Raymond Parcon

Bacillus amyloliquefaciens N2B2 and its potential for co-cultivation with chitinolytic bacteria to control the growth of Agroathelia rolfsii and other fungal pathogens of tomatoes (Solanum lycopersicum L.)

Fri, 13 Mar 2026 00:00:00 GMT

Abstract

Tomato farming suffers from yield losses due to outbreaks of fungal diseases. Current management strategies heavily rely on the use of synthetic fungicides. However, dependence on synthetic fungicides imposes risk on the environment and human health. An effective and sustainable alternative to managing fungal plant diseases is the use of biological control. This study aimed to test the efficacy of B. amyloliquefaciens N2B2 and its potential in combination with a chitinase-producing microorganism as a microbial biological control agent (MBCA) against fungal pathogens of tomato, namely, Agroathelia rolfsii, Alternaria sp., Cladosporium cladosporioides, Cladosporium tenuissimum, Colletotrichum scovillei, Fusarium equiseti, Fusarium oxysporum, and Geotrichum candidum. Screening 176 microbial isolates for chitinase activity provided three isolates producing the highest amount of chitinase. However, the chitinase production was not correlated with the control of fungal growth. Dual culture plate assays showed that B. amyloliquefaciens N2B2 inhibited the hyphal growth of all the fungal pathogens in the study. The effect of co-cultivation and the type of fungus significantly affected the zone of inhibition, and their interaction plays a significant role, suggesting that the effect of co-cultivation depends on the specific fungal species involved. In vitro studies showed that B. amyloliquefaciens N2B2 was 62.7% effective against Alternaria sp. in dual plate assays and 60.9% effective in suppressing fungal growth of A. rolfsii on detached tomato fruits. This study demonstrated the efficacy of B. amyloliquefaciens and showed the importance of bioprospecting for alternative and sustainable ways to control the fungal pathogens of tomatoes.

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Marilao-Meycauayan-Obando River System (MMORS) Harbors Multidrug- Resistant Bacteria Indicating High Risk of Antimicrobial Contamination

Sarah Jean G. Supnet — Mon, 30 Nov 2020 00:00:00 GMT

Abstract

Marilao-Meycauayan-Obando River System (MMORS) is among the dirtiest and most polluted places in the world but it is still utilized for aquaculture, recreation, and water supply. Since it is contaminated with various industrial and commercial wastes, it is likely that effluents with antibiotics are also dumped into the river system. Antibiotic resistance is one of the biggest threats to global health, food security, and development. Nine (9) bacteria isolated from MMORS were screened for antibiotic resistance using eight (8) antibiotics of different classes, i.e., ciprofloxacin (5mcg), erythromycin (15mcg), ampicillin (25mcg), ertapenem (10mcg), ceftriaxone (30mcg), linezolid (30mcg), cephalothin (30mcg), and piperacillin/tazobactam (100/10mcg). MS1 and MS5 had the highest multiple antibiotic resistance (MAR) index at 0.625, followed by MS4, MS6, MS7, and MS8 at 0.375. MS2 and MS9 had MAR index of 0.125. The proportion of isolates with MAR index greater than 0.2 (66.66%) was higher than isolates with MAR index below 0.2 (33.33%), suggesting a high risk of contamination in sampling sites. Sequence analysis revealed that MS1 had 99.87% sequence similarity with Bacillus pumilus, MS2 with 99.30% Bacillus sp. sequence similarity, MS3 with 93.08% Brevibacillus sp. sequence similarity, MS4 with 99.90% Morganella morganii sequence similarity, MS5 with 100.00% Bacillus cereus sequence similarity, MS6 with 99.78% Escherichia coli sequence similarity, MS7 with 100.00% Bacillus anthracis sequence similarity, and MS9 with 100.00% Bacillus sp. sequence similarity. This study provides initial insight into multidrug-resistant bacteria and its possible risk in safety and public health in MMORS.

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Variations in enzymatic activity and response to abiotic factors of endophytic bacteria isolated from Narra (Pterocarpus indicus) growing in a forest environment and urban arboretum

Liezel D.C. Atole — Sun, 08 Nov 2020 00:00:00 GMT

Abstract

Endophytic microorganisms are plant-colonizing microorganisms that cause no significant harm to the host. They are widely studied due to their production of secondary metabolites that are useful for the pharmaceutical, agricultural and food industries. The production of these metabolites also helps plants to better adapt to their environment. The species composition of endophytes can be greatly affected by environmental conditions and the location of their hosts. This study aimed to compare species and enzymatic production of endophytes isolated from Narra (Pterocarpus indicus) growing in two different locations in the Philippines i.e. the Mount Makiling Forest Reserve (MMFR) and the UP Arboretum in Quezon City. The results show that there was a higher number of bacterial genera isolated from MMFR compared to UP Arboretum. Staphylococcus, Pseudomonas, Serratia, Pantoea, and Microbacterium were uniquely found in the MMFR while Lysinibacillus was only found in the UP Arboretum. More isolates from MMFR were able to produce amylase, cellulase, chitinase and protease than those from the UP Arboretum. On the other hand, a greater percentage of endophytes from the UP Arboretum were able to produce laminarinase, L-asparaginase and xylanase. The results agree with previous studies that show that location affects the physiological activity of endophytes.

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Bacillus amyloliquefaciens, a Narra (Pterocarpus indicus) leaf endophyte, possesses antifungal activity against phytopathogenic fungi due to laminarinase activity and production of antimicrobial compounds

Mon, 24 Jun 2019 00:00:00 GMT

Abstract

Microbial endophytes are microorganisms that live within plant tissues but do not confer disease. Endophytes benefit their host plant by promotion of plant growth, reduction of disease severity, induction of the defense mechanisms of plants, secretion of products that prevent herbivory, fixation of nitrogen, and increasing nutrient uptake. The benefits such as resistance to pathogens and insect herbivory that they confer on plants make them ideal sources of antimicrobial compounds which can be developed into biocontrol agents against phytopathogenic fungi or biofungicides. Laminarin or 1,3-β-glucan is a major component of fungal cell walls; thus one approach in identifying potential antifungal agents is to determine whether they secrete the enzyme laminarinase which hydrolyses laminarin into its component 1,3-linked β-D-glucose residues. As an initial step in the development of a biofungicide, 249 endophytic bacteria and yeasts were screened for the production of laminarinase. One isolate, N2B2, recovered from the leaves of Narra (Pterocarpus indicus), was able to grow with laminarin as sole carbon source and exhibit antifungal activity against three phytopathogenic fungi, namely, Cladosporium sp., Diaporthe sp., and Fusarium oxysporum. In vitro assays showed that the antifungal activity was correlated with laminarinase production. However, antifungal ability of N2B2 was sustained when grown in a medium that did not contain laminarin, suggesting that antimicrobial ability of the isolate may be due to multiple mechanisms. Identification of N2B2 by sequencing of its 16s rDNA revealed it to be B. amyloliquefaciens. This is the first mention in the literature of the isolation of B. amyloliquefaciens from Narra.

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