Citrate and malonate increase microbial activity and alter microbial community composition in uncontaminated and diesel-contaminated soil microcosms

Petroleum hydrocarbons (PHCs) are among the most prevalent sources of environmental contamination. It has been hypothesized that plant root exudation of low molecular weight organic acid anions (carboxylates) may aid degradation of PHCs by stimulating heterotrophic microbial activity. To test their potential implication for bioremediation, we applied two commonly exuded carboxylates (citrate and malonate) to uncontaminated and diesel-contaminated microcosms (10 000 mg kg−1; aged 40 days) and determined their impact on the microbial community and PHC degradation. Every 48 h for 18 days, soil received 5 µmol g−1 of (i) citrate, (ii) malonate, (iii) citrate + malonate or (iv) water. Microbial activity was measured daily as the flux of CO2. After 18 days, changes in the microbial community were assessed by a community-level physiological profile (CLPP) and 16S rRNA bacterial community profiles determined by denaturing gradient gel electrophoresis (DGGE). Saturated PHCs remaining in the soil were assessed by gas chromatography–mass spectrometry (GC-MS). Cumulative soil respiration increased 4- to 6-fold with the addition of carboxylates, while diesel contamination resulted in a small, but similar, increase across all carboxylate treatments. The addition of carboxylates resulted in distinct changes to the microbial community in both contaminated and uncontaminated soils but only a small increase in the biodegradation of saturated PHCs as measured by the n-C17 : pristane biomarker. We conclude that while the addition of citrate and malonate had little direct effect on the biodegradation of saturated hydrocarbons present in diesel, their effect on the microbial community leads us to suggest further studies using a variety of soils and organic acids, and linked to in situ studies of plants, to investigate the role of carboxylates in microbial community dynamics

Evaluation of 16S next-generation sequencing of hypervariable region 4 in wastewater samples: An unsuitable approach for bacterial enteric pathogen identification

Recycled wastewater can carry human-infectious microbial pathogens and therefore wastewater treatment strategies must effectively eliminate pathogens before recycled wastewater is used to supplement drinking and agricultural water supplies. This study characterised the bacterial composition of four wastewater treatment plants (WWTPs) (three waste stabilisation ponds and one oxidation ditch WWTP using activated sludge treatment) in Western Australia. The hypervariable region 4 (V4) of the bacterial 16S rRNA (16S) gene was sequenced using next-generation sequencing (NGS) on the Illumina MiSeq platform. Sequences were pre-processed in USEARCH v10.0 and denoised into zero-radius taxonomic units (ZOTUs) with UNOISE3. Taxonomy was assigned to the ZOTUs using QIIME 2 and the Greengenes database and cross-checked with the NCBI nr/nt database. Bacterial composition of all WWTPs and treatment stages (influent, intermediate and effluent) were dominated by Proteobacteria (29.0-87.4%), particularly Betaproteobacteria (9.0-53.5%) and Gammaproteobacteria (8.6-34.6%). Nitrifying bacteria (Nitrospira spp.) were found only in the intermediate and effluent of the oxidation ditch WWTP, and denitrifying and floc-forming bacteria were detected in all WWTPs, particularly from the families Comamonadaceae and Rhodocyclales. Twelve pathogens were assigned taxonomy by the Greengenes database, but comparison of sequences from genera and families known to contain pathogens to the NCBI nr/nt database showed that only three pathogens (Arcobacter venerupis, Laribacter hongkongensis and Neisseria canis) could be identified in the dataset at the V4 region. Importantly, Enterobacteriaceae genera could not be differentiated. Family level taxa assigned by Greengenes database agreed with NCBI nr/nt in most cases, however, BLAST analyses revealed erroneous taxa in Greengenes database. This study highlights the importance of validating taxonomy of NGS sequences with databases such as NCBI nr/nt, and recommends including the V3 region of 16S in future short amplicon NGS studies that aim to identify bacterial enteric pathogens, as this will improve taxonomic resolution of most, but not all, Enterobacteriaceae species

Low molecular weight organic anions (carboxylates) increase microbial activity and alter microbial community composition in uncontaminated and diesel contaminated soil

Petroleum hydrocarbons (PHCs) are among the most prevalent sources of environmental contamination. It has been hypothesized that plant root exudation of low molecular weight organic acid anions (carboxylates) may aid degradation of PHCs by stimulating heterotrophic microbial activity. We, therefore, applied two commonly-exuded carboxylates (citrate and malonate) to uncontaminated and diesel contaminated microcosms (10,000 mg kg–1; aged 40 days) to determine their impact on the microbial community and PHC degradation. Every 48 hours for 18 days, soil received 5 μmol g–1 of i) citrate, ii) malonate, iii) citrate + malonate or iv) water. Microbial activity was measured daily as the flux of CO2. After 18 days, changes in the microbial community were assessed by community level physiological profiles and 16S rRNA bacterial community profiles determined by denaturing gradient gel electrophoresis. Saturated PHCs remaining in the soil were assessed by GCMS. Cumulative soil respiration increased four- to six-fold with the addition of carboxylates, while diesel contamination resulted in a small, but similar, increase across all carboxylate treatments. The addition of carboxylates resulted in distinct changes to the microbial community, but only a small decrease in the n-C17: pristane biomarker. We conclude that carboxylate addition can increase microbial activity and modify the microbial community in both uncontaminated and diesel-contaminated soils. The impact of these changes on PHC biodegradation and rhizosphere processes, more generally, merits further research

Administration of human chorionic gonadotropin at embryo transfer induced ovulation of a first-wave dominant follicle and increased progesterone and transfer pregnancy rates

