•The current findings of the heterogeneous composition of flocs are summarized.•The effect of the composition of flocs on their structure and dynamics is reviewed.•The interaction among heterogeneous ...components within flocs is explained.•Human activities affecting the heterogeneous composition of flocs are also summarized.
Flocculation is a key process for controlling the fate and transport of suspended particulate matter (SPM) in water environments and has received considerable attention in the field of water science (e.g., oceanography, limnology, and hydrology), remaining an active area of research. The research on flocculation has been conducted to elucidate the SPM dynamics and to diagnose various environmental issues. The flocculation, sedimentation, and transportation of SPM are closely linked to the compositional and structural properties of flocs. In fact, flocs are highly heterogeneous in terms of composition. However, the lack of comprehensive research on floc composition and structure has led to misconceptions regarding the temporal and spatial dynamics of SPM. This review summarizes the current understanding of the heterogeneous composition of flocs (e.g., minerals, organic matter, metals, microplastic, engineered nanoparticles) and its effect on their structure and on their fate and transport within aquatic environments. Furthermore, the effects of human activities (e.g., pollutant discharge, construction) on floc composition are discussed.
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Microbial exopolysaccharides (EPS) are an abundant and important group of compounds that can be secreted by bacteria, fungi and algae. The biotechnological production of these substances represents a ...faster alternative when compared to chemical and plant-derived production with the possibility of using industrial wastes as substrates, a feasible strategy after a comprehensive study of factors that may affect the synthesis by the chosen microorganism and desirable final product. Another possible difficulty could be the extraction and purification methods, a crucial part of the production of microbial polysaccharides, since different methods should be adopted. In this sense, this review aims to present the biotechnological production of microbial exopolysaccharides, exploring the production steps, optimization processes and current applications of these relevant bioproducts.
Tomato (Solanum lycopersicum) is a model for climacteric fleshy fruit ripening studies. Tomato ripening is regulated by multiple transcription factors together with the plant hormone ethylene and ...their downstream effector genes. Transcription Factors APETALA2a (AP2a), NON-RIPENING (NOR) and FRUITFULL (FUL1/TDR4 and FUL2/MBP7) were reported as master regulators controlling tomato fruit ripening. Their proposed functions were derived from studies of the phenotype of spontaneous mutants or RNAi knock-down lines rather than, as it appears now, actual null mutants. To study TF function in tomato fruit ripening in more detail, we used CRISPR/Cas9-mediated mutagenesis to knock out the encoding genes, and phenotypes of these mutants are reported for the first time. While the earlier ripening, orange-ripe phenotype of ap2a mutants was confirmed, the nor null mutant exhibited a much milder phenotype than the spontaneous nor mutant. Additional analyses revealed that the severe phenotype in the spontaneous mutant is caused by a dominant-negative allele. Our approach also provides new insight into the independent and overlapping functions of FUL1 and FUL2. Single and combined null alleles of FUL1 and FUL2 illustrate that these two genes have partially redundant functions in fruit ripening, but also unveil an additional role for FUL2 in early fruit development.
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•New procedure for separation of EPS into the main components from one sample.•Analysis of the main components of EPS from only one sample.•Characterization of EPS for a deeper ...insight into the state of the cells.•100 % recovery rates of synthetic EPS containing polysaccharides, proteins and lipids.•Successful transfer to real EPS samples from different cultivations.
Phototrophic biofilms produce a matrix of extracellular polymeric substances (EPS), which holds the cells together and functions inter alia as nutrient storage and protection layer. EPS mainly consist of water, polysaccharides, proteins, lipids and nucleic acids as well as lysis and hydrolysis products which makes the composition very complex. Thus, rough simplifications are used and commonly one or at most two components of the EPS are examined. In this work a new procedure for separation and analysis of EPS in the main components (i) polysaccharides, (ii) proteins and (iii) lipids is presented with recovery rates of nearly 100 %. The method was established with synthetic EPS, which based on the composition of real EPS described in literature. Afterwards, the method was transferred to real EPS samples allowing a deeper insight in the composition of EPS from only one sample. The composition of EPS-extracts from Nostoc spec, cultivated under heterotrophic and mixotrophic batch and fed-batch conditions, was analysed during a cultivation period of 14 days. It was observed that mixotrophic cultivation led to higher amounts of carbohydrates, lipids and proteins than heterotrophic cultivation respectively, regardless of batch or fed-batch culture. While the amount of proteins in the EPS increased during the cultivation period, carbohydrates and lipids were dominant in the beginning and decreased afterwards.
