Computational approach for identifying immunogenic epitopes and optimizing peptide vaccine through in-silico cloning against Mycoplasma genitalium

Mycoplasma genitalium is a pathogenic microorganism linked to a variety of severe health conditions including ovarian cancer, prostate cancer, HIV transmission, and sexually transmitted diseases. A more effective approach to address the challenges posed by this pathogen, given its high antibiotic resistance rates, could be the development of a peptide vaccine. In this study, we used experimentally validated 13 membrane proteins and their immunogenicity to identify suitable vaccine candidates. Thus, based on immunogenic properties and high conservation among other Mycoplasma genitalium sub-strains, the P110 surface protein is considered for further investigation. Later on, we identified T-cell epitopes and B-cell epitopes from the P110 protein to construct a multiepitope-based vaccine. As a result, the 'NIAPISFSFTPFTAA' T-cell epitope and 'KVKYESSGSNNISFDS' B-cell epitope have shown 99.53% and 87.50% population coverage along with 100% conservancy among the subspecies, and both epitopes were found to be non-allergenic. Furthermore, focusing on molecular docking analysis showed the lowest binding energy for MHC-I (-137.5 kcal/mol) and MHC-II (-183.3 kcal/mol), leading to a satisfactory binding strength between the T-cell epitopes and the MHC molecules. However, the constructed multiepitope vaccine (MEV) consisting of 54 amino acids demonstrates favorable characteristics for a vaccine candidate, including a theoretical pI of 4.25 with a scaled solubility of 0.812 and high antigenicity probabilities. Additionally, structural analyses reveal that the MEV displays substantial alpha helices and extended strands, vital for its immunogenicity. Molecular docking with the human Toll-like receptors TLR1/2 heterodimer shows strong binding affinity, reinforcing its potential to elicit an immune response. Our immune simulation analysis demonstrates immune memory development and robust immunity, while codon adaptation suggests optimal expression in E. coli using the pET-28a(+) vector. These findings collectively highlight the MEV's potential as a valuable vaccine candidate against M. genitalium.

Labile assembly of a tardigrade protein induces biostasis

Tardigrades are microscopic animals that survive desiccation by inducing biostasis. To survive drying tardigrades rely on intrinsically disordered CAHS proteins, which also function to prevent perturbations induced by drying in vitro and in heterologous systems. CAHS proteins have been shown to form gels both in vitro and in vivo, which has been speculated to be linked to their protective capacity. However, the sequence features and mechanisms underlying gel formation and the necessity of gelation for protection have not been demonstrated. Here we report a mechanism of fibrillization and gelation for CAHS D similar to that of intermediate filament assembly. We show that in vitro, gelation restricts molecular motion, immobilizing and protecting labile material from the harmful effects of drying. In vivo, we observe that CAHS D forms fibrillar networks during osmotic stress. Fibrillar networking of CAHS D improves survival of osmotically shocked cells. We observe two emergent properties associated with fibrillization; (i) prevention of cell volume change and (ii) reduction of metabolic activity during osmotic shock. We find that there is no significant correlation between maintenance of cell volume and survival, while there is a significant correlation between reduced metabolism and survival. Importantly, CAHS D's fibrillar network formation is reversible and metabolic rates return to control levels after CAHS fibers are resolved. This work provides insights into how tardigrades induce reversible biostasis through the self-assembly of labile CAHS gels.

Effects of supplementing milk replacer with essential amino acids on blood metabolites, immune response, and nitrogen metabolism of Holstein calves exposed to an endotoxin

