ABSTRACT
Aims@#The study aims to investigate the potential of the endophytic bacteria as an alternative to control the devastating brown eyespot disease caused by Cercospora sp. in coffee plants. The fungal phytopathogen causes severe leaf fall and berry damages resulting in serious yield losses in coffee farms in the Philippines and worldwide. Currently, the management of this fungal infection relies heavily on synthetic fungicides, which may be of major environmental concern. @*Methodology and results@#Endophytic bacteria were isolated from the intercellular tissues of Coffea liberica leaves by surface sterilization, maceration, dilution technique, plating on trypticase soy agar and colony characterization. Fourteen isolated endophytic bacteria were screened for their ability to inhibit the mycelial growth of Cercospora sp. through modified dual culture assay. Isolates HCC10-3SC3, HCC10-3SC2, HCC10-1SC1, ICC10-3SC1, and ICC10-1SC1 yielded the highest percent inhibition of radial growth (PIRG) with 59.56%, 60.92%, 60.96%, 64.36%, and 67.06% respectively and are statistically significant (p<0.05) compared to the antibiotic control nystatin. The top five performing endophytic bacteria were subjected to hydrolytic enzyme production assays and found to exhibit amylolytic, lipolytic, proteolytic, chitinolytic, and cellulolytic activities. Based on the morphological and molecular identification by the 16S rRNA sequence analysis, isolates showed the similarity with Staphylococcus cohnii, Bacillus siamensis, Staphylococcus hominis, and Kosakonia cowanii found in GENBANK. @*Conclusion, significance and impact of study@#The study revealed the biological control potential of endophytic bacteria agents against the brown eyespot-causing fungus in coffee.
ABSTRACT
Aims@#The specific aim of this study was to evaluate for the first time the phytochemical constituents, functional group assignment, and antibacterial activities of the Philippine green-leafed Acalypha amentacea Roxb. (Maslakot-Ambulong), a wildcrafted medicinal plant of local traditional healers in the southern most region of Mindoro province. @*Methodology and results@#Aqueous leaf extracts of A. amentacea Roxb. were lyophilized and subjected to qualitative phytochemical screening and FT-IR analysis. The antibacterial activity of the plant using agar-well diffusion assay revealed highest Zone of Inhibition (ZOI) in 500 mg/mL concentration for Staphylococcus aureus (21.78 mm), Escherichia coli, (21.36 mm), Serratia marcescens (21.90 mm), Klebsiella pneumoniae (21.44 mm), and Enterococcus faecalis (20.52 mm) among other concentrations suggesting a dose dependent bioactivity. Also, compared to the antibiotic Rifampicin, A. amentacea Roxb. demonstrated better bioactivity against all the selected bacteria except S. aureus (p<0.05) and comparable to Ofloxacin when against E. faecalis. The minimum inhibitory concentration (MIC) of the extract was found to be at 15.6 mg/mL for all the bacteria except for S. marcescens with 31.25 mg/mL as MIC. The bioactivity of the plant may be accounted to the presence of alkaloid, phenol, flavonoid, tannin, and saponin which were supported by its functional groups like carboxylic acid, alcohols, amine, conjugated alkene, aromatic esters, and alkyl aryl ether. @*Conclusion, significance and impact of study@#The results of this investigation, proved that A. amentacea Roxb. has bioactive antibacterial principles against the selected microorganisms. This also confirms its potentiality as a new source of antibacterial agents.