Chemical cleaning is vital for the optimal operation of membrane systems. Membrane chemical cleaning protocols are often developed in the laboratory flow cells (e.g., Membrane Fouling Simulator ...(MFS)) using synthetic feed water (nutrient excess) and short experimental time of typically days. However, full-scale Reverse Osmosis (RO) membranes are usually fed with nutrient limited feed water (due to extensive pre-treatment) and operated for a long-time of typically years. These operational differences lead to significant differences in the efficiency of chemical Cleaning-In-Place (CIP) carried out on laboratory-scale and on full-scale RO systems. Therefore, we investigated the suitability of lab-scale CIP results for full-scale applications. A lab-scale flow cell (i.e., MFSs) and two full-scale RO modules were analysed to compare CIP efficiency in terms of water flux recovery and biofouling properties (biomass content, Extracellular Polymeric Substances (EPS) composition and EPS adherence) under typical lab-scale and full-scale conditions. We observed a significant difference between the CIP efficiency in lab-scale (~50%) and full-scale (9–20%) RO membranes. Typical biomass analysis such as Total Organic Carbon (TOC) and Adenosine triphosphate (ATP) measurements did not indicate any correlation to the observed trend in the CIP efficiency in the lab-scale and full-scale RO membranes. However, the biofilms formed in the lab-scale contains different EPS than the biofilms in the full-scale RO modules. The biofilms in the lab-scale MFS have polysaccharide-rich EPS (Protein/Polysaccharide ratio = 0.5) as opposed to biofilm developed in full-scale modules which contain protein-rich EPS (Protein/Polysaccharide ratio = 2.2). Moreover, EPS analysis indicates the EPS extracted from full-scale biofilms have a higher affinity and rigidity to the membrane surface compared to EPS from lab-scale biofilm. Thus, we propose that CIP protocols should be optimized in long-term experiments using the realistic feed water.
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•CIP efficiency in full-scale RO is lower than “typical” lab-scale MFS.•CIP efficiency are not correlated to biomass removal indicators (ATP and TOC).•Full-scale RO biofilms have protein-rich EPS while lab-scale EPS has sugar-rich EPS.•Biofilm from full-scale EPS has higher affinity to membrane than lab-scale EPS.•CIP protocols should be developed using real feed water and for longer experiment.
Engineering C₄ photosynthesis into C₃ crops could substantially increase their yield by alleviating photorespiratory losses. This objective is challenging because the C₄ pathway involves complex ...modifications to the biochemistry, cell biology, and anatomy of leaves. Forward genetics has provided limited insight into the mechanistic basis of these properties, and there have been no reports of significant quantitative intraspecific variation of C₄ attributes that would allow trait mapping. Here, we show that accessions of the C₄ species Gynandropsis gynandra collected from locations across Africa and Asia exhibit natural variation in key characteristics of C₄ photosynthesis. Variable traits include bundle sheath size and vein density, gas-exchange parameters, and carbon isotope discrimination associated with the C₄ state. The abundance of transcripts encoding core enzymes of the C₄ cycle also showed significant variation. Traits relating to water use showed more quantitative variation than those associated with carbon assimilation. We propose that variation in these traits likely adapted the hydraulic system for increased water use efficiency rather than improving carbon fixation, indicating that selection pressure may drive C₄ diversity in G. gynandra by modifying water use rather than photosynthesis. The accessions analyzed can be easily crossed and produce fertile offspring. Our findings, therefore, indicate that natural variation within this C₄ species is sufficiently large to allow genetic mapping of key C₄ traits and regulators.
► We study EPS from wild type and exoY strains of bacterium Sinorhizobium meliloti. ► EPS extracted by centrifugation, EDTA and formaldehyde/NaOH were compared. ► Two major components of ...proteinaceous and polysaccharide nature were found. ► Extraction methods influenced TOC, TN and total protein content in EPS. ► Molar mass distributions also differed among treatments and bacterial strains.
The influence of the extraction methods on the composition, size diversity, molar mass and size distributions of exopolymeric substances (EPS) from the bacterium Sinorhizobium meliloti wild type (WT) and by the exoY strain deficient in exopolysaccharide production was investigated. EPS obtained by centrifugation, EDTA and formaldehyde/NaOH were compared. It was found that the extraction method influenced TOC, TN and total protein content in EPS from both strains. However, no difference between EDTA and formaldehyde/NaOH methods was observed for the exopolysaccharide components. Similar functional groups and fluorescence pattern were found in the EPS obtained by different methods; however their relative abundance was method dependent. The extraction method also affected the molar mass and size distribution, HP SEC diversity among different treatment and bacterial strains.