This study evaluated the effects of supplementing calf milk replacer with essential AA on immune responses, blood metabolites, and nitrogen metabolism of 32 Holstein bull calves [28 d of age, 44 ± 0.8 kg of body weight (BW)] exposed to lipopolysaccharide (LPS). Calves were bottle-fed a commercial milk replacer (20% crude protein and 20% fat, dry matter basis) twice daily along with a calf starter (19% crude protein, dry matter basis) for 45 d. The experiment was a randomized complete block design and treatments were a 2 × 2 factorial arrangement. Treatments were milk replacer (fed twice daily at 0.5 kg/d of powder) supplemented with or without 10 essential AA (+AA vs. -AA), and subcutaneous injection of sterile saline with or without LPS (+LPS vs. -LPS) at 3 h after the morning feeding on d 15 (4 µg LPS per kg of BW) and 17 (2 µg LPS per kg of BW). Calves also received a 2-mL subcutaneous injection of ovalbumin (6 mg of ovalbumin/mL) on d 16 and 30. Rectal temperature and blood samples were collected on d 15 before LPS injection and at h 4, 8, 12, and 24 thereafter. From d 15 to 19, total fecal and urinary output were collected, and feed refusals were documented. Rectal temperature was greater in +LPS than -LPS calves at h 4, 8, and 12 after LPS injection. Serum cortisol was greater for +LPS than -LPS at h 4 after LPS exposure. At d 28, serum antiovalbumin IgG level was greater in +LPS +AA calves compared with +LPS -AA. Serum glucose was lower for +LPS than -LPS at h 4 and 8. Serum insulin was greater in +LPS than -LPS calves. Plasma concentrations of Thr, Gly, Asn, Ser, and hydroxyproline were lower for +LPS versus -LPS calves. Plasma concentrations of Met, Leu, Phe, His, Ile, Trp, Thr, and Orn were greater in +AA calves than -AA calves. Plasma urea N and N retention were not different among LPS and AA treatments. The lower concentrations of AA in +LPS than -LPS calves indicate higher demand for AA in immuno-compromised calves fed milk replacer. Additionally, higher concentration of ovalbumin-specific IgG level in +LPS calves supplemented with +AA compared with +LPS calves with -AA suggests that supplementing AA to immune-compromised calves might improve immune status.

Nasopharyngeal competition dynamics are likely to be altered following vaccine introduction: bacteriocin prevalence and diversity among Icelandic and Kenyan pneumococci

Bacteriocins are antimicrobial peptides produced by bacteria to inhibit other bacteria in the surrounding environment. Streptococcus pneumoniae is a leading cause of disease worldwide and colonises the healthy human nasopharynx, where it competes for space and nutrients. Pneumococcal conjugate vaccines have reduced the incidence of disease, but they also restructure the bacterial population, and this restructuring likely alters the nasopharyngeal competition dynamics. Here, the distribution of bacteriocins was examined in over 5000 carriage and disease-causing pneumococci from Iceland and Kenya, recovered before and after the introduction of pneumococcal vaccination. Overall, up to eleven different bacteriocin gene clusters were identified per pneumococcus. Significant differences in the prevalence of bacteriocins were observed before and after vaccine introduction, and among carriage and disease-causing pneumococci, which were largely explained by the bacterial population structure. Genetically similar pneumococci generally harboured the same bacteriocins although sometimes different repertoires of bacteriocins were observed, which suggested that horizontal transfer of bacteriocin clusters had occurred. These findings demonstrated that vaccine-mediated changes in the pneumococcal population altered the prevalence and distribution of bacteriocins. The consequences of this for pneumococcal colonisation and disease remain to be determined.

Bacterial profile, antimicrobial resistance, and molecular detection of ESBL and quinolone resistance gene of uropathogens causing urinary tract infection in the southeastern part of Bangladesh

Humans frequently contract urinary tract infections (UTIs), which can be brought on by uropathogens (UPs) that are multi-drug resistant. Treatment for UTIs brought on by pathogenic UPs that produce extended-spectrum lactamases (ESBLs) is more costly and potentially fatal. As a result, the objective of this study was to use culture, biochemical, and 16S rRNA sequencing to identify and characterize UPs isolated from outpatients in Noakhali, Bangladesh, who had symptoms of UTIs. ESBL gene identification and quinolone resistance gene typing were then performed on the isolates using polymerase chain reaction (PCR). Throughout the trial's 8-month duration, 152 (76%) of 200 urine samples were positive for the presence of UPs. The overall number of UPs recovered was 210, with 39 individuals having multiple UPs present in their samples. Among all of the isolates, Escherichia coli (45.24%, 95/210; 95% confidence interval (CI): 35.15-57.60%), Enterobacter spp. (24.76%, 52/210; CI: 19.15-35.77%), Klebsiella spp. (20.95%; 44/210; CI: 15.15-30.20%), and Providencia spp. (9.05%; 19/210; CI: 4.95-19.25%) were the four most prevalent bacteria found in the isolates. The UPs displayed a very high level of resistance to piperacillin 96.92% (126/130), ampicillin 90% (117/130), nalidixic acid 77.69% (101/130), cefazolin 70% (91/130), amoxicillin 50% (55/130), cefazolin 42.31% (55/130), nitrofurantoin 43.08% (56/130), and ciprofloxacin 33.08% (43/130), whereas resistance to netilmicin (3.85%), amikacin (4.62%), and imipenem (9.23%) was low. Individually, every species of E. coli and Providencia spp. showed greater ampicillin, amikacin, cefazolin, cefazolin, and nalidixic acid resistance than the others. The bivariate results indicate several antibiotic pairings, and isolates had meaningful associations. All MDR isolates were subjected to PCR, which revealed that blaCTX-M-15 genes predominated among the isolates, followed by the blaTEM class (37%). Isolates also had the qnrS, aac-6´-Ib-cr, and gyrA genes. The findings provide worrying indications of a major expansion of MDR isolates in the study locations, particularly the epidemiological balCTX-M 15, with the potential for the transmission of multi-drug-resistant UP strains in the population.

