Summary
To quantify the major environmental drivers of stream bacterial population dynamics, we modelled temporal differences in stream bacterial communities to quantify community shifts, including ...those relating to cyclical seasonal variation and more sporadic bloom events. We applied Illumina MiSeq 16S rRNA bacterial gene sequencing of 892 stream biofilm samples, collected monthly for 36‐months from six streams. The streams were located a maximum of 118 km apart and drained three different catchment types (forest, urban and rural land uses). We identified repeatable seasonal patterns among bacterial taxa, allowing their separation into three ecological groupings, those following linear, bloom/trough and repeated, seasonal trends. Various physicochemical parameters (light, water and air temperature, pH, dissolved oxygen, nutrients) were linked to temporal community changes. Our models indicate that bloom events and seasonal episodes modify biofilm bacterial populations, suggesting that distinct microbial taxa thrive during these events including non‐cyanobacterial community members. These models could aid in determining how temporal environmental changes affect community assembly and guide the selection of appropriate statistical models to capture future community responses to environmental change.
High-frequency (850 kHz) ultrasound was used to inactivate bacteria and yeast at different growth phases under controlled temperature conditions. Three species of bacteria, Enterobacter aerogenes, ...Bacillus subtilis and Staphylococcus epidermidis as well as a yeast, Aureobasidium pullulans were considered. The study shows that high-frequency ultrasound is highly efficient in inactivating the bacteria in both their exponential and stationary growth phases, and inactivation rates of more than 99% were achieved. TEM observation suggests that the mechanism of bacteria inactivation is mainly due to acoustic cavitation generated free radicals and H2O2. The rod-shaped bacterium B. subtilis was also found to be sensitive to the mechanical effects of acoustic cavitation. The study showed that the inactivation process continued even after ultrasonic processing cessed due to the presence of H2O2, generated during acoustic cavitation. Compared to bacteria, the yeast A. pullulans was found to be more resistant to high-frequency ultrasound treatment.
•Different bacteria were treated with high-power low-frequency ultrasound.•The log reduction of some bacteria increased with increasing ultrasound power.•Bacterial particle size distributions were ...measured and TEM micrographs were taken.•E. aerogenes was more sensitive to ultrasonication in exponential growth phase.•Bacterial cells with capsules were more resistant to ultrasound treatment.
The aim of this study was to determine the effects of high-intensity low-frequency (20kHz) ultrasound treatment on the viability of bacteria suspension. More specifically, we have investigated the relationship between the deactivation efficiency and the physical (size, hydrophobicity) and biological (gram-status, growth phase) properties of the microbes. Enterobacter aerogenes, Bacillus subtilis, Staphylococcus epidermidis, S. epidermidis SK and Staphylococcus pseudintermedius were chosen for this study owing to their varying physical and biological properties. The survival ratio of the bacteria suspension was measured as a function of the ultrasound power (up to 13W) for a constant sonication time of 20min. Transmission electron microscopy was used to evaluate the ultrasound-induced damages to the microbes. Ultrasound treatment resulted in lethal damage to E. aerogenes and B. subtilis (up to 4.5-log reduction), whereas Staphylococcus spp. were not affected noticeably. Further, E. aerogenes suspensions were more sensitive to ultrasonication in exponential growth phase than when they were in stationary phase. The results of this study demonstrate that the main reason for bacterial resistance to ultrasonic deactivation is due to the properties of the bacterial capsule. Microbes with a thicker and “soft” capsule are highly resistant to ultrasonic deactivation process.
