Regrowth Potential Research Articles

Ecological effects of stress drive bacterial evolvability under sub-inhibitory antibiotic treatments

Stress is thought to increase mutation rate and thus to accelerate evolution. In the context of antibiotic resistance, sub-inhibitory treatments could then lead to enhanced evolvability, thereby fuelling the adaptation of pathogens. Combining wet-lab experiments, stochastic simulations and a meta-analysis of the literature, we found that the increase in mutation rates triggered by antibiotic treatments is often cancelled out by reduced population size, resulting in no overall increase in genetic diversity. A careful analysis of the effect of ecological factors on genetic diversity showed that the potential for regrowth during recovery phase after treatment plays a crucial role in evolvability, being the main factor associated with increased genetic diversity in experimental data.

Enhanced solar inactivation of fungal spores by addition of low-dose chlorine: Efficiency and mechanism

This work demonstrated that the solar inactivation of fungal spores was enhanced by addition of low-dose chlorine. Although the effect of low-dose chlorine alone (2.0 mg/L) on culturability of fungal spores was negligible, the solar/chlorine inactivation on fungal spores performed better than solar alone inactivation, with a lower shoulder length and a higher maximum inactivation rate constant. The enhanced inactivation of Aspergillus niger can be ascribed to the membrane oxidation by chlorine, and the enhanced inactivation of Penicillium polonicum can be ascribed to the membrane oxidation by chlorine and ·OH (·OH plays a major role). The oxidization by chlorine and ·OH led to an increase in membrane permeability of fungal spores, which enhanced the solar inactivation, resulting in an increase in intracellular ROS and more serious morphological damage. Due to the presence of background substances such as dissolved organic matter and metal ions (Fe2+, Mn2+, etc.), the inactivation efficiency in real water matrices was decreased. The main disinfection by-products (DBPs) produced in the inactivation of fungal spores in chlorine alone and solar/chlorine treatments were dichloroacetic acid, trichloroacetic acid, trichloroacetone and trichloromethane. Generally, DBPs formation in solar/chlorine treatment was lower than those in chlorine alone treatment. Moreover, the regrowth potential of the two genera of fungal spores in R2A medium could be inhibited by adding low-dose chlorine.

Inactivation of fungal spores in water by CuO-activated peracetic acid: Kinetics, mechanism and regrowth

The disinfection of pathogenic microorganisms in water treatment by peracetic acid (PAA)-based advanced oxidation processes (AOPs) has been gaining increasing concern. In this work, the inactivation mechanism, influencing factors and regrowth of two pathogenic Aspergillus species in the system of CuO-activated PAA were studied for the first time. The k values of A. niger and A. flavus inactivated by PAA/CuO system were 3.9 and 2.1-fold higher than those inactivated by PAA alone. PAA concentration and CuO dose were positively correlated with the inactivation efficiency, while humic acid and pH were negatively correlated. The main active species that contributed to the inactivation of fungal spores in PAA/CuO system were •OH, CH3C(O)OO• and 1O2. PAA/CuO system had more intense oxidative stimulation and more serious damage to fungal spores according to the analysis of cell membrane integrity and intracellular ROS levels. In addition, the PAA/CuO system was less impacted by the water matrix and kept a good inactivation efficiency in real water samples. The regrowth potential of fungal spores after disinfection was also reduced in PAA/CuO system so as to avoid the risk of biological regrowth. This study provides a feasible PAA-based advanced oxidation method for activating PAA and inactivating fungal spores.

A systematic review on chlorine tolerance among bacteria and standardization of their assessment protocol in wastewater.

Though chlorine is a cost-effective disinfectant for water and wastewaters, the bacteria surviving after chlorination pose serious public health and environmental problems. This review critically assesses the mechanism of chlorine disinfection as described by various researchers; factors affecting chlorination efficacy; and the re-growth potential of microbial contaminations in treated wastewater post chlorination to arrive at meaningful doses for ensuring health safety. Literature analysis shows procedural inconsistencies in the assessment of chlorine tolerant bacteria, making it extremely difficult to compare the tolerance characteristics of different reported tolerant bacteria. A comparison of logarithmic reduction after chlorination and the concentration-time values for prominent pathogens led to the generation of a standard protocol for the assessment of chlorine tolerance. The factors that need to be critically monitored include applied chlorine doses, contact time, determination of chlorine demands of the medium, and the consideration of bacterial counts immediately after chlorination and in post chlorinated samples (regrowth). The protocol devised here appropriately assesses the chlorine-tolerant bacteria and urges the scientific community to report the regrowth characteristics as well. This would increase the confidence in data interpretation that can provide a better understanding of chlorine tolerance in bacteria and aid in formulating strategies for effective chlorination.

