Some alternative control strategies of currently emerging plant diseases are based on the use of resistance inducers. This review highlights the recent advances made in the characterization of ...natural compounds that induce resistance by a priming mechanism. These include vitamins, chitosans, oligogalacturonides, volatile organic compounds, azelaic and pipecolic acid, among others. Overall, other than providing novel disease control strategies that meet environmental regulations, natural priming agents are valuable tools to help unravel the complex mechanisms underlying the induced resistance (IR) phenomenon. The data presented in this review reflect the novel contributions made from studying these natural plant inducers, with special emphasis placed on hexanoic acid (Hx), proposed herein as a model tool for this research field. Hx is a potent natural priming agent of proven efficiency in a wide range of host plants and pathogens. It can early activate broad-spectrum defenses by inducing callose deposition and the salicylic acid (SA) and jasmonic acid (JA) pathways. Later it can prime pathogen-specific responses according to the pathogen's lifestyle. Interestingly, Hx primes redox-related genes to produce an anti-oxidant protective effect, which might be critical for limiting the infection of necrotrophs. Our Hx-IR findings also strongly suggest that it is an attractive tool for the molecular characterization of the plant alarmed state, with the added advantage of it being a natural compound.
Abstract
Microbial ecology provides insights into the ecological and evolutionary dynamics of microbial communities underpinning every ecosystem on Earth. Microbial communities can now be ...investigated in unprecedented detail, although there is still a wealth of open questions to be tackled. Here we identify 50 research questions of fundamental importance to the science or application of microbial ecology, with the intention of summarising the field and bringing focus to new research avenues. Questions are categorised into seven themes: host–microbiome interactions; health and infectious diseases; human health and food security; microbial ecology in a changing world; environmental processes; functional diversity; and evolutionary processes. Many questions recognise that microbes provide an extraordinary array of functional diversity that can be harnessed to solve real-world problems. Our limited knowledge of spatial and temporal variation in microbial diversity and function is also reflected, as is the need to integrate micro- and macro-ecological concepts, and knowledge derived from studies with humans and other diverse organisms. Although not exhaustive, the questions presented are intended to stimulate discussion and provide focus for researchers, funders and policy makers, informing the future research agenda in microbial ecology.
We identify research questions in the field of microbial ecology, with emerging themes that recognise vast microbial functions that could benefit humanity, and the need to integrate knowledge across organisms.
Sink waste traps and drains are a reservoir for multi-drug resistant Gram-negative bacteria in the hospital environment. It has been suggested that these bacteria can migrate through hospital ...plumbing. Hospital waste traps were installed in a laboratory model system where sinks were connected through a common wastewater pipe. Enterobacterales populations were monitored using selective culture, MALDI-TOF identification and antibiotic resistance profiling before and after a wastewater backflow event. When transfer between sinks was suspected, isolates were compared using whole-genome sequencing. Immediately after the wastewater backflow, two KPC-producing Enterobacter cloacae were recovered from a waste trap in which Carbapenemase-producing Enterobacterales (CPE) had not been detected previously. The isolates belonged to ST501 and ST31 and were genetically indistinguishable to those colonising sinks elsewhere in the system. Following inter-sink transfer, KPC-producing E. cloacae ST501 successfully integrated into the microbiome of the recipient sink and was detected in the waste trap water at least five months after the backflow event. Seven weeks and three months after the backflow, other inter-sink transfers involving Escherichia coli ST5295 and KPC-producing E. cloacae ST501 were also observed.
The transmission of SARS-CoV-2 is likely to occur through a number of routes, including contact with contaminated surfaces. Many studies have used reverse transcription-PCR (RT-PCR) analysis to ...detect SARS-CoV-2 RNA on surfaces, but seldom has viable virus been detected. This paper investigates the viability over time of SARS-CoV-2 dried onto a range of materials and compares viability of the virus to RNA copies recovered and whether virus viability is concentration dependent. Viable virus persisted for the longest time on surgical mask material and stainless steel, with a 99.9% reduction in viability by 122 and 114 h, respectively. Viability of SARS-CoV-2 reduced the fastest on a polyester shirt, with a 99.9% reduction within 2.5 h. Viability on the bank note was reduced second fastest, with 99.9% reduction in 75 h. RNA on all surfaces exhibited a 1-log reduction in genome copy number recovery over 21 days. The findings show that SARS-CoV-2 is most stable on nonporous hydrophobic surfaces. RNA is highly stable when dried on surfaces, with only 1-log reduction in recovery over 3 weeks. In comparison, SARS-CoV-2 viability reduced more rapidly, but this loss in viability was found to be independent of starting concentration. Expected levels of SARS-CoV-2 viable environmental surface contamination would lead to undetectable levels within 2 days. Therefore, when RNA is detected on surfaces, it does not directly indicate the presence of viable virus, even at low cycle threshold values.
