Total Petroleum Hydrocarbon Degradation by Endophytic Fungi from the Ecuadorian Amazon

The capacity of 133 fungal endophyte isolates for degrading petroleum hydrocarbons was evaluated. The endophytes were isolated from leaf and stem tissues from 23 plants collected in a natural habitat contaminated with crude oil in southwestern Ecuador. Their capacity for hydrocarbon biodegradation was tested by an in vitro colorimetric qualitative test during 10 days, using the Minimal Salt Medium and crude oil as the carbon source. Taxonomic identification of the endophytic fungi that showed bioactivity in the qualitative test was carried out by analysis of the ITS gene of the region 18S of the rDNA. Endophytes showed the best results in the previous qualitative test where selected for a quantitative in vitro test for 30 days. Residual hydrocarbons were tracked by infrared spectroscopy (IR) and gas chromatography (GC) with a flame ionization detector. The maximum removal rates of total petroleum hydrocarbons were 99.6% (IR) and 99.8% (GC), corresponding to fungi of the genus Verticillium sp. and Xylaria sp. 1 respectively. This is the first report of biodegradation of crude oil hydrocarbons by endophytic fungi in a tropical ecosystem. The results suggest these fungal isolates are potential hydrocarbon biodegraders that could be used in bioremediation processes.

The maximum likelihood identification method applied to insect morphometric data

To distinguish species or populations using morphometric data is generally processed through multivariate analyses, in particular the discriminant analysis. We explored another approach based on the maximum likelihood method. Simple statistics based on the assumption of normal distribution at a single variable allows to compute the chance of observing a particular data （or sample） in a given reference group. When data are described by more than one variable, the maximum likelihood （MLi） approach allows to combine these chances to find the best fit for the data. Such approach assumes independence between variables. The assumptions of normal distribution of variables and independence between them are frequently not met in morphometrics, but improvements may be obtained after some mathematical transformations. Provided there is strict anatomical correspondence of variables between unknown and reference data, the MLi classification produces consistent classification. We explored this approach using various input data, and compared validated classification scores with the ones obtained after the Mahalanobis distance-based classification. The simplicity of the method, its fast computation, performance and versatility, make it an interesting complement to other classification techniques.

Antibacterial and Antifungal Activity of Organic and Peptidic Extracts of Ecuadorian Endophytic Fungi

Antibacterial and antifungal activities of 32 organic and 14 peptidic extracts obtained from twelve endophytic fungi of the Collection of Endophytes Quito-Catolica were tested against the pathogenic bacteria Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens, Escherichia coli and Salmonella enteritidis, and against the fungal oomycete Pythium ultimum. It was observed that the extracts of Marasmiellus candidus (CEQCA-O1113), Xylaria laevis (CEQCA-O1399), Fusarium solani (CEQCA-O1393), Diaporthe helianthi (CEQCA-O1394) and Xylaria sp. (CEQCA-O1400) partially or totally inhibited the microorganisms tested. The extracts CEQCA-O1399.P1 and CEQCA-O1113.D1 showed fungistatic and fungicidal effects against P. ultimum, respectively. Six extracts strongly inhibited S. aureus, and E. coli was strongly inhibited by the extract CEQCA-O1113.E2. Based on a bioassay-guided approach, the extracts with strong bioactivity in the antibacterial assays by an agar diffusion method were also tested by a disk diffusion method, and the minimal inhibitory concentrations were determined by a microdilution assay. The most bioactive extract, CEQCA-O1113.D1, was also purified by high performance liquid chromatography. The extract recovered its initial bioactivity against S. aureus in two fractions after the purification. Overall, the results of this study highlight the potential of the fungal endophytes as producers of bioactive compounds.