Differential Regulation of Amino Acids and Nitrogen for Drought Tolerance and Poststress Recovery in Creeping Bentgrass

Effects of amino acids and nitrogen on plant regrowth or recovery from drought stress remain largely unknown. The objectives of this study were to examine how gamma-aminobutyric acid (GABA) or proline, alone and in combination, or inorganic nitrogen [ammonium nitrate (NN)] may differentially affect turf performance during drought stress and rewatering, and to determine which specific endogenous amino acids regulated by GABA, proline, or NN priming were associated with plant tolerance to drought stress and postdrought recuperation in cool-season grass species. Creeping bentgrass (Agrostis stolonifera cv. Penncross) planted in porous ceramic fritted clay medium were exposed to well-watered conditions or drought stress by withholding irrigation for 21 days in growth chambers. Plants were treated with water (untreated control), GABA, or proline alone and in combination, or NN through foliar spray before drought stress and every 7 days during the 21-day stress period. For postdrought recovery, at 21 days of drought treatment, plants were rewatered for 14 days to return soil water content to prestress levels. Plants treated with GABA or proline alone or in combination maintained higher turf quality (TQ), dark green color index (DGCI), and stolon length by 21 days of drought stress, whereas proline-treated plants also maintained higher leaf relative water content (RWC) during drought as well as longer stolon length during rewatering. Plants treated with NN maintained higher TQ and leaf RWC during drought and had improved percent canopy cover, DGCI, and stolon length during postdrought rewatering. Accumulation of endogenous amino acids under drought stress, including proline and alanine, for proline-treated creeping bentgrass may have contributed to the enhancement of drought tolerance and postdrought regrowth. Nitrogen-enhanced accumulation of GABA, proline, and glutamic acid may have played a role in active amino acid assimilation and subsequent postdrought regrowth. Results from this study indicate that GABA or proline were mainly effective in promoting the tolerance of creeping bentgrass to drought stress while inorganic NN was effective in promoting rapid postdrought recovery and regrowth potential through the activation of amino acid metabolism. Endogenous amino acids, including GABA, proline, alanine, and glutamic acid, may be used as biomarkers to select for drought-tolerant plants and biostimulant components for improvement of drought stress tolerance and poststress recovery in cool-season turfgrass species.

Abstract 3967: A novel translation program regulates tumor-initiating potential and chemoresistance in multiple myeloma

Abstract Background: Despite the introduction of novel therapies, the majority of the multiple myeloma (MM) patients eventually relapse and develop chemoresistance, and the factors responsible for disease progression are not fully understood. Relapse suggest that MM cells that are resistant to chemotherapy and have the clonogenic growth potential to produce tumor cells exist, and we have found that tumor cells lacking the plasma cell antigen CD138 are enriched in these properties. Understanding the mechanisms regulating these MM cancer stem cells (CSCs) may lead to novel targeting strategies. Aberrant translation is a widespread characteristic of tumor cells and plays a major role in drug resistance. Thus, therapeutic agents that target translation hold promise as novel anti-cancer drugs. MM cells are characterized by heightened protein production in the form of immunoglobulin (Ig) and are highly dependent on proteolytic pathways such as the proteasome to maintain protein homeostasis. As a consequence, proteasome inhibitors (PIs) such as bortezomib (BTZ) have been established as a frontline therapy for the disease. Immature plasma cells with diminished Ig production are resistant to BTZ, and patients with low Ig producing tumors are more likely to relapse. Therefore, low protein synthesis may confer growth advantages to cancer cells such as chemoresistance and enhanced tumor regrowth potential. Methods & Results: To examine alterations in the translational landscape in therapy resistant MM, we treated MM cells with BTZ, and found that eukaryotic translation initiation factor-5 (eIF5) was highly upregulated. Importantly, over-expression of eIF5 led to increased chemotherapy resistance and enhanced clonogenicity. O-propargyl-puromycin incorporation showed a global translational reduction in cells over-expressing eIF5. Matched transcriptional RNA sequencing (RNA-seq) and ribosome profiling revealed that a subset of genes, including MSI2 and EZH1, escaped translation suppression by maintaining efficient translation in eIF5 over-expressing cells. In addition, clonogenic (CD138neg) MM cells exhibited increased eIF5 expression and decreased protein synthesis. Discussion: Understanding the mechanisms of chemoresistance in the cell populations responsible for residual disease and re-growth may lead to novel targeting strategies. Recent studies have indicated that stem cell behavior is coupled to protein synthesis regulation. However, the role of translational control in the maintenance of tumor-initiating cells has been explored only recently. Studies have implicated deregulation of initiation factors in various types of cancer. However, the role of eIF5 in cancer remains elusive. Our data reveals, for the first time, a novel eIF5-directed translational program that enhances chemoresistance and tumor-initiating potential in MM cells, making it a promising therapeutic target. Citation Format: Kiera Rycaj, Eun-Hee Park, Tori Tonn, Qiuju Wang, Can Cenik, Christian Gocke, William Matsui. A novel translation program regulates tumor-initiating potential and chemoresistance in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3967.