This study shows the impact of material type on the viability of SARS-CoV-2 on surfaces. It demonstrates that the decay rate of viable SARS-CoV-2 is independent of starting concentration. However, RNA shows high stability on surfaces over extended periods. This has implications for interpretation of surface sampling results using RT-PCR to determine the possibility of viable virus from a surface, where RT-PCR is not an appropriate technique to determine viable virus. Unless sampled immediately after contamination, it is difficult to align RNA copy numbers to quantity of viable virus on a surface.
The virucidal activity of the Zoono Z71 Microbe Shield surface sanitizer and protectant, a quaternary ammonium compound (QAC)-based antimicrobial coating that was used by the United Kingdom rail ...industry during the COVID-19 pandemic, was evaluated, using the bacteriophage ɸ6 as a surrogate for SARS-CoV-2. Immediately after application and in the absence of interfering substances, the product effectively reduced (>3 log
) the viability of ɸ6 on some materials that are typically used in rail carriages (stainless steel, high-pressure laminate, plastic). If, after the application of the product, these surfaces remained undisturbed, the antimicrobial coating retained its efficacy for at least 28 days. However, efficacy depended on the material being coated. The product provided inconsistent results when applied to glass surfaces and was ineffective (i.e., achieved <3 log
reduction) when applied to a train arm rest that was made of Terluran 22. Regardless of the material that was coated or the time since application, the presence of organic debris (fetal bovine serum) significantly reduced the viricidal activity of the coating. Wiping the surface with a wetted cloth after the deposition of organic debris was not sufficient to restore efficacy. We conclude that the product is likely to be of limited effectiveness in a busy, multiuser environment, such as public transport.
This study evaluated the performance of a commercially available antimicrobial coating that was used by the transport industry in the United Kingdom during the COVID-19 pandemic. While the product was effective against ɸ6, the efficacy of the coating depended upon the material to which it was applied. Similarly, and regardless of the surface material, the presence of organic debris severely impaired viricidal activity, and efficacy could not be recovered through wiping (cleaning) the surface. This highlights the importance of including relevant materials and conditions when evaluating antimicrobial coatings in the laboratory. Further efforts are required to identify suitable infection prevention and control practices for the transport industry.
Octenidine-based disinfection products are becoming increasingly popular for infection control of multidrug-resistant (MDR) Gram-negative isolates. When a waste trap was removed from a hospital and ...allowed to acclimatize in a standard tap rig in our laboratory, it was shown that
,
, and
and
spp. were readily isolated. This study aimed to understand the potential impact of prolonged exposure to low doses of a commercial product containing octenidine on these bacteria. Phenotypic and genotypic analyses showed that
strains had increased tolerance to octenidine, which was characterized by mutations in the Tet repressor SmvR.
species demonstrated increased tolerance to many other cationic biocides, although not octenidine, as well as the antibiotics ciprofloxacin, chloramphenicol, and ceftazidime, through mutations in another Tet repressor, RamR.
species with mutations in RamR and MarR were identified following octenidine exposure, and this is linked to development of resistance to ampicillin, piperacillin, and chloramphenicol, as well as an increased MIC for ciprofloxacin. Isolates were able to retain fitness, as characterized by growth, biofilm formation, and virulence in
, after prolonged contact with octenidine, although there were strain-to-strain differences. These results demonstrate that continued low-level octenidine exposure in a simulated sink trap environment selects for mutations that affect
It may also promote microbial adaptation to other cationic biocides and cross-resistance to antibiotics, while not incurring a fitness cost. This suggests that hospital sink traps may act as a reservoir for more biocide-tolerant organisms.
