Science
Permanent URI for this communityhttp://repository.kln.ac.lk/handle/123456789/1
Browse
4157 results
Search Results
Item Comparative study of nature and activities of soil fungi along with soil characteristics inKanneliya natural forest reserve and adjacent disturbed forest patch(International Conference on Applied and Pure Sciences, 2025Faculty of Science, University of Kelaniya, Sri Lanka, 2025) Dissanayake W. G. M. P.; Kannangara S. D.; Ratnayake R. M. C. S.; Daranagama D. A. D. A.Soil fungi in forests are crucial for ecosystem functioning by nutrient cycling through organic matterdecomposition. The Kanneliya forest reserve in Sri Lanka faces an ecological threat due to the invasionof the fern Dicranopteris Linearis, affecting the soil fungal community and challenging the restorationefforts. This study investigates the soil physicochemical properties along with substrate utilisationability of the dominantly isolated fungi in two ecosystems: the native forest patch and in adjacentdisturbed forest patch in the Kanneliya Forest Reserve. Soil pH, electrical conductivity, moisturecontent, and temperature were measured using standard methods. The Warcup soil plate method wascarried out using PDA medium to isolate soil fungi, and pure cultures of fungi were identified at thegenus level using morphological and microscopic observations. The percentage frequency ofoccurrence of each fungus was calculated separately for the two study sites. Aspergillus sp.1,Trichoderma sp.4, Rhizomucor sp.1, White sterile sp.1, and Trichoderma sp.5, the dominantly isolatedfungal species were tested for their substrate utilisation abilities (starch, cellulose and lignin) usingstandard methods. The soil temperature was significantly different within the adjacent disturbed land,but not within the native forest patch. The soil moisture content within the two study sites was notsignificantly different. The soil pH varied significantly within the undisturbed forest patch, but notwithin the disturbed land. The soil electrical conductivity within the two study sites was significantlydifferent. There were significant differences in soil electrical conductivity, moisture content, and pHbetween the two study sites, while soil temperature did not differ significantly. Among the isolatedeighteen (18) fungal species, 14 and 11 species were isolated from undisturbed and disturbed sites,respectively. Aspergillus sp.1, Aspergillus sp.2, Aspergillus sp.4, Trichoderma sp.3, Trichoderma sp.4,Trichoderma sp.5 and white sterile sp.1 were commonly isolated from both sites. Aspergillus sp.1,Rhizomucor sp.1 and White sterile sp.1 were able to utilise starch, and all fungi tested were able toutilise cellulose. Aspergillus sp.1, Trichoderma sp.4, White sterile sp.1, and Trichoderma sp.5 exhibitedthe ability to produce lignin-degrading enzyme(laccase), while none of the other fungal species testedwere able to produce peroxidase and tyrosinase, other lignin-degrading enzymes. The presentinvestigation provides insights into fungal composition and some physicochemical parameters inundisturbed and adjacent disturbed land in the Kanneliya forest reserve. Common fungal species to bothsites were isolated in a higher frequency of occurrence from the undisturbed forest patch compared tothe adjacent disturbed forest patch; this may be due to the presence of anti-fungal allelopathic chemicalsin the fern land. Further investigations on the allelopathic effect of Dicranopteris linearis on fungalgrowth are crucial to ensure the sustainability of the Kanneliya forest ecosystem.Item Geospatial Profiling and Environmental Risk Analysis of Cadmium and Lead Dispersion in Dry Zone Soils and Sediments of Sri Lanka.(Soil and Sediment Contamination: An International Journal, 2025) Dayananda, N. R.; Liyanage, J. A.; Kannangara, S. D.This study delves into the contamination, spatial dispersion, and geoaccumulation of Cadmium (Cd) and Lead (Pb) in soils and reservoir sediments within Sri Lanka’s dry zone, emphasizing their environmental and public health ramifications, particularly in CKDu-endemic areas. Elevated concentrations of Cd and Pb in soils from Girandurukotte (GK), Kusumpokuna (KP), and Horowpathana (HP) originate from anthropogenic inputs, including intensive agriculture. The spatial distribution coupled with spatial autocorrelation (Moran’s Index values) of Cd (GK = -0.044, KP = -0.074, HP = -0.035) and Pb (GK = 0.197, KP = .181, HP = .314) in soils and sediments reflects mainly diffuse and clustered contamination patterns driven by agricultural runoff, irrigation practices, and geogenic sources. Cd showed considerable to very high contamination across sites, with Cf values ranging from 4.22 to 6.46, while Pb remained low to moderate (Cf: 0.23–2.01). The ecological risk