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Rajarao, Gunaratna Kuttuva
Publications (4 of 4) Show all publications
Eneh, L., Fillinger, U., Borg-Karlson, A.-K., Rajarao, G. K. & Lindh, J. (2019). Anopheles arabiensis oviposition site selection in response to habitat persistence and associated physicochemical parameters, bacteria and volatile profiles. Medical and Veterinary Entomology, 33(1), 56-67
Open this publication in new window or tab >>Anopheles arabiensis oviposition site selection in response to habitat persistence and associated physicochemical parameters, bacteria and volatile profiles
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2019 (English)In: Medical and Veterinary Entomology, ISSN 0269-283X, E-ISSN 1365-2915, Vol. 33, no 1, p. 56-67Article in journal (Refereed) Published
Abstract [en]

A better understanding of the oviposition behaviour of malaria vectors might facilitate the development of new vector control tools. However, the factors that guide the aquatic habitat selection of gravid females are poorly understood. The present study explored the relative attractiveness of similar artificial ponds (0.8 m(2)) aged at varying lengths prior to opening in such a way that wild Anopheles arabiensis could choose between ponds that were freshly set up, or were aged 4 or 17 days old, to lay eggs. Physicochemical parameters, bacterial profile and volatile organic compounds emitted from ponds were investigated over three experimental rounds. Fresh ponds contained on average twice as many An. arabiensis instar larvae (mean 50, 95% confidence interval (CI) = 29-85) as the ponds that had aged 4 days (mean = 24, 95% CI = 14-42) and 17 days (mean = 20, 95% CI: 12-34). Fresh ponds were associated with a significantly higher turbidity combined with higher water temperature, higher nitrite levels and a lower pH and chlorophyll level than the older ponds. Round by round analyses suggested that bacteria communities differed between age groups and also that 4-heptanone, 2-ethylhexanal and an isomer of octenal were exclusively detected from the fresh ponds. These characteristics may be useful with respect to developing attract and kill strategies for malaria vector control.

Place, publisher, year, edition, pages
WILEY, 2019
Keywords
Malaria, oviposition, denaturing gradient gel electrophoresis, volatile compounds, physicochemical parameter
National Category
Microbiology
Identifiers
urn:nbn:se:kth:diva-244502 (URN)10.1111/mve.12336 (DOI)000457739700005 ()30168151 (PubMedID)2-s2.0-85052815471 (Scopus ID)
Note

QC 20190328

Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2019-03-28Bibliographically approved
Azeem, M., Barba Aliaga, M., Borg-Karlson, A.-K., Terenius, O., Broberg, A. & Rajarao, G. K. (2019). Heterobasidion-growth inhibiting Bacillus subtilis A18 exhibits medium- and age-dependent production of lipopeptides. Microbiology Research, 223-225, 129-136
Open this publication in new window or tab >>Heterobasidion-growth inhibiting Bacillus subtilis A18 exhibits medium- and age-dependent production of lipopeptides
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2019 (English)In: Microbiology Research, ISSN 0944-5013, E-ISSN 1618-0623, Vol. 223-225, p. 129-136Article in journal (Refereed) Published
Abstract [en]

Heterobasidion annosum s.s. and H. parviporum are severe pathogens of conifers causing butt rot and root rot thus reducing the economic value of timber. Here, the antifungal activity of Bacillus subtilis isolate A18 against these two Heterobasidion species was investigated. Five different culture media with different culture age were investigated to study the effect of substrate composition and culture age for metabolite production. Bacterial cultures and cell-free culture filtrates were tested for antifungal activity. Inhibition of fungal growth was analysed using the agar disc-diffusion method. MALDI-TOF and LC-HRMS analyses were used to identify the antifungal metabolites. Substrate composition and age of culture were found to be active variables with direct effect on the antifungal activity of bacterial culture extracts. High anti-fungal activity was observed when B. subtilis was cultured in PDB, SGB and LB media for four days. Mass-spectrometry analysis showed the presence of lipopeptides in culture filtrates identified as members of the surfactins, polymixins, kurstakins and fengycins. A culture filtrate containing fengycin-type lipopeptides showed the highest bioactivity against Heterobasidion species. Bacterial cultures had higher bioactivity compared to their respective cell free culture filtrates. The results of the present study suggest that B. subtilis A18 is a powerful biocontrol agent against Heterobasidion infections of tree wounds and stumps.

