Diversity of cultivable bacteria from East Dongting Lake in winter

Abstract:

[Background] East Dongting Lake occupies a special geographical location and harbors abundant species resources, including a variety of microorganisms with unique physiological and biochemical characteristics. [Objective] To obtain the bacterial resources with tolerance to heavy metals and polycyclic aromatic hydrocarbons (PAHs) by the culturable methods and clarify their physiological characteristics. [Method] Forty samples were collected from five different regions of East Dongting Lake in January 2022 for the measurement of environmental factors. The bacteria were isolated, microbial strain resources were obtained, and the correlations of bacteria with environmental factors were analyzed. [Results] A total of 253 bacterial strains were isolated, including 210 strains with tolerance to heavy metals and 43 strains with tolerance to PAHs. The strains belonged to 42 genera, which were dominated by Pseudomonas (46.6%), Fictibacillus (7.5%), Pseudarthrobacter (6.7%) and Bacillus (5.1%). After re-screening, 30 strains with strong tolerance to heavy metals and 7 strains with strong tolerance to PAHs were obtained. Specifically, 20, 4, 3 and 3 strains showed tolerance to Mg²⁺, Mn²⁺, Ni²⁺ and Zn²⁺, with the maximum tolerance concentrations (MTCs) of 500, 500, 30 and 25 mmol/L, respectively. 5 and 2 strains had tolerance to naphthalene and phenanthrene, with the MTCs of 0.04 g/mL and 0.02 g/mL, respectively. Two strains of potentially novel species and one strain of potentially novel genus were identified in this study. [Conclusion] The bacterial diversity varied among the samples from five regions, being higher in Yueshan, Yueyanglou, and Junshan than that in Lujiao and Nanhu. The temperature, total dissolved solids, electrical conductivity, and dissolved oxygen had the greatest influences on the composition of bacterial community, while pH and salinity had the least influences. The low number of strains with strong tolerance to heavy metals and PAHs in this study may be associated with the effective pollution control in East Dongting Lake.