediation properties of wheat was studied in model vegetation experiments using a culture solution. Plants were grown in a Hoagland nutrient solution. A complex exposure to heavy metals was simulated using 10 pmol/L CdSO4, 25 and 50 pmol/L CuSO4, 500 and 1000 pmol/L Pb(NO3)2 in various combinations with or without the addition of a peat humic acid formulation (0.005%).The phytoremediation efficiency of the humic acid formulation was determined by the removal of heavy metals during the heading stage of wheat growth. The research results showed that the phytoremediation efficiency of the humic acid formulation is defined by both an increase in the absorption of heavy metals and a decrease in their toxic action on the plants. In the case of mixed contamination of the solution with highly toxic heavy metals, the samples with humic acids showed a 1.2-2.5-fold increase in the accumulation of copper and cadmium by wheat plants. The data demonstrates the possibility of using the formulation of peat humic acids in phytoremediation technologies as an effector of heavy metal phytoextraction.