Chlorophyll a fluorescence of microalgae is a compelling indicator of toxicity of dissolved water contaminants, because it is easily measured and responds rapidly. While different chl a fluorescence ...parameters have been examined, most studies have focused on single species and/or a narrow range of toxins. We assessed the utility of one chl a fluorescence parameter, the maximum quantum yield of PSII (Fv/Fm), for detecting effects of nine environmental pollutants from a range of toxin classes on 5 commonly found freshwater algal species, as well as the USEPA model species, Pseudokirchneriella subcapitata. Fv/Fm declined rapidly over <20 min in response to low concentrations of photosynthesis-specific herbicides Diuron® and metribuzin (both <40 nM), atrazine (<460 nM) and terbuthylazine (<400 nM). However, Fv/Fm also responded rapidly and in a dose-dependent way to toxins glyphosate (<90 μM), and KCN (<1 mM) which have modes of action not specific to photosynthesis. Fv/Fm was insensitive to 30–40 μM insecticides methyl parathion, carbofuran and malathion. Algal species varied in their sensitivity to toxins. No single species was the most sensitive to all nine toxins, but for six toxins to which algal Fv/Fm responded significantly, the model species P. subcapitata was less sensitive than other taxa. In terms of suppression of Fv/Fm within 80 min, patterns of concentration-dependence differed among toxins; most showed Michaelis–Menten saturation kinetics, with half-saturation constant (Km) values for the PSII inhibitors ranging from 0.14 μM for Diuron® to 6.6 μM for terbuthylazine, compared with a Km of 330 μM for KCN. Percent suppression of Fv/Fm by glyphosate increased exponentially with concentration. Fv/Fm provides a sensitive and easily-measured parameter for rapid and cost-effective detection of effects of many dissolved toxins. Field-portable fluorometers will facilitate field testing, however distinct responses between different species may complicate net Fv/Fm signal from a community.
► Algal chlorophyll fluorescence Fv/Fm declines within minutes with toxin exposure. ► Fv/Fm suppression shows dose-dependence (Km are nanomolar range for PSII inhibitors). ► Fv/Fm suppression also shows concentration-dependence to toxins KCN and glyphosate. ► Effects of toxic pollutants can be effectively and rapidly detected using algal Fv/Fm. ► Field testing of natural communities will be complicated by taxon-specific responses.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
An integrated photo-bioelectrochemical (IPB) system uses microalgae in the cathode of a microbial fuel cell to achieve higher electricity generation and nutrient removal from wastewater. Using ...multivariate analysis and surveys of IPB studies, this paper identifies key algal and bacterial taxa and discusses their functions critical for IPB performance. Unicellular algae with high photosynthetic oxygen production and biofilm formation can enhance IPB energy production. Diverse bacterial taxa achieve nitrogen transformations and can improve total nitrogen removal. Understanding bacteria–algae interactions via quorum sensing in the IPB cathode may potentially aid in boosting system performance. Future advances in development of IPBs for wastewater treatment will benefit from interdisciplinary collaboration in analysis of microbial community functions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
De novo protein synthesis supports long-lasting functional and structural plasticity and is a molecular requirement for new memory formation. Recent evidence has suggested that microRNAs may be ...involved in regulating the molecular mechanisms underlying neural plasticity. MicroRNAs are endogenous, noncoding RNAs capable of post-transcriptional repression of their mRNA targets. To explore the potential for microRNA-mediated regulation of amygdala-dependent memory formation, we performed expression profiling of microRNAs in the lateral amygdala of rats 1 h after auditory fear conditioning. Microarray analysis revealed that over half of all known microRNAs are endogenously expressed in the lateral amygdala, with 7 microRNAs upregulated and 32 downregulated by auditory fear training. Bioinformatic analysis identified several of the downregulated microRNAs as potential repressors of actin-regulating proteins known to be involved in plasticity and memory. Downregulation of one of these microRNAs by auditory fear conditioning, miR-182, was confirmed by quantitative real-time PCR. Overexpression of miR-182 within the lateral amygdala resulted in decreased expression of the protein but not mRNA of two synapse-enriched regulators of actin known to modulate structural plasticity, cortactin and Rac1. The overexpression of miR-182 also disrupted long-term but not short-term auditory fear memory. These data indicate that learning-induced suppression of miR-182, a microRNA previously uncharacterized in the brain, supports long-term memory formation in the amygdala and suggests it does so, at least in part, through the derepression of key actin-regulating proteins. These findings further indicate that microRNAs may represent a previously underappreciated mechanism for regulating protein synthesis during memory consolidation.
