Diseases caused by Sclerotinia sclerotiorum have caused severe losses of many economically important crops worldwide. Due to the long-term persistence of sclerotia in soil and the production of air-borne ascospores, synthetic fungicides play limited roles in controlling the diseases. The application of antagonistic microorganisms can effectively reduce the number of sclerotia and eventually eradicate S. sclerotiorum from soil, and therefore considerable interest has been focused on biological control. Streptomyces sp. NEAU-S7GS2 was isolated from the root of Glycine max and its rhizosphere soil. It showed significant inhibitory activity against the mycelial growth of S. sclerotiorum (99.1%) and completely inhibited sclerotia germination. Compared to the control, in the pot experiment the application of NEAU-S7GS2 not only demonstrated excellent potential to control sclerotinia stem rot of soybean with 77 and 38% decrease in disease incidence and disease index, respectively, but could promote the growth of soybean. The light microscopy and scanning electron microscopy showed that co-culture of NEAU-S7GS2 with S. sclerotiorum on potato dextrose agar could lead to contorted and fragmented mycelia of S. sclerotiorum, which was associated with the secretion of hydrolytic glucanase and cellulase and the production of active secondary metabolites by NEAU-S7GS2. The plant growth promoting activity of NEAU-S7GS2 was related to the solubilization of inorganic phosphate, and production of 1-aminocyclopropane-1-carboxylate (ACC) deaminase and indole acetic acid (IAA). To further explore the plant growth promoting and antifungal mechanisms, the complete genome of strain NEAU-S7GS2 was sequenced. Several genes associated with ammonia assimilation, phosphate solubilization and IAA synthesis, together with genes encoding ACC deaminase, glucanase and α-amylase, were identified. AntiSMASH analysis led to the identification of four gene clusters responsible for the biosynthesis of siderophores including desferrioxamine B and enterobactin. Moreover, the biosynthetic gene clusters of lydicamycins, phenazines, and a glycosylated polyol macrolide showing 88% gene similarity to PM100117/PM100118 were identified. These results suggested that strain NEAU-S7GS2 may be a potential biocontrol agent and biofertilizer used in agriculture.

Avermectin and milbemycin are important 16-membered macrolides that have been widely used as pesticides in agriculture. However, the wide use of these pesticides inevitably causes serious drug resistance, it is therefore imperative to develop new avermectin and milbemycin analogs. The biosynthetic gene clusters of avermectin and milbemycin have been identified and the biosynthetic pathways have been elucidated. Combinatorial biosynthesis by domain swap provides an efficient strategy to generate chemical diversity according to the module polyketide synthase (PKS) assembly line. The substitution of aveDH2-KR2 located in avermectin biosynthetic gene cluster in the industrial avermectin-producing strain Streptomyces avermitilis NA-108 with the DNA regions milDH2-ER2-KR2 located in milbemycin biosynthetic gene cluster in Streptomyces bingchenggensis led to S. avermitilis AVE-T27, which produced ivermectin B1a with high yield of 3450 ± 65 μg/ml. The subsequent replacement of aveLAT-ACP encoding the loading module of avermectin PKS with milLAT-ACP encoding the loading module of milbemycin PKS led to strain S. avermitilis AVE-H39, which produced two new avermectin derivatives 25-ethyl and 25-methyl ivermectin (1 and 2) with yields of 951 ± 46 and 2093 ± 61 μg/ml, respectively. Compared to commercial insecticide ivermectin, the mixture of 25-methyl and 25-ethyl ivermectin (2:1 = 3:7) exhibited 4.6-fold increase in insecticidal activity against Caenorhabditis elegans. Moreover, the insecticidal activity of the mixture of 25-methyl and 25-ethyl ivermectin was 2.5-fold and 5.7-fold higher than that of milbemycin A3/A4 against C. elegans and the second-instar larva of Mythimna separate, respectively. Two new avermectin derivatives 25-methyl and 25-ethyl ivermectin were generated by the domain swap of avermectin PKS. The enhanced insecticidal activity of 25-methyl and 25-ethyl ivermectin implied the potential use as insecticide in agriculture. Furthermore, the high yield and genetic stability of the engineered strains S. avermitilis AVE-T27 and AVE-H39 suggested the enormous potential in industrial production of the commercial insecticide ivermectin and 25-methyl/25-ethyl ivermectins, respectively.

