Diversity of culturable aerobic denitrifying bacteria in the sediment, water and biofilms in Liangshui River of Beijing, China

Pengyi Lv,Jinxue Luo,Zhihui Bai,Xuliang Zhuang,Dongqing Zhang,Zhanbin Huang

doi:10.1038/s41598-017-09556-9

Abstract

Aerobic denitrification is a process reducing the nitrate into gaseous nitrogen forms in the presence of oxygen gas, which makes the nitrification and denitrification performed simultaneously. However, little was known on the diversity of the culturable aerobic denitrifying bacteria in the surface water system. In this study, 116 strains of aerobic denitrifying bacteria were isolated from the sediment, water and biofilm samples in Liangshui River of Beijing. These bacteria were classified into 14 genera based on the 16 S rDNA, such as Pseudomonas, Rheinheimera, and Gemmobacter. The Pseudomonas sp., represented by the Pseudomonas stutzeri, Pseudomonas mendocina and Pseudomonas putida, composed the major culturable aerobic denitrifiers of the river, followed by Ochrobactrum sp. and Rheinheimera sp. The PCA plot showed the unclassified Pseudomonas sp. and Rheinheimera pacifica preferred to inhabit in biofilm phase while one unclassified Ochrobactrum sp. and Pseudomonas resinovorans had higher abundance in the sediment. In the overlying water, the Pseudomonas stutzeri and Ochrobactrum rhizosphaerae were found to have higher abundance, indicating these aerobic denitrifiers had different habitat-preferable characteristics among the 3 phases of river system. The findings may help select the niche to isolate the aerobic denitrifiers and facilitate the bioaugmentation-based purification of the nitrate polluted surface water.

Highlights

The pollution of nitrate in surface water has increasingly become a serious environmental problem in modern world due to the increasing anthropogenic activities, such as discharge of industrial and domestic sewage, leaching of animal manure from the farming industry[1] and excessive utilization of fertilizers in agriculture[2]
Some aerobic denitrifying bacteria have been isolated from different niches, such as the Bacillus methylotrophicus L7 isolated from wastewater[17], Pseudomonas putida AD-21 isolated from soil[18], Pseudomonas stutzeri TR2 isolated from domestic wastewater[19] and Zoogloea sp
In this study, the aerobic denitrifying bacterial strains were isolated from 3 types of niches in the Liangshui River, including the overlying water where the bacteria live in planktonic mode, biofilm phase where the microorganisms live in a sessile mode and sediment where high concentrations of nutrients, e.g. nitrogen and phosphorus, were usually deposited and absorbed from the overlying water phase[21, 22]

Summary

Introduction

The pollution of nitrate in surface water has increasingly become a serious environmental problem in modern world due to the increasing anthropogenic activities, such as discharge of industrial and domestic sewage, leaching of animal manure from the farming industry[1] and excessive utilization of fertilizers in agriculture[2]. Oxygen is a crucial factor affecting the transformation of nitrogen in water, e.g. the oxidation of ammonia and reduction of nitrate Ammonia is another toxic nitrogen contaminant in surface water, which can be removed through being oxidized to nitrate (nitrification) in the presence of oxygen gas[12]. The different requirement of oxygen determines the aerobic nitrification and anaerobic denitrification processes cannot be operated under the same condition. In this study, the aerobic denitrifying bacterial strains were isolated from 3 types of niches in the Liangshui River, including the overlying water where the bacteria live in planktonic mode, biofilm phase where the microorganisms live in a sessile mode and sediment where high concentrations of nutrients, e.g. nitrogen and phosphorus, were usually deposited and absorbed from the overlying water phase[21, 22]. The classification and compositions of the aerobic denitrifying consortiums were studied

Methods

Results

Conclusion