was driven primarily by Cd, with Er values up to 193.8, resulting in PERI scores of 203.85 (HP), 169.50 (KP), and 132.75 (GK). These results highlight Cd as the dominant ecological concern in the study area. Irrigation networks facilitating the transport of Cd and Pb into reservoirs like Ulhitiya, Diwulankadawala, and Wahalkada, where sediment Igeo values indicate significant anthropogenic enrichment and demonstrated Cd concentrations exceeding sediment quality guidelines, such as LEL, CB-TEC, ERL, and SEPA. Cd, existing primarily as Cd2 +, demonstrates high mobility under slightly acidic conditions, forming soluble complexes and precipitating in reducing environments. Conversely, Pb exhibits reduced bioavailability due to its strong affinity for adsorption onto clay minerals, Fe-Mn oxides, and its precipitation as pyromorphite. Reservoir sediments, enriched with fine silts and clays, act as sinks for metal-laden runoff, while arid environmental conditions and cyclic irrigation-induced redox fluctuations further modulate metal speciation, mobility, and ecological risks, necessitating integrated soil and water management interventions.Item Evaluation of Fermentation Dynamics and Volatile Compound Profiles of Pro biotic Lactobacillus spp. Inhabiting! Tender Coconut Water(ICIET/Food Security, Nutrition, and Processing Technology, 2025) Pavalakumar, D.; Undugoda, L.J.S.; Managec, P.M.; Nugara, N.N.R.N.; Kannangara, S.Lactic acid bacteria fermentation of tender coconut water creates a beverage with enhanced probiotic and biopreservation properties. This study examines the potential fermenters with a preferred volatile profile among four indigenous lactic acid bacteria inhabiting tender coconut water: Lactiplantibacillus plantarum CWJ3, Lacticaseibacillus rhamnosus CWKu-12, Lacticaseibacillus paracasei CWKu-14, and Lacticaseibacillus casei CWM15. The lactic acid bacteria strains were cultured in de Man, Rogosa, and Sharpe broth, and inoculated into pasteurized tender coconut water. Their fermentation characteristics were monitored over 48 hours at 37 °C, and volatile profiles were analyzed using gas chromatography-mass spectrometry coupled with solid-phase microextraction (GCMS-SPME). In all samples, pH and residual sugar levels consistently decreased, while viable cell counts increased during fermentation. L. plantarum CWJ3 exhibited the significantly lowest pH (3.86±0.26) and Brix (3.78±0.54) values while maintaining high cell viability (5×10⁶ CFU mL-1). This strain also demonstrated relatively stable viable cell productivity (78,194 to 102,950 CFU mL-1h-1), and a growth rate (0.0417 to 0.0516 h -1), making it the most suitable strain for fermentation. GCMS-SPME analysis confirmed the production of acids, esters, ketones, lactones, and aldehydes during fermentation. L. plantarum CWJ3 produced the significantly highest amounts of acetic acid (13.12±1.21%), and acetaldehyde (1.25±0.23%), and the lowest ethanol levels (4.56±0.87%). Conversely, L. rhamnosus CWKu-12 produced elevated levels of ketones and lactones, such as 2-heptanone (8.15±1.02%) and 2,3-butanedione (4.16±0.81%), contributing to a unique volatile profile. Ethyl acetate was the primary ester produced by all strains, with L. paracasei CWKu-14 generating the significantly highest amount (7.65±0.54%). Notably, L. plantarum CWJ3 was the only strain to produce ethyl isobutyrate. The volatile compounds from L. plantarum CWJ3 and L. rhamnosus CWKu-12 contribute to a fruitier flavor, while their increased acetic acid and reduced ethanol levels enhance the product’s biopreservation.Item Comprehensive In Vitro Evaluation of the Biocontrol Potential of Trichoderma virens Against Selected Phytopathogenic Fungi: Integration of Interaction Dynamics and Best-Fit Mathematical Modeling(Asian Journal of Mycology, 2025) Munasinghe, J; Poornima V.A; Dissanayake, T.; Kannangara, S; Undugoda, L; Thambugala K.MIn the context of plant disease management, biocontrol is often used as an environmentally friendly alternative to synthetic chemical pesticides. The genus Trichoderma is known for its ability to suppress various plant diseases caused by pathogenic fungi through antagonism, competition, and induced resistance. This research attempt was to evaluate the mechanisms employed by Trichoderma virens isolate (KP985643.1) in controlling three plant pathogenic fungi (Fusarium oxysporum, Colletotrichum gloeosporioides, and Lasiodiplodia theobromae) under in vitro conditions, along with the selection of the best-fitting mathematical models for their interactions. The biocontrol potential of T. virens against the selected plant pathogenic fungi was evaluated using the dual culture method. Further biocontrol mechanism was identified using the analysis of volatile and non-volatile