Multidrug-resistant (MDR) strains of bacteria are a major clinical problem, and several reports have linked outbreaks of MDR bacteria with bacterial populations in hospital sinks. Biocides such as octenidine are used clinically in body washes and other products, such as wound dressings for infection control. Therefore, increased tolerance to these biocides would be detrimental to infection control processes. Here, we exposed bacterial populations originally from hospital sink traps to repeated dosing with an octenidine-containing product over several weeks and observed how particular species adapted. We found mutations in genes related to biocide and antibiotic susceptibility, which resulted in increased tolerance, although this was species dependent. Bacteria that became more tolerant to octenidine also showed no loss of fitness. This shows that prolonged octenidine exposure has the potential to promote microbial adaptation in the environment and that hospital sink traps may act as a reservoir for increased biocide- and antibiotic-tolerant organisms.
Hospital sinks in the UK have recently been under scrutiny as possible reservoirs for Gram-negative bacteria, especially carbapenem resistant Enterobacterales (CRE). These strains have been found in ...intensive care wards across the country and can re-enter the clinical environment, representing a risk to vulnerable patients.
Two sink waste traps known to be colonized with CRE were collected from a hospital and fitted to a vertical-draining and rear-draining handwash sink installed within a laboratory model sink system. Sinks were automatically flushed four times a day and, as per usual in the model, TSB was provided once daily to maintain microbial populations. Gram-negative bacteria were regularly monitored using selective culture, MALDI-TOF and antibiotic disk diffusion. The short-term effect of adding simulated IV fluids (5% glucose or 0.9% NaCl) and the impact of sink design on Gram-negative proliferation were investigated.
Communities included
Enterobacter asburiae
;
Klebsiella oxytoca
;
Pseudomonas aeruginosa
and
Citrobacter freundii
, among others, including CRE. The addition of simulated IV fluids did not induce Gram-negative bacterial proliferation in the time frame of the experiment. Differences were observed in the fluctuation of Gram-negative levels after flushing between the different sink designs. Gram-negative numbers in vertical-draining sinks decreased immediately after the tap was flushed and subsequently increased between flushes. However, in rear-draining sinks, little fluctuation was observed.
Hospital sink waste traps can harbour Gram-negative bacteria resistant to antibiotics. In our experimental conditions, the type of sink was the determining factor in the magnitude of fluctuation in Gram-negative populations while simulated IV fluids had little effect.
To monitor severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) RNA contamination in vehicles operating in England during the pandemic, to better understand transmission risk of SARS-CoV-2 on ...public transport.
We collected 1314 surface samples between December 2020 and April 2022 on trains and buses managed by five different transport operators. The presence of SARS-CoV-2 RNA was investigated through reverse transcription polymerase chain reaction (RT-PCR). SARS-CoV-2 RNA was found on 197 (15%) of the 1314 surfaces sampled, including seat head rests, handholds, and air extract grilles, but the levels of RNA recovered on those samples (median value of 23.4, interquartile range: 14.3-35.4, N gene copies per extraction) made the presence of infectious virus at the time of sampling extremely unlikely. However, detection rates varied over time with peaks broadly coinciding with times of high community transmission, when it was more likely that people infected with SARS-CoV-2 were travelling on public transport.
During the pandemic, and as in other public spaces, low levels of SARS-CoV-2 RNA were found on surfaces associated with public transport.
The level of cellulolytic activity in different areas of the gut of the terrestrial slug Arion ater was assayed at different temperatures and pH values. To do this, crude gut proteins were isolated ...and assayed using modified dinitrosalicylic acid reducing sugar assay. Crude protein samples were also separated and cellulolytic activity identified using in gel CMC zymography and esculin hydrate activity gel assays. pH and temperature profiling revealed optimum cellulolytic activity between pH5.0 and 6.0 for different gut regions and retention of up to 90% of activity at temperatures up to 50°C. Zymograms and activity gels revealed multiple endoglucanase and β-glucosidase enzymes. To further investigate the source of this cellulolytic activity bacterial isolates from the gut were tested for endoglucanase and β-glucosidase activity using growth plate assays. 12 cellulolytic microbes were identified using 16S rDNA gene sequencing. These include members of the genera Buttiauxella, Enterobacter, Citrobacter, Serratia and Klebsiella. Gut metagenomic DNA was then subjected to PCR, targeting a 400bp region of the 16SrDNA gene which was subsequently separated and individuals identified using DGGE. This identified members of the genera Citrobacter, Serratia, Pectobacterium, Acinetobacter, Mycoplasma, Pantoea and Erwinia. In summary, multiple glycoside hydrolase enzymes active over a broad range of temperature and pH values in a relatively under studied organism were detected, indicating that the gut of A. ater is a viable target for intensive study to identify novel carbohydrate active enzymes that may be used in the biofuel industry.
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