Insomnia and job stressors among healthcare workers who served COVID-19 patients in Bangladesh

BACKGROUND

The global outbreak of COVID-19 has created unprecedented havoc among health care workers, resulting in significant psychological strains like insomnia. This study aimed to analyze insomnia prevalence and job stressors among Bangladeshi health care workers in COVID-19 units.

METHODOLOGY

We conducted this cross-sectional study to assess insomnia severity from January to March 2021 among 454 health care workers working in multiple hospitals in Dhaka city with active COVID-dedicated units. We selected 25 hospitals conveniently. We used a structured questionnaire for face-to-face interviews containing sociodemographic variables and job stressors. The severity of insomnia was measured by the Insomnia Severity Scale (ISS). The scale has seven items to evaluate the rate of insomnia, which was categorized as the absence of Insomnia (0-7); sub-threshold Insomnia (8-14); moderate clinical Insomnia (15-21); and severe clinical Insomnia (22-28). To identify clinical insomnia, a cut-off value of 15 was decided primarily. A cut-off score of 15 was initially proposed for identifying clinical insomnia. We performed a chi-square test and adjusted logistic regression to explore the association of different independent variables with clinically significant insomnia using the software SPSS version 25.0.

RESULTS

61.5% of our study participants were females. 44.9% were doctors, 33.9% were nurses, and 21.1% were other health care workers. Insomnia was more dominant among doctors and nurses (16.2% and 13.6%, respectively) than others (4.2%). We found clinically significant insomnia was associated with several job stressors (p < 0.05). In binary logistic regression, having sick leave (OR = 0.248, 95% CI = 0.116, 0.532) and being entitled to risk allowance (OR = 0.367, 95% CI = 0.124.1.081) showed lower odds of developing Insomnia. Previously diagnosed with COVID-19-positive health care workers had an OR of 2.596 (95% CI = 1.248, 5.399), pointing at negative experiences influencing insomnia. In addition, we observed that any training on risk and hazard increased the chances of suffering from Insomnia (OR = 1.923, 95% CI = 0.934, 3.958).

CONCLUSION

It is evident from the findings that the volatile existence and ambiguity of COVID-19 have induced significant adverse psychological effects and subsequently directed our HCWs toward disturbed sleep and insomnia. The study recommends the imperativeness to formulate and implement collaborative interventions to help HCWs cope with this crisis and mitigate the mental stresses they experience during the pandemic.