A novel Gram-stain-positive, motile, endospore-forming, rod-shaped bacterium, designated strain NEAU-3TGS17T, was isolated from the head of an ant (Lasius fuliginosus). The isolate grew at 0–35 °C (optimum 28–30 °C), at pH 6.0–11.0 (optimum pH 7.0–8.0) and with 0–6 % (w/v) NaCl (optimum 0 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain NEAU-3TGS17T belonged to the genus Psychrobacillus . Sequence similarities between strain NEAU-3TGS17T and members of the genus Psychrobacillus with validly published names ( Psychrobacillus psychrotolerans DSM 11706T, Psychrobacillus insolitus DSM 5T, Psychrobacillus psychrodurans DSM 11713T and Psychrobacillus soli NBRC 110600T) were 98.4–99.1 %. DNA–DNA relatedness values between strain NEAU-3TGS17T and its closest relatives were below 70 %. The major cellular fatty acids (>5 %) were iso-C14 : 0, anteiso-C15 : 0, C16 : 0 and iso-C15 : 0. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. The cell-wall peptidoglycan type was A4β with ornithine as the diamino acid and the predominant menaquinones were MK-8 and some MK-7. The DNA G+C content was 35.8 mol%. On the basis of phenotypic data and phylogenetic inference, strain NEAU-3TGS17T was classified as representing a novel species in the genus Psychrobacillus , for which the name Psychrobacillus lasiicapitis sp. nov. is proposed. The type strain is NEAU-3TGS17T (=DSM 100484T=CGMCC 1.15308T).

A novel strain of actinobacteria, designated strain NEAU-ZJC8T, was isolated from a saline–alkaline soil collected from Heilongjiang Province, north-east China and characterized using a polyphasic approach. Strain NEAU-ZJC8T exhibited morphological, cultural and chemotaxonomic features consistent with its classification as representing a member of the genus Streptomyces. Growth occurred at 16–35 °C, pH 5.0–11.0 and in the presence of 0–11 % (w/v) NaCl. The cell-wall peptidoglycan contained ll-diaminopimelic acid and glycine. Whole-cell hydrolysates mainly contained glucose, galactose and ribose. Predominant menaquinones were MK-9(H6), MK-9(H4) and MK-9(H8). The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside and two unidentified phospholipids. The major cellular fatty acids (>10 %) were iso-C16 : 0, iso-C15 : 0, anteiso-C17 : 0 and C16 : 0. The G+C content of the DNA was 72.7 mol%. A phylogenetic tree based on 16S rRNA sequences showed that strain NEAU-ZJC8T formed a distinct clade within the genus Streptomyces and was closely related to Streptomyces haliclonae DSM 41970T (98.56 % similarity) and Streptomyces marinus NBRC 105047T (97.96 % similarity). A combination of DNA–DNA hybridization results and some phenotypic characteristics demonstrated that strain NEAU-ZJC8T could be distinguished from its closest phylogenetic relatives. Therefore, strain NEAU-ZJC8T represents a novel species of the genus Streptomyces, for which the name Streptomyces daqingensis sp. nov. is proposed. The type strain is NEAU-ZJC8T ( = CGMCC 4.7178T = JCM 30057T).

A novel Gram-stain-positive, strictly aerobic strain, NEAU-SA1T, which showed a rod–coccus growth life cycle, was isolated from forest soil from Zhangjiajie, Hunan Province, China. The isolate grew at 10–40 °C (optimum 28 °C), at pH 5.0–10.0 (optimum pH 7.0) and in the presence of up to 5 % (w/v) NaCl, although NaCl was not required for growth. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain NEAU-SA1T belonged to the genus Arthrobacter and was closely related to Arthrobacter cupressi DSM 24664T (98.1 % similarity). Average nucleotide identity values between NEAU-SA1T and A. cupressi DSM 24664T were 88.91 and 87.41 % by ANIm and ANIb analysis, respectively. The in silico DNA–DNA hybridization value between strain NEAU-SA1T and A. cupressi DSM 24664T was 34.20 %, again indicating they belong to different taxa. The genomic DNA G+C content was 66.74 mol%. The major cellular fatty acids (>10 %) were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and two unidentified glycolipids. The predominant menaquinone was MK-9(H2). The peptidoglycan type was A3α with an interpeptide bridge comprising l-Lys and l-Ala. Glucose, ribose and galactose were the whole-cell sugars. On the basis of morphological, physiological, biochemical and chemotaxonomic analysis, strain NEAU-SA1T was classified as representing a novel species in the genus Arthrobacter , for which the name Arthrobacter silvisoli sp. nov. is proposed. The type strain is NEAU-SA1T (=DSM 106716T=CCTCC AB 2017271T).