Biological control studies have been increasingly performed against agricultural and forest pests. To develop a biological control agent, bacteria was isolated from harmful pests and identified using various tests. Xylosandrus germanus (Blandford, 1894) (Coleoptera: Curculionidae) is a harmful pest in the hazelnut orchards and other fruit-tree cultures. In this study, we identified 16 bacteria isolates from healthy X. germanus collected in hazelnut orchards in Turkey. Isolates were characterized based on morphological, physiological and biochemical properties using the VITEK 2 Identification System and the fatty acid methyl esters (FAME) analysis. In addition, 16S rRNA gene sequencing of bacterial isolates was performed. Associated bacteria were identified as Acinetobacter psychrotolerans (2 strains), Stenotrophomonas maltophilia, Pseudomonas fluorescens (two strains), Staphylococcus sciuri, Staphylococcus warneri, Pantoea agglomerans (two strains), Staphylococcus hominis subsp. hominis, Erwinia billingiae (two strains), Brevibacterium linens, Advenella sp., Pantoea cedenensis and Brevibacterium permense. Several species of these bacteria are used in biological control as an antifungal and insecticidal against agricultural pest. In the future, their biological control properties will be investigated. This is the first study on the bacterial community of X. germanus. Key words: Xylosandrus germanus, hazelnut, 16S rRNA, fatty acid methyl esters (FAME), VITEK 2, bacterial symbionts, mutualism, biological control.

Bacteriocins are peptides produced by various types of bacteria. Members of the Bacillus genus are known to produce compounds with inhibitory activity in protein structure against pathogenic and non-pathogenic microorganisms. In this study, a bacteriocin-like inhibitory substance (BLIS) synthesized by Bacillus sp. T68 strain, which was previously isolated from soil, was characterized. T68 strain was grown on different media to produce bacteriocin. Crude BLIS obtained was tested by well diffusion method against indicator bacterium. It was investigated within the temperature range of 10-121 C and pH range from 3.0 to 10.0. It was examined in terms of different organic solvents, enzymes and chemicals. Extracellularly produced BLIS was partially purified by ammonium sulphate precipitation method and analyzed on SDS-PAGE. Activity of partially purified BLIS was investigated. It was observed that BLIS produced in Luria Bertani Broth medium was higher as compared to the other media against indicator bacterium at 30 °C for 24 h. BLIS activity maintained at low temperatures (10-40 °C) and lost completely at high temperatures (> 60 °C). It was detected that BLIS exhibited activity in the pH range between 5.0 and 10.0. The effect of EDTA on BLIS activity was slightly positive. Proteinase K and trypsin inhibited BLIS activity. Among the detergents, sodium dodecyl sulphate and Triton X-100 reduced BLIS activity, while Tween 20 and Tween 80 retained it. Additionally, it was determined that application of Tween 20 at 30 °C for 5 hours increased the BLIS activity by 40%. It was found that the solvents used other than butan 1-ol preserved the BLIS activity over 80%. Chloroform and isopropanol increased the BLIS activity slightly. An inhibitory zone formed by the BLIS corresponding to a molecular weight of about 15 kDa was detected. This BLIS exhibited stability over wide pH and temperature ranges and in organic solvent treatments.

Bacterial secondary metabolites play an essential role in biotechnological and biomedical applications. Actinomycetes are important bacterial sources of antibiotics and enzymes. Most of the antimicrobials known today have been isolated from actinomycetes, especially from the genus Streptomyces. In this study, actinomycete isolation was performed from Cystoseira barbata (Stackhouse) C. Agardh compost, collected from the Black Sea coast, by serial dilution method. A total of 73 actinomycetes isolates (BSC) were obtained from the compost samples. The ability of the isolates to produce different extracellular enzymes was investigated qualitatively. It was determined that 68.5% of the isolates have amylase, 100% cellulase, 47.9% chitinase, 94.5% pectinase, 98.6% protease and 96.3% lipase/esterase activity. Antibacterial activities of the isolates were investigated primarily using cross-streak method. Isolates showed high antibacterial activities, with 98.6 and 84.9 % against Staphylococcus aureus Rosenbach and Enterococcus faecalis (Andrewes & Horder) Schleifer & Kilpper-Bäl, respectively. Three out of six isolates (BSC-13, BSC-17, BSC-37, BSC-38, BSC-45, BSC-49) with high antibacterial activity, were screened secondarily for their antibacterial activities using double-layer method. At day 7, BSC-37 isolate showed a high inhibition (57 mm) against S. aureus. Furthermore, these six isolates were identified according to their morphological and physiological characteristics and 16S rDNA sequence analysis. 16S rDNA sequence analysis showed that the isolates with high antibacterial activity belong to Streptomyces genus. Results indicated that these isolates have great potential and may serve as a good source for the studies on bioactive natural products.

In this study, we aimed to screen for Janthinobacterium kumbetense GKT strain production of industrially important enzymes and to assess its antimicrobial resistance profile. Additionally, to enhance violacein production by GKT strain, we investigated the optimum cultivation conditions for this bacterium and the biological properties of crude violacein extract, including its antimicrobial and antioxidant activities. The GKT strain demonstrated proteolytic, lipolytic, and chitinolytic activities. Furthermore, the antibiotic susceptibility test showed that it was resistant to 5 out of the 15 antibiotics tested. Subsequently, the effects of different growth media, temperatures, pH levels, agitation rates, inoculum amounts, incubation times, carbon and nitrogen sources, and NaCl concentrations on violacein production by the GKT strain were examined. The maximum violacein yield of 28.7 μg/ml was achieved when the strain was incubated at 22°C for 72 hours under static conditions in nutrient broth with a pH of 6.4. Also, violacein yield increased with the addition of 1% pepton and 1% glucose as nitrogen and carbon sources, respectively. Violacein pigment, extracted using either methanol or ethanol, was found to inhibit the growth of S. aureus, S. epidermidis, B. cereus and E. faecalis. However, no-activity was seen on tested fungus strains. Additionally, violacein showed antioxidant activity against ABTS and DPPH radicals with IC50 values of 307 μg/ml and 261 μg/ml, respectively. Current research findings suggest that violacein pigment of GKT strain has potent antimicrobial and antioxidant activities and can be used in applications in the pharmaceutical industry.

Blue Lake, a newly discovered soda lake in Giresun Province, Türkiye, is characterized by alkaline water and moderate salinity, creating a unique and unexplored habitat for microorganisms. This study aimed to investigate the prokaryotic diversity of Blue Lake using both culture-dependent and culture-independent approaches and to evaluate the industrial enzyme-producing potential of the cultivable isolates. Physicochemical properties of water and sediment samples were analyzed, followed by 16S rRNA gene-based metagenomic sequencing and conventional cultivation techniques. Metagenomic analyses revealed a highly diverse prokaryotic community comprising 52 phyla and 311 species, with Proteobacteria being the dominant phylum (65.79 ± 4.94%) and Gammaproteobacteria being the most abundant class (46.58 ± 5.18%). Acinetobacter was identified as the predominant genus, while Sphingobacterium multivorum was the most prevalent species. A total of 87 bacterial isolates were obtained using culture-dependent methods, several of which exhibited significant enzymatic activities, including protease, lipase, amylase, cellulase, chitinase, and pectinase production. The presence of enzyme-producing alkaliphilic and halotolerant bacteria highlights the biotechnological and environmental potential of Blue Lake. This study provides the first integrated metagenomic and cultivation-based characterization of the prokaryotic ecosystem of Blue Lake, contributing valuable insights into soda lake microbiomes and their industrial relevance.