Radiometal chelators for infection diagnostics

Infection of native tissues or implanted devices is common, but clinical diagnosis is frequently difficult and currently available noninvasive tests perform poorly. Immunocompromised individuals (for example transplant recipients, or those with cancer) are at increased risk. No imaging test in clinical use can specifically identify infection, or accurately differentiate bacterial from fungal infections. Commonly used [¹⁸F]fluorodeoxyglucose (18FDG) positron emission computed tomography (PET/CT) is sensitive for infection, but limited by poor specificity because increased glucose uptake may also indicate inflammation or malignancy. Furthermore, this tracer provides no indication of the type of infective agent (bacterial, fungal, or parasitic). Imaging tools that directly and specifically target microbial pathogens are highly desirable to improve noninvasive infection diagnosis and localization. A growing field of research is exploring the utility of radiometals and their chelators (siderophores), which are small molecules that bind radiometals and form a stable complex allowing sequestration by microbes. This radiometal-chelator complex can be directed to a specific microbial target in vivo, facilitating anatomical localization by PET or single photon emission computed tomography. Additionally, bifunctional chelators can further conjugate therapeutic molecules (e.g., peptides, antibiotics, antibodies) while still bound to desired radiometals, combining specific imaging with highly targeted antimicrobial therapy. These novel therapeutics may prove a useful complement to the armamentarium in the global fight against antimicrobial resistance. This review will highlight current state of infection imaging diagnostics and their limitations, strategies to develop infection-specific diagnostics, recent advances in radiometal-based chelators for microbial infection imaging, challenges, and future directions to improve targeted diagnostics and/or therapeutics.

Neuropharmacological Effects of Chassalia curviflora (Rubiaceae) Leaves in Swiss Albino Mice Model

The current study aimed to investigate the neuropharmacological properties of ethanol, acetone, and ethyl acetate leaf extracts of Chassalia curviflora (C. curviflora) in mouse models. The neuropharmacological properties of this plant were studied on Swiss albino mice at dosages of 50, 100, and 200 mg/kg body weight in thiopental sodium-induced sleeping time test, and at dosages of 100 and 200 mg/kg body weight in other tests. The extracts caused a marked reduction in the initiation and sleep length (P<0.05) in studies on thiopental sodium-induced sleeping time at dosages of 100 and 200 mg/kg and a significant decrease (P<0.05) was found in terms of unconstrained locomotor and explorative activities in both hole crossing and open field tests at dosages of 100 and 200 mg/kg. Furthermore, the extracts increased sleeping time with a dosage-dependent onset of action. The hole-board test extracts also reduced the number of head dips at dosages of 100 and 200 mg/kg (P<0.05). It was found in this study that C. curviflora had the best neuropharmacological properties at a dosage of 200 ml/kg. Our findings also showed that all of the extracts from C. curviflora were experimentally active in an in vivo model. The study results suggested that the leaves had strong anti-depressant and hypnotic CNS properties that might be exploited for neuropharmacological adjuvant therapy in conventional medicine. However, pharmacological studies are warranted to explore the active substances and the mode of action.

Water stress and nitrogen supply affect floral traits and pollination of the white mustard, Sinapis alba (Brassicaceae)

Changes in environmental conditions are likely to have a complex effect on the growth of plants, their phenology, plant-pollinator interactions, and reproductive success. The current world is facing an ongoing climate change along with other human-induced environmental changes. Most research has focused on the impact of increasing temperature as a major driving force for climate change, but other factors may have important impacts on plant traits and pollination too and these effects may vary from season to season. In addition, it is likely that the effects of multiple environmental factors, such as increasing temperature, water availability, and nitrogen enrichment are not independent. Therefore, we tested the impact of two key factors-water, and nitrogen supply-on plant traits, pollination, and seed production in Sinapis alba (Brassicaceae) in three seasons defined as three temperature conditions with two levels of water and nitrogen supply in a factorial design. We collected data on multiple vegetative and floral traits and assessed the response of pollinators in the field. Additionally, we evaluated the effect of growing conditions on seed set in plants exposed to pollinators and in hand-pollinated plants. Our results show that water stress impaired vegetative growth, decreased flower production, and reduced visitation by pollinators and seed set, while high amount of nitrogen increased nectar production under low water availability in plants grown in the spring. Temperature modulated the effect of water and nitrogen availability on vegetative and floral traits and strongly affected flowering phenology and flower production. We demonstrated that changes in water and nitrogen availability alter plant vegetative and floral traits, which impacts flower visitation and consequently plant reproduction. We conclude that ongoing environmental changes such as increasing temperature, altered precipitation regimes and nitrogen enrichment may thus affect plant-pollinator interactions with negative consequences for the reproduction of wild plants and insect-pollinated crops.

