Chromolaena laevigata (Asteraceae) as a source of endophytic non-aflatoxigenic Aspergillus flavus: chemical profile in different culture conditions and biological applications

Endophytes are microorganisms that form symbiotic relationships with their host. These microorganisms can produce a variety of secondary metabolites, some of which have inhibitory effects on pests and pathogens or even act to promote plant growth. Due to these characteristics, these microorganisms are used as sources of biologically active substances for a wide range of biotechnological applications. Based on that, the aim of this study was to evaluate the production of metabolites of the endophytic Aspergillus flavus CL7 isolated from Chromolaena laevigata, in four different cultivation conditions, and to determine the antimicrobial, cytotoxic, antiviral, and antioxidant potential of these extracts. The multiphasic approach used to identify this strain was based on morphology and ITS gene sequence analysis. The chemical investigation of A. flavus using potato dextrose and minimal medium, using both stationary and agitated methods, resulted in the isolation of kojic acid, α-cyclopiazonic acid, and 20,25-dihydroxyaflavinine. Another 18 compounds in these extracts were identified by UHPLC-HRMS/MS, of which dideacetyl parasiticolide A has been described for the first time from A. flavus. Aflatoxins, important chemomarkers of A. flavus, were not detected in any of the extracts, thus indicating that the CL7 strain is non-aflatoxigenic. The biological potential of all extracts was evaluated, and the best results were observed for the extract obtained using minimal medium against Trichophyton rubrum and Mycobacterium tuberculosis.

Comparative Study of the Colonization of Chromolaena and Tobacco Plants by Bacteria safensis CS4 using Different Methods of Inoculation

BACKGROUND AND OBJECTIVES

This study entails the effectiveness of colonization of bacterial endophytes following inoculation of the cells in plants.

METHODOLOGY

Different methods of inoculation including seed immersion, root immersion and foliar spray were studied on Chromolaena odorata and Nicotiana tabacum for 10, 20 and 30 days. This was to ascertain the colonization ability of the endophytic strain amongst the two set of plants. The foliar parts of the plants were assessed post inoculation for the presence of the bacteria strain, followed by the growth parameters in the plant. Significant differences at p<0.05 of colonization were established by the different inoculation methods.

RESULTS

Foliar spray demonstrated the highest colonization in both Chromolaena and tobacco plants followed by root immersion. Leaf inoculation in tobacco plant demonstrated a positive colonization which is not significant. However, seed inoculation provided colonization in Chromolaena plant at 10, 20 and 30 days post inoculation at a frequency lower than that of tobacco. With root immersion in Chromolaena, there was colonization at 10 days post inoculation, no colonization at 20 days post inoculation, but colonization re-appeared at 30 days (PI). Growth index measured demonstrated a positive relationship between the inoculation of the endophyte and the growth parameters which included stem length and germination rate.

CONCLUSION

This study, therefore, showed that the bacteria strain B. safensis CS4 can effectively be horizontally transferred into tobacco and Chromolaena plants using different methods. Foliar spraying demonstrated the optimal colonization of the strain in the plant leaves.

Phytoremediation of fuel oil and lead co-contaminated soil by Chromolaena odorata in association with Micrococcus luteus

Phytoremediation is widely promoted as a cost-effective technology for treating heavy metal and total petroleum hydrocarbon (TPH) co-contaminated soil. This study investigated the concurrent removal of TPHs and Pb in co-contaminated soil (27,000 mg kg(-1) TPHs, 780 mg kg(-1) Pb) by growing Siam weed (Chromolaena odorata) in a pot experiment for 90 days. There were four treatments: co-contaminated soil; co-contaminated soil with C. odorata only; co-contaminated soil with C. odorata and Micrococcus luteus inoculum; and co-contaminated soil with M. luteus only. C. odorata survived and grew well in the co-contaminated soil. C. odorata with M. luteus showed the highest Pb accumulation (513.7 mg kg(-1)) and uptake (7.7 mg plant(-1)), and the highest reduction percentage of TPHs (52.2%). The higher TPH degradation in vegetated soils indicated the interaction between the rhizosphere microorganisms and plants. The results suggested that C. odorata together with M. luteus and other rhizosphere microorganisms is a promising candidate for the removal of Pb and TPHs in co-contaminated soils.