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"biological methods"
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Bacillus velezensis: a versatile ally in the battle against phytopathogens—insights and prospects
by
Esmaeel, Qassim
,
Ait-Barka, Essaid
,
Kenfaoui, Jihane
in
agricultural biotechnology
,
Agriculture
,
Agriculture - methods
2024
The escalating interest in
Bacillus velezensis
as a biocontrol agent arises from its demonstrated efficacy in inhibiting both phytopathogenic fungi and bacteria, positioning it as a promising candidate for biotechnological applications. This mini review aims to offer a comprehensive exploration of the multifaceted properties of
B. velezensis
, with particular focus on its beneficial interactions with plants and its potential for controlling phytopathogenic fungi. The molecular dialogues involving
B. velezensis
, plants, and phytopathogens are scrutinized to underscore the intricate mechanisms orchestrating these interactions. Additionally, the review elucidates the mode of action of
B. velezensis
, particularly through cyclic lipopeptides, highlighting their importance in biocontrol and promoting plant growth. The agricultural applications of
B. velezensis
are detailed, showcasing its role in enhancing crop health and productivity while reducing reliance on chemical pesticides. Furthermore, the review extends its purview in the industrial and environmental arenas, highlighting its versatility across various sectors. By addressing challenges such as formulation optimization and regulatory frameworks, the review aims to chart a course for the effective utilization of
B. velezensis
.
Key points
•
B. velezensis fights phytopathogens, boosting biotech potential
•
B. velezensis shapes agri-biotech future, offers sustainable solutions
•
Explores plant-B. velezensis dialogue, lipopeptide potential showcased
Journal Article
Adjacent spillover efficacy of Wolbachia for control of dengue: emulation of a cluster randomised target trial
2025
Background
Matings between male
Aedes aegypti
mosquitoes infected with
w
AlbB strain of
Wolbachia
and wild-type females yield non-viable eggs, thereby suppressing
Ae. aegypti
abundance in the field. We evaluated the spillover efficacy of releasing
w
AlbB-infected
Ae. aegypti
male mosquitoes to suppress dengue in sites adjacent to release sites (spillover sites).
Methods
The protocol of a two-arm cluster-randomised test-negative controlled trial (cRCT) was specified and emulated using a nationally representative dengue test-negative/positive database of 454,437 individuals reporting for febrile illness to primary or secondary care in public healthcare institutions. Spillover intervention sites were defined by geolocating locations which were adjacent to, i.e. shared geographical borders with, actual
Wolbachia
intervention sites. We built a cohort of individuals who resided in spillover sites versus a comparator control group who resided in sites which did not receive
Wolbachia
interventions. We emulated a constrained randomisation protocol used in cRCTs to balance dengue risk between spillover and control arms in the pre-intervention period. We matched individuals reporting for testing in intervention and control groups by calendar time and a high-dimensional battery of sociodemographic, environmental and anthropogenic variables. Intention-to-treat analysis was conducted to estimate the protective efficacy against dengue given spillover
Wolbachia
exposure.
Results
The final cohort consisted of 2354 matched individuals residing in
Wolbachia
spillover and control sites for at least 3 months in the study period. Compared to the controls, individuals residing in spillover sites for 3 or more months were associated with a 45% (OR: 0.55, 95% CI: 0.42‒0.74) reduction in risk of contracting dengue. Higher durations of spillover
Wolbachia
exposure also modestly increased protective efficacies. Compared to the control arm, the proportion of virologically confirmed dengue cases was lower in the spillover arm overall and across each subgroup. Protective efficacies were found across all years, age and sex subgroups.
Conclusions
Our results demonstrated the potential of
Wolbachia
-mediated sterility for reducing the risk of contracting dengue even in sites which were not directly treated by the intervention.