We surveyed the functional gene composition and diversity of microbial biofilm communities in 18 New Zealand streams affected by different types of catchment land use, using a comprehensive ...functional gene array, GeoChip 3.0. A total of 5,371 nutrient cycling and energy metabolism genes within 65 gene families were detected among all samples (342 to 2,666 genes per stream). Carbon cycling genes were most common, followed by nitrogen cycling genes, with smaller proportions of sulphur, phosphorus cycling and energy metabolism genes. Samples from urban and native forest streams had the most similar functional gene composition, while samples from exotic forest and rural streams exhibited the most variation. There were significant differences between nitrogen and sulphur cycling genes detected in native forest and urban samples compared to exotic forest and rural samples, attributed to contrasting proportions of nitrogen fixation, denitrification, and sulphur reduction genes. Most genes were detected only in one or a few samples, with only a small minority occurring in all samples. Nonetheless, 42 of 65 gene families occurred in every sample and overall proportions of gene families were similar among samples from contrasting streams. This suggests the existence of functional gene redundancy among different stream biofilm communities despite contrasting taxonomic composition.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Discharge of inadequately treated human wastewater into surface waters used for recreation, drinking water, irrigation and shellfish cultivation may present a public health hazard due to the ...potential shedding of high concentrations of pathogenic viruses from the human gastrointestinal tract. Human adenovirus (HAdV) and human polyomavirus (HPyV) are ubiquitous in humans and have excellent survival characteristics in the environment, so are potential candidates for indicators of human sewage contamination. Using qPCR assays, the prevalence and quantity of HAdV and HPyV JC and BK were determined in influent and effluent wastewater and receiving waters (river, urban stream, estuarine), then compared with norovirus (NoV) presence, a significant human pathogen which is not necessarily ubiquitously excreted into the environment. HAdV and HPyV were frequently detected in high concentrations in wastewater and wastewater-contaminated waters confirming their use as potential indicators for the presence of human sewage. Overall, there was a correlation between the presence of HAdV and HPyV with NoV but there were some notable exceptions including the higher frequency of NoV compared to HAdV and HPyV in estuarine waters impacted by wastewater overflows. We found that HAdV and HPyV detection by qPCR was a suitable tool for evaluating water quality and that their detection can aid in determining pollution sources, thus providing useful information for health risk assessments.
•HAdV and HPyV prevalence in environmental matrices were determined by qPCR.•HAdV and HPyV were suitable as human sewage indicators.•NoV were more frequently detected in estuarine water than HAdV and HPyV.•NoV were more frequently detected in urban stream water than HAdV and HPyV.•No strong correlations between different virus concentrations were observed.
Human adenovirus (AdV and AdV species F), enterovirus (EV) and norovirus (NoV) concentrations entering wastewater treatment plants (WWTP) serving different-sized communities, and effectiveness of ...different treatment processes in reducing concentrations were established. Data was combined to create a characteristic and unique descriptor of the individual viral composition and termed as the sample virus profile.
Virus profiles were generally independent of population size and treatment process (moving bed biofilm reactors, activated sludge, waste stabilisation ponds). AdV and EV concentrations in wastewater were more variable in small (<4000) and medium-sized (10,000–64,000) WWTP than in large-sized (>130,000 inhabitants) plants. AdV and EV concentrations were detected in influent of most WWTP (AdV range 1.00–4.08
log
10 infectious units (IU)/L, 3.25–8.62
log
10 genome copies/L; EV range 0.7–3.52
log
10 plaque forming units (PFU)/L; 2.84–6.67
log
10 genome copies/L) with a reduced median concentration in effluent (AdV range 0.70–3.26
log
10 IU/L, 2.97–6.95
log
10 genome copies/L; EV range 0.7–2.15 log
10PFU/L, 1.54–5.28
log
10 genome copies/L). Highest culturable AdV and EV concentrations in effluent were from a medium-sized WWTP. NoV was sporadic in all WWTP with GI and GII concentrations being similar in influent (range 2.11–4.64 and 2.19–5.46
log
10 genome copies/L) as in effluent (range 2.18–5.06 and 2.88–5.46
log
10 genome copies/L).
Effective management of WWTP requires recognition that virus concentration in influent will vary – particularly in small and medium plants. Irrespective of treatment type, culturable viruses and NoV are likely to be present in non-disinfected effluent, with associated human health risks dependent on concentration and receiving water usage.
► Influent virus concentrations were independent of population size served by the WWTP. ► Small WWTP were characterised by variable virus concentrations with sporadic spikes. ► NoV prevalence was sporadic in both influent and effluent wastewater. ► A similar NoV concentration range was found in influent and effluent wastewater. ► Irrespective of treatment type, viable viruses are likely to be present in effluent.
•A theoretical model based on shear forces from ultrasound cavities is proposed.•Two microbes with different sizes were treated by high-power low frequency ultrasound.•The log microbial reduction ...increased linearly with increasing treat time or power.•The rate of inactivation increased as the decreasing initial cell number.•The fits from the model are in very good agreement with the experimental data.
