Chanratana Mak, Han Gwang Hyun, Roy Choudhury Aritra, Sundaram Seshadri, Halim Md Abdul, Krishnamoorthy Ramasamy, Kang Yeongyeong, Sa Tongmin
Department of Environmental and Biological Chemistry, College of Agriculture, Life and Environment Sciences, Chungbuk National University, Cheongju, Chungbuk, 361-763, Republic of Korea.
Indegenous and Frontiers Technology Research (IFTR) Centre, Chennai, India.
AMB Express. 2017 Nov 21;7(1):208. doi: 10.1186/s13568-017-0518-7.
Salinity is one of the major factors contributing to the loss of crop productivity and thereby impacting livelihood of people in more than 100 countries of the world and the area of land affected by salinity is increasing day by day. This will worsen due to various factors such as drought that might result in high soil salinity. Use of plant growth promoting rhizobacteria is one of the promising eco-friendly strategies for salinity stress management as part of sustainable agricultural practices. However, it requires selecting rhizobacteria with good survivability and adaptation to salt stress. In this study we report aggregation of Methylobacterium oryzae CBMB20 cells grown in media containing high C/N ratio (30:1) than in media containing low C/N ratio (7:1). Aggregated Methylobacterium oryzae CBMB20 cells exhibited enhanced tolerance to UV irradiation, heat, desiccation, different temperature regimes, oxidative stress, starvation and supported higher population in media. Poly-β-hydroxybutyrate accumulation, exopolysaccharide production, proline accumulation and biofilm formation were good at 100 mM salt concentration with good microbial cell hydrophobicity at both 50 and 100 mM than other concentrations. Both the aggregated and non-aggregated cells grown under 0-200 mM salt concentrations produced IAA even at 200 mM salt concentration with a peak at 100 mM concentration with aggregated cells producing significantly higher quantities. ACC deaminase activity was observed in all NaCl concentrations studied with gradual and drastic reduction in aggregated and non-aggregated cells over increased salt concentrations.
盐度是导致作物生产力损失的主要因素之一，进而影响世界上100多个国家人民的生计，而且受盐度影响的土地面积日益增加。由于干旱等各种因素，这种情况可能会恶化，干旱可能导致土壤盐度升高。使用植物促生根际细菌是作为可持续农业实践一部分的盐胁迫管理的一种有前景的生态友好策略。然而，这需要选择具有良好生存能力和适应盐胁迫能力的根际细菌。在本研究中，我们报告了在高碳氮比（30:1）培养基中生长的米氏甲基杆菌CBMB20细胞比在低碳氮比（7:1）培养基中生长的细胞聚集情况。聚集的米氏甲基杆菌CBMB20细胞对紫外线照射、热、干燥、不同温度条件、氧化应激、饥饿表现出更高的耐受性，并在培养基中支持更高的种群数量。聚-β-羟基丁酸酯积累、胞外多糖产生、脯氨酸积累和生物膜形成在100 mM盐浓度下表现良好，在50 mM和100 mM时的微生物细胞疏水性均优于其他浓度。在0-200 mM盐浓度下生长的聚集细胞和非聚集细胞即使在200 mM盐浓度下也能产生吲哚-3-乙酸（IAA），在100 mM浓度时达到峰值，聚集细胞产生的量显著更高。在所研究的所有氯化钠浓度下均观察到1-氨基环丙烷-1-羧酸（ACC）脱氨酶活性，随着盐浓度增加，聚集细胞和非聚集细胞中的该活性逐渐急剧降低。