Sorafenib and nitazoxanide disrupt mitochondrial function and inhibit regrowth capacity in three-dimensional models of hepatocellular and colorectal carcinoma

Quiescent cancer cells in malignant tumors can withstand cell-cycle active treatment and cause cancer spread and recurrence. Three-dimensional (3D) cancer cell models have led to the identification of oxidative phosphorylation (OXPHOS) as a context-dependent vulnerability. The limited treatment options for advanced hepatocellular carcinoma (HCC) and colorectal carcinoma (CRC) metastatic to the liver include the multikinase inhibitors sorafenib and regorafenib. Off-target effects of sorafenib and regorafenib are related to OXPHOS inhibition; however the importance of this feature to the effect on tumor cells has not been investigated in 3D models. We began by assessing global transcriptional responses in monolayer cell cultures, then moved on to multicellular tumor spheroids (MCTS) and tumoroids generated from a CRC patient. Cells were treated with chemotherapeutics, kinase inhibitors, and the OXPHOS inhibitors. Cells grown in 3D cultures were sensitive to the OXPHOS inhibitor nitazoxanide, sorafenib, and regorafenib and resistant to other multikinase inhibitors and chemotherapeutic drugs. Furthermore, nitazoxanide and sorafenib reduced viability, regrowth potential and inhibited mitochondrial membrane potential in an additive manner at clinically relevant concentrations. This study demonstrates that the OXPHOS inhibition caused by sorafenib and regorafenib parallels 3D activity and can be further investigated for new combination strategies.

The stress sigma factor σS/RpoS counteracts Fur repression of genes involved in iron and manganese metabolism and modulates the ionome of Salmonella enterica serovar Typhimurium.

In many Gram-negative bacteria, the stress sigma factor of RNA polymerase, σS/RpoS, remodels global gene expression to reshape the physiology of quiescent cells and ensure their survival under non-optimal growth conditions. In the foodborne pathogen Salmonella enterica serovar Typhimurium, σS is also required for biofilm formation and virulence. We have previously identified sRNAs genes positively controlled by σS in Salmonella, including the two paralogous sRNA genes, ryhB1 and ryhB2/isrE. Expression of ryhB1 and ryhB2 is repressed by the ferric uptake regulator Fur when iron is available. In this study, we show that σS alleviates Fur-mediated repression of the ryhB genes and of additional Fur target genes. Moreover, σS induces transcription of the manganese transporter genes mntH and sitABCD and prevents their repression, not only by Fur, but also by the manganese-responsive regulator MntR. These findings prompted us to evaluate the impact of a ΔrpoS mutation on the Salmonella ionome. Inductively coupled plasma mass spectrometry analyses revealed a significant effect of the ΔrpoS mutation on the cellular concentration of manganese, magnesium, cobalt and potassium. In addition, transcriptional fusions in several genes involved in the transport of these ions were regulated by σS. This study suggests that σS controls fluxes of ions that might be important for the fitness of quiescent cells. Consistent with this hypothesis, the ΔrpoS mutation extended the lag phase of Salmonella grown in rich medium supplemented with the metal ion chelator EDTA, and this effect was abolished when magnesium, but not manganese or iron, was added back. These findings unravel the importance of σS and magnesium in the regrowth potential of quiescent cells.

Inflammatory Tumor Microenvironment in Cranial Meningiomas: Clinical Implications and Intraindividual Reproducibility.