Journal Article
Evaluation of coatings for application in raffia big bags in conditioned storage of soybean cultivars in seed processing units
by
Cândido, Ana Carina da Silva
,
Teodoro, Paulo Eduardo
,
Alves, Charline Zaratin
in
Agricultural production
,
Ambient temperature
,
Biology and Life Sciences
2020
Different regions have different environmental conditions, which may be unfavorable for the preservation of the quality of stored soybean seeds over time. Thus, it is necessary to adopt specific technologies to control the storage environment conditions. Big raffia bags are widely used for the storage of soybean seeds, however these consist of a porous, permeable material that allows the exchange of gases between the packaging and the storage environment. In an effort to find a solution to this problem, in this study we evaluated low cost big bag coating alternatives, in order to minimize the effects of temperature and intergranular humidity on stored seeds. Thus, the aim of this work was to evaluate the quality of soybean cultivars subjected to different temperature and storage duration conditions and stored in raffia bags with or without internal coating. We used a completely randomized, three-factor (10 × 6 × 5) experimental design. We assessed 10 soybean cultivars, six storage environments, and five evaluation periods. Our results showed that seeds of the M-SOY 8866, M7110 IPRO, CD 2737 RR, and BMX DESAFIO 8473 RSF soybean cultivars preserved their physiological quality better in different storage environments. The storage duration had a cumulative effect on the negative factors that favor the deterioration of the quality of the stored seeds. The storage temperature was the main factor that affected the physiological quality of the stored seeds. The use of coated packaging was beneficial in preserving the physiological quality of stored soybean seeds; however, its effect was greater at ambient temperature than in a cold environment. The best storage environment for the preservation of the quality of the seeds was characterized by 10°C temperature conditions and the use of coated packaging, while the worst storage environment was characterized by ambient temperature conditions without the use of coated packaging. Thus, it was concluded that the use of coatings in raffia big bags can be an alternative for maintaining the quality of seeds of different soybean cultivars during storage in seed processing units.
Journal Article
The AWED trial (Applying Wolbachia to Eliminate Dengue) to assess the efficacy of Wolbachia-infected mosquito deployments to reduce dengue incidence in Yogyakarta, Indonesia: study protocol for a cluster randomised controlled trial
2018
Background
Dengue and other arboviruses transmitted by
Aedes aegypti
mosquitoes, including Zika and chikungunya, present an increasing public health challenge in tropical regions. Current vector control strategies have failed to curb disease transmission, but continue to be employed despite the absence of robust evidence for their effectiveness or optimal implementation. The World Mosquito Program has developed a novel approach to arbovirus control using
Ae. aegypti
stably transfected with
Wolbachia
bacterium, with a significantly reduced ability to transmit dengue, Zika and chikungunya in laboratory experiments. Modelling predicts this will translate to local elimination of dengue in most epidemiological settings. This study protocol describes the first trial to measure the efficacy of
Wolbachia
in reducing dengue virus transmission in the field.
Methods/design
The study is a parallel, two-arm, non-blinded cluster randomised controlled trial conducted in a single site in Yogyakarta, Indonesia. The aim is to determine whether large-scale deployment of
Wolbachia
-infected
Ae. aegypti
mosquitoes leads to a measurable reduction in dengue incidence in treated versus untreated areas. The primary endpoint is symptomatic, virologically confirmed dengue virus infection of any severity. The 26 km
2
study area was subdivided into 24 contiguous clusters, allocated randomly 1:1 to receive
Wolbachia
deployments or no intervention. We use a novel epidemiological study design, the cluster-randomised test-negative design trial, in which dengue cases and arbovirus-negative controls are sampled concurrently from among febrile patients presenting to a network of primary care clinics, with case or control status classified retrospectively based on the results of laboratory diagnostic testing. Efficacy is estimated from the odds ratio of
Wolbachia
exposure distribution (probability of living in a
Wolbachia
-treated area) among virologically confirmed dengue cases compared to test-negative controls. A secondary per-protocol analysis allows for individual
Wolbachia
exposure levels to be assessed to account for movements outside the cluster and the heterogeneity in local
Wolbachia
prevalence among treated clusters.