compounds and the hyphal growth patterns. In addition to that the results of the dual culture method were used to analyse the best-fitting growth models for each pathogenic fungus separately for two conditions which were in the absence of T. virens and in the presence of T. virens. These mathematical models of microbial growth serve as powerful tools for predicting the future performance of fungal biocontrol agents in managing plant diseases under diverse environmental conditions. Such predictive capabilities are crucial for optimizing field applications, improving consistency in biocontrol outcomes, and supporting the development of sustainable, environmentally friendly plant disease management strategies in agricultural systems. Results of the dual culture experiment demonstrated a significant growth control of L. theobromae and F. oxysporum and a moderate growth control of C. gloeosporioides by T. virens. Considering the growth models, the best fitted models were given by Gompertz, Exponential, and Exponential, respectively, for C. gloeosporioides, F. oxysporum, and L. theobromae in the absent condition of T. virens. In the present condition of T. virens, the best-fitted models were given by Brody, Exponential, and Brody respectively for L. theobromae, C. gloeosporioides, and F. oxysporum. The increase in volatile production was not uniform across all pathogens. For instance, the highest VOC production showed against F. oxysporum, suggesting that T. virens may be more efficient at preventing F. oxysporum from producing volatile compounds. Among many VOCs, ethanol and 6-Pentyl-2H-6-Pentyl-2H-pyran-2-one production were the highest when T. virens controlled the growth of F. oxysporum. However, non-volatile compounds produced by T. virens significantly controlled the growth of L. theobromae, with a moderate inhibition of F. oxysporum. It was further observed the ability of T. virens to inhibit the growth of L. theobromae through the production of coiling structures. Results of the present study clearly indicated the potential of T. virens in controlling the tested phytopathogenic fungi by employing a combination of mechanisms including the production of volatile and non-volatile compounds and hyphal interactions.Item Kinetic evaluation of anthracene biodegradation by Bacillus velezensis and mathematical model fitting under substrate inhibition conditions.(Bioremediation Journal, 2025) Nadeema Dharmasiri, R. B.; Munasinghe, J.; Madushika, R.; Pavalakumar, D.; Samarakoon Undugoda, L. J.; Kannangara, S. D.; Thambugala, K. M.Polycyclic aromatic hydrocarbons (PAHs) such as anthracene are persistent environmental pollutants that accumulate in ecosystems and contribute to harmful air pollution, posing risks to human health. Due to its significance, anthracene must be removed using nontoxic methods such as bioremediation. This study focuses on degrading anthracene with Bacillus velezensis and investigating the kinetics of this process. The bioremediation potential of B. velezensis in degrading anthracene under aerobic conditions was explored through batch experiments conducted at varying anthracene concentrations (100–600 ppm). The bacterium exhibited rapid biomass growth and efficient degradation at 100 ppm, while growth was inhibited at higher concentrations due to substrate toxicity. GC-MS analysis identified 9,10-anthracenedione as the primary intermediate, which was further broken down into carbon dioxide and water at 100 ppm. Phytotoxicity assays confirmed this intermediate was nontoxic to the bacterium and phyllosphere. The degradation kinetics deviated from the Michaelis–Menten model at high concentrations, indicating the influence of substrate inhibition. Among several models evaluated, the Wayman and Tseng model showed the best statistical fit, with a high adjusted R2 value (0.95191) and a low RMSE (0.0019), indicating accurate predictions. Data interpolation improved model performance, providing a more reliable framework for predicting anthracene degradation by B. velezensis.Item Effect of ampicillin and tetracycline on Xanthomonas spp. isolated from strawberry plants with Angular Leaf Spot (ALS) disease.