The MIB-1 index was demonstrated to be significantly correlated to meningioma recurrence. However, to date, the relationship of the intraindividual course of the MIB-1 index and the growth fraction, respectively, to clinical tumor recurrence has not been demonstrated in cranial WHO grade 1 and 2 meningiomas. In the present paper, we compare the MIB-1 indices of 16 solely surgically treated primary meningiomas and their recurrent tumors regarding the course of the MIB-1 indices, time to recurrence, reproducibility and factors influencing the intraindividual MIB-1 indices. Regression analyses revealed (1) a strong intra-lab reproducibility (r = 0.88) of the MIB-1 index at the second versus the first operation, corresponding to a constant intrinsic growth activity of an individual meningioma, (2) a significant inverse correlation of both primary (r = −0.51) and secondary (r = −0.70) MIB-1 indices to time to recurrence, and (3) male sex, low plasma fibrinogen and diffuse CD68+ macrophage infiltrates contribute to an increase in the MIB-1 index. A strong intraindividual reproducibility of the MIB-1 index and a direct relationship of the MIB-1 index to the time to recurrence were observed. Individual MIB-1 indices might be used for tailored follow-up imaging intervals. Further research on the role of macrophages and inflammatory burden in the regrowth potential of meningiomas are needed.

Effective inactivation of fungal spores by the combined UV/PAA: Synergistic effect and mechanisms

Peracetic acid (PAA) can effectively inactivate fungi in water, while may pose a potential risk of regrowth after disinfection. The inactivation kinetic and mechanism of fungal spores by combined UV and PAA (UV/PAA) was investigated in this study. The results showed that synergistic factor of the inactivation of A. niger and A. flavus was 1.44 and 1.37, which indicated significant synergistic effect of UV/PAA. The k of A. niger and A. flavus was similar at pH 5.0 and 7.0, while decreased 60.00% and 39.13% at pH 9.0 compared with that at pH 7.0. The effect of HA concentration on the inactivation efficiency of fungal spores by UV/PAA was negative, while the effect of PAA concentration was positive. The membrane permeabilized cell of A. niger and A. flavus caused by UV/PAA was 17.0% and 31.7%, which was higher than that caused by PAA and UV alone. The changes of morphology of fungal spores and the leakage of intracellular material indicated that the damage of cell structure caused by UV/PAA system was more serious than that of UV or PAA alone. In addition, the four parts that contributed in UV/PAA system was in the following order: UV > radical > PAA > synergistic effect. The inactivation efficiency of combined UV and chlorine (UV/Cl2) was higher than that of UV/PAA. Furthermore, the typical order of the inactivation efficiency in different matrix was: phosphate buffer solution > surface water > secondary effluent. The regrowth potential of fungal spores after UV/PAA treatment was significantly lower than that by PAA alone, indicating that UV/PAA could decrease the microbial regrowth potential after PAA disinfection alone.

Compromised Effectiveness of Thermal Inactivation of Legionella pneumophila in Water Heater Sediments and Water, and Influence of the Presence of Vermamoeba vermiformis.

Intermittent reduction of temperature set-points and periodic shutdowns of water heaters have been proposed to reduce energy consumption in buildings. However, the consequences of such measures on the occurrence and proliferation of Legionella pneumophila (Lp) in hot water systems have not been documented. The impact of single and repeated heat shocks was investigated using an environmental strain of L. pneumophila and a reference strain of V. vermiformis. Heat shocks at temperatures ranging from 50 °C to 70 °C were applied for 1 h and 4 h in water and water heaters loose deposits (sludge). The regrowth potential of heat-treated culturable L. pneumophila in presence of V. vermiformis in water heaters sludges was evaluated. A 2.5-log loss of culturability of L. pneumophila was observed in simulated drinking water at 60 °C while a 4-log reduction was reached in water heaters loose deposits. Persistence of Lp after 4 h at 55 °C was shown and the presence of V. vermiformis in water heater’s loose deposits resulted in a drastic amplification (5-log). Results show that thermal inactivation by heat shock is only efficient at elevated temperatures (50 °C) in both water and loose deposits. The few remaining organisms can rapidly proliferate during storage at lower temperature in the presence of hosts.