Discussion
The findings from this study will provide the first experimental evidence for the efficacy of
Wolbachia
in reducing dengue incidence. Together with observational evidence that is accumulating from pragmatic deployments of
Wolbachia
in other field sites, this will provide valuable data to estimate the effectiveness of this novel approach to arbovirus control, inform future cost-effectiveness estimates, and guide plans for large-scale deployments in other endemic settings.
Trial registration
ClinicalTrials.gov, identifier:
NCT03055585
. Registered on 14 February 2017.
Journal Article
Comparative transcriptomics revealed differential regulation of defense related genes in Brassica juncea leading to successful and unsuccessful infestation by aphid species
by
Duhlian, Lianthanzauva
,
Koramutla, Murali Krishna
,
Bhattacharya, Ramcharan
in
631/337
,
631/449
,
Agricultural research
2020
Productivity of Indian mustard (
B. juncea
), a major oil yielding crop in rapeseed-mustard group is heavily inflicted by mustard aphid,
L. erysimi
. Mustard aphid, a specialist aphid species on rapeseed-mustard crops, rapidly multiplies and colonizes the plants leading to successful infestation. In contrary, legume specific cowpea aphid,
A. craccivora
when released on
B. juncea
plants fails to build up population and thus remains unsuccessful in infestation. In the present study, differential host response of
B. juncea
to the two aphid species, one being successful insect-pest and the other being unsuccessful on it has been studied based on transcriptome analysis. Differential feeding efficiency of the two aphid species on mustard plants was evident from the amount of secreted honeydews. Leaf-transcriptomes of healthy and infested plants, treated with the two aphid species, were generated by RNA sequencing on Illumina platform and
de novo
assembly of the quality reads. A comparative assessment of the differentially expressed genes due to treatments revealed a large extent of overlaps as well as distinctness with respect to the set of genes and their direction of regulation. With respect to host-genes related to transcription factors, oxidative homeostasis, defense hormones and secondary metabolites,
L. erysimi
led to either suppression or limited activation of the transcript levels compared to
A
.
craccivora
. Further, a comprehensive view of the DEGs suggested more potential of successful insect-pests towards transcriptional reprogramming of the host. qRT-PCR based validation of randomly selected up- and down-regulated transcripts authenticated the transcriptome data.
Journal Article
Is biological larviciding against malaria a starting point for integrated multi-disease control? Observations from a cluster randomized trial in rural Burkina Faso
by
Bärnighausen, Till
,
Nikiema, Moustapha
,
Sauerborn, Rainer
in
Animals
,
Bacillus thuringiensis
,
Biology and Life Sciences
2021
To evaluate the impact of anti-malaria biological larviciding with Bacillus thuringiensis israelensis on non-primary target mosquito species in a rural African setting.
A total of 127 villages were distributed in three study arms, each with different larviciding options in public spaces: i) no treatment, ii) full or iii) guided intervention. Geographically close villages were grouped in clusters to avoid contamination between treated and untreated villages. Adult mosquitoes were captured in light traps inside and outside houses during the rainy seasons of a baseline and an intervention year. After enumeration, a negative binomial regression was used to determine the reductions achieved in the different mosquito species through larviciding.
Malaria larviciding interventions showed only limited or no impact against Culex mosquitoes; by contrast, reductions of up to 34% were achieved against Aedes when all detected breeding sites were treated. Culex mosquitoes were captured in high abundance in semi-urban settings while more Aedes were found in rural villages.
Future malaria larviciding programs should consider expanding onto the breeding habitats of other disease vectors, such as Aedes and Culex and evaluate their potential impact. Since the major cost components of such interventions are labor and transport, other disease vectors could be targeted at little additional cost.