Place, publisher, year, edition, pages
Elsevier GmbH, 2019
Keywords
Anti-fungal compounds, Biocontrol, Co-culturing, Conifers, Inhibition, Lipopeptides, Bacteria, Bacteriology, Enzyme inhibition, Forestry, Mass spectrometry, Metabolites, Substrates, Antifungal compounds, Antifungal metabolite, Heterobasidion annosum, Mass spectrometry analysis, Metabolite production, Substrate composition, Fungi, Bacillus subtilis, Bacteria (microorganisms), Coniferophyta, Heterobasidion, Heterobasidion parviporum
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-252448 (URN)10.1016/j.micres.2019.04.006 (DOI)2-s2.0-85065092748 (Scopus ID)
Note

QC 20190715

Available from: 2019-07-15 Created: 2019-07-15 Last updated: 2019-07-15Bibliographically approved
Feng, Z., Odelius, K., Rajarao, G. K. & Hakkarainen, M. (2018). Microwave carbonized cellulose for trace pharmaceutical adsorption. Chemical Engineering Journal, 346, 557-566
Open this publication in new window or tab >>Microwave carbonized cellulose for trace pharmaceutical adsorption
2018 (English)In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 346, p. 557-566Article in journal (Refereed) Published
Abstract [en]

A promising sustainable strategy to valorize cellulose to high-value adsorbents for trace pharmaceuticals, like diclofenac sodium (DCF), in the water is demonstrated. Carbon nanospheres (CN) as the DCF adsorbent were derived from cellulose through a one-pot microwave-assisted hydrothermal carbonization method. CN exhibited efficient DCF removal (100% removal of 0.001 mg/mL DCF in 30 s and 59% removal of 0.01 mg/mL DCF in 1 h). The adsorption kinetics and isotherm data were well-fitted with the pseudo-second-order kinetic model and Langmuir model, respectively. The adsorption process was endothermic and spontaneous as confirmed by the thermodynamic parameters. Multiple characterization techniques including SEM/EDS, FTIR, FTIR-imaging and zeta potential were applied to qualitatively investigate the adsorption process. π-π stacking and hydrogen bonding were proposed as the dominant adsorption interactions. CN also demonstrated effective adsorption capacity towards three other commonly-detected contaminants in the wastewater including ketoprofen (KP), benzophenone (BZP), and diphenylamine (DPA), each bearing partial structural similarity with DCF. The affinity of the contaminants towards CN followed the order DPA > BZP > DCF > KP, which could be explained by the different configurations and chemical units. It was speculated that for DCF and KP, the steric hindrance and electrostatic repulsion produced by dissociated carboxyl groups can impede the adsorption process as compared to DPA and BZP. This methodology could offer further insights into the drug adsorption on the cellulose-derived carbon adsorbents and the use of bioderived carbons for treatment of wastewaters contaminated with pharmaceuticals.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Adsorption, Carbon nanosphere, Carbonization, Cellulose, Diclofenac, Microwave
National Category
Chemical Sciences Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-227509 (URN)10.1016/j.cej.2018.04.014 (DOI)000432878400057 ()2-s2.0-85045434362 (Scopus ID)
Note

QC 20180518

Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2019-04-10Bibliographically approved
Axelsson, K., Konstanzer, V., Rajarao, G. K., Terenius, O., Seriot, L., Nordenhem, H., . . . Borg-Karlson, A.-K. (2017). Antifeedants Produced by Bacteria Associated with the Gut of the Pine Weevil Hylobius abietis. Microbial Ecology, 74(1), 177-184
Open this publication in new window or tab >>Antifeedants Produced by Bacteria Associated with the Gut of the Pine Weevil Hylobius abietis
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2017 (English)In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 74, no 1, p. 177-184Article in journal (Refereed) Published
Abstract [en]

The pine weevil, Hylobius abietis, is a severe forest pest insect as it feeds on newly planted conifer seedlings. To identify and develop an antifeedant could be one step towards the protection of seedlings from feeding damage by the pine weevil. With the aim to trace the origin of the antifeedants previously found in feces of the pine weevil, we investigated the culturable bacteria associated with the gut and identified the volatiles they produced. Bacterial isolates were identified by 16S ribosomal RNA gene analysis. The volatile emissions of selected bacteria, cultivated on NB media or on the grated phloem of Scots pine twigs dispersed in water, were collected and analyzed by solid-phase microextraction gas chromatography-mass spectrometry. The bacterial isolates released a variety of compounds, among others 2-methoxyphenol, 2-phenylethanol, 3-methyl-1-butanol, 1-octen-3-ol, 3-octanone, dimethyl disulfide, and dimethyl trisulfide. A strong antifeedant effect was observed by 2-phenylethanol, which could thus be a good candidate for use to protect planted conifer seedlings against feeding damage caused by H. abietis.

Place, publisher, year, edition, pages
SPRINGER, 2017
Keywords
Hylobius abietis, Rahnella, Brevundimonas, 2-Methoxyphenol, 2-Phenylethanol, Antifeedant
National Category
Water Treatment Microbiology
Identifiers
urn:nbn:se:kth:diva-210344 (URN)10.1007/s00248-016-0915-5 (DOI)000403255500017 ()2-s2.0-85009191802 (Scopus ID)
Note

QC 20170704

Available from: 2017-07-04 Created: 2017-07-04 Last updated: 2017-07-04Bibliographically approved
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