Assessment of contamination level, pollution risk and source apportionment of heavy metals in the Halda River water, Bangladesh

This study demonstrates the level of heavy metal pollution in the Halda River, the only natural breeding source of carps in Bangladesh. Water was collected from 12 different sampling points along the Halda River. Water at various locations was found satisfactory in terms of the assessed physicochemical parameters (pH, electrical conductivity, and total dissolved solids). The presence of various cations and anions was also studied using ion chromatography. Atomic absorption spectroscopy was used to identify and quantify various heavy metals in the collected water samples. Among the heavy metals, Cd, Cr, Fe, Pb, Cu, and As concentration exceeded the safe limit suggested by WHO. The calculated heavy metal pollution index and metal index were found higher than the critical index value. The single-factor assessment (P _i) and Nemerow's multi-factor index (P _N) of heavy metals was calculated to find out the degree of pollution in the Halda River. The maximum values of P _i (Cd), P _i (Pb), P _i (As), P _i (Cu), and P _i (Cr) were determined to be 26.67, 260.00, 17.00, 208.76 and 2.80 respectively. The maximum value of P _N was found to be 289.04. The discharge of effluents from various large and small industries near the Halda River is considered to be the major source of the identified heavy metals. Multivariate statistical analysis such as principal component analysis, Pearson correlation matrix and cluster analysis revealed that most of the heavy metals originated from different anthropogenic sources. Multivariate analysis also showed that Co, Mn, Cu, Cr, Pb, Cd, NH₄⁺, NO₃^- mainly came from artificial sources whereas Fe, Ca, As mainly originated from natural sources. Arsenic (As) also came from artificial sources with Cu.

Clinical characteristics and factors influencing the outcome of hospitalised COVID-19 patients in a semi-urban primary healthcare center

Background and objectives: Various new manifestations and risk factors for COVID-19 have been unveiled in the course of the current pandemic. Understanding the clinical spectrums as well as the risk factors associated with the adverse outcome of the disease is critical to combat this pandemic. This study was conducted to identify the clinical features, overall outcome and the factors associated with adverse outcome of the hospitalised COVID-19 patients in a semi-urban healthcare setting. Methods: This study was conducted at Debidwar Upazila (sub-district) Health Complex under the Cumilla district from April 2020 to October 2020. Reverse transcriptase-polymerase chain reaction (RT-PCR) positive COVID-19 patients, aged 18 years and above, admitted at the Health Complex were enrolled in the study. All patients were followed till their recovery, referral or death. The data were collected in a pre-designed semi-structured questionnaire that included demographic, epidemiological, clinical and laboratory parameters. Result: Out of 50 RT-PCR positiveCOVID-19 adult participants, 30 (60%) were males and 20 (40%) were females. Twenty-four percent, 36%, and 40% of the patients had mild, moderate and severe disease respectively. The most common clinical symptom was fever (96%), followed by cough (86%) and shortness of breath (60%). Hypertension (54%), diabetes mellitus (40%), bronchial asthma (20%) and chronic obstructive pulmonary disease (COPD, 14%) were the major co-morbid conditions. Of the total cases, 2 (4%) died and 8 (16%) required referral to tertiary care hospital while 40 (80%) recovered. COPD was associated with poor outcome (OR 19; 95% CI: 2.88, 125.31; p < 0.05). Smokers were 7 times more likely to exhibit the negative outcome than non-smokers (95% CI: 1.52, 32.33; p < 0.05). Conclusion: In this study, COPD was associated with a negative outcome. Further study with larger sample should be carried out to determine the spectrum of risk factors. Ibrahim Med. Coll. J. 2020; 14(2): 42-54

Pandemic Now and Then: A Historical Perspective of Non-Pharmaceutical Interventions Adopted In Covid-19

The coronavirus disease 2019 (COVID-19), first reported in Wuhan, China is now a major global health threat - a pandemic. Public health control measures are the cornerstones in the fight against COVID-19 in the absence of an effective vaccine or proven treatment. The aim of this review was to explore the historical use case of various public health measures adopted today to tackle COVID-19 spread. Although our knowledge about this novel coronavirus transmission is evolving over time, the fundamental non-pharmaceutical interventions e.g., handwashing, wearing a mask, physical distancing, isolation, quarantine and border control which are adopted globally at present are not new. This review highlighted that historically and religiously similar approaches were practised in the medieval past for controlling disease outbreaks. The successful implementation of the public health control measures largely depends on health systems resilience, community engagement and changes in population behaviour. Combined global efforts are essential to strengthen health systems, improve the capability of research and transparent information sharing with both public and international bodies to combat the pandemic.

