Elif Özlem Arslan Aydoğdu

Microbial metabolism encompasses the biochemical networks that enable cells to convert nutrients into the energy and biosynthetic precursors necessary for cellular function. Understanding microbial metabolism is crucial for ecology, microbiology, and applications in biotechnology, agriculture, and medicine, as it underpins the biological processes that sustain life in various environments. Microbial metabolic products can be broadly classified as primary or secondary metabolites. Primary metabolites, such as amino acids, carbohydrates, organic acids, and alcohols, are essential for energy generation, biosynthesis, and cellular maintenance, typically accumulating during the exponential growth phase. In contrast, secondary metabolites, including compounds such as antibiotics, toxins, and alkaloids, are predominantly synthesised during the stationary growth phase and are not essential for basic cellular functions. However, they are often involved in ecological interactions and may provide adaptive advantages to the organisms. This distinction emphasises the dual function of microbial metabolism in supporting life and influencing ecological processes. The regulation of microbial metabolite biosynthesis is influenced by nutrient availability, environmental stresses, and intricate genetic networks. Advances in metabolic engineering, synthetic biology, and CRISPR-based technologies have enabled the redirection of central carbon fluxes to enhance the yield of both primary and secondary metabolites. Multi-omics approaches and computational modeling now provide deeper insights into metabolic regulation, pathway optimization, and the discovery of novel bioactive molecules. In conclusion, microbial metabolites are an invaluable resource for biotechnological innovation. While primary metabolites are essential for metabolic physiology, secondary metabolites offer unique bioactivities that have transformed pharmaceutical development, sustainable agriculture and industrial microbiology. Research focusing on uncovering new microbial diversity and optimising biosynthetic pathways is expected to continue providing insights that could deliver sustainable strategies and innovative solutions to urgent global challenges such as food security, healthcare, and environmental restoration.

The antioxidant and antibacterial activities of leaf and fruit extracts from Cornus sanguinea L. subsp. australis (C. A. Mey.) Jáv. were comprehensively evaluated. Plant material was collected from the Bahçesaray district of Van province in Eastern Anatolia, Türkiye, a region characterized by semi-arid climatic conditions and high altitude. Antioxidant activity was measured using DPPH activity and CUPRAC capacity assays, as well as total phenolic and flavonoid content analyses. Antibacterial activity was tested using disk diffusion, well diffusion, and microdilution methods against Staphylococcus aureus, Staphylococcus epidermidis (Gram-positive), and Escherichia coli (Gram-negative). Leaf extracts contained significantly higher total phenolic and flavonoid content than fruit extracts and demonstrated stronger antioxidant capacity. In antibacterial assays, leaf extracts showed a pronounced inhibitory effect on Gram-positive bacteria but limited activity against E. coli. Microdilution analyses indicated that fruit extracts had notable antibacterial activity, especially against S. aureus and S. epidermidis, with low minimum inhibitory concentrations (MICs). Variations in MIC results between diffusion-based methods were attributed to differences in chemical composition, molecular weight, and diffusion capacity of the extracts. These findings suggest that C. sanguinea leaf and fruit tissues are promising natural resources for wound healing and dermatological applications due to their antioxidant and antibacterial properties. The results underscore the pharmaceutical potential of plants grown under environmental stress and provide a strong foundation for further phytochemical and in vivo research.

Consuming food contaminated with harmful microorganisms poses a significant public health risk, often occurring on indoor food contact surfaces like cutting boards in home kitchens. The study aimed to experimentally determine the survival of Salmonella on commonly used cutting board surfaces (glass, wood, polyethylene) and its potential to cause cross‐contamination of food samples (salami) over varying intervals and contact times. Salmonella bacteria persisted on polyethylene and glass cutting boards for up to 4 h, whereas on wooden surfaces, they were detected only up to 2 h. The transfer rates of bacteria to salami were found to vary depending on the type of board material and bacterial strain, with wooden boards demonstrating the lowest transfer rates. Additionally, the transfer rate increased proportionally with longer contact times. The study highlights that all types of cutting boards have the potential to transfer bacteria to food, although wooden boards showed lower transfer rates compared to polyethylene and glass surfaces.

Since minced meat provides a large contact surface, it is a food in which the total bacterial load and the enzymatic profiles of the species that make up this load should be addressed, even in cases where it does not contain pathogens. Therefore, this study aimed to investigate the effect of freezing, one of the most commonly used storage methods for minced meat, on total and proteolytic bacterial loads. To simulate the actual storage process, individuals belonging mainly to the genera Bacillus, Serratia, Pseudomonas, Citrobacter, Acinetobacter, and Escherichia were isolated from the samples examined directly and after 15 days of freezing, without any process that would cause a change in the microbial load. 71.11% of these isolates exhibited valine and cystine aminopeptidase activity, while 37.77 and 33.33% exhibited trypsin and α-chymotrypsin activity, respectively. In addition, the results show that cryopreservation allows psychrophilic proteolytic bacteria to increase their numbers in meat.

Permafrost, or permafrost, consists of soil, rock, and sedimentary materials frozen in regions below 0°C for at least two consecutive years. Permafrost areas are fascinating with their microbial load. The sub-zero atmospheres of these areas allow microorganisms to maintain their viability for years or even centuries. Climate change indicates a serious risk of melting in the Arctic and other permafrost regions. Due to their microbial load-induced metabolic activities, melting permafrost can increase the release of greenhouse gases and disrupt the environmental balance. Microbial load is essential not only for the release of carbon gases but also for the increase of microbial-borne diseases. It is known that apparent microbial and vector-borne diseases have increased in the Arctic region.The melting of permafrost areas due to atmospheric warming, which in turn exposes new soils and microorganisms, has the potential to trigger significant changes in the biosphere.