Vietnam Journal of Biotechnology 20(2): 351-358, 2022 351 IDENTIFICATION, CULTIVATION CONDITION OF PARASEVETIBACTER SP C101 AND ANTIMICROBIAL ACTIVITY OF THE BACTERIAL CULTURE EXTRACT Nguyen Manh Tuan 1, , Le Quang Vien 2 , Truong Phuc Hung 2 , Tran Minh Quan 1 , Do Thi Hien 1 , Do Bich Due 1 , Duong Thi Khuyen 1 1 Institute of Life Sciences, Thai Nguyen University of Agriculture and Forestry, Quyet Thang Commune, Thai Nguyen City, Thai Nguyen Province, Vietnam 2 Thai Nguyen University of Sciences, Thai Nguyen University, Tan Thinh Ward, Thai Nguyen City, Thai Nguyen Province, Vietnam  To whom correspondence should be addressed. E-mail: nguyenmanhtuan@tuaf.edu.vn Received: 06.6.2021 Accepted: 16.12.2021 SUMMARY During the recent decade, uncultured bacteria have been special interest as potential candidates for discovering novel antibacterial compounds. Two strains C101 and C102 were negative Gram bacteria, only growing on low nutrient media as R2A/3, NB/3, LB/10 and R4/10 compared to the usual. On R2A/3 medium, colonies of the isolates were round, convex, lemon yellow color with the size of 1-1.5 mm after six days of incubation at 28 o C. Cells were 0.2-0.3 × 0.8-1.3 μm. The strains C101 and C102 were able to grow at temperature ranging 15-37 o C (optimum at 25-28 o C), pH 5-8 (optimum in pH 6-7). The sequences of 16S rRNA genes from strain C101 (MT756087) and C102 (MT756088) shared 100% identity. Analysis of full-length 16S rRNA gene sequence of strain C101 via using NCBI Blast, EzTaxon Database revealed the highest similarity of 99.18-100% to uncultured clones, and 97.86% to type species as Parasegetibacter terrae SGM2-10 T . Genetic sequence analysis data showed that strain C101 should be considered a novel candidate species of the genus Parasegetibacter. Antibacterial compound was extracted from culture of strain C101 in R4/10 medium for ten days of shaking incubator at 28 o C and exhibited susceptible activity to inhibit Bacillus anthracis KEMB 211-146 at a concentration of 2 μg/L and Staphylococcus aureus ATCC 6538 at 4 μg/L; intermediate inhibiting Bacillus subtilis KEMB 51201-001 at 8 μg/L, Staphylococcus epidermidis ATCC 14990 at 8 μg/L, and S. aureus CCARM 3155 at 16 μg/L; inhibition of S. aureus CCARM 3095 at 64 μg/L, S. aureus CCARM 3192 at 32 μg/L, and S. epidermidis CCARM 3710 at 64 μg/L. Keywords: 16S rRNA gene sequence, antibacterial activity, slow-growing bacteria, uncultured bacteria INTRODUCTION Over the past 10 years, the number of newly discovered natural antibiotics has tended to decrease sharply, while pathogenic bacteria have evolved rapidly, allowing them to survive better in adverse conditions. As a result, many antibiotic resistant pathogens appear such as methicillin-resistant Staphylococcus (MRSA), vancomycin-resistant Enterococcus (VRE), vancomycin-resistant Staphylococcus (VRSA), and multi-drug resistant (MDR), extremely-drug resistant (XDR), extended spectrum β-lactamase (ESBL) (Davies, Davies, 2010; Tacconelli et al., 2018; Centers for Disease Control and Prevention, 2019). Consequence of antibiotic