Prophages and satellite prophages are widespread in Streptococcus and may play a role in pneumococcal pathogenesis

Prophages (viral genomes integrated within a host bacterial genome) can confer various phenotypic traits to their hosts, such as enhanced pathogenicity. Here we analyse >1300 genomes of 70 different Streptococcus species and identify nearly 800 prophages and satellite prophages (prophages that do not encode their own structural components but rely on the bacterial host and another helper prophage for survival). We show that prophages and satellite prophages are widely distributed among streptococci in a structured manner, and constitute two distinct entities with little effective genetic exchange between them. Cross-species transmission of prophages is not uncommon. Furthermore, a satellite prophage is associated with virulence in a mouse model of Streptococcus pneumoniae infection. Our findings highlight the potential importance of prophages in streptococcal biology and pathogenesis.

Prophages are viral genomes integrated within bacterial genomes. Here, Rezaei Javan et al. identify nearly 800 prophages and satellite prophages in > 1300 Streptococcus genomes, and show that a satellite prophage is associated with virulence in a mouse model of pneumococcal infection.

Experimental loss of generalist plants reveals alterations in plant-pollinator interactions and a constrained flexibility of foraging

Species extinctions undermine ecosystem functioning, with the loss of a small subset of functionally important species having a disproportionate impact. However, little is known about the effects of species loss on plant-pollinator interactions. We addressed this issue in a field experiment by removing the plant species with the highest visitation frequency, then measuring the impact of plant removal on flower visitation, pollinator effectiveness and insect foraging in several sites. Our results show that total visitation decreased exponentially after removing 1–4 most visited plants, suggesting that these plants could benefit co-occurring ones by maintaining high flower visitor abundances. Although we found large variation among plant species, the redistribution of the pollinator guild affected mostly the other plants with high visitor richness. Also, the plant traits mediated the effect of removal on flower visitation; while visitation of plants which had smaller inflorescences and more sugar per flower increased after removal, flower visitors did not switch between flower shapes and visitation decreased mostly in plants visited by many morpho-species of flower visitors. Together, these results suggest that the potential adaptive foraging was constrained by flower traits. Moreover, pollinator effectiveness fluctuated but was not directly linked to changes of flower visitation. In conclusion, it seems that the loss of generalist plants alters plant-pollinator interactions by decreasing pollinator abundance with implications for pollination and insect foraging. Therefore, generalist plants have high conservation value because they sustain the complex pattern of plant-pollinator interactions.

Proximate composition, texture analysis and sensory evaluation of keropok lekor formulated with herbs and spices

Keropok lekor a fish-based sausage is a popular traditional food item in Terengganu state, Malaysia. This study aimed to develop a new flavor and taste of keropok lekor. Common spices such as cumin, coriander, cinnamon, cardamom, bay leaf, nutmeg, clove, onion, ginger, garlic were used to develop a new flavor of keropok lekor. A total of 5 samples, including two original and three developed keropok lekor samples were prepared. This study also evaluated the proximate composition of two raw samples (Original and developed). The results of the proximate analysis showed a significant difference (p<0.05) in all parameters except the fiber content. Hardness, springiness, and chewiness of the samples were measured by using TA-XTplus texture analyzer. There was a significant difference in the hardness level between original and developed sample. Finally, sensory evaluation according to six attributes such as color, odors, texture, flavor, taste and overall acceptability was done by 39 panelists. A 7-point hedonic scale ranging from “dislike very much” to “like very much” was employed in sensory testing. There was a significant difference (p<0.05) in all the sensory parameters evaluated. The results showed that most of the respondents preferred the developed samples over the original samples. Developed fried keropok lekor with bread crumb was the most acceptable one.