(Faculty of Technology, University of Ruhuna, 2025) Hapuarachchi, K. M.; Halmillawewa, A. P.Fragaria ananassa(strawberry) is a perennial crop belonging to the family Rosaceae. Parallel to the increase in strawberry production, various strawberry diseases have also become common. One such is Angular Leaf Spot (ALS), which can lead to severe losses in yield. Xanthomonas fragariae, a Gram-negative rod, has been identified as the causative agent of this disease. Control of ALS is currently achieved commonly through preventive measures such as using disease-free stocks, but these may fail to counter an established pathogen. Therefore, it is important to explore other viable options such as the controlled use of antibiotics. In the current study, we have isolated the causative agent of ALS in strawberries and have evaluated the efficiency of two antibiotics for the potential control of the pathogen. The causative agent of ALS was isolated from diseased plant leaves that showed characteristic symptoms. Based on the colony morphologies on nutrient agar, two isolates, namely I_1 and I_2 were selected, and their Gram‟s reaction, motility, and selected biochemical characteristics were evaluated for the preliminary identification of the isolates as belonging to the genus Xanthomonas. The effect of two commonly available antibiotics; ampicillin, and tetracycline, were tested against the isolates using the agar well diffusion method and both antibiotics showed an inhibitory effect against both I_1 and I_2. Using the broth microdilution method, the Minimum Inhibitory Concentration (MIC) of ampicillin was determined as 250 μg mL-1 and 200 μg mL-1 for I_1 and I_2 respectively, while the MIC of tetracycline for I_1 and I_2 was 300 μg mL- 1, and 250 μg mL-1 respectively. Although this study exhibited that antibiotics, ampicillin, and tetracycline can be effectively used against the bacterial pathogen, the practicality for large-scale use as well as the potential environmental and health implications should also be considered before their application.Item Isolation and characterization of black rot- causing bacteria of cabbage, and isolation of its bacteriophage as a biocontrol agent.(University of Ruhuna, 2025) Adhikari, A. M. H. S.; Halmillawewa, A. P.Black rot caused by Xanthomonas campestris pv. campestris (Xcc) is one of the most destructive bacterial diseases of economically important Brassicaceae vegetables including cabbage. Available methods to control black rot in cabbage are only preventive and ineffective in controlling the disease once the plant is infected. Phage-mediated biocontrol is considered as a more promising, safe, and environmentally friendly method to control bacterial plant diseases. Therefore, this study was focused on isolating the causative bacteria of black rot of cabbage and isolating their bacteriophages that can be used as a biocontrol agent. Bacterial pathogens were isolated from cabbage leaf samples showing typical black rot symptoms using standard microbiological techniques. Two isolates, namely Xcc-1 and Xcc-2, with yellow-coloured, mucoid colonies were purified and preliminarily identified as Xanthomonas spp. using morphological and biochemical characteristics. The UV-visible spectrophotometric analysis of the methanolic extract of the yellow intracellular pigment produced by the bacterial isolates showed a maximum peak near 440 nm with shoulder peaks, which was characteristic of the Xanthomonadin pigment of Xanthomonas spp. The pathogenicity of the two bacterial isolates was confirmed by inoculating healthy cabbage leaves. Characteristic disease symptoms were observed after 10 days of incubation. Further, bacteriophages were isolated from diseased cabbage leaves using agar overlay method. The phage isolate Xcc-Ph1, formed visible plaques with both bacterial isolates Xcc-1 and Xcc-2. Although further studies are needed to confirm the biocontrolling ability of Xcc-Ph1, these findings provide a great initiative to develop a bacteriophage-based method to manage Black rot disease in cabbage in the future.Item Exploring Plant Growth Promoting Salt-Tolerant Microorganisms Associated with Salicornia brachiata(Department of Forestry and Environmental Science, University of Sri Jayawardenepura, 2025) Herath, H. M. P.; Halmillawewa, A. P.; Perera, D.; Attanayake, R. N.Salicornia brachiata, a halophyte native to the regions extending from the Indian subcontinent to Myanmar. It is well established in salt marshes along the Northwest and Southeast coastlines of Sri Lanka. This plant stabilizes coastal ecosystems and hosts a rich diversity of salt-tolerant microorganisms, including endophytic and rhizosphere bacteria and fungi. These microbes are vital for the plant's growth under saline stress, aiding in nutrient uptake, growth promotion, and overall ecosystem resilience. Therefore, the aims of this study were to isolate salt-tolerant root endophytic and rhizosphere microorganisms and to explore the plant growth promoting microbial diversity associated with S. brachiata. Rhizosphere soil and root samples of S. brachiata were collected from Karative, along transects perpendicular to the shoreline. The samples were initially cultured on marine agar for isolation of the rhizosphere and root endophytic bacteria, on PDA amended with 20 g/L Na Cl for rhizosphere fungi, and Hagem minimal medium for root endophytic