Nocardioides lacusdianchii sp. nov., an attached bacterium of Microcystis aeruginosa

Abstract

Attached bacteria of Microcystis play important roles in the occurence, outbreak and decline of Microcystis water blooms. In this study, a novel actinobacterium, designated strain JXJ CY 38 ^T, was isolated from the culture mass of Microcystis aeruginosa FACHB-905 (MAF), collected from Lake Dianchi, south-west, China. The strain was found to be a Gram-stain positive, short rod, catalase positive and oxidase negative. The isolate was found to be able to grow at 5.0-38.0 °C (optimum, 28.0 °C), pH 4.0-11.0 (optimum, 7.0-8.0) and 0-3.0% (w/v, optimum, 0%) NaCl. Based on 16S rRNA gene sequences, strain JXJ CY 38 ^T shows high similarities to Nocardioides furvisabuli JCM 13813 ^T (99.0%) and Nocardioides alpinus JCM 18960 ^T (98.7%), and less than 98.2% similarities to other members of the genus. The major cellular fatty acids (> 10.0%) were identified as iso-C_16:0 (23.6%), C_18:1ω9c (18.2%) and C_17:1ω8c (16.4%), while the predominant menaquinone was found to be MK-8 (H₄). The diagnostic diamino acids in the cell wall peptidoglycan were identified as aspartic acid, glutamic acid, glycine and alanine, with mannose, ribose and arabinose as whole cell sugars. The polar lipids were found to be diphosphatidylglycerol, phosphatidylglycerol, a phospholipid, phosphatidylcholine and an unidentified lipid. The DNA G + C content was determined to be 71.3%. The digital DNA-DNA hybridization and average nucleotide identity values between strain JXJ CY 38 ^T and the type strains N. furvisabuli JCM 13813 ^T and N. alpinus JCM 18960 ^T were 49.4% and 37.7%, and 92.0% and 83.4%, respectively. On the basis of the above taxonomic data and differences in physiological characteristics from the closely related type strains, strain JXJ CY 38 ^T was determined to represent a novel species of genus Nocardioides, for which the name Nocardioides lacusdianchii sp. nov. is proposed. The type strain is JXJ CY 38 ^T (= KCTC 49381 ^T = CGMCC 4.7665 ^T). Strain JXJ CY 38 ^T apparently exhibits complex effects on the interactions between MAF and other attached bacteria, including the promotion or inhibition of the growth of MAF and bacteria, and the synthesis and release of microcystins by MAF.

Keywords: Attached bacteria; Microcystis aeruginosa; Nocardioides lacusdianchii sp. nov..