Distinguishing removal and regrowth potential of antibiotic resistance genes and antibiotic resistant bacteria on microplastics and in leachate after chlorination or Fenton oxidation

The prevalence of antibiotic resistance, as well as microplastics (MPs) as vectors for antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) has attracting growing attention. However, the fate of ARB/ARGs on MPs treated by chlorination and Fenton oxidation were poorly understood. Herein, the removal and regrowth of ARGs/ARB on MPs and in MPs-surrounding landfill leachate (an important reservoir of MPs and ARGs) after chlorination and Fenton oxidation were comparatively analyzed. Target ARGs on MPs were reduced obviously less than that in leachate, with the largest percentages reduction of 34.0–46.3% vs. 54.3–77.6% after chlorination and 92.1–97.3% vs. > 99.9% after Fenton oxidation, and similar removal patterns were observed for ARB. Moreover, a considerable regrowth of ARGs/ARB in leachate were found after 48 h of storage at the end of chlorination (5, 10, 20 and 50 mg/L), and a greater regrowth of ARGs and ARB occurred on MPs with up to 17 and 139 fold, respectively. In contrast, Fenton oxidation achieved a reduced regrowth of target ARGs/ARB. These findings indicated that the removal of ARGs/ARB on MPs were more difficult than that in leachate, and ARGs/ARB in leachate and especially on MPs exhibited a considerable potential for rapid regrowth after chlorination.

Survival and recovery of planktonic organisms in prolonged darkness and their implications on ballast water management

Understanding the population dynamics of transported organisms in the ship's ballast tanks during shipping operations and their ability to survive and colonize in the receiving environment (destination) can aid in developing effective ballast water treatment and management strategies. In the present study a natural plankton pool harvested from a tropical coast was used to study their survival in prolonged darkness and their regrowth potential upon re-illumination in laboratory conditions. In darkness, phytoplankton density and chlorophyll-a biomass decreased with increase in nutrient levels attributing to cell lysis. However, when subjected to vital staining using SYTOX® green, about 60% of phytoplankton survived in the dark tanks. Upon re-illumination after 36 days of incubation in darkness, >80% of recovered phytoplankton were pennate diatoms. On the other hand, zooplankton failed to survive/recover during the experiments when incubated in the dark. Less than 30% of the live zooplankton stained using Neutral Red in the dark tanks failed to recover during experiments. The data obtained clearly shows that prolonged dark incubation may promote the growth of opportunistic organisms and may alter their invasive potential through time and cause serious negative impacts to the receiving environment when transported by ballast water.

Natural forest regrowth under different land use intensities and landscape configurations in the Brazilian Atlantic Forest

Natural forest regrowth is considered the most cost-effective strategy to promote large-scale forest restoration, but regrowth trajectories and their consequences for nature and people can be highly variable. This uncertainty may obstruct devoting land, time and resources in promoting this restoration approach. Process-based models allow to simulate forest regrowth under different scenarios and may thus support decision making to manage areas in ways that maximize forest restoration based on natural forest regrowth. In the present study, we used the process-based model LandClim to assess the following questions:1) How does land use intensity affect forest growth, aboveground biomass (AGB) and tree species diversity in agricultural landscapes in the long term? 2) How do different land use configurations affect the structure and expansion of second-growth forests? We based our study on six 4 × 4 km agricultural landscapes, dominated by pastures and sugarcane, in the Brazilian Atlantic Forest region. We parameterized and validated LandClim for the study region by comparing model outputs with published estimates and information from field data collected across the six landscapes. We then simulated natural forest regrowth under different land use intensities in the six landscapes and analyzed how land use intensity and landscape configuration affect AGB, tree species diversity and the spatial dynamics of second-growth forests. Our results showed negative effects of increased land use intensity on landscape biomass accumulation due to limited forest cover expansion. Landscapes dominated by sugarcane had lower forest regrowth potential than pasture-dominated landscapes due to lower likelihood of abandonment, and limited rates of seed availability and seedling growth. Land use intensity and landscape configuration were also important factors for tree diversity changes. However, temporal patterns differed, and while AGB reached a plateau after 100–150 years, tree diversity peaked between 30 and 70 years. Thus, the effects of land use intensity and landscape configuration on forest AGB and tree diversity take decades to be fully expressed, highlighting the importance of a long-term commitment in restoration projects.