A simple theoretical model based on shear forces generated by the collapse of the ultrasound cavities near the surface of a microorganism is proposed. This model requires two parameters which take into account the number of acoustic cavitation bubbles, and the resistance of the cell wall of the microorganism to the shear forces generated by bubble collapse. To validate the model, high-power low frequency (20kHz) ultrasound was used to inactivate two microorganisms with very different sizes, viz., a bacterium, Enterobacter aerogenes and a yeast, Aureobasidium pullulans. The inactivation ratio was experimentally measured as a function of sonication time for different ultrasound power and for different initial cell numbers. For both E. aerogenes and A. pullulans the Log of the inactivation ratio decreased linearly with sonication time, and the rate of inactivation increased (D-value decreased) with the increase in sonication power. The rate of inactivation was also found, for both microorganisms, to increase with a decrease in the initial cell number. The fits, obtained using the proposed model, are in very good agreement with the experimental data.
Stream biofilms play an important ecological role in the supply of energy and organic matter to aquatic food webs. Bacterial community composition in stream biofilms is shaped by biotic interactions ...as well as physicochemical conditions which vary across space and time. However, knowledge of the relative importance of spatial versus temporal factors for microbial community composition is lacking. Here, we applied 16S rRNA gene sequencing to characterise the biofilm bacterial community composition of 732 stream biofilms. These biofilm samples were collected within six streams located a maximum of 118 km apart and draining different catchment types (forest, urban and rural land uses). Samples were collected at monthly intervals for 30 months over 2013-2015. Bacterial community composition was explained better by monthly changes (PERMANOVA; p < 0.01) than by differences observed among streams and catchment types (PERMANOVA; p = 0.44). Bacterial community composition over months and years followed a discernible cyclical seasonal pattern, as quantified using periodic regression analysis. Temperature, TN, light, and soil moisture deficit were identified as factors most significantly correlated with seasonal variation in bacterial community composition. Overall, these findings suggest that temporal changes are more important than spatial changes across the scales investigated in this study.
To investigate the current state of knowledge about emotional intelligence and affective events that arise during nursing students' clinical placement experiences.
Narrative literature review.
...CINAHL, MEDLINE, PsycINFO, Scopus, Web of Science, ERIC and APAIS-Health databases published in English between 1990 and 2016.
Data extraction from and constant comparative analysis of ten (10) research articles.
We found four main themes: (1) emotional intelligence buffers stress; (2) emotional intelligence reduces anxiety associated with end of life care; (3) emotional intelligence promotes effective communication; and (4) emotional intelligence improves nursing performance.
The articles we analysed adopted a variety of emotional intelligence models. Using the Ashkanasy and Daus “three-stream” taxonomy (Stream 1: ability models; 2: self-report; 3: mixed models), we found that Stream 2 self-report measures were the most popular followed by Stream 3 mixed model measures. None of the studies we surveyed used the Stream 1 approach. Findings nonetheless indicated that emotional intelligence was important in maintaining physical and psychological well-being. We concluded that developing emotional intelligence should be a useful adjunct to improve academic and clinical performance and to reduce the risk of emotional distress during clinical placement experiences. We call for more consistency in the use of emotional intelligence tests as a means to create an empirical evidence base in the field of nurse education.
•EI buffers the effect of stress and improves communication.•EI improves nursing performance.•Consistency in EI instruments used in nurse education will build an empirical evidence base.
The carcinogenic nitrogenous disinfection by-product, N-nitrosodimethylamine (NDMA), is challenging to adsorb due to its high polarity and solubility. Our previous research demonstrated that the ...adsorptive removal of NDMA can be improved using surface-modified activated carbon (AC800). The current study evaluated the efficacy of AC800 in removing NDMA in a continuous-flow column over 75 days, using both granular activated carbon (GAC) and biologically activated carbon (BAC) columns. The AC800 GAC column demonstrated extended breakthrough and exhaustion times of 10 days and 22 days, respectively, compared to the conventional GAC column at 4 days and 10.5 days. The surface modification effect persisted for 25 days before the removal trends became indistinguishable. The AC800 BAC column outperformed the conventional BAC column with a longer breakthrough time of 11.3 days compared to 7.4 days. BAC columns consistently showed greater NDMA removal, emphasizing the role of biodegradation in NDMA removal on carbon. The higher NDMA removal in the inoculated columns was attributed to increased microbial diversity and the dominance of six specific genera, Methylobacterium, Phyllobacterium, Curvibacter, Acidovorax, Variovorax, and Rhodoferax. This study provides new insights into using modified activated carbon as GAC and BAC media in a real-world continuous-flow setup.
Display omitted
•Thermally modified BAC performed well in removing NDMA in a continuous flow system.•The advantage of the thermally modified media persisted for 25 days.•Inoculated columns yielded higher NDMA removal (p < 0.05) than non-inoculated columns.•Some nitro-aromatic compounds-degraders likely contributed to NDMA biodegradation.
PDF
