Suppression of Ganoderma boninense Using Benzoic Acid: Impact on Cellular Ultrastructure and Anatomical Changes in Oil Palm Wood

Basal stem rot (BSR) caused by a wood degrading fungus, Ganoderma boninense, is the major constraint in palm oil production. It degrades the wood components and causes palms to collapse, leading to heavy losses. Inefficacy in controlling this disease could be caused by the lack of understanding in how the pathogen establishes itself on the host concerning wood decay stages. This study aimed to understand and determine the role of benzoic acid on the suppression of G. boninense and production of ligninolytic enzymes responsible for wood decay. Further, the alteration in wood component structure due to G. boninense infection and its prevention were studied. Benzoic acid treatment resulted in more than 80% of inhibition in G. boninense growth. SEM and HR-TEM analysis confirmed the antifungal activity of benzoic acid by disruption of mycelial morphology and cellular ultrastructure. Moreover, the membrane permeability assay recorded enhanced cell mortality in benzoic acid treated mycelium. The degradation of oil palm woodblock caused 58.86 % wood dry weight loss at day 120. In contrast, reduction in dry weight loss (58.82%) was recorded in woodblock treated with concentrations of benzoic acid of 5 mM and above. It is concluded that the use of benzoic acid could inhibit or delay pathogen establishment in oil palm wood, leading to the sustainable management of BSR disease. Further, glasshouse and field trials are required to prove the consistency in current findings which may contribute to reduced land expansion to create new disease-free land for oil palm planting.

Robust Segmentation of Cellular Ultrastructure on Sparsely Labeled 3D Electron Microscopy Images using Deep Learning

A deeper understanding of the cellular and subcellular organization of tumor cells and their interactions with the tumor microenvironment will shed light on how cancer evolves and guide effective therapy choices. Electron microscopy (EM) images can provide detailed view of the cellular ultrastructure and are being generated at an ever-increasing rate. However, the bottleneck in their analysis is the delineation of the cellular structures to enable interpretable rendering. We have mitigated this limitation by using deep learning, specifically, the ResUNet architecture, to segment cells and subcellular ultrastructure. Our initial prototype focuses on segmenting nuclei and nucleoli in 3D FIB-SEM images of tumor biopsies obtained from patients with metastatic breast and pancreatic cancers. Trained with sparse manual labels, our method results in accurate segmentation of nuclei and nucleoli with best Dice score of 0.99 and 0.98 respectively. This method can be extended to other cellular structures, enabling deeper analysis of inter- and intracellular state and interactions.

Ionic gold demonstrates antimicrobial activity against Pseudomonas aeruginosa strains due to cellular ultrastructure damage

Due to the ever-increasing rise of antimicrobial resistant (AMR) bacteria, the development of alternative antimicrobial agents is a global priority. The antimicrobial activity of ionic gold was explored against four Pseudomonas aeruginosa strains with different AMR profiles in order to determine the antimicrobial activity of ionic gold and elucidate the mechanisms of action. Disc diffusion assays (zone of inhibition: ZoI) coupled with minimum inhibitory/bactericidal concentrations (MIC/MBC) were conducted to determine the antimicrobial efficacy of ionic gold. Scanning electron microscopy (SEM) was used to visualise morphological changes to the bacterial cell ultrastructure. Strains with increased AMR were slower to grow which is likely a fitness cost due to the enhanced AMR activity. Although greater concentrations of ionic gold were required to promote antimicrobial activity, ionic gold demonstrated similar antimicrobial values against all strains tested. Lowry assay results indicated that protein leakage was apparent following incubation with ionic gold, whilst SEM revealed cellular ultrastructure damage. This study suggests that the application of ionic gold as an alternative antimicrobial is promising, particularly against AMR P. aeruginosa. The antimicrobial activity of ionic gold against P. aeruginosa could potentially be utilised as an alternative therapeutic option in wound management, an approach that could benefit healthcare systems worldwide.

Individual Cryptomeria fortunei Hooibrenk Clones Show Varying Degrees of Chilling Stress Resistance

Low temperature (LT) is an important abiotic factor affecting plant survival, growth and distribution. The response of Cryptomeria fortunei (Chinese cedar) to LT is not well known, limiting its application in production and ornamental value. In this study, we first screened ten clones (#3, #25, #32, #42, #54, #57, #68, #66, #74, #X1), originating from five different locations in China, for their degrees of cold resistance. We then selected the two showing the highest (#32) and lowest (#42) cold resistance to see the physiological and morphological response of different cold-resistant C. fortunei clones to LT. We found that the electrolyte leakage of all ten clones increased strongly between 0 and −8 °C, while below −8 or between 4 and 0 °C did not yield additional increases. Under cold stress, clones #32 and #42 showed different degrees of needle browning. From 25 to −20 °C, maximum and effective quantum yields of photosystem II (Fv/Fm and YII) and photochemical and non-photochemical quenching (qP and NPQ) decreased continuously in two clones with decreasing temperature, where #42 was more strongly affected compared with #32. The chlorophyll content first decreased significantly to the lowest from 25 to −12 °C, then increased significantly at −16/−20 °C compared with −12 °C. We observed changes in needle cellular ultrastructure at −8 °C, with chloroplasts of #32 swelling, while those of #42 were destroyed. Correlation analysis indicated that needle browning and chlorophyll fluorescence were closely related to temperature, and cellular ultrastructure changed notably around semi-lethal temperature (LT50), which can be used as physiological indicators for the identification of cold resistance. We found a clear difference in cold tolerance between clones of #32 and #42, with #32 being more tolerant, which can be exploited in breeding programs. We conclude that strongly cold-resistant clones have more stable physiological states and a wider adaptability to LT compared with weak ones.