Background Memories associated with drugs of abuse, such as methamphetamine (METH), increase relapse vulnerability to substance use disorder by triggering craving. The nucleus accumbens (NAc) is ...essential to these drug-associated memories, but underlying mechanisms are poorly understood. Posttranslational chromatin modifications, such as histone methylation, modulate gene transcription; thus, we investigated the role of the associated epigenetic modifiers in METH-associated memory. Methods Conditioned place preference was used to assess the epigenetic landscape in the NAc supporting METH-associated memory ( n = 79). The impact of histone methylation (H3K4me2/3) on the formation and expression of METH-associated memory was determined by focal, intra-NAc knockdown (KD) of a writer, the methyltransferase mixed-lineage leukemia 1 ( Mll1 ) ( n = 26), and an eraser, the histone lysine (K)-specific demethylase 5C ( Kdm5c ) ( n = 38), of H3K4me2/3. Results A survey of chromatin modifications in the NAc of animals forming a METH-associated memory revealed the global induction of several modifications associated with active transcription. This correlated with a pattern of gene activation, as revealed by microarray analysis, including upregulation of oxytocin receptor ( Oxtr ) and FBJ osteosarcoma oncogene ( Fos ), the promoters of which also had increased H3K4me3. KD of Mll1 reduced H3K4me3, Fos and Oxtr levels and disrupted METH-associated memory. KD of Kdm5c resulted in hypermethylation of H3K4 and prevented the expression of METH-associated memory. Conclusions The development and expression of METH-associated memory are supported by regulation of H3K4me2/3 levels by MLL1 and KDM5C, respectively, in the NAc. These data indicate that permissive histone methylation, and the associated epigenetic writers and erasers, represent potential targets for the treatment of substance abuse relapse, a psychiatric condition perpetuated by unwanted associative memories.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Si cycling is linked with processes from global carbon sequestration to community composition and is especially important in aquatic ecosystems. Lake Michigan has seen dramatic fluctuations in ...dissolved silica (dSi) over several decades, which have been examined in the context of planktonic processes (diatom blooms), but the role of benthic organisms (macroalgae and their epiphytes) in Si cycling have not been explored. To assess significance of nearshore benthic algae in Si dynamics, we assembled dSi data from an offshore site sampled since the late 1980's, and sampled off three Milwaukee beaches during 2005-19. Using colorimetric assays and alkaline digestion, we measured dSi, biogenic silica in particulate suspended material (pSi) and biogenic silica in benthic macroalgae (Cladophora) and epiphytic diatoms (bSi). Offshore, dSi increased about 1 μM per year from 25 μM in the late 1980's to nearly 40 μM in 2019. Nearshore dSi fluctuated dramatically annually, from near zero to concentrations similar to offshore. Both Cladophora and its epiphytes contained significant bSi, reaching up to 30% of dry mass (300 mg Si g dry mass-1) of the assemblage in summer. Microscopic analyses including localization with a Si-specific-stain and X-ray microanalysis showed bSi in epiphytic diatom cells walls, but the nature and localization of Si in macroalgae remained unclear. A simple model was developed estimating Si demand of algae using the areal macroalgal biomass, growth rates inferred from P-content, and bSi content, and comparing Si demand with dSi available in the water column. This indicated that 7-70% of the dSi in water overlying nearshore benthic algal beds could be removed per day. Key elements of the Si cycle, including which organisms sequester bSi and how rapidly Si is recycled, remain unclear. This work has implications for coastal marine waters where large macroalgal biomass accumulates but bSi content is virtually unknown.