Beef Cattle Research, 2011 is known as Cattlemen’s Day, 2011Embryo transfer (ET) has become more widespread in recent years as a way to improve cattle genetics. According to the annual statistical survey of the American Embryo Transfer Association, more than 200,000 fresh and frozen bovine embryos were transferred in 2008. But despite advancements in reproductive technologies that have occurred since ET was commercialized in the 1970s, industrywide pregnancy rates are only 62.4 and 56.9% for fresh and frozen-thawed ET, respectively. Using ET helps avoid problems from failed fertilization; however, fertilization failure has been characterized as a relatively unimportant factor of pregnancy loss. Approximately 10% of pregnancy failures resulted from fertilization failure and another 10% from failed embryo development. Approximately 20 to 25% of the pregnancy loss in an ET program could be characterized as early embryonic loss

Anisotropic splitting of intersubband spin plasmons in quantum wells with bulk and structural inversion asymmetry

In semiconductor heterostructures, bulk and structural inversion asymmetry and spin-orbit coupling induce a k-dependent spin splitting of valence and conduction subbands, which can be viewed as being caused by momentum-dependent crystal magnetic fields. This paper studies the influence of these effective magnetic fields on the intersubband spin dynamics in an asymmetric n-type GaAs/AlGaAs quantum well. We calculate the dispersions of intersubband spin plasmons using linear response theory. The so-called D'yakonov-Perel' decoherence mechanism is inactive for collective intersubband excitations, i.e., crystal magnetic fields do not lead to decoherence of spin plasmons. Instead, we predict that the main signature of bulk and structural inversion asymmetry in intersubband spin dynamics is a three-fold, anisotropic splitting of the spin plasmon dispersion. The importance of many-body effects is pointed out, and conditions for experimental observation with inelastic light scattering are discussed.Comment: 8 pages, 6 figure

Improving root cause analysis of bacteriological water quality failures at water treatment works

© 2015 Published by Elsevier Ltd. Variations in spot-sampled and continuously-monitored water quality data were assessed to determine whether they could be linked to regulatory coliform failures. Data were available from raw water to the final monitoring point at water treatment works (WTW)-B and included climate, physico-chemical and bacteriological data. These were analysed using cross-correlation and self-organising maps in MATLAB®. The results highlighted rainfall and upstream coliforms and turbidity as important factors in the coliform failures. Further examination showed that failures correlated with low turbidity and low coliform loading, but relatively high rainfall. This outcome could be used to improve bacteriological compliance at WTW-B and similar sites

The effect of underwater sounds on shark behaviour

The effect of sound on the behaviour of sharks has not been investigated since the 1970s. Sound is, however, an important sensory stimulus underwater, as it can spread in all directions quickly and propagate further than any other sensory cue. We used a baited underwater camera rig to record the behavioural responses of eight species of sharks (seven reef and coastal shark species and the white shark, Carcharodon carcharias) to the playback of two distinct sound stimuli in the wild: an orca call sequence and an artificially generated sound. When sounds were playing, reef and coastal sharks were less numerous in the area, were responsible for fewer interactions with the baited test rigs, and displayed less ‘inquisitive’ behaviour, compared to during silent control trials. White sharks spent less time around the baited camera rig when the artificial sound was presented, but showed no significant difference in behaviour in response to orca calls. The use of the presented acoustic stimuli alone is not an effective deterrent for C. carcharias. The behavioural response of reef sharks to sound raises concern about the effects of anthropogenic noise on these taxa

Ward Identities, B-> \rho Form Factors and |V_ub|

The exclusive FCNC beauty semileptonic decay B-> \rho is studied using Ward identities in a general vector meson dominance framework, predicting vector meson couplings involved. The long distance contributions are discussed which results to obtain form factors and |V_ub|. A detailed comparison is given with other approaches.Comment: 30 pages+four postscript figures, an Appendix adde

Quantum walk on distinguishable non-interacting many-particles and indistinguishable two-particle

We present an investigation of many-particle quantum walks in systems of non-interacting distinguishable particles. Along with a redistribution of the many-particle density profile we show that the collective evolution of the many-particle system resembles the single-particle quantum walk evolution when the number of steps is greater than the number of particles in the system. For non-uniform initial states we show that the quantum walks can be effectively used to separate the basis states of the particle in position space and grouping like state together. We also discuss a two-particle quantum walk on a two- dimensional lattice and demonstrate an evolution leading to the localization of both particles at the center of the lattice. Finally we discuss the outcome of a quantum walk of two indistinguishable particles interacting at some point during the evolution.Comment: 8 pages, 7 figures, To appear in special issue: "quantum walks" to be published in Quantum Information Processin

Positive association between epiphytes and competitiveness of the brown algal genus Lobophora against corals

Observations of coral–algal competition can provide valuable information about the state of coral reef ecosystems. Here, we report contact rates and apparent competition states for six shallow lagoonal reefs in Fiji. A total of 81.4% of examined coral perimeters were found to be in contact with algae, with turf algae (54.7%) and macroalgae of the genus Lobophora (16.8%) representing the most frequently observed contacts. Turf algae competitiveness was low, with 21.8% of coral–turf contacts being won by the algae (i.e. overgrowth or bleaching of coral tissue). In contrast, Lobophora competitiveness against corals was high, with 62.5% of contacts being won by the alga. The presence of epiphytic algae on Lobophora was associated with significantly greater algal competitiveness against corals, with 75.8% and 21.1% of interactions recorded as algal wins in the presence and absence of epiphytes, respectively. Sedimentation rate, herbivorous fish biomass, and coral colony size did not have a significant effect on Lobophora–coral interactions. This research indicates a novel and important role of epiphytes in driving the outcome of coral–algal contacts