Response of the bacterial community structure to inorganic nutrient loading determined via a pyrosequencing method: a mesocosm study

Abstract

To understand the effect of inorganic nutrient loading on microbial biodiversity and function, a mesocosm (1,000 L) experiment was carried out for 10 days in southern Korean coastal waters and the bacterial community structure (BCS) was investigated using 16S rRNA amplicon pyrosequencing method that allows a more comprehensive understanding of the communities in natural samples. As a result, among the three treatments, +NP and +N treatments resulted in the largest and second-largest increases in phytoplankton abundance, respectively, whereas there was relatively less variation under the +P treatment. Enhanced growth of phytoplankton not only induced increases in pH and bacterial abundance (p<0.05) but also led to changes in community structure: theorders Flavobacteria, Micrococcales, Oceanospirillales, and Rhodobacterales exhibited increases in relative abundance, whereas Methylophilales, Puniceicoccales, SAR11, SAR116, and SAR86 showed a decreasing trend. Inorganic nutrients may also contribute to the variation in BCS, as the relative abundance of Sphingobacteriales, containing members that undergo chemotaxis toward inorganic nutrients, was increased by the +N treatment. Given that these findings, inorganic nutrients loading may lead to variations in the BCS through both direct and indirect ways.estigated using 16S rRNA amplicon pyrosequencing method that allows a more comprehensive understanding of the communities in natural samples. As a result, among the three treatments, +NP and +N treatments resulted in the largest and second-largest increases in phytoplankton abundance, respectively, whereas there was relatively less variation under the +P treatment. Enhanced growth of phytoplankton not only induced increases in pH and bacterial abundance (p<0.05) but also led to changes in community structure: theorders Flavobacteria, Micrococcales, Oceanospirillales, and Rhodobacterales exhibited increases in relative abundance, whereas Methylophilales, Puniceicoccales, SAR11, SAR116, and SAR86 showed a decreasing trend. Inorganic nutrients may also contribute to the variation in BCS, as the relative abundance of Sphingobacteriales, containing members that undergo chemotaxis toward inorganic nutrients, was increased by the +N treatment. Given that these findings, inorganic nutrients loading may lead to variations in the BCS through both direct and indirect ways.2