Journal Article
Update to: Assessing the efficacy of male Wolbachia-infected mosquito deployments to reduce dengue incidence in Singapore
by
Lee, Caleb
,
Ng, Lee Ching
,
Liew, Jonathan
in
Aedes - microbiology
,
Aedes - virology
,
Analysis
2024
Background
This trial is a parallel, two-arm, non-blinded cluster randomised controlled trial that is under way in Singapore, with the aim of measuring the efficacy of male
Wolbachia
-infected
Aedes aegypti
deployments in reducing dengue incidence in an endemic setting with all four dengue serotypes in circulation. The trial commenced in July 2022 and is expected to conclude in September 2024. The original study protocol was published in December 2022. Here, we describe amendments that have been made to the study protocol since commencement of the trial.
Methods
The key protocol amendments are (1) addition of an explicit definition of
Wolbachia
exposure for residents residing in intervention sites based on the duration of
Wolbachia
exposure at point of testing, (2) incorporation of a high-dimensional set of anthropogenic and environmental characteristics in the analysis plan to adjust for baseline risk factors of dengue transmission, and (3) addition of alternative statistical analyses for endpoints to control for post hoc imbalance in cluster-based environmental and anthropogenic characteristics.
Discussion
The findings from this study will provide the first experimental evidence for the efficacy of releasing male-
Wolbachia
infected mosquitoes to reduce dengue incidence in a cluster-randomised controlled trial. The trial will conclude in 2024 and results will be reported shortly thereafter.
Trial registration
ClinicalTrials.gov, identifier: NCT05505682. Registered on 16 August 2022. Retrospectively registered. Last updated 11 November 2023.
Journal Article
Evaluation of long-lasting microbial larvicide for malaria vector control in Kenya
by
Gilbreath III, Thomas M.
,
Yan, Guiyun
,
Afrane, Yaw A.
in
Animals
,
Anopheles
,
Anopheles - microbiology
2016
Background
Outdoor malaria transmission is becoming an increasingly important problem in malaria control in Africa. Larval control is a promising intervention as it can target both indoor and outdoor biting mosquitoes. However, the currently available biolarvicide formulations have a short effective duration, and consequently larval control incurs a high operational expense due to the requirement for frequent re-treatment of larval habitats. Formulations of biolarvicides with long-lasting effects is highly desired. A recently developed FourStar® slow-release briquet formulation of
Bacillus thuringiensis israelensis
and
Bacillus sphaericus
was evaluated to test its efficacy on malaria vectors.
Methods
The study evaluated FourStar™ briquets 180-days formulation under semi-natural and natural conditions to test their efficacy in reducing the mosquito population in western Kenya. The semi-natural habitats used the formulation dissolved in rainwater with appropriate concentrations, and second-instar larvae of
Anopheles gambiae
were introduced and the number of surviving larvae and pupae produced was recorded daily as the outcome. The briquets formulation was then tested in natural habitats for efficacy on pupal productivity reduction in highland and lowland sites in western Kenya. The formulation was finally tested for efficacy in reducing adult mosquito populations in randomized clusters in western Kenya highland.
Results
In semi-natural conditions, the FourStar™ briquets 180-days formulation completely inhibited mosquito pupal production in the first 3 months, and then reduced pupal productivity by 87–98% (P < 0.001) 4–6 months after application. In natural habitats, during the first 2 months no pupae were detected from any of the treated habitats in highland sites, and
Anopheles
spp. pupal density was reduced by 60–90% in the next 3–5 months (P < 0.001). In the lowland site, pupal productivity reduction was 100% in the first 3 months, and 75–90% in the next 4–5 months (P < 0.001). The randomized cluster trial found that the application of the briquets formulation reduced mean densities of indoor-biting mosquitoes by 76–82% (P < 0.001) and by 67–75% (P < 0.001) for outdoor-biting mosquitoes.
Conclusion
This study demonstrated that long-lasting biological larviciding was effective in reducing pupal productivity of larval habitats, and reducing indoor and outdoor resting mosquitoes. The study suggests that long-lasting microbial larviciding may be a promising complementary malaria vector control tool and warrants further large-scale evaluation.
Journal Article