Abstract
Ralstonia solanacearum is a major phytopathogenic bacterium that attacks many crops and other plants around the world. In this study, a novel actinomycete, designated strain NEAU-SSA 1T, which exhibited antibacterial activity against Ralstonia solanacearum, was isolated from soil collected from Mount Song and characterized using a polyphasic approach. Morphological and chemotaxonomic characteristics of the strain coincided with those of the genus Streptomyces. The 16S rRNA gene sequence analysis showed that the isolate was most closely related to Streptomyces aureoverticillatus JCM 4347T (97.9%). Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain formed a cluster with Streptomyces vastus JCM4524T (97.4%), S. cinereus DSM43033T (97.2%), S. xiangluensis NEAU-LA29T (97.1%) and S. flaveus JCM3035T (97.1%). The cell wall contained LL-diaminopimelic acid and the whole-cell hydrolysates were ribose, mannose and galactose. The polar lipids were diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), hydroxy-phosphatidylethanolamine (OH-PE), phosphatidylinositol (PI), two phosphatidylinositol mannosides (PIMs) and an unidentified phospholipid (PL). The menaquinones were MK-9(H4), MK-9(H6), and MK-9(H8). The major fatty acids were iso-C17:0, C16:0 and C17:1 ω9c. The DNA G+C content was 69.9 mol %. However, multilocus sequence analysis (MLSA) based on five other house-keeping genes (atpD, gyrB, recA, rpoB, and trpB), DNA–DNA relatedness, and physiological and biochemical data showed that the strain could be distinguished from its closest relatives. Therefore, it is proposed that strain NEAU-SSA 1T should be classified as representatives of a novel species of the genus Streptomyces, for which the name Streptomyces sporangiiformans sp. nov. is proposed. The type strain is NEAU-SSA 1T (=CCTCC AA 2017028T = DSM 105692T).
Highlights
Ralstonia solanacearum is the causal agent of bacterial wilt, one of the most devastating plant pathogenic bacteria around the world [1], which has an unusually wide host range, infecting over 200 plant species [2], including many important agricultural crops such as potato, tomato, banana and pepper
Because of a lacking number of genome sequences of Streptomyces aureoverticillatus JCM4347T, Streptomyces vastus JCM4524T, S. cinereus DSM43033T, and S. xiangluensis NEAU-LA29T, DNA–DNA relatedness tests between strain NEAU-SSA 1T and those strains were carried out as described by De Ley et al [40] under consideration of the modifications described by Huss et al [41], using a model Cary 100 Bio UV/VIS-spectrophotometer (Hitachi U-3900, Hitachi Co., Tokyo, Japan) equipped with a Peltier-thermostatted 6 × 6 multicell changer and a temperature controller with in situ temperature probe (Varian)
The antibacterial activity of strain NEAU-SSA 1T against two pathogenic bacteria (Micrococcus luteus and Ralstonia solanacearum) was evaluated using the agar well diffusion method [44] with the cultures growth on International Streptomyces Project (ISP) 3 medium at 28 ◦C for four weeks as follows: All the spores and mycelia were collected from one ISP 3 plate and extracted using 1 mL methanol with an ultrasonic step (300 W, 30–60 min)
Summary
Ralstonia solanacearum is the causal agent of bacterial wilt, one of the most devastating plant pathogenic bacteria around the world [1], which has an unusually wide host range, infecting over 200 plant species [2], including many important agricultural crops such as potato, tomato, banana and pepper. The search and discovery of novel, environmentally friendly, commercially significant, naturally bioactive compounds are in demand to control this disease at present. The genus Streptomyces, within the family Streptomycetaceae, is the largest genus of the phylum Actinobacteria, first proposed by Waksman and Henrici (1943) [7] and currently encompasses more than 800 species with valid published names (http://www.bacterio.net/streptomyces.html), which are widely distributed in soils throughout the world. Members of novel Streptomyces species are in demand as sources of novel, environmentally friendly, commercially significant, naturally bioactive compounds [8,9]. Results demonstrated that the strain represents a novel species of the genus Streptomyces, for which the name Streptomyces sporangiiformans sp. nov. is proposed
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