fungi. A total of 73 morphologically distinct bacteria and fungi were subcultured on 20 g/L NaCl salt-amended nutrient agar and PDA plates, respectively. Pure cultures were tested for their growth-promoting abilities, including phosphate solubilization on Pikovskaya's agar containing 0.5% Ca3(PQ4)2, Indole-3-acetic acid (IAA) production using Salkowski's reagent, and biofilm formation using crystal violet assay in a microtiter plate. Molecular identification of potential endophytic bacterial and fungal isolates was performed by comparing their ITS and 16S rDNA sequences using BLASTn. Aspergillus sp., Aureobasidium sp., Geotrichum candidum, Proteus mirabilis, and Stagonosporopsis cucurbitacearum, produced IAA concentrations ranging from 5.72±0.24 μg/mL to 32.41±0.96 μg/mL. One-way AN OVA indicated significant differences (p < 0.05) in IAA concentrations among the endophytic isolates, with Proteus mirabilis exhibiting the highest concentration. Aspergillus sp., Meyerozyma sp., Talaromyces sp., and Virgibacillus sp. were among the best phosphate solubilizers. Brevibacterium sp. exhibited the highest biofilm formation (OD600=0.3754± 0.028) among the endophytic bacterial isolates, and it is significantly different (p<0.05) from all other isolates. In conclusion, these findings underscore the vital role of microbial communities in plant growth and resilience of S. brachiata, a vulnerable salt marsh species in the coastal line. Conserving these microbial communities is essential for ensuring the long-term sustainability of Sri Lanka's coastal biodiversity.Item Studying the antibiotic-resistant patterns of bacteria isolated from commercially available chicken manure samples(International Conference on Emerging Technologies (ICET 2025), Sabaragamuwa University of Sri Lanka., 2025) Parakramasinghe, N. K.; Halmillawewa, A. P.Chicken manure is widely applied as a fertilizer in agricultural fields in Sri Lanka. However, the extensive usage of antibiotics in the chicken farming industry may carry a risk of having soil contaminated with antibiotic residues and antibiotic-resistant bacteria. This may increase the potential threat to public health due to the mobilization of antibiotic resistance within bacterial populations. In this study, antibiotic-resistant bacteria were isolated from commercially available chicken manure samples, and the antibiotic-resistant profiles of these isolates were studied. Two chicken manure samples obtained from Kosgama and Beruwala were used to isolate a total of 20 antibiotic resistant bacteria using nutrient agar supplemented with ampicillin (50 μgmL-1), tetracycline (30 μgmL-1) and kanamycin (30 μgmL-1) separately. Antibiotic resistance of selected isolates was determined using a standard well diffusion assay with 3 different concentrations (100, 150 and 200 μgmL-1) of each of the antibiotic used. The multidrug-resistant isolates, exhibiting resistance to the highest concentrations of all three antibiotics tested, were selected for further analysis. These isolates were subsequently exposed to higher concentrations of ampicillin, tetracycline, and kanamycin (200, 250, and 300 μgmL-1), as well as chloramphenicol, erythromycin, and rifampicin (100 and 150 μgmL-1). Out of the antibiotic-resistant bacterial isolates, 50% were resistant to 2 or more antibiotics tested, while 20% of the isolates were resistant to all 3 antibiotics at 200 μgmL-1 concentration. Among the selected multidrug-resistant isolates (S1AmpC4, S1KanC2, S1TetC3 and S1TetC4), S1AmpC4 exhibited resistance to ampicillin (300 μgmL-1), kanamycin (300 μgmL-1) and chloramphenicol (150 μgmL-1). S1TetC3 exhibited resistance to ampicillin (300 μgmL-1), tetracycline (300 μgmL-1), kanamycin (300 μgmL-1) and erythromycin (150 μgmL-1) and S1TetC4 exhibited resistance to ampicillin (300 μgmL-1), tetracycline (300 μgmL-1) and erythromycin (150 μgmL-1). Isolate S1AmpC4, S1TetC3, S1TetC4 were resistant to four out of six antibiotics used. The results of this study suggest that the application of untreated chicken manure to the soil can facilitate the mobility of antibiotic resistance through the ecosystem via these multidrug-resistant bacteria.Item Genomes of two siphophages infecting Rhizobiumleguminosarum: B1VFA and V1VFA-S, exhibiting phage-plasmid-like features(Microbiology Resource Announcements, 2025) Gunathilake, Damitha; Halmillawewa, A. P.; MacKenzie, K. D.; Yost, C. K.; Hynes, M. F.We report the genome sequences of two Rhizobium-infecting siphophages,B1VFA and V1VFA-S, isolated from Canadian agricultural soils. Both encode genesassociated with plasmid maintenance, including parA, parB, and repC, and share similargenome architecture. These phages expand the diversity of rhizobiophages and mayrepresent a distinct siphophage lineage.