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Understanding microbial roles in ecosystem function requires integrating microscopic processes into food webs. The carnivorous pitcher plant, Sarracenia purpurea, offers a tractable study system ...where diverse food webs of macroinvertebrates and microbes facilitate digestion of captured insect prey, releasing nutrients supporting the food web and host plant. However, how interactions between these macroinvertebrate and microbial communities contribute to ecosystem functions remains unclear. We examined the role of the pitcher plant mosquito, Wyeomyia smithii, in top-down control of the composition and function of pitcher plant microbial communities. Mosquito larval abundance was enriched or depleted across a natural population of S. purpurea pitchers over a 74-day field experiment. Bacterial community composition and microbial community function were characterized by 16S rRNA amplicon sequencing and profiling of carbon substrate use, bulk metabolic rate, hydrolytic enzyme activity, and macronutrient pools. Bacterial communities changed from pitcher opening to maturation, but larvae exerted minor effects on high-level taxonomic composition. Higher larval abundance was associated with lower diversity communities with distinct functions and elevated nitrogen availability. Treatment-independent clustering also supported roles for larvae in curating pitcher microbial communities through shifts in community diversity and function. These results demonstrate top-down control of microbial functions in an aquatic microecosystem.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
An integrated photobioelectrochemical (IPB) system was developed by installing a microbial fuel cell (MFC) inside an algal bioreactor. This system achieves the simultaneous removal from a synthetic ...solution of organics (in the MFC) and nutrients (in the algal bioreactor), and the production of bioenergy in electricity and algal biomass through bioelectrochemical and microbiological processes. During the one-year operation, the IPB system removed more than 92% of chemical oxygen demand, 98% of ammonium nitrogen, and 82% of phosphate and produced a maximum power density of 2.2 W/m3 and 128 mg/L of algal biomass. The algal growth provided dissolved oxygen to the cathode reaction of the MFC, whereas electrochemical oxygen reduction on the MFC cathode buffered the pH of the algal growth medium (which was also the catholyte). The system performance was affected by illumination and dissolved oxygen. Initial energy analysis showed that the IPB system could theoretically produce enough energy to cover its consumption; however, further improvement of electricity production is desired. An analysis of the attached and suspended microbes in the cathode revealed diverse bacterial taxa typical of aquatic and soil bacterial communities with functional roles in contaminant degradation and nutrient cycling.
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IJS, KILJ, NUK, PNG, UL, UM
Processes influencing recruitment of diverse bacteria to plant microbiomes remain poorly understood. In the carnivorous pitcher plant
model system, individual pitchers open to collect rainwater, ...invertebrates and a diverse microbial community, and this detrital food web is sustained by captured insect prey. This study examined how potential sources of bacteria affect the development of the bacterial community within pitchers, how the host plant tissue affects community development and how established vs. assembling communities differ. In a controlled greenhouse experiment, seven replicate pitchers were allocated to five treatments to exclude specific bacterial sources or host tissue: milliQ water only, milliQ + insect prey, rainwater + prey, established communities + prey, artificial pitchers with milliQ + prey. Community composition and functions were examined over 8-40 weeks using bacterial gene sequencing and functional predictions, measurements of cell abundance, hydrolytic enzyme activity and nutrient transformations. Distinct community composition and functional differences between artificial and real pitchers confirm an important influence of host plant tissue on community development, but also suggest this could be partially related to host nutrient uptake. Significant recruitment of bacteria to pitchers from air was evident from many taxa common to all treatments, overlap in composition between milliQ, milliQ + prey, and rainwater + prey treatments, and few taxa unique to milliQ only pitchers. Community functions measured as hydrolytic enzyme (chitinase, protease) activity suggested a strong influence of insect prey additions and were linked to rapid transformation of insect nutrients into dissolved and inorganic sources. Bacterial taxa found in 6 of 7 replicate pitchers within treatments, the "core microbiome" showed tighter successional trajectories over 8 weeks than all taxa. Established pitcher community composition was more stable over 8 weeks, suggesting a diversity-stability relationship and effect of microinvertebrates on bacteria. This study broadly demonstrates that bacterial composition in host pitcher plants is related to both stochastic and specific bacterial recruitment and host plants influence microbial selection and support microbiomes through capture of insect prey.