A single mouse blastomere from an embryo until the 8-cell stage can generate an entire blastocyst. Whether laboratory-cultured cells retain a similar generative capacity remains unknown. Starting ...from a single stem cell type, extended pluripotent stem (EPS) cells, we established a 3D differentiation system that enabled the generation of blastocyst-like structures (EPS-blastoids) through lineage segregation and self-organization. EPS-blastoids resembled blastocysts in morphology and cell-lineage allocation and recapitulated key morphogenetic events during preimplantation and early postimplantation development in vitro. Upon transfer, some EPS-blastoids underwent implantation, induced decidualization, and generated live, albeit disorganized, tissues in utero. Single-cell and bulk RNA-sequencing analysis revealed that EPS-blastoids contained all three blastocyst cell lineages and shared transcriptional similarity with natural blastocysts. We also provide proof of concept that EPS-blastoids can be generated from adult cells via cellular reprogramming. EPS-blastoids provide a unique platform for studying early embryogenesis and pave the way to creating viable synthetic embryos by using cultured cells.
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•A method that enables the generation of blastocyst-like structures from EPS cells•EPS-blastoids resemble blastocysts in morphology and cell-lineage allocation•EPS-blastoid formation recapitulates early developmental events in vitro•EPS-blastoids are able to implant in utero
A blastocyst-like structure is generated from a single stem-cell type as well as from somatic reprogrammed cells, and these artificial embryo-like structures can implant, induce decidualization, and give rise to cells of the three embryonic founding tissues: epiblast, trophectoderm, and primitive endoderm.
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Extracellular polymeric substances (EPS) released by bacteria play a crucial role in microbial aggregation during wastewater treatment. Various environmental factors including ...substrate, anaerobic and aerobic conditions might contribute to the formation and properties of EPS, and thereby affect the properties of microbial aggregation and sludge. To reveal the relationship between these environmental factors and EPS properties, the characteristics of EPS generated in four types of sludge were investigated, including anammox granular sludge (ANMX), aerobic granular sludge (AGS) fed with glucose as carbon source (AGS-GLUC), AGS fed with liquor wastewater as carbon source (AGS-LIQ), and flocculent sludge from a real sewage plant (FLOC). Results indicated a positive correlation of EPS contents with granulation of sludge. As the dominant content of EPS, an increased proteins (PN) concentration facilitated the formation of microbial aggregates and the granulation of sludge. Bacteria in anaerobic environment (i.e., ANMX) or in aerobic environment with easily biodegradable carbon sources (i.e., AGS-GLUC) would generate more PN and EPS; yet, these conditions restrained the generation of humic acid (HA). The sludge from the sewage treatment plant (i.e., FLOC) had the lowest EPS and PN content, but the highest HA, showing flocculent structure sludge. In addition, a higher protein/polysaccharide (PN/PS) ratio and a lower zeta potential of EPS were conductive to sludge granulation. The hydrophobicity of EPS confirmed via analysis of chemical structures by FTIR would improve the microbial aggregation.
The rapid formation or restoration of biocrusts by human intervention, such as constructing artificial biocrusts, is considered a promising technology for desertification control. To date, most of ...the studies mainly focused on the role of cyanobacteria and their excreted exopolysaccharides (EPSs) in the process of biocrusts formation and development, while few studies have been concerned about clay minerals, which play an important role in soil development as the abiotic factor. In this study, two clay minerals (montmorillonite and kaolinite) were added to crushed natural biocrusts at different ratios(0.5 %, 1 %, 2 %, 5 %, 10 %; w/w), aiming to explore the effects and mechanism of clay minerals on the formation of biocrusts. The results showed that low-level montmorillonite (0.5–2 %; w/w) addition significantly increased the photosynthetic biomass by about 50 % (indicated by Chlorophyll-a and gene copies) and promoted the accumulation of total nitrogen, nitrate nitrogen, ammonia nitrogen, and total organic carbon. The results of the structural equation model showed that the enhancement effect of clay minerals on the formation of biocrusts is mainly ascribed to its direct positive effect on biocrust physical stability and indirect positive effects through increasing both the cyanobacterial biomass and EPS excretion. Notably, the addition of montmorillonite increased the physical stability of the biocrusts by 18 %-53 %, while kaolinite did not play a positive role in the formation of biocrusts. Moreover, excessive montmorillonite (more than 2 %) and kaolinite caused the significant shift of dominance from Cyanobacteria to Proteobacteria, and a sharp decrease in EPS excretion, posing a high risk of biocrust disintegration. Overall, our findings demonstrate the stimulation mechanism of clay addition on restoring natural biocrusts, providing new insight for constructing artificial biocrusts and restoring degraded biocrusts in dryland.
•The type and content of clay both affect the formation of biocrusts.•Cyanobacterial biomass, EPS content, and clay determine biocrusts’ stability.•Montmorillonite promotes cyanobacteria growth and EPSs excretion.•There is a negative feedback mechanism between biocrust growth and kaolinite.•Montmorillonite enhances the biocrusts’ physical stability and nutrient retention.
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