Flower visitation by hoverflies (Diptera: Syrphidae) in a temperate plant-pollinator network

Hoverflies (Diptera: Syrphidae) are among the most important pollinators, although they attract less attention than bees. They are usually thought to be rather opportunistic flower visitors, although previous studied demonstrated that they show colour preferences and their nectar feeding is affected by morphological constraints related to flower morphology. Despite the growing appreciation of hoverflies and other non-bee insects as pollinators, there is a lack of community-wide studies of flower visitation by syrphids. The aim of this paper is to provide a detailed analysis of flower visitation patterns in a species rich community of syrphids in a Central European grassland and to evaluate how species traits shape the structure of the plant-hoverfly flower visitation network. We found that different species varied in the level of specialisation, and while some species visited a similar spectre of flowers, others partitioned resources more strongly. There was a consistent difference in both specialisation and flower preferences between three syrphid subfamilies. Eristalinae and Pipizinae were more specialised than Syrphinae. Trait-based analyses showed that relative flower visitation (i) increased with plant height, but most strongly in Eristalinae; (ii) increased with inflorescence size in small species from all three subfamilies, but was independent of inflorescence size in large species of Eristalinae and Syrphinae; and (iii) depended on flower colour, but in a subfamily-specific way. Eristalinae showed the strongest flower colour preferences for white flowers, Pipizinae visited mostly white and yellow flowers, while Syrphinae were less affected by flower colour. Exploration of the structure of the plant-hoverfly flower visitation network showed that the network was both modular and nested. We also found that there were almost no differences in specialisation and relative visitation frequency between males and females. Overall, we showed that flower visitation in syrphids was affected by phylogenetic relatedness, body size of syrphids and several plant traits.

Effects of small-scale clustering of flowers on pollinator foraging behaviour and flower visitation rate

Plants often grow in clusters of various sizes and have a variable number of flowers per inflorescence. This small-scale spatial clustering affects insect foraging strategies and plant reproductive success. In our study, we aimed to determine how visitation rate and foraging behaviour of pollinators depend on the number of flowers per plant and on the size of clusters of multiple plants using Dracocephalum moldavica (Lamiaceae) as a target species. We measured flower visitation rate by observations of insects visiting single plants and clusters of plants with different numbers of flowers. Detailed data on foraging behaviour within clusters of different sizes were gathered for honeybees, Apis mellifera, the most abundant visitor of Dracocephalum in the experiments. We found that the total number of flower visitors increased with the increasing number of flowers on individual plants and in larger clusters, but less then proportionally. Although individual honeybees visited more flowers in larger clusters, they visited a smaller proportion of flowers, as has been previously observed. Consequently, visitation rate per flower and unit time peaked in clusters with an intermediate number of flowers. These patterns do not conform to expectations based on optimal foraging theory and the ideal free distribution model. We attribute this discrepancy to incomplete information about the distribution of resources. Detailed observations and video recordings of individual honeybees also showed that the number of flowers had no effect on handling time of flowers by honeybees. We evaluated the implications of these patterns for insect foraging biology and plant reproduction.

Modelling the failure modes in geobag revetments

In recent years, sand filled geotextile bags (geobags) have been used as a means of long-term riverbank revetment stabilization. However, despite their deployment in a significant number of locations, the failure modes of such structures are not well understood. Three interactions influence the geobag performance, i.e. geobag-geobag, geobag-water flow and geobag-water flow-river bank. The aim of the research reported here is to develop a detailed understanding of the failure mechanisms in a geobag revetment using a discrete element model (DEM) validated by laboratory data. The laboratory measured velocity data were used for preparing a mapped velocity field for a coupled DEM simulation of geobag revetment failure. The validated DEM model could identify well the critical bag location in varying water depths. Toe scour, one of the major instability factors in revetments, and its influence on the bottom-most layer of the bags were also reasonably represented in this DEM model. It is envisaged that the use of a DEM model will provide more details on geobag revetment performance in riverbanks.

Screening of Ethanol, Petroleum Ether and Chloroform Extracts of Medicinal Plants, Lawsonia inermis L. and Mimosa pudica L. for Antibacterial Activity

Organic extracts (ethanol, petroleum ether and chloroform) of two medicinal plants Lawsonia inermis L. and Mimosa pudica L. were proven for antibacterial properties against 15 Gram-positive and Gram-negative human pathogenic bacteria. Among the three types of extracts tested, ethanol extract was found to possess maximum antibacterial activity. The diameter of the zone of inhibition of bacterial growth showed that Gram-negative bacteria are more sensitive than Gram-positive bacteria to plant extracts. Between the two plants species studied, Lawsonia inermis extract showed more antibacterial activity compared to Mimosa pudica extract.