An integrated photo-bioelectrochemical system (IPB) for wastewater treatment combines a microbial fuel cell with an algal bioreactor, eliminating requirements for aeration, promoting electricity ...generation, remediating nutrients and producing algal biomass for conversion into biofuel or other bioproducts. To examine strategies for improving IPB functions of electrochemical output and nutrient removal efficiency, this study tested effects of cathode bacterial inoculation and nitrogen loading on cathode microbial community and IPB performance. IPB cathodes were inoculated with the green alga Chlorella vulgaris, in combination with nitrite-oxidizing bacteria (NOB) Nitrobacter winogradskyi, and/or ammonium-oxidizing bacteria (AOB) Nitrosomonas europaea. IPB performance was examined before and after nitrifying bacteria inoculations and under three ammonium loading concentrations in the wastewater medium. Bacterial communities in the cathode suspension and biofilm were examined by 16S rRNA gene sequence analysis. Relative to the algae only control, cathode inoculation with NOB and/or AOB improved net nutrient removal, but resulted in reduced dissolved oxygen availability, which impaired electricity generation. Higher ammonium loading increased electricity production and nutrient removal, possibly by overcoming algal-bacterial competition. Inoculation with nitrifying bacteria resulted in minor changes to total bacterial composition and AOB or NOB comprised <3% of total sequences after 1 month. Community composition changed more dramatically following increase in ammonium-N concentration from 40 to 80 mg L−1. Manipulation of N loading could be a useful strategy to improve IPB performance, while inoculation of AOB or NOB may be beneficial for treatment of water with high ammonium loading when N removal is the primary system goal.
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•Algae and bacteria collaborate in a wastewater bioremediation system.•Changes in bacterial composition influence nutrient uptake and electrical output.•Inoculation with nitrifying bacteria had limited effect on composition or performance.•Higher ammonium loading changed bacteria and improved system performance.•Resource manipulation is most effective strategy to optimize performance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A high rate of relapse is a defining characteristic of substance use disorder for which few treatments are available. Exposure to environmental cues associated with previous drug use can elicit ...relapse by causing the involuntary retrieval of deeply engrained associative memories that trigger a strong motivation to seek out drugs. Our lab is focused on identifying and disrupting mechanisms that support these powerful consolidated memories, with the goal of developing therapeutics. A particularly promising mechanism is regulation of synaptic dynamics by actin polymerization within dendritic spines. Emerging evidence indicates that memory is supported by structural and functional plasticity dendritic spines, for which actin polymerization is critical, and that prior drug use increases both spine and actin dynamics. Indeed we have found that inhibiting amygdala (AMY) actin polymerization immediately or twenty-four hours prior to testing disrupted methamphetamine (METH)-associated memories, but not food reward or fear memories. Furthermore, METH training increased AMY spine density which was reversed by actin depolymerization treatment. Actin dynamics were also shifted to a more dynamic state by METH training. While promising, actin polymerization inhibitors are not a viable therapeutic, as a multitude of peripheral process (e.g. cardiac function) rely on dynamic actin. For this reason, we have shifted our focus upstream of actin polymerization to nonmuscle myosin II. We and others have demonstrated that myosin IIb imparts a mechanical force that triggers spine actin polymerization in response to synaptic stimulation. Similar to an actin depolymerizing compound, pre-test inhibition of myosin II ATPase activity in the AMY produced a rapid and lasting disruption of drug-seeking behavior. While many questions remain, these findings indicate that myosin II represents a potential therapeutic avenue to target the actin cytoskeleton and disrupt the powerful, extinction-resistant memories capable of triggering relapse.
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