Regrowth potential of chlorine-resistant bacteria in drinking water under chloramination

The regrowth of chlorine-resistant bacteria in drinking water can deteriorate water quality. The study evaluated the relationship between organic carbon and the regrowth potential of chlorine-resistant bacteria remaining in chloraminated water samples. The results showed that the community structure of bacteria changed with the increase of chloramine dosage. The order in which organic carbon utilized by bacteria was affected by the composition of bacterial community. The biodegradable dissolved organic carbon (BDOC), assimilable organic carbon (AOC), bacterial regrowth potential (BRP) and total cell concentration (TCC) in cultivated water sample after disinfection with 1.8 mg/L chloramine increased form 0.22 mg/L, 33.68 µg/L, 2.70 × 105 cells/mL and 3.48 × 104 cells/mL before cultivation to 1.20 mg/L, 193.90 µg/L, 4.74 × 105 cells/mL and 1.46 × 105 cells/mL, respectively. The increase of TCC did not result in the decrease of BDOC, AOC and BRP in the cultivated water samples. The results showed that other biodegradable organic carbon in chloraminated water samples assimilated by residual chlorine-resistant bacteria besides AOC, BDOC, and organic carbon assimilated by indigenous bacteria. AOC, BDOC, and BRP indicators used to characterize the biostability of drinking water were not enough to accurately assess the regrowth potential of chlorine-resistant bacteria remaining in drinking water. It is suggested to supplement the index of TCC in cultivated water samples, which might be able to more accurately evaluate the regrowth potential of chlorine-resistant bacteria remaining in drinking water.

Regrowth of Escherichia coli in environmental waters after chlorine disinfection: shifts in viability and culturability.

Bacterial regrowth after water/wastewater disinfection poses severe risks to public health. However, regrowth studies under realistic water conditions that might critically affect bacterial regrowth are scarce. This study aimed to assess for the first time the regrowth of Escherichia coli (E. coli) in terms of its viability and culturability in environmental waters after chlorine disinfection, which is the most widely used disinfection method. Post-chlorination regrowth tests were conducted in 1) standard 0.85% NaCl solution, 2) river water receiving domestic wastewater effluents, and 3) river water that is fully recharged by domestic wastewater effluents. The multiplex detection of plate count and fluorescence-based viability test was adopted to quantify the culturable and viable E. coli to monitor the regrowth process. The results confirmed that chlorine treatment (0.2, 0.5 and 1.0 mg L-1 initial free chlorine) induced more than 99.95% of E. coli to enter a viable but non-culturable (VBNC) state and the reactivation of VBNC E. coli is presumably the major process of the regrowth. A second-order regrowth model well described the temporal shift of the survival ratio of culturable E. coli after the chlorination (R2: 0.73-1.00). The model application also revealed that the increase in initial chlorine concentration and chlorine dose limited the maximum regrowth rate and the maximum survival ratio, and the regrowth rate and percentage also changed with the water type. This study gives a better understanding of the potential regrowth after chlorine disinfection and highlights the need for investigating the detailed relation of the regrowth to environmental conditions such as major components of water matrices.

Impact of pH and removed filtrate on E. coli regrowth and microbial community during storage of electro-dewatered biosolids

Residual biosolids can be land applied if they meet microbiological requirements at the time of application. Electro-dewatering technology is shown to reduce biosolids bacterial counts to detection limits with little potential for bacterial regrowth during incubations. Here, we investigated the impacts on Escherichia coli regrowth and microbial communities of biosolids pH, removed nutrients via the filtrate, and inhibitory compounds produced in electro-dewatered biosolids. Findings suggest pH as the primary mechanism impacting E. coli regrowth in electro-dewatered biosolids. Propidium monoazide treatments were effective at removing DNA from dead cells, based on the removal of obligate anaerobes observed after anaerobic incubation. Analyses of high throughput sequenced data showed lower alpha-diversities associated with electro-dewatering treatment and incubation time. Moreover, biosolids pH and incubation period were the main factors contributing to the variations in microbial community compositions after incubation. Results highlight the role of electro-dewatered biosolids' low pH on inhibiting the regrowth of culturable bacteria as well as reducing the microbial community variance.

Grazed rain-fed small-grain cereals as a forage option for small-scale dairy systems in central Mexico.

Small-scale dairy systems face reduced availability of water for irrigation of pastures and disruption in the amount or pattern of rains due to climate change, so research on alternative short-cycle rain-fed forages is needed. Grazing reduces feeding costs and small-grain cereals may be an option. The objective was to assess on-farm the performance of dairy cows grazing 6h/day of three small-grain cereals: rye (RYE), wheat (WHT), and triticale (TRT), and supplemented 4.5kg dry matter (DM)/cow/day of concentrate. Twelve Holstein cows were used in repeated 3 × 3 Latin squares with 14-day experimental periods. Pasture variables were analysed with a split-plot design, and economic analysis was performed with partial budgets. Sampling of forage (sward height, net herbage accumulation, botanical and chemical composition of herbage) and animal variables (milk yield and composition, live weight, and body condition score) were at the end of each period. The RYE showed a trend (P > 0.05) for higher net herbage accumulation (NHA) with highly significant differences (P < 0.001) among periods. The RYE had higher DM, a lower crude protein (CP) content (P < 0.05), and no differences for other chemical components between treatments (P > 0.05). The RYE proportion in pasture was consistently higher, whilst the lowest cereal proportion was in WHT. There were no differences (P > 0.05) for any animal variable. The RYE and TRT treatments proved useful as rain-fed forage alternatives under grazing. WHT showed lower crop and economic performance. However, given the higher cereal component in pastures, regrowth potential, and post-grazing herbage mass, as well as better economic performance, the RYE treatment was better ranked by the participating farmer.

Inactivation of antibiotic resistant bacterium Escherichia coli by electrochemical disinfection on molybdenum carbide electrode

Antibiotic-resistant bacteria (ARB) pose a substantial threat to public health worldwide. Electrochemistry, as a low energy consumption and environmentally friendly technique, is ideal for inactivating ARB. This study explored the utility of electrochemical disinfection (ED) for inactivating ARB (Escherichia coli K-12 LE392 resistant to kanamycin, tetracycline, and ampicillin) and the regrowth potential of the treated ARB. The results revealed that 5.12-log ARB removal was achieved within 30 min of applying molybdenum carbide as the anode and cathode material under a voltage of 2.0 V. No ARB regrowth was observed in the cathode chamber after 60 min of incubation in unselective broth, demonstrating that the process in the cathode chamber was more effective for permanent inactivation of ARB. The mechanisms underlying the ARB inactivation were verified based on intercellular reactive oxygen species (ROS) measurement, membrane integrity detection, and genetic damage assessment. Higher ROS production and membrane permeability were observed in the cathode and anode groups (p < 0.001) compared to the control group (0 V). In addition, the DNA was more likely to be damaged during the ED process. Collectively, our results demonstrate that ED is a promising technology for disinfecting water to prevent the spread of ARB.

A comprehensive investigation of the microbial risk of secondary water supply systems in residential neighborhoods in a large city

Secondary water supply systems (SWSSs) are characterized by long water stagnation and low levels of chlorine residuals, which may pose a high microbial risk to terminal users. In this study, the SWSSs of 12 residential neighborhoods in a metropolitan area of 5 million people in southeastern China were seasonally investigated to assess their microbial risks by determining more than 30 physicochemical and biological parameters. Although the microbiological quality of SWSS water met the requirements of the standards for drinking water quality of China, it did deteriorate in various aspects. The heterotrophic plate counts with R2A media were high (> 100 CFU/mL) in some SWSS tank and tap water samples. Propidium monoazide (PMA)-qPCR revealed a one magnitude higher abundance of viable bacteria in the tank and tap water samples (average 103.63±1.10 and 103.65±1.25 gene copies/mL, respectively) compared with the input water samples, and Enterococcus, Acanthamoeba, and Hartmannella vermiformis were only detected in the tanks. In particular, the high detection frequency of Legionella in 35% tank and 21% tap water samples suggested it is a supplementary microbial safety indicator in SWSSs. The microbial regrowth potential was more obvious in summer, and Illumina sequencing also demonstrated distinct seasonal changes in the relative abundance of bacterial gene sequences at the genus level. Turbidity and residual chlorine were closely connected with total bacterial biomass, and the latter seemed responsible for microbial community structure alteration. The extremely low chlorine residuals associated with a high abundance of total bacteria (as high as 106.48 gene copies/mL) and Legionella (as high as 106.71 gene copies/100 mL) in the closed valve tanks highlighted the high microbial risk increased by mishandling the operation of SWSSs. This study found that SWSSs possessed a higher microbial risk than the drinking water network, which suggested that the frequency and scope of monitoring the microbial risk of SWSSs in megacities should be strengthened for the purpose of waterborne epidemic disease prevention and control.